WO2005088876A1 - 光伝送システム、光伝送システムの光送信装置及び光受信装置 - Google Patents
光伝送システム、光伝送システムの光送信装置及び光受信装置 Download PDFInfo
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- WO2005088876A1 WO2005088876A1 PCT/JP2005/004817 JP2005004817W WO2005088876A1 WO 2005088876 A1 WO2005088876 A1 WO 2005088876A1 JP 2005004817 W JP2005004817 W JP 2005004817W WO 2005088876 A1 WO2005088876 A1 WO 2005088876A1
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/58—Compensation for non-linear transmitter output
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- G—PHYSICS
- G02—OPTICS
- G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
- G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour
- G02F1/0121—Operation of devices; Circuit arrangements, not otherwise provided for in this subclass
- G02F1/0123—Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5051—Laser transmitters using external modulation using a series, i.e. cascade, combination of modulators
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5055—Laser transmitters using external modulation using a pre-coder
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/501—Structural aspects
- H04B10/503—Laser transmitters
- H04B10/505—Laser transmitters using external modulation
- H04B10/5057—Laser transmitters using external modulation using a feedback signal generated by analysing the optical output
- H04B10/50575—Laser transmitters using external modulation using a feedback signal generated by analysing the optical output to control the modulator DC bias
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/50—Transmitters
- H04B10/516—Details of coding or modulation
- H04B10/54—Intensity modulation
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/60—Receivers
- H04B10/66—Non-coherent receivers, e.g. using direct detection
Definitions
- the present invention relates to an optical transmission system, an optical transmission device and an optical reception device of an optical transmission system.
- the present invention relates to an optical transmission system to which the DPSK-DD system is applied, and an optical transmission device and an optical reception device of the optical transmission system.
- Wavelength multiplexing technology (WDM technology) is making it possible to relatively easily achieve large capacity.
- Higher bit rates per wavelength are also being actively studied. The reason is that, by increasing the bit rate per wavelength at high speed, the device cost can be reduced, and the device can be reduced in size and power consumption, so that the total initial cost and running cost of the system can be reduced.
- RZ Return-to-Zero
- DPSK method and CS (Carrier
- the input power limit is that the RZ code is more resistant than the NRZ code (Non-Return-Zero code) often used in the conventional optical transmission system.
- the receiving apparatus converts the phase modulated signal to a signal using a demodulator such as a Matsuhazunda interferometer.
- the power is converted to a modulation code and the force is directly detected by the light receiver.
- the use of a double-balanced receiver enables differential light reception, and the discrimination sensitivity is reduced by one intensity modulation signal. Since it is improved by 3 dB compared to the case of direct detection by the receiver, it is common to use a double-noise receiver for the receiver.
- a path difference between two paths of the Mach-Zehnder interferometer is controlled at a wavelength level following a fluctuation of a signal light wavelength.
- a method for controlling these for example, as described in Patent Document 1, one of the interferometers is detected so that a constant output can be obtained by detecting the output level of the balanced-type photodetector.
- Patent Document 1 JP-A-63-52530
- the wavelength interval of WDM and the repetition frequency of a Matsuhazunda interferometer generally do not match, so the path difference of the Mach-Zehnder interferometer must be controlled. (If this is expressed on the frequency axis, the passband wavelength of the Mach-Zehnder interferometer must be controlled.)
- the control range increases. For example, for a signal of 40 Gbit / s, the repetition frequency of the Mach-Zehnder interferometer is 40 GHz, so the difference between the oscillation wavelength and the pass band of the Mach-Zehnder interferometer is 20 GHz at the maximum.
- the present invention has been made in view of such circumstances, and has an optical transmission system that can be set to an optimum operating point of a Mach-Zehnder interferometer that matches the optical frequency of a light source on a transmission side. It is an object of the present invention to provide an optical transmission device and an optical reception device of an optical transmission system. Means for solving the problem
- an optical transmission system includes an optical transmission device that outputs differentially encoded phase modulated light, and an optical receiving device that receives and demodulates the phase modulated light.
- the optical transmitting apparatus comprises: an encoder for converting an input signal of an NRZ code into a signal of an NRZ-1 code; and a phase amplitude ⁇ of 0 for a mark and a space encoded by the encoder.
- phase modulator that outputs a phase-modulated light given in a range of ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ , wherein the optical receiving device divides the received phase-modulated light into two, and one of the two branched signal lights
- a Mach-Zehnder interferometer having a phase adjustment terminal for delaying the two signal lights by interference with each other, converting the two signal lights into intensity-modulated light, and setting a phase difference between the two interfering signals.
- a balanced detection circuit that photoelectrically converts light and outputs a difference between the converted electric signals; and a low-frequency signal that applies a first low-frequency signal of frequency fl to the phase adjustment terminal of the Mach-Zehnder interferometer.
- a small-modulation signal component detection circuit for detecting a second low-frequency signal from a signal supplied from the balanced detection circuit; and the second low-frequency signal output from the small-modulation signal component detection circuit.
- a synchronous detection circuit for detecting the amount of deviation from the wavelength and the direction thereof, a control circuit for outputting a control signal for adjusting the phase difference between the two branched signal lights so as to correct the amount of deviation, and control A based, a driver circuit for driving the phase adjustment terminal Te, the No..
- the minute modulation signal component detection circuit includes an eye opening monitor circuit that outputs a signal obtained by monitoring an eye opening of a signal obtained by branching a signal output from the balanced detection circuit.
- a band-pass filter that passes the second low-frequency signal included in the output signal of the eye opening monitor circuit, wherein the synchronous detection circuit is configured to output the second low-frequency signal based on an output signal of the band-pass filter. And the deviation amount and its direction The direction may be detected.
- the minute modulation signal component detection circuit has a function of detecting and recovering an error in the code therein while recognizing and reproducing the electric signal output from the balanced detection circuit card.
- a data recovery circuit an error detection number monitoring circuit that outputs a signal monitoring error detection number information output from the data recovery circuit, and an error detection number monitoring circuit.
- a band-pass filter that allows a second low-frequency signal to pass therethrough, wherein the synchronous detection circuit detects the amount of deviation and its direction based on the output signal of the band-pass filter. Good ⁇ .
- the balanced detection circuit has an equalization amplifier circuit, and the minute modulation signal component detection circuit outputs a signal that monitors a current consumption of the equalization amplifier circuit.
- a current consumption monitor circuit and a band-pass filter that passes the second low-frequency signal included in a signal output from the current consumption monitor circuit. The shift amount and the direction thereof may be detected based on the output signal.
- the balanced detection circuit is divided by an optical branching unit that branches each of the two output ports of the Mach-Zehnder interferometer into two, and the optical branching unit.
- An optical coupling unit that causes the two lights to interfere with each other; and an optical detection unit that converts an optical signal output from the optical coupling unit into an electric signal, wherein the minute modulation signal component detection circuit includes the optical detection unit.
- a band-pass filter that passes the second low-frequency signal included in the electric signal output from the band-pass filter, wherein the synchronous detection circuit is configured to detect the shift amount and the shift amount based on an output signal of the band-pass filter. The direction may be detected.
- the free spectrum range of the Matsuhazunda interferometer is slightly shifted from the clock rate of the main signal, and the minute modulation signal component detection circuit constitutes the balanced optical detection circuit.
- a first amplifier for amplifying a photocurrent of one of the photodetectors; and a band-pass filter for extracting a component of the second low-frequency signal from an output of the first amplifier. The shift amount and its direction may be detected based on the output signal of the band-pass filter.
- the minute modulation signal component detection circuit includes a second amplifier that amplifies a photocurrent of the other photodetector included in the balanced photodetector circuit, and the first amplifier A subtractor that outputs a difference between an output of the amplifier and an output of the second amplifier, wherein the band-pass filter extracts a component of the second low-frequency signal from an output of the subtractor. May be.
- the minute modulation signal component detection circuit includes a clock extraction circuit that extracts a signal train clock output from the balanced detection circuit, and an output signal that is output from the clock extraction circuit.
- a low-frequency signal extraction circuit that extracts the second low-frequency signal superimposed on a clock signal that is superimposed on the second low-frequency signal output from the low-frequency signal extraction circuit. It is also possible to detect the deviation amount and its direction based on the above.
- the optical transmission device includes a clock signal generation circuit that generates a clock signal having the same signal bit rate, and the phase-modulated light generated by the clock signal output from the clock signal generation circuit.
- An intensity modulator that performs intensity modulation of the optical branching circuit, wherein the balanced detection circuit includes: an optical branching circuit that branches one of the two output ports in the Matsuhazu-Panda interferometer; A small-modulation signal component detection circuit connected to the monitoring light-receiving device, wherein the small-modulation signal component detection circuit extracts a clock on which the second low-frequency signal is superimposed, the intensity-modulated light power output from the monitoring light-receiving device. And a power detection circuit for extracting the second low-frequency signal from the extracted clock.
- the synchronous detection circuit is configured to output the second low-frequency signal based on an output signal of the power detection circuit. Then, the deviation amount and its direction may be detected.
- the minute modulation signal component detection circuit includes a data reproduction circuit that identifies and reproduces the electric signal output from the balanced detection circuit, and the data reproduction circuit.
- a correlation detection circuit that detects a correlation between the output signal and the signal before identification, and a low-frequency signal extraction circuit that extracts the second low-frequency signal from the output of the correlation detection circuit.
- the optical transmission system intensifies the phase-modulated light by a signal having a frequency f2 high enough to superimpose the low-frequency signal having the frequency fl.
- the second low-frequency signal having the frequency fl may be extracted.
- the optical transmission device may include:
- An oscillator circuit for generating the signal of the frequency ⁇ and directly modulating the intensity of the light source of the optical transmitter may be provided.
- the optical receiving device may be configured as the intensity modulating means.
- An oscillator circuit for generating the signal of the frequency f2 and an intensity modulator for intensity-modulating the signal light with an output signal of the oscillator circuit may be provided.
- the optical receiving device may be configured as the intensity modulating means.
- An oscillation circuit for generating the signal of the frequency f2, and an optical amplifier connected to the oscillation circuit, and the gain of the optical amplifier may be modulated at the frequency f2 by the oscillation circuit.
- the optical receiving device may include, as the intensity modulation component detecting means, an optical branching circuit that branches one of the two output ports of the Matsuhatsu Honda interferometer.
- a monitor light receiver connected to the optical branch circuit, and an extraction circuit for extracting the component of the frequency f2, which is the intensity-modulated optical power output from the monitor light receiver, may be provided.
- the optical receiving device may be configured such that, as the intensity modulation component detecting means, an input level adjustment for asymmetrically changing an input level of the converted intensity modulation light input to the balanced detection circuit.
- the minute modulation signal component detection circuit has a data reproduction circuit for recognizing and reproducing the electric signal output from the balanced detection circuit. Further, a logic inversion circuit for inverting and outputting the logic of the output signal of the data reproduction circuit, and selectively one of the output of the data reproduction circuit and the output of the logic inversion circuit according to a predetermined logic designation signal.
- Selecting means for outputting to the Polarity selecting means for inverting the polarity of the feedback error signal in the control circuit when the output of the inverter circuit is selected, wherein the central wavelength of the phase modulated light output from the optical transmitter is selected.
- the amount of correction of the deviation from the passband wavelength of the Mach-Zehnder interferometer may be set to 1Z2 or less of the repetition frequency of the Mach-Zehnder interferometer.
- the optical receiving device further includes a temperature detection circuit for detecting a substrate temperature state of the Mach-Zehnder interferometer, and a loop for turning ON / OFF a feedback control to the Mach-Zehnder interferometer.
- a temperature detection circuit for detecting a substrate temperature state of the Mach-Zehnder interferometer
- a loop for turning ON / OFF a feedback control to the Mach-Zehnder interferometer.
- An opening / closing switch and when the substrate temperature of the Mach-Zehnder interferometer is within an appropriate range, a loop for performing the feedback control is opened, and when the substrate temperature of the Mach-Zehnder interferometer is within the appropriate range, The feedback control may be performed by closing the loop.
- the control circuit may further include a lock detection circuit that detects a lock state of a loop that performs feedback control to the Matsuhatsu Panda interferometer, and a lock state that locks the loop.
- a lock-in circuit for re-locking to the lock state when it indicates that the lock state has been released.When the lock detection circuit detects the lock state, normal feedback control is performed.
- a lock detection circuit detects the lock state, and if not, sweeps a drive signal applied to the phase adjustment terminal of the Mach-Zehnder interferometer, and if the lock detection circuit detects the lock state again, The state may be switched to the state in which the normal feedback control is performed.
- the Mach-Zehnder interferometer includes two independent phase adjustment terminals, and applies the output of the small modulation signal oscillation circuit to one of the two phase adjustment terminals, A feedback error signal in the control circuit may be applied to the other of the two phase adjustment terminals.
- the optical receiving device determines a relative position between an optical carrier frequency and an optical frequency characteristic of the Mach-Zehnder interferometer based on the received signal light detected by the balanced detection circuit.
- an offset setting circuit for giving an offset to a feedback error signal in the control circuit, wherein the position of the optical carrier frequency and the peak of the optical frequency characteristic of the Mach-Zehnder interferometer are provided. Or, adjust the offset value of the offset setting circuit so as to match the bottom position. You may do it.
- the optical transmission device uses a modulation state control unit that ONZO-FFs the modulation of the main signal and a control line provided separately from the main signal line.
- a first control signal communication means for communicating with a receiving device, wherein the optical receiving device obtains an optical carrier frequency and an optical frequency of the Mach-Zehnder interferometer from the received signal light detected by the balanced detection circuit.
- An optical carrier frequency detecting means for detecting a relative position with respect to the characteristic; an offset setting circuit for giving an offset to a feedback error signal in the control circuit; and a communication with the optical transmitting apparatus using the control line.
- a second control signal communication unit for performing the operation.
- the optical transmission device turns off the modulation of the main signal by the modulation state control unit, and transmits only the optical carrier.
- the receiving device detects a relative position between the frequency of the optical carrier sent from the optical transmitting device by the optical carrier frequency detecting means and the optical frequency characteristic of the Mach-Zehnder interferometer, and The offset of the offset setting circuit is adjusted so that the position of the carrier frequency and the position of the peak or the bottom of the optical frequency characteristic of the Mach-Zehnder interferometer are matched, indicating that the optical receiver has completed the offset adjustment.
- a control signal may be transmitted to the optical transmitter using the second control signal communication unit, and the optical transmitter may turn on modulation of the main signal after receiving the control signal.
- the optical transmitter according to the first aspect of the present invention includes an optical transmitter that outputs differentially encoded phase modulated light, and an optical receiver that receives and demodulates the phase modulated light.
- An optical transmitter that converts an input signal of an NRZ code into a signal of an NRZ-I code; and a phase amplitude ⁇ ⁇ of 0 for a mark and a space encoded by the encoder.
- phase modulator that outputs phase-modulated light given in the range of ⁇
- the optical receiving device divides the received phase-modulated light into two, and one of the two branched signals
- a Matsuhazuda interferometer having a phase adjustment terminal for delaying the light by one bit, causing the two signal lights to interfere with each other to convert the light into intensity-modulated light, and setting a phase difference between the two interfering signals; and
- Optical transmission of an optical transmission system having a balanced photodetector that photoelectrically converts signal light from two output ports of a Matsuhatsu-Donda interferometer and outputs the difference between the converted electric signals
- a clock signal generating circuit for generating a clock signal having the same signal bit rate; and an intensity for performing intensity modulation of the phase-modulated light with a clock signal output from the clock signal generating circuit.
- the optical transmission device includes an optical transmission device that outputs differentially encoded phase modulated light, and an optical reception device that receives and demodulates the phase modulated light.
- An optical transmitter that converts an input signal of an NRZ code into a signal of an NRZ-I code; and a phase amplitude ⁇ ⁇ of 0 for a mark and a space encoded by the encoder.
- An optical transmission device for an optical transmission system comprising: a balanced light-receiving device that photoelectrically converts signal light from two output ports of a Matsuhatsu-Donda interferometer and outputs a difference between the converted electric signals, wherein the optical transmission device is An oscillation circuit for generating a signal having a frequency f2 high enough to superimpose a low-frequency signal having a frequency fl for directly modulating the intensity of the light source of the optical transmitter.
- An optical receiving device of the present invention includes: an optical transmitting device that outputs differentially encoded phase modulated light; and an optical receiving device that receives and demodulates the phase modulated light.
- the phase amplitude ⁇ was given in the range of 0 ⁇ for the encoder that converts the input signal of the NRZ code to the signal of the NRZ-I code, and for the mark and space encoded by the encoder.
- An optical transmission device having a phase modulator that outputs phase-modulated light, wherein the optical receiver divides the received phase-modulated light into two, and one of the two branched signal lights.
- a Mach-Zehnder interferometer having a phase adjustment terminal for delaying by one bit, interfering both signal lights to convert them into intensity-modulated light, and setting a phase difference between the two interfering signals; From two output ports on the meter A balanced detection circuit that photoelectrically converts the signal light and outputs a difference between the converted electric signals; and a low-frequency signal that applies a first low-frequency signal of frequency f1 to the phase adjustment terminal of the Mach-Zehnder interferometer. From the signal supplied from the generation circuit and the balanced detection circuit. A minute modulation signal component detection circuit for detecting a second low frequency signal; and the first low frequency signal output from the low frequency signal generation circuit for outputting the second low frequency signal output from the small modulation signal component detection circuit.
- a synchronous detection circuit for detecting the amount of deviation between the center wavelength of the phase-modulated light output from the optical transmitter and the passband wavelength of the Mach-Zehnder interferometer and the direction thereof by synchronous detection with the low-frequency signal.
- a control circuit for outputting a control signal for adjusting a phase difference between the two branched signal lights so as to correct the shift amount, and a driver circuit for driving the phase adjustment terminal based on the control signal
- the small modulation signal component detection circuit is an eye opening monitor circuit that outputs a signal obtained by monitoring an eye opening of a signal obtained by branching a signal output from the balanced detection circuit. And a band-pass filter that passes the second low-frequency signal included in the output signal of the eye opening monitor circuit, wherein the synchronous detection circuit is configured to output the second low-frequency signal based on an output signal of the band-pass filter.
- the displacement amount and the direction thereof may be detected.
- the small modulation signal component detection circuit discriminates and reproduces an electric signal output from the balance type detection circuit, and has a data error recovery circuit having a code error detection function therein.
- An error detection number monitor circuit that outputs a signal monitoring error detection number information output from the data reproduction circuit; and the second low frequency signal included in a signal output from the error detection number monitor circuit.
- a band pass filter for passing a signal may be provided, and the synchronous detection circuit may detect the shift amount and the direction thereof based on an output signal of the band pass filter.
- the balanced detection circuit has an equalization amplifier circuit, and the minute modulation signal component detection circuit outputs a signal monitoring a current consumption of the equalization amplifier circuit.
- the balanced detection circuit includes the Matsuhatsu Honda.
- An optical branching unit for branching the two output ports of the interferometer into two, an optical coupling unit for interfering the two lights branched by the optical branching unit, and an optical signal output from the optical coupling unit.
- An optical detection means for converting the signal into an electric signal, wherein the minute modulated signal component detection circuit includes a band-pass filter for passing the second low-frequency signal included in the electric signal output from the optical detection means.
- the synchronous detection circuit may include a filter, and the shift amount and the direction may be detected based on an output signal of the bandpass filter.
- the free spectrum range of the Matsuhatsu Panda interferometer is slightly shifted from the clock rate of the main signal
- the micro-modulation signal component detection circuit includes the balanced optical detection circuit.
- a first amplifier for amplifying a photocurrent of one of the photodetectors, and a band-pass filter for extracting a component of the second low-frequency signal from an output of the first amplifier, wherein the synchronous detection is performed.
- the circuit may detect the shift amount and the direction thereof based on the output signal of the band-pass filter.
- the minute modulation signal component detection circuit includes a second amplifier that amplifies a photocurrent of the other photodetector that forms the balanced photodetector circuit, and the first amplifier. And a subtractor that outputs a difference between the output of the second amplifier and the output of the second amplifier, wherein the band-pass filter extracts the component of the second low-frequency signal from the output of the subtractor. Is also good.
- the micro-modulated signal component detection circuit includes a clock extraction circuit for extracting a signal train clock output from the balance detection circuit, and an output from the clock extraction circuit.
- a low-frequency signal extraction circuit that extracts the second low-frequency signal superimposed on a clock signal, wherein the synchronous detection circuit includes a second low-frequency signal output from the low-frequency signal extraction circuit. The deviation amount and the direction thereof may be detected based on the information.
- the minute modulation signal component detection circuit includes a data reproduction circuit that identifies and reproduces the electric signal output from the balanced detection circuit, and an output signal of the data reproduction circuit.
- a correlation detection circuit for detecting a correlation with a signal before discrimination, and a low-frequency signal extraction circuit for extracting the second low-frequency signal from an output of the correlation detection circuit. May be provided.
- intensity modulation means for intensity-modulating the phase-modulated light with a signal having a frequency ⁇ high enough to superimpose the low-frequency signal with the frequency fl;
- an intensity modulation component detecting means for detecting the intensity modulation component of the frequency f2, wherein the minute modulation signal component detection circuit is configured to detect the second frequency of the frequency fl superimposed on the detected intensity modulation component of the frequency f2. It is good to extract the low frequency signal of.
- the optical receiving device includes, as the intensity modulating means, an oscillation circuit that generates a signal of the frequency f2, and an intensity that intensity modulates the signal light with an output signal of the oscillation circuit. And a modulator.
- the optical receiving device includes, as the intensity modulating means, an oscillation circuit that generates a signal of the frequency f2, and an optical amplifier connected to the oscillation circuit.
- the gain of the optical amplifier may be modulated by the oscillation circuit at the frequency f2.
- the optical receiving device may include, as the intensity modulation component detecting means, an optical branching circuit that branches one of the two output ports of the Mach-Zehnder interferometer.
- a monitor light receiver connected to the optical branching circuit and an extraction circuit for extracting a component of the intensity-modulated light power frequency f2 output from the monitor light receiver may be provided.
- the optical receiving device may be configured such that, as the intensity modulation component detecting means, an input for asymmetrically inputting the converted intensity modulated light input to the balanced detection circuit.
- the apparatus may include a level adjusting unit and an extraction circuit that extracts the component of the frequency f2 from the output signal power of the balanced detection circuit.
- the minute modulation signal component detecting circuit includes a data reproducing circuit that identifies and reproduces the electric signal output from the balanced detection circuit.
- the optical receiving device further includes: A logic inversion circuit for inverting the logic of the output signal of the data recovery circuit and outputting the inverted signal, and selecting one of the output of the data recovery circuit and the output of the logic inversion circuit in accordance with a predetermined logic designation signal Selecting means for selectively outputting a signal, and inverting the polarity of a feedback error signal in the control circuit when the output of the logic inversion circuit is selected. And a correction amount for the deviation between the center wavelength of the phase-modulated light output from the optical transmitter and the passband wavelength of the Mach-Zehnder interferometer.
- the repetition frequency may be set to 1Z2 or less.
- the Mach-Zehnder interferometer includes a temperature detection circuit for detecting a substrate temperature state, and a loop opening / closing switch for turning ON / OFF the feedback control to the Matsuhatsu-Dah sand meter.
- a loop for performing the feedback control is opened, and when the substrate temperature of the Mach-Zehnder interferometer is in the appropriate range, the loop is closed and Feedback control may be performed.
- the control circuit further includes a lock detection circuit that detects a lock state of a loop that performs feedback control to the Mach-Zehnder interferometer, and a lock state of the loop that locks the loop.
- a re-pull circuit for re-pulling to the lock state when indicating that the lock state has been released, and performing normal feedback control when the lock detection circuit detects the lock state; If the lock detection circuit detects the lock state, and if not, sweeps a drive signal applied to the phase adjustment terminal of the Mach-Zehnder interferometer, and if the lock detection circuit detects the lock state again, It is also possible to switch to a state in which the normal return control state is performed.
- the Matsuhatsu-Donda interferometer has two independent phase adjustment terminals, and applies the output of the micro-modulation signal oscillation circuit to one of the two phase adjustment terminals.
- a feedback error signal in the control circuit may be applied to the other of the two phase adjustment terminals.
- a relative position between an optical carrier frequency and the optical frequency characteristic of the Mach-Zehnder interferometer is detected from the received signal light detected by the balanced detection circuit.
- the offset value of the offset setting circuit may be adjusted so as to match.
- the phase difference between the signal lights of the two arms of the Mach-Zehnder interferometer included in the optical receiving device! Is modulated at a constant frequency and the phase of that frequency component is detected, making it possible to set the optimum operating point of the Mach-Zehnder interferometer that matches the optical frequency of the transmitting side light source.
- Light receiving characteristics can be obtained.
- FIG. 1 is a block diagram showing a configuration of an optical transmission system according to a first embodiment of the present invention.
- FIG. 2 is a block diagram showing a configuration of an optical transmission system according to a second embodiment of the present invention.
- FIG. 3 is a block diagram showing a configuration of an optical transmission system according to a third embodiment of the present invention.
- FIG. 4 is a block diagram showing a configuration of an optical transmission system according to a fourth embodiment of the present invention.
- FIG. 5 is a block diagram showing a configuration of an optical transmission system according to a fifth embodiment of the present invention.
- FIG. 6 is a block diagram showing a configuration of an optical transmission system according to a sixth embodiment of the present invention.
- FIG. 7 is a block diagram showing a configuration of an optical transmission system according to a seventh embodiment of the present invention.
- FIG. 8 is a block diagram showing a configuration of an optical transmission system according to an eighth embodiment of the present invention.
- FIG. 9 is a block diagram showing a configuration of an optical transmission system according to a ninth embodiment of the present invention.
- FIG. 10A is a diagram showing input / output characteristics of a Mach-Zehnder interferometer.
- FIG. 10B is a diagram showing input / output characteristics of a Mach-Zehnder interferometer.
- FIG. 10C is a diagram showing input / output characteristics of a Mach-Zehnder interferometer.
- FIG. 10D A diagram showing a relationship between an input / output port and two Arms of a Mach-Zehnder interferometer.
- FIG. 11 is a block diagram showing a basic configuration of an optical receiver in the optical transmission system according to the present invention.
- FIG. 12 is an explanatory diagram showing the phase shift dependency of the output of the balanced photodetector.
- FIG. 13 is a block diagram showing a configuration of an optical transmission system according to a tenth embodiment of the present invention.
- FIG. 14 is a block diagram showing a configuration of an optical transmission system according to an eleventh embodiment of the present invention.
- FIG. 15 is a block diagram showing a configuration of an optical transmission system according to a twelfth embodiment of the present invention.
- FIG. 16] is a block diagram showing a configuration of an optical transmission system according to a thirteenth embodiment of the present invention.
- [17] a block diagram showing a configuration of an optical transmission system according to a fourteenth embodiment of the present invention.
- FIG. 18 is a diagram showing an FSR shift of the Mach-Zehnder interferometer.
- Fig. 19 is a diagram illustrating the relationship between the FSR shift amount of the Mach-Zehnder interferometer and the detection sensitivity of the minute modulation signal component.
- FIG. 20 is a diagram showing an eye opening penalty due to an FSR shift of a Mach-Zehnder interferometer.
- ⁇ 21] is a block diagram showing a configuration of an optical transmission system according to a fifteenth embodiment of the present invention.
- ⁇ 22] is a block diagram showing a configuration of an optical transmission system according to a sixteenth embodiment of the present invention.
- ⁇ 23] [Fig. 24] Fig. 24 is a block diagram illustrating a configuration of an optical transmission system according to a seventeenth embodiment of the invention. [24] A block diagram illustrating a configuration of a control circuit with a re-entry function.
- FIG. 25 is a diagram showing the operation of the triangular wave generation circuit of the control circuit with a re-drawing function.
- FIG. 26 is a block diagram showing a configuration of a lock detection circuit.
- FIG. 27 is a diagram showing the operation of the lock detection circuit and the triangular wave generation circuit.
- FIG. 28 is a block diagram illustrating a configuration of an optical transmission system according to an eighteenth embodiment of the present invention.
- FIG. 29 is a block diagram showing a configuration of an optical transmission system according to a nineteenth embodiment of the present invention.
- FIG. 30 is a block diagram showing a configuration of an optical transmission system according to a twentieth embodiment of the present invention.
- Oscillation circuit 11 0 Modulation state control circuit 111: Control signal communication circuit 20: MZI (Mach-Zehnder interferometer) for DPSK code demodulation 201: Phase adjustment terminal 202: Balanced photodetector 203: Amplifier 204: Data recovery circuit 205: ⁇ Clock extraction circuit 207 ⁇ Controller 209 ⁇ Logical inversion circuit 210 ⁇ Monitor light receiver 211 ⁇ Narrow band amplifier 212 ⁇ Differential circuit 21 3 ⁇ Filter 214 ⁇ Amplifier 215 ⁇ Intensity modulator 216 ⁇ Oscillation circuit 217 ⁇ Optical amplifier 218... Oscillation circuit 219... Optical attenuator 220... Optical branch circuit 221... Balanced detection circuit 222... Small modulation signal component detection circuit 223... Synchronous detection circuit 224... Small modulation signal oscillation circuit 225... Adder 226 ⁇ Driver 231... Eye opening monitor circuit 232 ⁇ Bandpass filter 241... Er
- FIGS. 10A to 10D Prior to the description of the embodiment of the present invention, the principle of the present invention will be described with reference to FIGS. 10A to 10D, FIGS. 11 and 12.
- the difference between the wavelength of the signal light and the pass band of the interferometer is required.
- a low-frequency signal is added to a phase shifter provided in the interferometer, and the level or phase of the low-frequency signal is detected.
- FIGS. 10A to 10C show input / output characteristics of a Mach-Zehnder interferometer (hereinafter, referred to as MZI) for converting phase-modulated light into intensity-modulated light.
- FIG. 10A shows the light intensity of the output portl, 2 with respect to the phase difference of the light of Arml, 2.
- the upper part of Fig. 10A shows the output port2, and the lower part shows the output portl.
- FIGS. 10B and 10C show the transmittance from the input port to the output ports 1 and 2, respectively, as a function of the frequency of the input light.
- the phase-modulated light input from the input port (Port) of the MZI200 is split into two arms, Arm1 and Arm2.
- the lights of both Arms interfere with each other and are output from the output port (Port).
- the light intensity output to the output port depends on the delay difference between the two Arms. For example, at the output port 1, the light intensity becomes maximum when the phase difference is 0, and becomes minimum when the phase difference is ⁇ or ⁇ . In other words, when the phase of the phase-modulated light is 0 for two consecutive time slots, the output intensity of output port 1 is minimum, and when the two consecutive time slots are 0, ⁇ or ⁇ , 0, the output intensity is Is the largest.
- this point is the optimal operating point of ⁇ .
- the phase difference between the two arms deviates from 0 due to some factor, the minimum value of the light intensity increases, and conversely, the maximum value decreases. As a result, the light receiving sensitivity of the optical receiver deteriorates.
- the repetition frequency is equal to the signal bit rate and has the #filter characteristics.
- the frequency indicating the maximum transmittance of the MZI matches the center frequency of the signal light.
- FIG. 11 shows a basic configuration of an optical receiver in the optical transmission system according to the present invention.
- the optical receiving apparatus generates an MZI 200, a phase adjustment terminal 201, a balanced detection circuit 221, a minute modulation signal component detection circuit 222, a synchronous detection circuit 223, and a low frequency signal of frequency fl. It has a small modulation signal oscillation circuit 224 and a controller 207 that supplies a bias voltage to the phase adjustment terminal 201 via the adder 225.
- the circuit 223 may be a circuit for detecting amplitude and phase information such as a multiplier or a mixer, or a circuit for detecting phase information such as a phase comparator or a phase detection circuit.
- the output signal of the balanced detection circuit 221 has the maximum amplitude at the optimum operating point of the DPSK code demodulation MZI (hereinafter, referred to as MZI) 200.
- MZI DPSK code demodulation
- a low-frequency signal of frequency fl superimposed thereon is extracted from the output of the noise detection circuit 221 by the minute modulation signal component detection circuit 222, and the low-frequency signal is extracted by the low frequency fl.
- the low-frequency signal output from the micro-modulation signal oscillation circuit 224 that applies the frequency signal to the phase adjustment terminal 201, and the synchronous detection is performed by the synchronous detection circuit 223 to shift the operating point (in terms of the frequency axis, The direction (corresponding to the difference between the center frequency of the light source and the pass band of the MZI 200) is detected, and the voltage (or current) applied to the phase adjustment terminal 201 of the MZI 200 is controlled.
- the received signal is converted, if necessary, by using a logic inversion circuit provided at the subsequent stage of a not-shown discriminator in the minute modulation signal component detection circuit 222.
- a logic inversion circuit provided at the subsequent stage of a not-shown discriminator in the minute modulation signal component detection circuit 222.
- the operating point of the MZI is at the position of ⁇ in the initial state where the phase control is not performed
- the operating point is adjusted by adjusting the temperature of the substrate in ⁇ or adjusting the phase. It must be shifted to a point where the phase difference is zero. However, the phase difference between the outputs of both Arms If the point ⁇ is set as the operating point, this adjustment becomes unnecessary. However, in this case, the logic of the output intensity modulation signal is inverted. Therefore, if the logic of the signal is inverted again after the data identification and reproduction, the original signal logic is restored.
- FIG. 1 shows the configuration of the optical transmission system according to the first embodiment of the present invention.
- the optical transmission system includes an optical transmitter 1 that outputs differentially encoded phase modulated light, and an optical receiver 2 that receives and demodulates the phase modulated light transmitted from the optical transmitter 1.
- an optical transmitter 1 that outputs differentially encoded phase modulated light
- an optical receiver 2 that receives and demodulates the phase modulated light transmitted from the optical transmitter 1.
- the optical transmitter 1 is encoded by an encoder 100 that converts an NRZ code input signal into an NRZ-I (Inverted) code signal, a light source 101, a modulator driving circuit 102, and the encoder 100. And a phase modulator 103 that outputs phase-modulated light having a phase amplitude ⁇ in the range of 0 ⁇ ⁇ ⁇ ⁇ with respect to the mark and the space.
- the optical receiver 2 splits the received phase-modulated light from the optical transmitter 1 into two, delays one of the two split signal lights by one bit, and causes the two signal lights to interfere with each other.
- a Mach-Zehnder interferometer 200 having a phase adjustment terminal 201 capable of setting the phase difference between the two interfering signals by converting the signal into an intensity-modulated light and a Mach-Zehnder interferometer 200.
- a balanced detection circuit 221 that photoelectrically converts the signal light from the port and outputs a difference between the converted electric signals.
- the optical receiver 2 includes a minute modulation signal component detection circuit 222, a synchronous detection circuit 223, a controller 207, a minute modulation signal oscillation circuit 224, an adder 225, and a driver 226.
- the micro-modulation signal component detection circuit 222 detects a micro-modulation signal (frequency fl) component applied to the phase adjustment terminal 201 of the Matsuhatsu-Zonda interferometer 200 using the signal output from the balanced detection circuit 221. In addition to outputting the data to the synchronous detection circuit 223, the output power of the balanced detection circuit 221 also identifies and reproduces the data, and outputs the identified and reproduced data as an output signal of the optical receiver 2.
- the synchronous detection circuit 223 synchronously detects the minute modulation signal detected by the minute modulation signal component detection circuit 222 and the minute modulation signal directly input from the minute modulation signal oscillation circuit 224.
- the amplitude and the phase of the minute modulation signal component superimposed on the optical signal that has passed through the Matsuhatsu-Donda interferometer 200 are detected.
- the amplitude and phase detected here are error signal components resulting from the difference between the optical signal carrier frequency and the optical frequency characteristics of the Mach-Zehnder interferometer.
- the amplitude and phase signals are transmitted to the controller 207 (generally, a loop filter). + PID control).
- the controller 207 uses a control signal for adjusting the phase difference between the two branched signal lights as a bias signal based on the signal supplied from the synchronous detection circuit 223 so as to correct the above-described shift, as an adder. Output to 225.
- the adder 225 adds the minute modulation signal output from the minute modulation signal oscillation circuit 224 to the bias signal, and outputs the added signal to the driver 226.
- the driver 226 drives the phase adjustment terminal 201 of the Mach-Zehnder interferometer 200 based on the added signal.
- the feedback loop works to reduce the error signal component to 0, and finally matches the peak or bottom of the optical frequency characteristic of the Matsuhatsu-Zander interferometer 200 with the carrier frequency of the optical signal.
- FIG. 2 shows the configuration of the optical transmission system according to the second embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the optical transmission system according to the first embodiment in that a balanced detection circuit 221 is constituted by a balanced photodetector 202 and an amplifier 203, and a minutely modulated signal component detection circuit 222.
- a circuit constituted by a circuit constituted by a data reproduction circuit 204, a clock extraction circuit 205, and a power detection circuit 2080 is provided.
- Other configurations are the same as those of the optical transmission system of the first embodiment, and thus the same components are denoted by the same reference numerals.
- the illustration of the driver 226 shown in FIG. 1 is omitted.
- the optical receiver 2 includes a balanced light receiver 202, an amplifier 203 for amplifying a signal output from the balanced light receiver 202, and data reproduction for identifying and reproducing data from the output of the amplifier 203.
- a power detection circuit 2080 for extracting a low-frequency signal of the folded frequency fl, a low-frequency signal of the frequency fl output from the power detection circuit 2 080, and a low-frequency signal of the frequency fl output from the minute modulation signal oscillation circuit 224
- a synchronous detection circuit 223 for detecting the amount of deviation between the center wavelength of the phase-modulated light output from the optical transmitter
- a controller 207 that outputs a control signal for adjusting the phase difference between the two branched signal lights to an adder 225, and an output of the micro-modulation signal oscillation circuit 224 and an output of the controller 207 to add a phase adjustment terminal 201 And an adder 225 for adding the value to
- the clock extraction circuit 205 needs to perform linear extraction so that the clock power is proportional to the clock component power included in the signal.
- FIG. 3 shows the configuration of the optical transmission system according to the third embodiment of the present invention.
- the optical transmission system according to the present embodiment is different in configuration from the optical transmission system according to the second embodiment in that a logical designation in which an external force is also input after the data reproducing circuit 204 of the optical receiver 2 is applied.
- a logic inversion circuit 209 for performing a logic inversion of a signal by a signal is added, and a logic designation signal is supplied to a controller 207.
- the optical transmitter 1 is not shown.
- the data reproducing circuit 204 of the optical receiver 2 discriminates and reproduces the signal sequence output from the balanced photodetector 202, and the logical inversion circuit 209 converts the logic of the output signal of the data reproducing circuit 204.
- External force Inverts and outputs based on the input logic designation signal, that is, if necessary.
- the logic designation signal input from the outside selectively outputs to the logic inversion circuit 209 either the output signal of the data reproduction circuit 204 or the signal inverted by the logic inversion circuit 209.
- the optical receiver has a function of outputting the signal, but may be provided inside the optical receiver.
- This logic designation signal or a functional unit that generates this logic designation signal corresponds to the selection means of the present invention.
- the logical inversion circuit 209 performs logical inversion as needed, thereby correcting the deviation between the center wavelength of the phase-modulated light from which the power of the optical transmitter 1 is also output and the passband wavelength of the Mach-Zehnder interferometer 200. In both cases where the pass band of the MZI 200 is maximum or minimum at the center wavelength of the phase-modulated light output from the optical transmission device 1, the repetition frequency of the MZI 200 can be 1Z2 or less.
- the logic inversion circuit 209 can be easily formed by an EXOR (Exclusive OR) circuit.
- the logical designation signal is input from outside, but this logical designation signal can be generated by detecting the frame information of the output signal of the optical receiver 2 and automatically determining the logic to be designated. There is also a method of manually inputting commands and commands.
- the logic designation signal is also input to the controller 207, and when logic inversion is required, the polarity of the bias voltage applied to the phase adjustment terminal 201 is inverted (or the direction of the bias current to be passed). Needs to be inverted).
- FIG. 3 shows a case where the present invention is applied to the second embodiment, the present invention may be applied to other embodiments.
- FIG. 4 shows the configuration of the optical transmission system according to the fourth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs in configuration from the optical transmission system according to the second embodiment in that a clock signal generation circuit that generates a clock signal having the same signal bit rate is provided to the optical transmission device 1.
- a clock signal generation circuit that generates a clock signal having the same signal bit rate is provided to the optical transmission device 1.
- an intensity modulator 104 that performs intensity modulation with a clock signal output from a clock signal generation circuit 105, and the optical receiver 2 has one of two output ports of the MZI200 instead of the clock extraction circuit.
- Optical branching circuit 220 for branching the port of the optical branching circuit, the monitoring light receiver 210 connected to the optical branching circuit 220, and the intensity modulated optical power output from the monitoring light receiver 210 are also superimposed with the low frequency signal of the frequency fl.
- a narrow-band amplifier 211 that extracts a clock that has been extracted, and a power detection circuit 2080 extracts a low-frequency signal of a frequency fl superimposed on the clock based on the output signal of the narrow-band amplifier 211, and synchronizes it.
- the wave circuit 223 detects, based on the output of the power detection circuit 2080, the amount of deviation between the center wavelength of the phase-modulated light output from the optical transmitter 1 and the passband wavelength of the MZI 200, and its direction. And other Since the configuration is the same as that of the optical transmission system according to the second embodiment shown in FIG. 2, the same elements are denoted by the same reference numerals, and redundant description will be omitted.
- the RZ-DPSK signal is generated by the intensity modulator 104 provided in the optical transmitter 1 performing intensity modulation with the clock signal output from the clock signal generation circuit 105.
- the clock extraction circuit in the optical reception device 2 can be simplified.
- the modulation code of the optical signal generated on the optical transmitter 1 side may be CSRZ-DPSK.
- FIG. 5 shows the configuration of the optical transmission system according to the fifth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs in configuration from the optical transmission system according to the second embodiment in that the output signal of the data reproduction circuit 204 and the signal before data identification are different in the optical receiver 2.
- the difference is that a differential circuit 212 for detecting the correlation, that is, the difference, is provided in place of the clock extraction circuit 205, and the other configuration is the same as that of the optical transmission system according to the second embodiment shown in FIG.
- the same elements are denoted by the same reference numerals, and overlapping description will be omitted.
- the differential circuit 212 corresponds to the correlation detection circuit of the present invention.
- the illustration of the optical transmitter 1 is omitted.
- the power detection circuit 2080 extracts the differential circuit 212
- the correlation between the data signal before identification reproduction by the data reproduction circuit 204 and the data signal after identification reproduction is performed, a low-frequency signal of frequency fl is extracted from the output of the differential circuit 212, and the synchronous detection circuit 223 is Based on the output of 2080, the shift amount and the direction between the center wavelength of the phase-modulated light of the optical transmitter 1 and the passband wavelength of the MZI 200 are detected.
- a low frequency fl is superimposed on the data signal before data identification and reproduction in the data reproduction circuit 204 !, but a low frequency is superimposed on the data signal after identification and reproduction.
- the dynamic circuit 212 can detect only the low-frequency component.
- FIG. 6 shows the configuration of the optical transmission system according to the embodiment.
- the optical transmission system according to the present embodiment differs from the optical transmission system according to the second embodiment in configuration in that a low-frequency signal of the frequency fl for directly modulating the intensity of the light source 101 is superimposed on the optical transmitter 1.
- An oscillation circuit 106 for generating a signal having a frequency ⁇ high enough to perform the operation, and an optical branching circuit 220 for branching one of the two output ports at 200 in the optical receiver 2.
- a monitoring light receiver 210 connected to the optical branching circuit 220; an amplifier 214 for extracting a component of the frequency f2 on which the low-frequency signal of the frequency fl is superimposed from the intensity-modulated light output from the monitoring light receiver 210;
- the filter 213 is provided in place of the clock extraction circuit 205, and the other configuration is the same as that of the optical transmission system according to the second embodiment shown in FIG. And duplicate explanations are omitted. To do.
- the power detection circuit 2080 is output from the filter 213 instead of synchronously detecting and extracting the low-frequency signal of the frequency fl superimposed on the clock signal output from the clock extraction circuit 205 in the second embodiment.
- the low frequency signal of the frequency fl superimposed on the component of the frequency f2 is extracted, and the synchronous detection circuit 223 detects the phase modulated light output from the optical transmitter 1 based on the output of the power detection circuit 2080.
- the shift amount and the direction between the center wavelength and the pass band wavelength of the MZI 200 are detected.
- the amplifier 214 and the filter 213 correspond to the signal detecting means of the present invention.
- the output of the light source 101 is intensity-modulated at the frequency f2 by the output signal of the oscillation circuit 106.
- the frequency f2 needs to be high enough to superimpose the low-frequency signal of the frequency fl, and the frequency higher than the low-frequency cutoff area of the optical amplifier installed in the transmission path. You need to choose.
- the frequency fl is superimposed on the intensity modulation component of the frequency f2 superimposed on the output signal light of the optical transmitter 1 by the MZI 200 of the optical receiver 2 and output.
- the monitoring light receiver 210 detects the optical signal branched from one port of the MZI 200, amplifies the amplified signal at the amplifier 214, and detects the signal of the frequency f2 superimposed thereon at the filter 213.
- the advantage of this method is that it does not require the use of products with excellent high-frequency characteristics for the monitoring photodetector and the subsequent amplifier, power detection circuit, and synchronous detection circuit.
- the intensity-modulated component that is intensity-modulated on the transmission side is not output by the balanced photodetector 202, and thus does not significantly affect signal reproduction in the data reproduction circuit 204.
- the two input signal levels to the balanced photodetector 202 need to be matched.
- a monitor terminal is provided on one port, it is necessary to add a loss equivalent to this loss to the other port.
- FIG. 7 shows the configuration of the optical transmission system according to the seventh embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the optical transmission system according to the sixth embodiment in configuration in that a signal of frequency f2 is transmitted to the optical receiver 2 instead of intensity-modulating the light source on the transmission side.
- an intensity modulator 215 for intensity-modulating the signal light with the output signal of the oscillation circuit 216, and the other configuration is the same as the optical transmission according to the sixth embodiment shown in FIG. Since the system is the same as that of the system, the same elements are denoted by the same reference numerals, and redundant description is omitted. It should be noted that the illustration of optical transmission device 1 is omitted!
- intensity modulator 215 is provided at the input stage of receiving device 2, and intensity is modulated by a signal of frequency f2 output from oscillation circuit 216.
- the intensity modulator 215 may be, for example, any of an LN (Lithium Niobate) modulator, an AO (AcoustoOptic) modulator, and an electroabsorption modulator.
- FIG. 8 shows the configuration of the optical transmission system according to the eighth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the optical transmission system according to the seventh embodiment in configuration in that an optical amplifier 217 is provided instead of the intensity modulator 215 in the optical receiver 2.
- the point that the gain of the optical amplifier 217 is modulated at the frequency f2 by the oscillation circuit 218 that generates the signal of the frequency f2 is the same as that of the optical transmission system according to the seventh embodiment shown in FIG. Since they are the same, the same elements are denoted by the same reference numerals, and redundant description will be omitted.
- the illustration of the optical transmission device 1 is omitted.
- the SN ratio degradation due to insertion loss becomes a problem.
- the gain of the optical amplifier 217 is modulated.
- it is effective because the receiving amplifier can perform modulation at once.
- the intensity modulation component is not output from the balanced photodetector 202 even if the intensity is modulated here, but this greatly affects the signal reproduction. I can't.
- the two input signal levels to the balanced photodetector 202 need to be matched S.
- a monitor terminal is provided on one port, so it is necessary to add a loss equivalent to this loss to the other port.
- FIG. 9 shows the configuration of the optical transmission system according to the ninth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the optical transmission system according to the eighth embodiment in the configuration in that the receiving device 2 includes the optical branch circuit 220 and the monitoring light receiver 210.
- the input level adjusting means for asymmetrically changing the input level of the converted intensity-modulated light input to the balanced receiver 202 is provided, and the other configuration is the same as that of the eighth embodiment shown in FIG. Since they are the same as the optical transmission system according to the embodiment, the same elements are denoted by the same reference numerals, and overlapping description will be omitted.
- the illustration of the optical transmitter 1 is omitted.
- the signal light intensity-modulated at the frequency f2 has the same average signal power input to the two input ports of the balanced optical receiver 202. No output.
- the intensity modulation component can be detected by intentionally reducing the input average power of one input port.
- an optical attenuator 219 for that purpose is connected to one input port.
- the optical attenuator 219 corresponds to the input level adjusting means of the present invention.
- the intensity modulation component of frequency f2 detected by balanced photodetector 202 is input to power detection circuit 2080 via filter 213, and used for controlling MZI 200.
- the capacitor C1 By connecting the capacitor C1 to the input end of the data reproducing circuit 204 to cut off the intensity modulation component, the signal reproducing in the data reproducing circuit 204 is not largely affected.
- three types of intensity modulation by the frequency f 2 Two types of direct intensity modulation of the light source in the optical transmitter 1, intensity modulation in the optical receiver 1 using an intensity modulator, intensity modulation in the optical receiver 1 using an optical amplifier), and detection of the frequency f2 (Monitoring one port of the MZI 200 and connecting the optical attenuator 219 to one input port of the balanced photodetector 202)
- the configuration is not limited to the configurations described in the sixth to ninth embodiments. May be combined arbitrarily.
- FIG. 13 shows the configuration of the optical transmission system according to the tenth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the first embodiment in that, as in FIG. 2 and the like, the nonce-type detection circuit 221 is composed of a non-lance type photodetector 202 and an amplifier 203.
- a small-modulation-signal-component detection circuit 222 discriminates and reproduces data from the output of the amplifier 203, and an opening of the eye pattern of the main signal output from the lance-type detection circuit 221.
- This is constituted by an eye opening monitor circuit 231 that monitors the frequency, and a band-pass filter 232 that passes the minute modulation signal component (fl).
- the other configuration is the same as that of the optical transmission system shown in FIG. 1, and therefore, the same components are denoted by the same reference numerals and overlapping description will be omitted.
- the greatest advantage of this embodiment is that the eye opening can always be stabilized at the maximum point.
- FIG. 14 shows the configuration of the optical transmission system according to the eleventh embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the first embodiment in that the balanced detection circuit 221 is composed of the balanced photodetector 202 and the amplifier 203, and the output power of the small-modulation signal component detection circuit 222 and the amplifier 203 also uses data. It is composed of a data reproduction circuit 204 that identifies and reproduces data and has a code error detection function inside it, an error detection number monitor circuit 241 that monitors the number of error detections, and a bandpass filter 232 shown in FIG. It is to be done.
- Other configurations are the same as those of the optical transmission system shown in FIG. 1, and therefore, the same elements are denoted by the same reference numerals and overlapping description will be omitted.
- the greatest advantage of the present embodiment is that it can be stabilized to a point where the bit error rate is always minimized.
- FIG. 15 shows the configuration of the optical transmission system according to the twelfth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the first embodiment in that the balanced detection circuit 221 is composed of the balanced photodetector 202 and an equivalent amplifier circuit equivalent to the amplifier 203, and that the minute modulation A signal component detection circuit 222 identifies a data from the output of the equivalent amplification circuit and reproduces the data, a current recovery monitor circuit 251 that monitors the current consumption of the equivalent amplification circuit included in the balanced detection circuit 221, and 13 is constituted by the band-pass filter 232 shown in FIG.
- the equivalent amplifier circuit generally includes a transimpedance amplifier 252 (TIA) and a limiting amplifier (LIM) 253.
- the current consumption monitor circuit 251 includes a resistor 254 inserted between the power supply terminal of the limiting amplifier 253 and the power supply, and an amplifier 255 for amplifying and outputting the voltage of the power supply terminal.
- the other configuration is the same as that of the optical transmission system shown in FIG. 13, and therefore, the same elements are denoted by the same reference numerals and overlapping description will be omitted.
- the transistor amplifier circuit that constitutes the equivalent amplifier circuit generally has an asymmetric current value flowing through the transistor when the input signal voltage (current) swings to the + side and the input signal voltage (current) swings to the + side.
- the current consumption differs depending on the amplitude of the signal.
- the current consumption of the equivalent amplifier circuit is monitored by the current consumption monitor circuit 251 and the minute modulation signal component (fl) is extracted by the band-pass filter 232, so that the optical signal passing through the Mach-Zehnder interferometer 200 is The amplitude and phase of the superimposed minute modulation signal component can be detected.
- An error signal component can be extracted by synchronous detection of this signal by the synchronous detection circuit 223, and the desired state can be locked by feeding back the error signal component.
- the greatest advantage of the present embodiment is that it is possible to detect the peak of the main signal using a main signal branch that has a large effect on the main signal.
- FIG. 16 shows the configuration of the optical transmission system according to the thirteenth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the first embodiment in the following points.
- the balanced detection circuit 221 couples the optical branch circuits 261 and 262 provided in the two output arms of the Matsuhazunda interferometer 200 with the two optical signals branched by these branch circuits, respectively.
- the minute modulation signal component detection circuit 222 includes a data reproduction circuit 204 that identifies and reproduces data from the output of the amplifier 203, and a band that passes the minute modulation signal component (fl) output from the amplification circuit 265.
- a pass filter 232 At this time, the two optical paths that are split and recombined are equal in length with respect to the bit and opposite in phase with respect to the optical phase.
- the other configuration is the same as that of the optical transmission system shown in FIG. 1, and therefore, the same components are denoted by the same reference numerals and overlapping description will be omitted.
- the peak or bottom force of the optical frequency characteristics of the Mach-Zehnder interferometer 200 also deviates, the light output to the two output ports of the Mach-Zehnder interferometer 200 will have a reduced peak power on the mark side. Then, the peak power on the space side increases.
- the carrier frequency of the signal light also shifts the peak or bottom force of the optical frequency characteristics of the Matsuhatsu Panda interferometer 200.
- the light on the mark side where the peak power has decreased and the light on the space side where the peak power has increased interfere in opposite phases, so that the peak power and the average power of the interfered light decrease.
- This power fluctuation was detected by the photodetector 264, and the minute modulation signal component (f1) was extracted by the band-pass filter 232 through the amplifier circuit 265, and was superimposed on the optical signal that passed through the Mach-Zehnder interferometer 200.
- the amplitude and phase of the minute modulation signal component can be detected.
- An error signal component can be extracted by synchronously detecting this signal with the synchronous detection circuit 223, and the desired state can be locked by feeding back the error signal component.
- the greatest advantage of the present embodiment is that a small modulation signal component can be detected by a relatively low-speed (f 1) photodetector without branching the main signal in the electric domain.
- FIG. 17 shows the configuration of the optical transmission system according to the fourteenth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the first embodiment in that a bias voltage is applied to the balanced photodetector 202 from a balanced photodetector 202, an amplifier 203, and a positive (+) power supply.
- a bias voltage is applied to the balanced photodetector 202 from a balanced photodetector 202, an amplifier 203, and a positive (+) power supply.
- a data reproduction circuit 204 that identifies and reproduces data and a balanced photodetector 202 are configured.
- An amplification circuit 272 that detects and amplifies the photocurrent flowing through one of the photodetectors and a small modulation by a bandpass filter 232 shown in Fig. 13.
- the signal component detection circuit 222 is configured, and the FSR (free spectral range) of the Mach-Zehnder interferometer 200 is slightly smaller than the clock rate of the main signal (that is, the range in which the penalty of the main signal can be ignored as described later). (Predetermined amount in the box).
- the optical signal modulation band is wider than the FSR of the Matsuhazunda interferometer, and the optical carrier frequency is almost the same even if the peak or bottom force of the optical frequency characteristic of the Matsuhatsuda interferometer deviates. There is no change in optical power. Therefore, it becomes difficult to detect the minute modulation signal component superimposed on the optical signal.
- the RZ-based DPSK signal is more difficult to detect than the NRZ-based DPSK signal because the modulation spectrum is wider.
- the Mach-Zehnder interferometer 200 by increasing the FSR of the Mach-Zehnder interferometer 200 to such a degree that a penalty does not appear from the main signal clock rate, it becomes equivalent to a relatively narrow optical signal modulation band, and a minute modulation signal component is reduced. Can be easily detected.
- FIG. 18 is a diagram showing the FSR shift of the Mach-Zehnder interferometer 200.
- the MZI transmission characteristic 1 is the optical frequency characteristic of a Matsuhatsu Panda interferometer having an FSR (FSR1 (reference) in the figure) equal to the main signal clock rate
- the MZI transmission characteristic 2 is an FSR slightly larger than the main signal clock rate (in the figure)
- the optical frequency characteristics of a Mach-Zehnder interferometer having a shifted FSR2 Note that the FSR shift amount is obtained by FSR2-FSR1.
- FIG. 19 is a diagram illustrating a relationship between the FSR shift amount and the sensitivity of detecting a minute modulation signal component (the average value of the variation in the optical power value Z). It can be seen that as the FSR shift amount is increased, the fluctuation amount of the optical power average value is increased.
- FIG. 20 is a diagram showing an eye opening penalty of the main signal due to the FSR shift.
- the eye opening penalty can be suppressed to less than 0.1 dB if the bit rate is within about 10%. I understand. Therefore, by setting the FSR slightly higher than the clock rate of the main signal, the average optical power of the main signal is detected with almost no penalty applied to the main signal, and the signal is synchronously detected by the synchronous detection circuit 223. By doing so, an error signal component can be extracted, and by feeding back this error signal component, a desired state can be locked.
- the greatest advantage of the present embodiment is that control is performed with a relatively low-speed (f 1) signal obtained from the power supply terminal power of the balanced receiver 202 without branching the main signal in the electric domain. What you can do.
- FIG. 21 shows the configuration of the optical transmission system according to the fifteenth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the fourteenth embodiment in that the resistance of the photodetector on one side (positive power supply side) of the lance type photodetector 202 is not the same as that of the photodetector.
- the amplifier circuit 275 detects the photocurrent of the photodetector on the other side of the balanced photodetector 202 connected to the negative power supply via the amplifier, and the power supply terminal power of the photodetectors on both sides is also extracted, and the subtractor 274 extracts the signal.
- the difference between the two signals is obtained, and the difference is used to perform feedback control in the same manner as in the fourteenth embodiment.
- the other configuration is the same as that of the optical transmission system shown in FIG. 17, and therefore, the same components are denoted by the same reference characters and overlapping description will be omitted.
- the detection sensitivity can be increased by performing balanced detection of the control feedback signal.
- control is performed with a relatively low-speed (f 1) signal that does not branch the main signal in the electric domain and also provides the power supply terminal power of the balanced receiver 202. And relatively high detection sensitivity.
- FIG. 22 shows the configuration of the optical transmission system according to the sixteenth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the first embodiment in that a logical inversion circuit 209 is connected to a stage subsequent to the minute modulation signal component detection circuit 222.
- This embodiment is the technical concept of the third embodiment. This is a case where the concept is applied to the first embodiment, and the logical inversion circuit 209 is the same as that shown in FIG.
- the greatest advantage of this embodiment is that the maximum value of the initial set value applied to the phase adjustment terminal of the Mach-Zehnder interferometer can be reduced to 1Z2 or less when no logic inversion circuit is used. .
- FIG. 23 shows the configuration of the optical transmission system according to the seventeenth embodiment of the present invention.
- the optical transmission system according to the present embodiment is different from the first embodiment in that the optical receiver 2 detects the warm-up state from the temperature state of the Mach-Zehnder interferometer 200, and an MZI warm-up detection circuit 281.
- a loop opening / closing switch 282 that turns ON / OFF the feedback control to the Mach-Zehnder interferometer 200 by opening and closing a control loop that performs feedback control to the Zach-Zehnder interferometer 200, and a minute modulation signal detected by the minute modulation signal component detection circuit 222.
- a synchronous detection circuit 223 that outputs an error signal by comparing the phase of the micro-modulation signal output from the micro-modulation signal oscillation circuit 224 and a phase of the micro-modulation signal oscillation circuit 224, and locks the control loop based on the error signal from the synchronization detection circuit 223.
- a lock detection circuit 284 that outputs a lock detection signal when a lock state is detected, and a loop recovery circuit that has a redraw function when the optical frequency lock of the control loop is released. It is that it has a can-inclusive function with control circuit 285.
- the MZI warm-up detection circuit 281 monitors the temperature of the substrate of the Mach-Zehnder interferometer 200 and outputs a voltage corresponding to the temperature, an MZI temperature monitor 286, an output voltage from the MZI temperature monitor 286, It has a comparator 287 that compares the reference voltage Vrefl and outputs a signal indicating the result of comparison indicating whether the temperature of the substrate is within an appropriate range to the loop opening / closing switch 282.
- the Mach-Zehnder interferometer Since the Mach-Zehnder interferometer is used while keeping the overall temperature constant, it takes some time for the temperature to reach the set value when the system is started. At this time, the optical frequency characteristics of the Mach-Zehnder interferometer are flowing violently (drift), and there is a risk of runaway if control is attempted here. Therefore, in the present embodiment, the Mach-Zehnder interferometer 200 After the warm-up is over, the force control loop is closed, which can eliminate unnecessary sources of instability.
- the lock is detected again by using the lock detection circuit 284 and the control circuit 285 with a loop re-pulling function. You can take it to a state.
- FIG. 24 shows a configuration example of the control circuit with loop re-entry function 285.
- the control circuit with loop re-pull function 285 adds the output of the triangular wave generating circuit 2851 and the output of the triangular wave generating circuit 2851, the triangular wave generating circuit 2851 that operates based on the lock detection signal and the error signal, the amplifier 2852 that amplifies the error signal.
- An output adder 2853 is provided.
- the triangular wave generation circuit 2851 includes a switch 2854 for switching between the reference voltage Vref and the ground in accordance with the lock detection signal, a signal B and a signal C described later, and a comparison result as an output signal A and its inverted output signal.
- a comparator 2855 that outputs an output signal
- a switch 2856 that operates in conjunction with the switch 2854, and switches the error signal and the output signal A of the comparator 2855 in accordance with the lock detection signal.
- An integration circuit 2857 that integrates the difference between the two signals, and resistors 2858 and 2859 that generate a signal C by dividing the inverted output signal of the comparator 2855.
- one input of the integration circuit 2857 is connected to the reference voltage Vref by the switch 2854, and an error signal is supplied to the other input of the integration circuit 2857 by the switch 2856.
- the loop of the integration circuit 2857 is closed and a normal feedback control state is set. Thereby, the deviation of the error signal with respect to the reference voltage Vref is integrated so that the error signal becomes the reference voltage Vref.
- one input of the integration circuit 2857 is grounded by the switch 2854, and the output of the comparator 2855 (output signal A) and the other input of the integration circuit 2857 are connected by the switch 2856. By connecting, the integration loop is opened and the comparator 2855 and the integration circuit 2857 generate a triangular wave.
- FIG. 25 is a diagram showing the operation of the triangular wave generation circuit 2851.
- output signal A is the output of comparator 2855
- signal C is the inverted output of output signal A.
- the signal B which is turned back to the input side of, is the triangular wave output from the integrator 2857.
- comparator 2855 repeats the operation of detecting that signal B exceeds signal C and inverting output signal A and signal C, and can output a triangular wave like signal B. .
- FIG. 26 shows a configuration example of the lock detection circuit 284.
- the illustrated lock detection circuit 284 includes a resistor 2841-2843 and a lock detection circuit 284 that divide the voltage between the positive and negative power supplies and output the voltages VH and VL corresponding to the upper and lower limits of the appropriate substrate temperature range described above. It has a comparator 2844 for comparing the input voltage Vpc and the voltage VH, a comparator 2845 for comparing the voltage Vpc and the voltage VL, and an AND circuit 2846 for calculating the logical product of the comparators 2844 and 2845.
- This lock detection circuit is a threshold circuit that determines lock if the voltage Vpc, which is the voltage of the error signal of the synchronous detection circuit 223 shown in FIG. 23, is between the voltages VH and VL.
- FIG. 27 is a diagram showing operations of the lock detection circuit 284 and the triangular wave generation circuit 2851. If the lock detection circuit 284 determines that the lock has been released, the operation of the control circuit 285 with loop redrawing function switches to the operation of the triangular wave generation circuit, and the triangular wave is applied to the phase adjustment terminal 201 (see Fig. 23) as shown in the figure. Sweeps the applied current. If the output voltage of the synchronous detection circuit 223 enters the lock determination area between the voltage VH and the voltage VL while sweeping, the operation of the control circuit 285 with the loop redraw function changes from the operation of the triangular wave generation circuit to the operation of the integration circuit. Switch to the operation and close the control loop.
- the greatest advantage of the present embodiment is that the locked state can be restored again even if the control circuit becomes unstable and loses lock.
- FIG. 23 shows the case where the present invention is applied to the first embodiment, the present invention may be applied to other embodiments.
- FIG. 28 shows the configuration of the optical transmission system according to the eighteenth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the first embodiment in that the Mach-Zehnder interferometer 200 has two phase adjustment terminals on its two arms (that is, the phase adjustment terminal 201 in addition to the phase adjustment terminal 201 described above). Terminal 291), and a small modulation signal is applied to one of them (phase modulation terminal 291 in the figure). Applying a feedback control signal (feedback error signal) to the other (phase modulation terminal 201 in the figure).
- feedback error signal feedback error signal
- phase adjustment efficiency differs depending on the operating point of the drive circuit. If the minute modulation signal and the feedback control signal are added by the adder 225 and connected to the same phase adjustment terminal, the efficiency of the minute modulation changes depending on the magnitude of the feedback control signal. It becomes very difficult. In the present embodiment, the above problem can be solved by dividing the phase adjustment terminals for minute modulation and feedback control.
- a minute modulation operating point setting circuit 292 and an MZI offset setting circuit 294 are provided as reference voltage setting circuits, so that each operating point can be independently set. It can be adjusted.
- phase adjustment terminals 201 and 291 are provided on the two arms of Matsuhatsu Panda interferometer 200, respectively.
- the electrodes are divided, the same effect as providing these phase adjustment terminals can be realized.
- a plurality of electrodes may be provided on one arm, and a minute modulation signal and a feedback control signal may be applied to each arm. .
- the greatest advantage of the present embodiment is that a minute modulation signal can always be applied with stable efficiency.
- the force shown when applied to the first embodiment may be applied to other embodiments.
- FIG. 29 shows the configuration of the optical transmission system according to the embodiment.
- the optical transmission system according to the present embodiment is different from the eighteenth embodiment in that the optical receiver 2 uses the detected received signal light to determine the relative relationship between the optical carrier frequency and the optical frequency characteristics of the Mach-Zehnder interferometer 200.
- An optical carrier frequency detection circuit 295 for detecting a proper position is provided.
- the other configuration is the same as that of the optical transmission system shown in FIG. 28, so that the same components are denoted by the same reference numerals and overlapping description will be omitted.
- the optical modulation when performing control to set the peak or bottom of the optical frequency characteristic of the Mach-Zehnder interferometer 200 at the point of the maximum average power of the optical signal, the optical modulation It is conceivable that the control stability point does not always match the frequency of the optical carrier due to the asymmetry of the optical spectrum of the signal.
- the position of the optical carrier is detected by the optical carrier frequency detection circuit 295, and the MZI offset setting circuit 294 is configured to stabilize the peak or bottom of the optical frequency characteristic of the Matsuhatsu Panda interferometer 200 at that point. Give the offset value.
- the optical carrier frequency detection circuit 295 needs to find the position of the carrier even for the modulated signal power without the carrier.
- the Fabry-Perot resonator is scanned to find the two minimum points of the optical spectrum. It is conceivable to use a method in which the midpoint between the two frequencies is used as the optical carrier frequency.
- FIG. 29 shows a case where the present invention is applied to the eighteenth embodiment based on the first embodiment, the present invention may be applied to a configuration based on another embodiment.
- FIG. 30 shows the configuration of the optical transmission system according to the twentieth embodiment of the present invention.
- the optical transmission system according to the present embodiment differs from the nineteenth embodiment in that the optical transmitter 1 is provided separately from a modulation state control circuit 110 capable of ONZOF F modulation of a main signal and a main signal line. And a control signal communication circuit 111 for exchanging control signals with the optical receiver 2 using the control line.
- the optical receiving apparatus 2 has a control signal communication circuit 297 for exchanging control signals with the optical transmitting apparatus 1 using the control line.
- the other configuration is the same as that of the optical transmission system shown in FIG. 29, so that the same components are denoted by the same reference numerals and overlapping description will be omitted.
- the optical carrier frequency detection circuit 295 uses the information on the optical carrier frequency received via the control signal communication circuit 297 to determine the optical carrier frequency and the peak or bottom of the optical frequency characteristic of the Mach-Zehnder interferometer 200. An offset value is given to the MZI offset setting circuit 294 so that the frequencies match.
- the optical transmission device 1 turns off modulation of the main signal and transmits only the optical carrier.
- the optical receiver 2 detects the relative position between the optical carrier frequency transmitted from the optical transmitter 1 and the optical frequency characteristic of the Mach-Zehnder interferometer 200, and determines the position of the optical carrier frequency and the position of the Mach-Zehnder interferometer 200. Adjust the offset value of the MZI offset setting circuit 294 to match the peak or bottom position of the optical frequency characteristics.
- the optical receiver 2 transmits a control signal indicating that the offset adjustment is completed from the control signal communication circuit 297 to the optical transmitter 1.
- the modulation state control circuit 110 controls the modulator drive circuit 102 to turn on the modulation of the main signal.
- the greatest advantage of this embodiment is that the optical carrier frequency can be easily detected even if the optical modulation signal spectrum is asymmetric, and the peak or bottom of the optical frequency characteristic of the Mach-Zehnder interferometer is changed to the optical carrier frequency. That can be matched.
- FIG. 30 shows a case where the present invention is applied to the nineteenth embodiment based on the first embodiment, the present invention may be applied to a configuration based on another embodiment.
- the present invention relates to an optical transmission system employing the DPSK-DD system or the like, an optical transmission device and an optical reception device of the optical transmission system, wherein a phase difference between signal lights of two arms of a Mach-Zehnder interferometer provided in the optical reception device.
- a phase difference between signal lights of two arms of a Mach-Zehnder interferometer provided in the optical reception device By modulating the frequency at a constant frequency and detecting the phase of that frequency component, it is possible to set the optimal operating point of the Matsuhazunda interferometer that matches the optical frequency of the light source on the transmitting side, and the best light reception Properties can be obtained.
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Abstract
Description
Claims
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
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EP05721004.9A EP1727301B1 (en) | 2004-03-17 | 2005-03-17 | Optical transmission system, optical transmission device and optical reception device of optical transmission system |
US10/555,710 US7734194B2 (en) | 2004-03-17 | 2005-03-17 | Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system |
CN2005800002379A CN1771679B (zh) | 2004-03-17 | 2005-03-17 | 光传输***、光传输***的光发送装置及光接收装置 |
JP2006515321A JP4494401B2 (ja) | 2004-03-17 | 2005-03-17 | 光伝送システム、光伝送システムの光送信装置及び光受信装置 |
US12/723,210 US8005374B2 (en) | 2004-03-17 | 2010-03-12 | Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system |
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JP2004076746 | 2004-03-17 | ||
JP2004-076746 | 2004-03-17 |
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US10/555,710 A-371-Of-International US7734194B2 (en) | 2004-03-17 | 2005-03-17 | Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system |
US12/723,210 Division US8005374B2 (en) | 2004-03-17 | 2010-03-12 | Optical transmission system, optical transmitter for optical transmission system, and optical receiver for optical transmission system |
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WO2005088876A1 true WO2005088876A1 (ja) | 2005-09-22 |
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US (2) | US7734194B2 (ja) |
EP (1) | EP1727301B1 (ja) |
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Also Published As
Publication number | Publication date |
---|---|
EP1727301B1 (en) | 2018-05-16 |
CN1771679B (zh) | 2010-05-26 |
EP1727301A4 (en) | 2016-08-17 |
US7734194B2 (en) | 2010-06-08 |
JPWO2005088876A1 (ja) | 2007-08-09 |
JP4494401B2 (ja) | 2010-06-30 |
US8005374B2 (en) | 2011-08-23 |
US20100172653A1 (en) | 2010-07-08 |
CN1771679A (zh) | 2006-05-10 |
US20070058988A1 (en) | 2007-03-15 |
EP1727301A1 (en) | 2006-11-29 |
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