CN103856262A - System for measuring in-band OSNR through one-code-element delay interference and balance detection - Google Patents

System for measuring in-band OSNR through one-code-element delay interference and balance detection Download PDF

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CN103856262A
CN103856262A CN201410036766.5A CN201410036766A CN103856262A CN 103856262 A CN103856262 A CN 103856262A CN 201410036766 A CN201410036766 A CN 201410036766A CN 103856262 A CN103856262 A CN 103856262A
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code element
time delay
signal
osnr
element time
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CN103856262B (en
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杨爱英
周骥
乔耀军
冯立辉
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Beijing Institute of Technology BIT
Beijing University of Posts and Telecommunications
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Beijing University of Posts and Telecommunications
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Abstract

The invention relates to a system for measuring the in-band OSNR through one-code-element delay interference and balance detection, and belongs to the technical field of high-speed optical communication. The system comprises a one-code-element delay interferometer, a first optical power detection module, a second optical power detection module, a direct-current stabilized voltage supply, an OSNR calculation unit and a feedback control module. According to the system, the SNR of a monitored optical signal is worked out through one-code-element delay interference and balance detection; the system can be applied to DWDM systems to monitor the OSNR, and is suitable for the DWDM systems with various modulation formats such as PDM-QPSK and PDM-16QAM, various channel spaces like 25 GHZ or 50 GHZ and various symbol rates like 25 G baud of a commercial 100 G system. The system is simple, easy to integrate, suitable for the various modulation formats and rates and capable of achieving accurate measurement conveniently.

Description

Optical Signal To Noise Ratio measuring system in balance detection band is interfered in one code element time delay
Technical field
The present invention relates to an a kind of code element time delay and interfere Optical Signal To Noise Ratio measuring system in balance detection band, belong to high speed optical communication technical field.
Background technology
The following long period, along with wired and WiMAX access user quantity maintain sustained and rapid growth, the broadband applications such as HDTV (High-Definition Television) (HDTV), three-dimensional television (3DTV), Internet of Things and cloud computing continue to bring out, alone family bandwidth demand is multiplied, and following backbone network will face the pressure of transmission bandwidth for a long time.The large volume transport of 100G dense wave division multipurpose (DWDM) is the effective means of relieve transmission pressure; But the successful Application of 100G system is faced with many difficult problems, wherein Optical Signal To Noise Ratio (OSNR) monitoring is particularly thorny.OSNR is an important parameter of optical transmission system, and it has determined the without electronic relay transmission range of light amplification transmission system, performance that therefore can monitoring system by the monitoring of OSNR.
Along with the transmission capacity of optical communication network is more and more higher, modulation format becomes increasingly complex, the method for existing measurement OSNR is no longer applicable, needs the method for novel measurement OSNR a kind of badly, for the assessment of network performance.New method need to meet some and require:
According to the OSNR monitor of new method development should be simple, easy of integration, efficiency is high.Could extensively be distributed in optical-fiber network like this, help the problem in Accurate Diagnosis, fixer network.Coherent receiver can be measured OSNR by the method for Digital Signal Processing, but this method cost is high, can only apply at receiving terminal, is difficult to be distributed in network and applies.
2.OSNR monitor should be applicable to more modulation form and different transmission rates.For example should be able to measure point multiplexing-quarternary phase-shift keying (QPSK) (PDM-QPSK) or the more OSNR of high-order QAM light signal partially.
The test parameter of 3.OSNR monitor should have definition accurately, and measure error in the reasonable scope, the OSNR in Measurement accuracy optical-fiber network so easily.
Tradition OSNR method of testing mainly comprises two kinds: 1. band external test methods; 2. band build-in test method.
Band external test methods is to measure OSNR with noise in interchannel noise equivalent channel.In 100G optical transmission system, adopt the DWDM at 50GHz interval more.Because channel spacing diminishes and flashlight spectrum widening, the overlapping interchannel that makes of adjacent channel signal spectrum not only has noise power, also has part signal power, and the OSNR therefore measuring with external test methods is by less than normal.
Most representative in numerous band build-in test methods is polarization state partition method.The method is regarded noise as light source without polarization, and signal is polarised light, therefore the flashlight with polarization state is separated from the noise light without polarization state, and test signal and noise power separately, obtains OSNR in channel.This is the at present unique effective ways that can really realize the harmless on-line testing of OSNR in channel.In another band, method is the interior noise of channel that shutdown signal light is directly tested respective wavelength, need to interrupt the business of tested wavelength when this method test, cannot realize non-destructive testing.
100G wavelength-division system adopts PDM-QPSK modulation technique, and therefore polarization state partition method can not be with interior OSNR to measure to 100G wavelength-division system.Available method shutdown signal light carries out integration to interchannel noise now, and the method needs disconnecting link, and defect is very large.Therefore in 100GDWDM system channel, the harmless on-line testing of OSNR is a current difficult problem, needs solution badly.
Summary of the invention
The object of inventing is the difficult problem for solving the harmless on-line testing of OSNR, has proposed an a kind of code element time delay and has interfered Optical Signal To Noise Ratio measuring system in balance detection band, signal to noise ratio in the band of energy Measurement accuracy dwdm optical communication system.
Optical Signal To Noise Ratio measuring system in balance detection band is interfered in one code element time delay, comprises a code element time delay interferometer, the first optical power detecting module, the second optical power detecting module, D.C. regulated power supply, OSNR computing unit and feedback control module.Wherein, a code element time delay interferometer comprises 1 × 2 coupler, a code element delay line, a phase shifter, 2 × 2 couplers; OSNR computing module comprises memory cell, comparing unit and computing unit.
The annexation of above-mentioned each intermodule is: two output ports of a code element time delay interferometer are connected respectively to the first light rate detecting module and the second optical power detecting module, the first light rate detecting module and the second optical power detecting module are connected to the memory cell of OSNR computing module, the two-way output of memory cell connects comparing unit, the two-way output of comparing unit connects computing unit, the computing unit of OSNR computing module is connected to feedback control module, feedback control module is connected to D.C. regulated power supply module, D.C. regulated power supply module is connected to the phase shifter in a code element time delay interferometer.
Two outputs of 1 × 2 coupler connect respectively code element delay line and a phase shifter, and two outputs of a code element delay line and phase shifter are connected to the input of 2 × 2 couplers, and two output ports of 2 × 2 couplers are the output port of a code element time delay interferometer.
The time delay of one code element time delay interferometer is the inverse of signal baud rate, and the free spectral width (FSR) of a code element time delay interferometer equals the baud rate of signal.By the output control interferometer passband position of D.C. regulated power supply, its free spectrum peak position is aimed at the centre wavelength of measuring channel, adjustable range is 1 FSR.One code element time delay interferometer two ends output enters the first optical power detecting module and the second optical power detecting module, the output of the first optical power detecting module and the second optical power detecting module enters OSNR computing module, complete storage, comparison, computing function, calculate OSNR.
The effect of a described code element time delay interferometer is code element time delay interference and a balance detection.
The concrete grammar that a described code element time delay is interfered is: light signal is divided into two paths of signals by power averaging, first via signal is carried out to time delay one code element operation, obtain time delayed signal; The second road signal is carried out to phase shift operation, obtain phase shift signal, definite principle of phase-shift phase is: make light signal after phase shift and first via time delayed signal after follow-up balance detection, the difference maximum of the two ways of optical signals power again generating.
The concrete grammar of described balance detection is: first via time delayed signal and the second road phase shift signal after a code element time delay is interfered close ripple, and then are divided into two paths of signals by watt level; Survey respectively the power output that obtains two-way alignment light signal.
The first optical power detecting module and the second optical power detecting module adopt low speed photodetector to carry out power measurement, and its bandwidth is far smaller than signal rate.
The phase place of phase shifter is by a D.C. regulated power supply and feedback control module control, the difference of two detector output currents that feedback control module obtains according to comparing unit in OSNR computing module regulates the voltage of D.C. regulated power supply, thereby regulate the phase place of a code element time delay interferometer, make a code element time delay interferometer two ends Output optical power differ maximum.
A described code element time delay interferes the workflow of Optical Signal To Noise Ratio measuring system in balance detection band to be:
Step 1, according to monitored signal wavelength and chip rate, utilize optical sender to produce the alignment light signal of wavelength same with monitored light signal and speed, through adjustable light wave-filter, by alignment light signal after the filtering of adjustable light wave-filter output, input a code element time delay interferometer and carry out code element time delay interference and a balance detection, measure by the first optical power detecting module and the second optical power detecting module again, obtain the power output of two-way alignment light signal; Big or small with comparing unit, will wherein be designated as compared with great mono-road power
Figure BDA0000461949730000031
compare little mono-road power is designated as
Figure BDA0000461949730000032
calculate and output to feedback control module control phase shifter phase-shift phase, until obtain maximum
Figure BDA0000461949730000034
calculate the now ratio cc of power output,
Figure BDA0000461949730000035
The bandwidth of described adjustable light wave-filter and centre wavelength, meet and make two-way alignment light output power signal
Figure BDA0000461949730000036
with the principle of difference maximum, now adjustable light wave-filter bandwidth is effective noise bandwidth (NEB).
Step 2, utilize erbium-doped fiber amplifier to produce spontaneous emission noise as alignment light noise, the adjustable light wave-filter of input step one, optical noise after adjustable light wave-filter output filtering is inputted to a code element time delay interferometer and carry out code element time delay interference and a balance detection, measure by the first optical power detecting module and the second optical power detecting module again, obtain the power output of two-way optical noise, big or small with comparing unit, wherein the power output on compare great mono-tunnel is designated as
Figure BDA0000461949730000038
the power output on compare little mono-tunnel is designated as
Figure BDA0000461949730000039
power output ratio is designated as β,
Figure BDA00004619497300000310
Step 3, the power output ratio cc and the β that obtain by step 1 and step 2, correction calculation module.Then, monitored light signal is inputted to a code element time delay interferometer and carry out code element time delay interference and a balance detection, then measure by the first optical power detecting module and the second optical power detecting module, obtain two ways of optical signals power output, be designated as P 1with P 2, with relatively P of comparing unit 1with P 2size, the wherein larger P that is designated as max, the less P that is designated as min.
Step 4, computing unit calculates the power P of monitored light signal swith noise power P nsignal to noise ratio, concrete formula is:
P S/P N＝(α+1)(P max-βP min)/(β+1)(αP min-P max)
Step 5, the signal to noise ratio that computing unit obtains step 4 is revised, and the Optical Signal To Noise Ratio (OSNR) of correction is
OSNR = 101 g ( P S / P N ) + 101 g ( NEB / 12.5 ) = 101 g ( ( α + 1 ) ( P max - βP min ) ( β + 1 ) ( α P min - P max ) ) + 101 g ( NEB / 12.5 )
Beneficial effect
The present invention is applied to dense wave division multipurpose (DWDM) system, carries out Optical Signal To Noise Ratio (OSNR) monitoring; Be applicable to the dwdm system of more modulation form (PDM-QPSK, PDM-16QAM etc.), multiple channel spacing (25GHz or 50GHz), multiple character rate (as commercial 100G system 25Gbaud used etc.).The present invention is simple and easy to integrated, meets more modulation form and speed, convenient measurement accurately.
Brief description of the drawings
Fig. 1 is the structural representation that Optical Signal To Noise Ratio measuring system in balance detection band is interfered in the present invention's one code element time delay;
Fig. 2 is the structure chart of a code element time delay interferometer in embodiment;
Fig. 3 is the structure chart of OSNR computing module in embodiment;
Fig. 4 is the free spectrogram of code element time delay interferometer first output and the second output in embodiment;
Fig. 5 is that in embodiment, a code element time delay interferes balance detection to measure the typical application drawing of Optical Signal To Noise Ratio in band, in order to measure the Optical Signal To Noise Ratio of dwdm system channel;
Fig. 6 is the checking experimental system figure that measures dwdm system OSNR in embodiment;
Fig. 7 uses different bandwidth optical add/drop multiplexer (OADM) in embodiment, the present invention measures the experimental result picture that wavelength is 1549.1nm channel OSNR;
Fig. 8 is that when in embodiment, OADM bandwidth is 0.5nm, the present invention measures the experimental result picture that wavelength is 1549.1nm channel OSNR;
Fig. 9 is when in embodiment, OADM bandwidth is 0.5nm, and the present invention measures 1549.1 and the experimental result picture of 1549.5nm channel OSNR;
Label declaration: 101-mono-code element time delay interferometer, 102-the first optical power detecting module, 103-the second optical power detecting module, 104-D.C. regulated power supply, 105-OSNR computing module, 106-FEEDBACK CONTROL, 201-1 × 23dB coupler, 202-mono-code element delay line, 203-phase shifter, 204-2 × 23dB coupler, 205-the first output, 206-the second output, the first optical add/drop multiplexer of the monitored light signal process of 401-, the optical fiber of the monitored light signal process of 402-, second optical add/drop multiplexer on road under the monitored light signal of 403-, 601-DWDM light transmitting terminal, 602-spontaneous radiation optical noise generation unit, 603-spectrometer.
Embodiment
Below in conjunction with drawings and Examples, summary of the invention is described further objects and advantages of the present invention in order better to illustrate.
Optical Signal To Noise Ratio tester in concrete enforcement, can can't harm OSNR test in band, and the signal to noise ratio scope of measurement is 5-30dB, measures accurately, and error is less than 0.5dB.The effect of measuring and the shape of spectrum are irrelevant, are more suitable for the OSNR monitoring of complicated DWDM optical-fiber network now.
The present embodiment proposes an a kind of code element time delay and interferes balance detection to measure Optical Signal To Noise Ratio system in band, as shown in Figure 1, comprise a code element time delay interferometer 101, the first optical power detecting module 102, the second optical power detecting module 103, D.C. regulated power supply 104, OSNR computing unit 105 and feedback control module 106.Wherein, a code element time delay interferometer 101 comprises 1 × 23dB coupler, a code element delay line, 203, one 2 × 23dB couplers of a phase shifter; OSNR computing module 105 comprises memory cell, comparing unit and computing unit.
The annexation of above-mentioned each intermodule is: two output ports of a code element time delay interferometer 101 are connected respectively to the first light rate detecting module 102 and the second optical power detecting module 103, the first light rate detecting module 102 and the second optical power detecting module 103 are connected to the memory cell of OSNR computing module 105, the two-way output of memory cell connects comparing unit, the two-way output of comparing unit connects computing unit, the computing unit of OSNR computing module 105 is connected to feedback control module 106, feedback control module 106 is connected to D.C. regulated power supply module 104, D.C. regulated power supply module 104 is connected to the phase shifter 203 in a code element time delay interferometer 101.
With 1 × 2 coupler 201, one code element delay lines 202, phase shifter 203 and 2 × 2 couplers 204 form a code element time delay interferometer, and as shown in Figure 2, the two-port of a code element time delay interferometer is output as 205 and 206 to structure.Two outputs of 1 × 2 coupler 201 connect respectively a code element delay line 202 and phase shifter 203, two outputs of one code element delay line 202 and phase shifter 203 are connected to the input of 2 × 2 couplers 204, two output ports of 2 × 2 couplers 204 are 205 and 206, are the output port of a code element time delay interferometer.
The time delay of one code element time delay interferometer 101 is the inverse of signal baud rate, and the free spectral width (FSR) of a code element time delay interferometer 101 equals the baud rate of signal.By the output control interferometer 101 passband positions of D.C. regulated power supply 104, its free spectrum peak position is aimed at the centre wavelength of measuring channel, adjustable range is 1 FSR.One code element time delay interferometer 101 two ends outputs enter the first optical power detecting module 102 and the second optical power detecting module 103, the first optical power detecting module 102 and the second optical power detecting module 103 adopt low speed photodetector to carry out power measurement, and its bandwidth is far smaller than signal rate.The output of the first optical power detecting module 102 and the second optical power detecting module 103 enters OSNR computing module 105, calculates OSNR.
The power transfer function of two outputs 205 and 206 is respectively:
T 205＝cos 2((2πτf+Δφ)2)
T 206＝sin 2((2πτf+Δφ)2)
Wherein τ is time delay, and Δ φ is phase shift.The cycle of transfer function is 1 τ, and the FSR of this filter is 1 τ.As τ=4ps, T 205and T 206as shown in Figure 3, FSR is 250GHz(2nm to corresponding transmission spectrum), and two transfer function phase place phase difference of pi.
The first optical power detecting module 102 and the second optical power detecting module 103 are used the photodiode of two low speed to survey the luminous power of a code element time delay interferometer two ends output, change output current into, enter computing module and obtain Optical Signal To Noise Ratio.
The phase place of phase shifter is by a D.C. regulated power supply and feedback control module control, feedback control module regulates the voltage of D.C. regulated power supply according to the output current of two detectors, thereby regulate the phase place of a code element time delay interferometer, make a code element time delay interferometer two ends Output optical power differ maximum.
The present invention has different output characteristic to the light signal of different extinction ratios and proposes according to a code element time delay interferometer.In dwdm system, the spectrum of light data-signal has distinct profile, and extinction ratio is higher; The power spectrum of noise can be similar to white noise conventionally, and extinction ratio is low.Therefore light data-signal and noise are simultaneously by time delay interferometer, and their transmission spectrum can separate light data-signal and noise range.Fig. 4 is freely composing of time delay interferometer, suppose that solid line is freely composing of the first output 205, dotted line is freely composing of the second output 206, the first output 205 freely compose with the second output 206 freely compose the phase place that just differs 180 degree, and be all that periodicity has limit for length's unit impulse response (FiniteImpulseResponse-FIR) filter.Interferometer FSR equals the inverse of its time delay, by the adjusting of phase shifter phase place in interferometer, and peak value (valley) position that can tuningly freely compose.In the present invention, in interferometer, delay adjustments is a symbol period, makes free spectrum peak (valley) be positioned at the centre wavelength of channel by phase control, can distinguish better like this light data-signal and noise.
Optical Signal To Noise Ratio is defined as the ratio of the noise power that light data-signal power and equivalent bandwidth are 12.5GHz, and definition is
OSNR＝10log(P iN i)+10log(NEB/12.5)
Wherein, P ibe the signal power in i channel, N iit is the noise power in equivalent noise bandwidth NEB.
Fig. 5 uses the present invention to measure the system diagram of certain channel OSNR in commercial dwdm system.Dwdm system comprises multiple optical add/drop multiplexers (OADM), between an OADM401 and the 2nd OADM403, is connected by optical fiber link 402.OADM major function is from dwdm system, to separate or insert one or more wavelength.The 2nd OADM403 separates certain channel (wavelength) from dwdm system, and this channel 1%-10% power is sent into according to the OSNR monitoring system of the inventive method design and carried out OSNR measurement, and residue 90%-99% power is sent into receiver.As shown in Figure 5, while measuring OSNR, first regulate D.C. regulated power supply to make a code element time delay interferometer freely compose maximum value position aligning and need to measure channel center's wavelength.According to measured signal wavelength and chip rate, utilize optical sender to produce the alignment light signal of same wavelength and speed, input one adjustable light wave-filter, then inputs alignment light signal one code element time delay interferometer, obtain two-way power through balance detection, wherein export compared with great mono-road power and be designated as
Figure BDA0000461949730000061
compare little mono-road power is designated as regulate bandwidth and the centre wavelength of adjustable light wave-filter, make the difference maximum of two-way power, and to record now adjustable light wave-filter bandwidth be effective noise bandwidth (NEB).Optical Signal To Noise Ratio (OSNR) computing module carries out data storage, comparison and calculating, and the ratio that the computing unit of OSNR computing module 105 calculates a code element time delay interferometer two-way power output is α,
Figure BDA0000461949730000063
utilize erbium-doped fiber amplifier to produce spontaneous emission noise as alignment light noise, the adjustable light wave-filter of centre wavelength and bandwidth has been determined in input, the noise inputs one code element time delay interferometer of adjustable light wave-filter output, obtain two-way power through balance detection, wherein export compared with great mono-road power and be designated as
Figure BDA0000461949730000064
compare little mono-road power is designated as.
Figure BDA0000461949730000065
optical Signal To Noise Ratio (OSNR) computing module carries out data storage, comparison and calculating, and the ratio that the computing unit of OSNR computing module 105 calculates a code element time delay interferometer two-way power output is β,
Figure BDA0000461949730000066
one filtering characteristic of code element time delay interferometer and the frequency spectrum of tested light signal determine the value of α and β.Because the time delay of time delay interferometer is fixed as a symbol period, if system symbol speed and modulation format are definite, the value of α and β has also just been determined, has not been needed duplicate measurements.Certain channel signal (comprising noise and signal) separating as OADM enters OSNR monitoring system, first enter a code element time delay interferometer, the two ends output of interferometer obtains two-way power through balance detection, by the comparing unit of OSNR computing module 105, wherein exported compared with great mono-road power and be designated as P max, compare little mono-road power is designated as P min, because a code element time delay interferometer is linear system, therefore
P max = α α + 1 P S + β β + 1 P N
P min = 1 α + 1 P S + 1 β + 1 P N
Wherein P sfor signal power, P nfor noise power.The ratio of signal power and noise power is
P S P N = ( α + 1 ) ( P max - βP min ) ( β + 1 ) ( αP min - P max )
Noise power is revised, and the OSNR of measurement is
OSNR = 10 log ( P S / P N ) + 10 log ( NEB / 12.5 ) = 10 log ( ( α + 1 ) ( P max - βP min ) ( β + 1 ) ( α P min - P max ) ) + 101 og ( NEB / 12.5 )
Wherein NEB is effective noise bandwidth, is determined by the effective filtering bandwidth of OADM.
The present invention is applicable to QPSK in dwdm system, 16QAM, and PDM-QPSK, the Optical Signal To Noise Ratio of the more modulation form light signals such as PDM-16QAM is measured.In dwdm system, different channels light signal will be through the OADM of varying number, therefore the spectrum of the each channel degree varies sample that distorts after by OADM filtering.Traditional OSNR method of measurement is very responsive to this distortion, and method of the present invention is insensitive to the distortion of spectrum for measuring OSNR.
For verify method of the present invention can Measurement accuracy dwdm system in the OSNR of channel, designed the experimental system shown in Fig. 6.Experimental system comprises DWDM transmitting terminal 601, ASE noise source 602, adjustable light wave-filter, spectrometer 603, OSNR monitoring system.The wavelength that laser in transmitting terminal 601 produces is respectively 1549.1nm, 1549.5nm, and 1549.9nm, 1550.3nm, channel spacing is 50GHz, and modulation format is PDM-QPSK, and modulation rate is 100Gbit/s, and character rate is 25GSymbol/s.The function of adjustable light wave-filter simulation OADM, bandwidth and centre wavelength are adjustable; In experiment, select 0.3nm, 0.4nm and 0.5nm bandwidth.The OSNR that spectrometer 603 is measured is fiducial value.603 measured values of the OSNR that OSNR monitoring system of the present invention is measured and spectrometer contrast.
Fig. 7 contrasted OSNR that OSNR monitoring system of the present invention measures under different filter bandwidhts with reference to OSNR.System channel interval 50GHz, modulation format is PDM-QPSK, and speed is 100Gbit/s, and the channel wavelength of surveying is 1549.1nm.In Fig. 7, X-axis is the OSNR that spectrometer 603 records, and as reference value, Y-axis is the OSNR that the present invention measures, and solid line is reference line.Can find out, adjustable light wave-filter bandwidth is respectively 0.3nm, 0.4nm, and when 0.5nm, the present invention can measure the OSNR of channel exactly, and measure error is less than 0.5dB, wherein when 0.5nm, measurement effect the best.
When setting tunable optic filter bandwidth and being 0.5nm, Fig. 8 contrasted OSNR that OSNR monitoring system of the present invention measures with reference to OSNR.System channel interval 50GHz, modulation format is PDM-QPSK, and speed is 100Gbit/s, and the channel wavelength of surveying is 1549.1nm.In Fig. 8, X-axis is the measured OSNR of spectrometer 603, is designated as reference value, Y-axis is the OSNR that this OSNR monitoring system is measured, the OSNR that visible OSNR monitoring system of the present invention is measured can coincide with spectrometer 603 OSNR that surveys, and measuring range is 5-30dB, and measure error is less than 0.5dB.
Set filter bandwidht while being 0.5nm, Fig. 9 contrasted OSNR that this OSNR monitoring system measures 1549.1nm and 1549.5nm two wavelength channels with reference to OSNR.System channel interval 50GHz, modulation format is PDM-QPSK, speed is 100Gbit/s.In Fig. 9, X-axis is the measured OSNR of spectrometer 603, and as reference value, Y-axis is the OSNR that OSNR monitoring system is measured, and solid line is reference line, can find out that the present invention can measure the OSNR of different channels, and can measure accurately.Major technique advantage of the present invention:
1. can Measurement accuracy channel OSNR, measuring range is wide, and measure error is low;
2. simple in structure, be easy to realize, cost is lower.Only need a code element time delay interferometer, 2 optical power detecting modules, simple calculations module (low volume data storage and addition subtraction multiplication and division function);
3. the present invention applicable to more modulation form and different transmission rates, comprises PDM-QPSK, PDM-16QAM etc.;
4. method of measurement is simple, and measurement parameter is easily determined.
Therefore, the present invention meets the measurement requirement of high-speed light network to OSNR, can be used in network OSNR is carried out to Measurement accuracy, for estimating transmission channel performance.
Specific embodiment of the invention form is not limited to this.The explanation of this enforcement is just for helping to understand method of the present invention and core concept thereof; , for one of ordinary skill in the art, according to thought of the present invention, all will change in specific embodiments and applications, in sum, this description should not be construed as limitation of the present invention meanwhile.In the case of not deviating from the various apparent change of the spirit of the method for the invention and claim scope, it being carried out all within protection scope of the present invention.

Claims (4)

1. Optical Signal To Noise Ratio measuring system in balance detection band is interfered in a code element time delay, it is characterized in that: comprise a code element time delay interferometer, the first optical power detecting module, the second optical power detecting module, D.C. regulated power supply, OSNR computing module and feedback control module; Wherein, a code element time delay interferometer comprises 1 × 2 coupler, a code element delay line, a phase shifter, 2 × 2 couplers; OSNR computing module comprises memory cell, comparing unit and computing unit;
The annexation of above-mentioned each intermodule is: two output ports of a code element time delay interferometer are connected respectively to the first light rate detecting module and the second optical power detecting module, the first light rate detecting module and the second optical power detecting module are connected to the memory cell of OSNR computing module, the two-way output of memory cell connects comparing unit, the two-way output of comparing unit connects computing unit, the computing unit of OSNR computing module is connected to feedback control module, feedback control module is connected to D.C. regulated power supply module, D.C. regulated power supply module is connected to the phase shifter in a code element time delay interferometer,
Two outputs of 1 × 2 coupler connect respectively code element delay line and a phase shifter, and two outputs of a code element delay line and phase shifter are connected to the input of 2 × 2 couplers, and two output ports of 2 × 2 couplers are the output port of a code element time delay interferometer;
The time delay of one code element time delay interferometer is the inverse of signal baud rate, and its free spectral width FSR equals the baud rate of signal; By the output control interferometer passband position of D.C. regulated power supply, its free spectrum peak position is aimed at the centre wavelength of measuring channel, adjustable range is 1 FSR; One code element time delay interferometer two ends output enters the first optical power detecting module and the second optical power detecting module, the output of the first optical power detecting module and the second optical power detecting module enters OSNR computing module, complete storage, comparison, computing function, calculate OSNR.
2. Optical Signal To Noise Ratio measuring system in balance detection band is interfered in a code element time delay according to claim 1, it is characterized in that: the effect of a described code element time delay interferometer is code element time delay interference and a balance detection; The concrete grammar that a described code element time delay is interfered is: light signal is divided into two paths of signals by power averaging, first via signal is carried out to time delay one code element operation, obtain time delayed signal; The second road signal is carried out to phase shift operation, obtain phase shift signal, definite principle of phase-shift phase is: make light signal after phase shift and first via time delayed signal after follow-up balance detection, the difference maximum of the two ways of optical signals power again generating; The concrete grammar of described balance detection is: first via time delayed signal and the second road phase shift signal after a code element time delay is interfered close ripple, and then are divided into two paths of signals by watt level; Survey respectively the power output that obtains two-way alignment light signal.
3. Optical Signal To Noise Ratio measuring system in balance detection band is interfered in a code element time delay according to claim 1, it is characterized in that: the first optical power detecting module and the second optical power detecting module adopt photodetector to carry out power measurement, and bandwidth is less than signal rate.
4. Optical Signal To Noise Ratio measuring system in balance detection band is interfered in a code element time delay according to claim 1, it is characterized in that: feedback control module regulates the voltage of D.C. regulated power supply according to the output current of two detectors, and then the phase place of adjusting one code element time delay interferometer, make a code element time delay interferometer two ends Output optical power differ maximum.
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