CN115412169A - System and method for simultaneously transmitting optical frequency, microwave and time signals of optical fiber - Google Patents
System and method for simultaneously transmitting optical frequency, microwave and time signals of optical fiber Download PDFInfo
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Abstract
The invention provides a system and a method for simultaneously transmitting optical frequency, microwave and time signals of an optical fiber, wherein one path of a time reference signal is sent to a time difference measuring module, the other path of the time reference signal is sent to a code modulation module, and a generated frequency reference signal is sent to a first femtosecond optical comb; demodulating and decoding the optical signal into a time signal by using a first demodulation and decoding module, sending the time signal into a time difference measuring module, and measuring the difference value of the time signal and the time signal; utilizing a coding modulation module to code and modulate the signal of the first femtosecond optical comb, the time signal of the atomic clock and the real-time measurement value of the time difference measurement module; and demodulating and decoding the signal from the beam splitter into a time signal and a real-time round-trip link time difference value through second demodulation and decoding, sending the time signal to the time signal generation module to calculate time compensation amount according to the difference value of the demodulated time signal, compensating the time signal, and outputting the time signal to a user, thereby improving the microwave and time transmission stability.
Description
Technical Field
The invention belongs to the field of optical fiber communication, and particularly relates to a system and a method for simultaneously transmitting optical frequency, microwave and time signals of an optical fiber.
Background
The time is one of seven international basic units with the highest measurement precision, and the precise time frequency plays a vital role in advanced scientific research such as deep space exploration, radio astronomy, basic physical research, geophysical measurement, navigation positioning, precise metering, geodetic measurement and observation and major infrastructure and engineering. With the rapid development of the optical frequency standard technology, the optical frequency standard technology has become a powerful competitor for the next generation of time frequency reference. Although optical frequency has high frequency transmission stability, the frequency standard which is commercially used globally is mainly microwave atomic clock. Therefore, the realization of the simultaneous transmission of the optical frequency signal, the microwave frequency signal and the time signal has important application value and practical significance. The application realizes the simultaneous transmission of optical frequency signals, microwave frequency signals and time signals.
Secondly, in the prior art, the microwave signal stability achieved by the broadband electro-optical coupling and frequency shift module is low, and the accuracy and stability of the optical fiber time transmission signal achieved based on time difference measurement comparison are low, for example, in patent document CN110061778a in the prior art, a device and a method for simultaneously transmitting the optical fiber microwave and the optical frequency are proposed, which achieve the broadband coupling of the microwave and the optical frequency and the system compensation of phase noise by the broadband electro-optical coupling and frequency shift module, and achieve the simultaneous transmission of the optical fiber microwave and the optical frequency.
Disclosure of Invention
In order to solve the above technical problem, the present invention provides a system for simultaneously transmitting optical frequency, microwave and time signals through an optical fiber, comprising: the time difference measuring device comprises an atomic clock, a time difference measuring module, a time signal generating module, a first femtosecond optical comb, a second femtosecond optical comb, an ultrastable optical module, a coding modulation module, a first demodulation decoding module, a second demodulation decoding module, a laser, an optical amplification module, an optical fiber optical frequency transmission transmitter, an optical fiber optical frequency transmission receiver, a first circulator, a second circulator, a first wavelength division multiplexer, a second wavelength division multiplexer, a beam splitter and an optical fiber link;
the atomic clock is respectively connected with the first femtosecond optical comb, the coding modulation module and the time difference measurement module and is used for sending one path of the generated time reference signal to the time difference measurement module as a reference, sending the other path of the generated time reference signal to the coding modulation module as a modulation signal and sending the generated frequency reference signal to the first femtosecond optical comb;
the first femtosecond optical comb is respectively connected with the ultra-stable optical module and the code modulation module and used for sending the generated repeated frequency signals into the code modulation module to serve as carrier signals and sending output optical signals to the ultra-stable optical module, the first femtosecond optical comb and the ultra-stable optical module jointly convert frequency reference signals into optical frequency signals, and the ultra-stable optical module is connected with the optical fiber optical frequency transmission transmitter and used for sending the optical frequency signals to the optical fiber optical frequency transmission transmitter;
the first wavelength division multiplexer is respectively connected with the optical fiber optical frequency transmission transmitter, the first circulator and the optical fiber link, and the first circulator is connected with the laser;
the optical fiber optical frequency transmission transmitter outputs an optical frequency signal to the first wavelength division multiplexer, and the first circulator is connected with the first demodulation and decoding module and is used for sending the optical signal from the first wavelength division multiplexer to the first demodulation and decoding module;
the first circulator is used for sending optical signals from the laser into the first wavelength division multiplexer, and the first wavelength division multiplexer is used for combining the optical signals from the optical fiber optical frequency transmission transmitter and the first circulator into one beam and sending the beam into the optical fiber link;
the first demodulation and decoding module is connected with the time difference measuring module and used for demodulating and decoding the optical signal into a time signal and sending the time signal to the time difference measuring module; the time difference measuring module is also connected with the coding modulation module and is used for measuring the difference value between the time signal from the atomic clock and the time signal of the first demodulation and decoding module and sending the difference value to the coding modulation module;
the coded modulation module is connected with the laser and is used for coding and modulating the signal of the first femtosecond optical comb, the time signal of the atomic clock and the real-time measurement value of the time difference measurement module and then sending the coded and modulated signal to the laser;
the laser is connected with the first circulator and used for modulating the signal from the coding modulation module on the laser with the fixed wavelength and sending the laser to the first circulator;
the second wavelength division multiplexer is respectively connected with the optical fiber optical frequency transmission receiver, the second circulator and the optical fiber link, and is used for combining an optical signal from the optical fiber optical frequency transmission receiver and an optical signal from the second circulator into one beam and sending the beam to the optical fiber link, and sending the optical signal from the optical fiber link to the optical fiber optical frequency transmission receiver and the second circulator;
the second circulator is connected with the beam splitter and is used for sending the received signal of the second wavelength division multiplexer into the beam splitter and sending the optical signal from the beam splitter into the second wavelength division multiplexer;
the optical fiber optical frequency transfer receiver is connected with a user and the second femtosecond optical comb and is used for sending the output optical frequency signals to the second femtosecond optical comb and the user;
the second femtosecond optical comb is connected with the time signal generation module and used for converting the optical frequency signal into a microwave signal, one path of the microwave signal is sent to the time signal generation module, and the other path of the microwave signal is output to a user;
the second demodulation and decoding module is connected with the time signal generating module and used for demodulating and decoding the signals from the beam splitter into time signals and real-time round-trip link time difference values and sending the time signals to the time signal generating module;
and the time signal generating module calculates time compensation amount according to the difference value of the demodulated time signals, compensates the time signals and outputs the time signals to a user.
Further, the device also comprises a first photoelectric detector, a second photoelectric detector and a light amplification module;
the first photoelectric detector is connected with the first circulator and the first demodulation decoding module, and is used for converting an optical signal from the first circulator into an electric signal and sending the electric signal to the first demodulation decoding module;
the second photoelectric detector is connected with the beam splitter and the second demodulation and decoding module, the light amplification module is respectively connected with the second circulator and the beam splitter, the second photoelectric detector is used for converting an optical signal into an electric signal and sending the electric signal to the second demodulation and decoding module, the light amplification module amplifies the received signal of the second circulator and then sends the amplified signal to the beam splitter, and the beam splitter outputs the optical signal to the second photoelectric detector and the second circulator according to the splitting ratio.
Further, the first femtosecond optical comb and the ultra-stable optical module jointly convert the frequency reference signal into lambda 1 Optical frequency signal of wave band, laser emitting wavelength is lambda 2 The wavelength channel of the first wavelength division multiplexer is lambda 1 And λ 2 For passing the light from the fiber-optic frequency transmitter at a wavelength λ 1 And the optical signal from the first circulator has a wavelength lambda 2 The optical signals are combined into a beam and sent into the optical fiber link, and simultaneously the optical signals from the optical fiber link are received, and the wavelength from the optical fiber optical frequency transmission receiver is lambda 1 Sending the optical signal into an optical fiber optical frequency transmission transmitter to transmit the optical signal with the wavelength of lambda 2 Is fed into the first circulator.
Furthermore, the time signal generating module is used for generating a 1PPS time signal and according to the difference value of the demodulated 1PPS time signal
Calculating the time compensation amount required by the time signal generation module
And compensating the 1PPS time signal and outputting the signal to a user.
The invention also provides a method for simultaneously transmitting optical frequency, microwave and time signals of the optical fiber, which is used for realizing the transmission system and comprises the following steps:
generating a time reference signal and a frequency reference signal by an atomic clock;
one path of the time reference signal is sent to a time difference measuring module to be used as a reference, and the other path of the time reference signal is sent to a code modulation module to be used as a modulation signal; sending the generated frequency reference signal to a first femtosecond optical comb;
sending a repetition frequency signal generated by the first femtosecond optical comb into a coding modulation module as a carrier signal, sending an optical signal output by the first femtosecond optical comb to a super-stable optical module, and converting a frequency reference signal into a lambda jointly 1 And sending the optical frequency signal to an optical fiber optical frequency transmission transmitter;
sending an optical frequency signal output by an optical fiber optical frequency transmission transmitter and an optical signal from a laser to a first wavelength division multiplexer, sending the optical signal to a first demodulation and decoding module by the first wavelength division multiplexer, combining the optical signals from the optical fiber optical frequency transmission transmitter and a first circulator into one beam, and sending the beam into an optical fiber link;
the first demodulation decoding module is used for demodulating and decoding the optical signal into a time signal, the time signal is sent to the time difference measuring module, the difference value between the time signal from the atomic clock and the time signal of the first demodulation decoding module is measured and sent to the coding modulation module;
a signal of the first femtosecond optical comb, a time signal of an atomic clock and a real-time measured value of the time difference measuring module are coded and modulated by a coding modulation module and then are sent to the laser;
the laser modulates the signal from the code modulation module on the laser with fixed wavelength and sends the laser into the first circulator;
combining the optical signal from the optical fiber optical-frequency transfer receiver and the optical signal of the second circulator into one beam by a second wavelength division multiplexer, sending the beam into the optical fiber link, and sending the optical signal from the optical fiber link into the optical fiber optical-frequency transfer receiver and the second circulator;
sending the received signal of the second wavelength division multiplexer into the beam splitter through the second circulator, and sending the optical signal from the beam splitter into the second wavelength division multiplexer;
the optical fiber optical frequency transmission receiver sends the output optical frequency signals to a second femtosecond optical comb and a user, the second femtosecond optical comb converts the optical frequency signals into microwave signals, one path of the microwave signals is sent to the time signal generating module, and the other path of the microwave signals is output to the user;
and the second demodulation and decoding module demodulates and decodes the signals from the beam splitter into time signals and real-time round-trip link time difference values, and sends the time signals to the time signal generation module to calculate time compensation amount according to the demodulated time signal difference values, compensate the time signals and output the time signals to a user.
Further, the first photoelectric detector converts the optical signal from the first circulator into an electric signal and sends the electric signal to the first demodulation and decoding module; the second photoelectric detector converts the optical signal into an electric signal and sends the electric signal to the second demodulation and decoding module, the optical amplification module amplifies the received signal of the second circulator and sends the amplified signal to the beam splitter, and the optical signal is output to the second photoelectric detector and the second circulator according to the beam splitting ratio.
Further, the first femtosecond optical comb and the ultra-stable optical module jointly convert the frequency reference signal into lambda 1 Optical frequency signal of wave band, laser emitting wavelength of lambda 2 The wavelength channel of the first wavelength division multiplexer is lambda 1 And λ 2 For passing the light from the fiber-optic frequency transmitter at a wavelength λ 1 And the optical signal from the first circulator has a wavelength lambda 2 The optical signals are combined into a beam and sent into the optical fiber link, and simultaneously the optical signals from the optical fiber link are received, and the wavelength from the optical fiber optical frequency transmission receiver is lambda 1 Sending the optical signal into an optical fiber optical frequency transmission transmitter to transmit the optical signal with the wavelength of lambda 2 Is fed into the first circulator.
Furthermore, the time signal generating module is used for generating a 1PPS time signal and according to the difference value of the demodulated 1PPS time signal
Calculating the time compensation amount required by the time signal generation module
And compensating the 1PPS time signal and outputting the signal to a user.
The technical scheme of the invention is based on the simultaneous transmission of optical frequency, microwave and time signals of the femtosecond optical comb. Locking a frequency reference signal of an atomic clock on a first femtosecond optical comb, and simultaneously locking a signal of a super-stable optical module on the first femtosecond optical comb; the frequency signal of the first femtosecond optical comb is used as the frequency reference for transmitting the optical fiber time signal; the microwave signal is also an optical signal output by the optical frequency transmission receiver and is generated by the second femtosecond optical comb; the femtosecond optical comb plays an important bridge role in the optical frequency, microwave and time transmission system and method of the optical fiber.
The output of the optical fiber microwave signal is transmitted based on the optical frequency of the optical fiber and is locked on the optical frequency signal through the second femtosecond optical comb, and the output precision of the optical fiber microwave signal is transmitted based on the optical frequency; the link time delay compensation of the optical fiber time signal is compensated by the time signal generation module, the variable quantity of the link time delay is compensated in real time by the optical fiber optical frequency transmission receiver and the frequency signal output by the second femtosecond optical comb; the optical fiber optical frequency, the microwave and the time signal transmission are all based on optical frequency signals transmitted by the optical fiber optical frequency, and the phases of the optical frequency signals are related; the precision of optical fiber microwave and time signals is based on the precision of optical fiber optical frequency transmission, 1550nm laser signals are adopted for optical frequency signals at present, the transmission precision is superior to 1e-15 according to the transmission principle, and the transmission precision of the optical fiber time signals and the microwave signals is based on the optical fiber optical frequency transmission precision and the femtosecond optical comb locking stability, so that the stability of microwave and time transmission is improved.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive labor.
FIG. 1 is a schematic diagram of optical frequency transfer through an optical fiber;
fig. 2 is a schematic diagram of a system for simultaneously transmitting optical frequency, microwave and time signals of the optical fiber of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the drawings of the embodiments of the present invention, in order to better and more clearly describe the working principle of each element in the system, the connection relationship of each part in the apparatus is shown, only the relative position relationship between each element is clearly distinguished, and the restriction on the signal transmission direction, the connection sequence, and the size, the dimension, and the shape of each part structure in the element or structure cannot be formed.
When the laser is transmitted in the optical fiber, the phase difference exists in the laser output by the optical fiber due to the existence of transmission delay. Under the influence of the external environment, the optical path of the transmission optical fiber is changed, the phase of the transmission optical field is fluctuated, and the method is equivalent to additional laser frequency noise. The optical fiber optical frequency transmission technology aims to eliminate the influence of various factors on the phase of an optical field as much as possible, so that a user can obtain an optical frequency signal with stability and accuracy similar to those of a local end of an optical fiber at the far end of the optical fiber, namely, the remote transmission of the optical frequency signal is realized.
As shown in fig. 1, which is a schematic diagram of optical fiber frequency transmission, a part of laser emitted by a laser is split into a beam and injected into a transmission optical fiber, and the beam is transmitted through the optical fiber to a user end, where a part of light is provided for the user, and a part of light is reflected and returned according to an original path, and performs beat frequency with reference laser, and a photo detector is used to detect a beat frequency signal, so that a total phase change introduced when the laser is transmitted back and forth on the optical fiber can be obtained:
with the above assumptions, the phase changes introduced by the laser light as it travels back and forth over the fiber are approximately equal, as detected by the laser beat frequencyThe phase noise introduced by the single-pass optical fiber can be obtained by measuring the phase change of the laser passing through the optical fiber twice
. Generating a response by servo control
And dynamically compensating the laser phase through the acousto-optic modulator.
As shown in fig. 2, the system for simultaneously transmitting optical frequency, microwave, and time signals through an optical fiber of the present invention includes: the atomic clock comprises an atomic clock 10, a time difference measuring module 20, a time signal generating module 21, a first femtosecond optical comb 30, a second femtosecond optical comb 31, an ultra-stable optical module 40, a coding modulation module 50, a first demodulation decoding module 51, a second demodulation decoding module 52, a laser 60, a first photoelectric detector 61, an optical amplification module 62, a second photoelectric detector 63, an optical fiber optical frequency transmission transmitter 70, an optical fiber optical frequency transmission receiver 71, a first circulator 80, a second circulator 81, a first wavelength division multiplexer 82, a second wavelength division multiplexer 83, a beam splitter 85 and an optical fiber link 90.
The atomic clock 10 generates a frequency reference signal and a time reference signal to be transmitted; one path of the time reference signal is sent to the time difference measuring module 20 as a reference, and the other path of the time reference signal is sent to the code modulation module 50 as a modulation signal; the frequency reference signal is fed to a first femtosecond optical comb 30. In this embodiment, the frequency reference signal is a 10MHz signal, and the time reference signal is a 1PPS second signal.
The atomic clock is regarded as the time frequency reference source recognized in the industry, the accuracy and the stability are high, the transmission precision of the transmission system and the transmission method is high, and if other reference sources are adopted, the system and the method are not needed.
The first femtosecond optical comb 30 sends the generated repetition frequency signal to the code modulation module 50 as a carrier signal, the first femtosecond optical comb 30 simultaneously sends the output optical signal to the ultrastable light module 40, and the first femtosecond optical comb 30 is locked on a 10MHz signal of the frequency reference signal. The repetition frequency signal in this embodiment is 200MHz.
The frequency of the optical signal output by the ultrastable optical module 40 is locked to the frequency of the optical signal of a certain comb tooth output by the first femtosecond optical comb, and the optical frequency signal of the communication waveband with the wavelength of 1550.12nm is output to the optical fiber optical frequency transmission transmitter 70.
The fiber optical frequency transfer transmitter 70 outputs an optical frequency signal to the first wavelength division multiplexer 82 and receives an optical frequency signal from the first wavelength division multiplexer 82.
The first wavelength division multiplexer 82 has wavelengths of 1550.12nm and 1550.92nm, and is configured to combine optical signals from the optical fiber optical frequency transmission transmitter 70 and the first circulator 80 into one optical signal, send the optical signal to the optical fiber link 90, receive the optical signal from the optical fiber link 90, send an optical signal having a wavelength of 1550.12nm to the optical fiber optical frequency transmission transmitter 70, and send an optical signal having a wavelength of 1550.92nm to the first circulator 80.
The code modulation module 50 receives the 200MHz signal of the first femtosecond optical comb 30, the 1PPS signal of the atomic clock 10 and the real-time measurement value of the time difference measurement module 20
The coded information is modulated by Manchester coding and then sent to the laser 60, wherein the coded information is 1 second to form a frame, a code element coded by a 1PPS signal is used as a frame header, a code element coded by a real-time measured value is filled with a code element 1 after the code element coded by a real-time measured value.
The laser 60 modulates the signal from the code modulation module 50 onto laser light having a wavelength of 1550.92nm and feeds the laser light into the first circulator 80.
The first circulator 80 is configured to send the optical signal from the laser 60 to the first wavelength division multiplexer 82, and receive the optical signal from the first wavelength division multiplexer 82 to send to the first photodetector 61.
The first photodetector 61 is used to convert the optical signal from the first circulator 80 into an electrical signal, and send the electrical signal to the first demodulation and decoding module 51.
The first demodulation and decoding module 51 is used for demodulating and decoding the mixed signal from the first photodetector 61 into a 1PPS time signal, and sending the time signal to the time difference measuring module 20.
The time difference measuring module 20 measures the difference between the 1PPS time signal from the atomic clock 10 and the 1PPS time signal from the first demodulation and decoding module 51, and records the difference as
And sent to the code modulation module 50.
The wavelength channels of the second wavelength division multiplexer 83 are 1550.12nm and 1550.92nm, and are configured to combine the optical signal with the wavelength of 1550.12nm from the optical fiber optical frequency transmission receiver 71 and the optical signal with the wavelength of 1550.92nm from the second circulator 81 into one beam, send the beam to the optical fiber link 90, send the optical signal with the wavelength of 1550.12nm from the optical fiber link 90 to the optical fiber optical frequency transmission receiver 71, and send the optical signal with the wavelength of 1550.92nm to the second circulator 81.
The fiber optical frequency transfer receiver 71 combines with the fiber optical frequency transfer transmitter 70 to realize the transfer of optical frequency signals through the real-time measurement and compensation in the system, and outputs optical frequency signals, and the output optical frequency signals are respectively sent to the second femtosecond optical comb 31 and the user for use.
The second femtosecond optical comb 31 is used for converting the optical frequency signal into a 200MHz signal, one path of the signal is sent to the time signal generating module 21, and the other path of the signal is output to the user.
The second circulator 81 sends the received signal of the second wavelength division multiplexer 83 to the optical amplification module 62, and receives the optical signal from the beam splitter 85 to send to the second wavelength division multiplexer 83.
The optical amplifying module 62 amplifies the received signal from the second circulator 81 and sends the amplified signal to the beam splitter 85.
The beam splitter 85 adopts an appropriate splitting ratio according to actual conditions, and the embodiment takes a splitting ratio of 1.
The second photodetector 63 is used for converting the optical signal into an electrical signal, and sending the electrical signal to the second demodulation and decoding module 52.
The second demodulating and decoding module 52 is used for demodulating and decoding the mixed signal from the second photodetector 63 to obtain the 1PPS time signal and the real-time round-trip link time difference value, and sending the time signal to the time signal generating module 21.
The time signal generating module 21 is configured to generate a 1PPS time signal and output the time signal to a user, where the time signal generating module 21 generates a difference value according to the demodulated 1PPS time signal
Calculating the time compensation amount required by the time signal generation module 21
Compensating the 1PPS time signal and outputting the signal to a user; the variation of the optical fiber link time delay is corrected and compensated by keeping the real-time frequency phase of the frequency division transmitted by the optical fiber frequency consistent with that of the frequency division transmitted by the optical fiber frequency.
The second femtosecond optical comb 31 is used for converting optical frequency signals into 200MHz signals, and can also be other frequency signals.
The signal output by the atomic clock 10 to the first femtosecond optical comb 30 may also be an optical signal, and the first femtosecond optical comb 30 may be locked on the optical signal.
The invention realizes the simultaneous transmission of optical frequency signals, microwave frequency signals and time signals.
According to the invention, based on the simultaneous transmission of optical frequency, microwave and time signals of the femtosecond optical comb, a frequency reference signal of an atomic clock 10 is locked on the first femtosecond optical comb 30, and a signal of an ultra-stable optical module 40 is locked on the first femtosecond optical comb 30, so that the transmission of optical frequency signals is realized through an optical fiber optical frequency transmission transmitter 70, an optical fiber optical frequency transmission receiver 71, a first wavelength division multiplexer 82, an optical fiber link 90 and a second wavelength division multiplexer 83.
The frequency signal of the first femtosecond optical comb 30 is provided as a reference to the code modulation module 50, the code modulation module 50 code-modulates the time reference signal of the atomic clock 10 and the round trip link time difference value measured by the time difference measurement module 20, and transmits the time reference signal and the round trip link time difference value to the time signal generation module 21 through the laser 60, the first circulator 80, the first wavelength division multiplexer 82, the optical fiber link 90, the second circulator 81, the second wavelength division multiplexer 83, the beam splitter 85, the second photodetector 63, and the second demodulation and decoding module 52, and transmits the time signal to the time signal generation module 21 through the optical amplification module 62, the second circulator 81, the second wavelength division multiplexer 83, the optical fiber link 90, the first wavelength division multiplexer 82, the first circulator 80, the first photodetector 61, the first demodulation and decoding module 51, demodulates the time signal to the time difference measurement module 20, and generates the time signal by the time signal generation module 21, and outputs the time signal to a user, thereby realizing the transmission of the optical fiber time signal.
The optical frequency signal output by the optical frequency transfer receiver 71 is used as an optical reference and locked on the second femtosecond optical comb 31, and the microwave signal generated by the second femtosecond optical comb 31 is provided for a user to use, so that the optical fiber microwave signal transfer is realized.
The frequency reference signal of the atomic clock 10 is locked on the first femtosecond optical comb 30, and simultaneously, the signal of the super-stable optical module 40 is locked on the first femtosecond optical comb 30; the frequency signal of the first femtosecond optical comb 30 is used as a frequency reference for optical fiber time signal transmission; the microwave signal is also an optical signal output by the optical frequency transfer receiver 71, and is generated by the second femtosecond optical comb 31; the femtosecond optical comb plays an important bridge role in the optical frequency, microwave and time transmission system and method of the optical fiber.
The output of the optical fiber microwave signal is based on optical frequency transmission of the optical fiber and is locked on the optical frequency signal through the second femtosecond optical comb 31, and the output precision of the optical fiber microwave signal is based on the optical frequency transmission signal; the link time delay of the optical fiber time signal is compensated by the time signal generating module 21, the variation of the link time delay is compensated in real time through the frequency signal output by the second femtosecond optical comb 31 based on the optical fiber optical frequency transfer receiver 71; the optical fiber optical frequency, the microwave and the time signal transmission are all based on optical frequency signals transmitted by the optical fiber optical frequency, and the phases of the optical frequency signals are related; the precision of optical fiber microwave and time signals is based on the precision of optical fiber optical frequency transmission, optical frequency signals adopt more 1550nm laser signals at present, the transmission precision is superior to 1e-15 according to the transmission principle, and the transmission precision of the optical fiber time signals and the microwave signals depends on the optical fiber optical frequency transmission precision and the femtosecond optical comb locking stability, so that the microwave and time transmission stability is improved.
According to the system and the method for simultaneously transmitting the optical fiber frequency, the microwave and the time signal, disclosed by the invention, the output phase is correlated, the transmission precision depends on the stability of the femtosecond optical comb and the stability of optical fiber frequency transmission, and the microwave and time transmission stability is improved.
In the above embodiments, all or part of the implementation may be realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. The procedures or functions described in accordance with the embodiments of the application are all or partially generated when the computer program instructions are loaded and executed on a computer. The computer may be a general purpose computer, a special purpose computer, a network of computers, or other programmable device. The computer instructions may be stored on or transmitted over a computer-readable storage medium. The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that includes one or more available media. The usable medium may be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid State Disk (SSD)), among others.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (8)
1. A fiber optic frequency, microwave, time signal simultaneous delivery system, comprising:
the atomic clock is used for respectively sending the generated time reference signals to the time difference measuring module and the coding modulation module and sending the generated frequency reference signals to the first femtosecond optical comb;
the first femtosecond optical comb sends the generated repetition frequency signal to the code modulation module and sends the output optical signal to the ultrastable optical module, and the first femtosecond optical comb and the ultrastable optical module jointly convert the frequency reference signal into an optical frequency signal and send the optical frequency signal to the optical fiber optical frequency transmission transmitter;
the optical fiber optical frequency transmission transmitter outputs an optical frequency signal to the first wavelength division multiplexer;
the first circulator sends the optical signal from the first wavelength division multiplexer to the first demodulation and decoding module and sends the optical signal from the laser to the first wavelength division multiplexer;
the first wavelength division multiplexer is used for combining optical signals from the optical fiber optical frequency transmission transmitter and the first circulator into one beam and sending the beam to the optical fiber link;
the first demodulation decoding module demodulates and decodes the optical signal into a time signal and sends the time signal to the time difference measuring module;
the time difference measuring module is used for measuring the difference value of the time signals from the atomic clock and the first demodulation and decoding module and sending the difference value to the coding and modulation module;
the code modulation module is used for coding and modulating the signal of the first femtosecond optical comb, the time signal of the atomic clock and the real-time measurement value of the time difference measurement module and then sending the coded and modulated signals to the laser;
the laser modulates the signal from the code modulation module and sends the signal into the first circulator;
the second wavelength division multiplexer is used for combining the optical signals from the optical fiber optical frequency transmission receiver and the second circulator into one beam and sending the beam to the optical fiber link, and meanwhile, sending the optical signals from the optical fiber link to the optical fiber optical frequency transmission receiver and the second circulator;
the second circulator sends the received signal of the second wavelength division multiplexer to the beam splitter, and simultaneously sends the optical signal from the beam splitter to the second wavelength division multiplexer;
the optical fiber optical frequency transmission receiver is used for transmitting the output optical frequency signal to the second femtosecond optical comb and a user;
the second femtosecond optical comb converts the optical frequency signal into a microwave signal and respectively sends the microwave signal to the time signal generation module and the user;
the second demodulation decoding module demodulates and decodes the signal from the beam splitter into a time signal and a real-time round-trip link time difference value, and sends the time signal and the time difference value to the time signal generating module;
and the time signal generating module calculates the time compensation amount, compensates the time signal and outputs the time signal to a user.
2. The transfer system defined in claim 1, further comprising a first photodetector, a second photodetector and a light amplification module;
the first photoelectric detector is connected with the first circulator and the first demodulation decoding module, and is used for converting an optical signal from the first circulator into an electric signal and sending the electric signal to the first demodulation decoding module;
the second photoelectric detector is connected with the beam splitter and the second demodulation and decoding module, the light amplification module is respectively connected with the second circulator and the beam splitter, the second photoelectric detector is used for converting an optical signal into an electric signal and sending the electric signal to the second demodulation and decoding module, the light amplification module amplifies the received signal of the second circulator and then sends the amplified signal to the beam splitter, and the beam splitter outputs the optical signal to the second photoelectric detector and the second circulator according to the splitting ratio.
3. The transfer system of claim 1 wherein the first femtosecond optical comb and the meta-stable optical module together transform the frequency reference signal to λ 1 Optical frequency signal of wave band, laser emitting wavelength is lambda 2 The wavelength channel of the first wavelength division multiplexer is lambda 1 And λ 2 For passing the light from the fiber-optic frequency transmitter at a wavelength λ 1 And the optical signal from the first circulator has a wavelength lambda 2 The optical signals are combined into a beam and sent into the optical fiber link, and simultaneously the optical signals from the optical fiber link are received, and the wavelength from the optical fiber optical frequency transmission receiver is lambda 1 Sending the optical signal into an optical fiber optical frequency transmission transmitter to transmit the optical signal with the wavelength of lambda 2 Is fed into the first circulator.
4. The delivery system of claim 1, wherein the time signal generation module is configured to generate a 1PPS time signal based on a difference between the demodulated 1PPS time signal
Calculating the time compensation amount required by the time signal generation module
And compensating the 1PPS time signal and outputting the signal to a user.
5. A method for simultaneously transmitting optical frequency, microwave and time signals of optical fibers, which is used for realizing the transmission system as claimed in any one of claims 1-4, and comprises the following steps:
generating a time reference signal and a frequency reference signal by an atomic clock;
one path of the time reference signal is sent to a time difference measuring module to be used as a reference, and the other path of the time reference signal is sent to a code modulation module to be used as a modulation signal; sending the generated frequency reference signal to a first femtosecond optical comb;
sending a repetition frequency signal generated by the first femtosecond optical comb into the coding modulation module as a carrier signal, sending an optical signal output by the first femtosecond optical comb to the ultrastable optical module, and converting a frequency reference signal into lambda 1 And sending the optical frequency signal to an optical fiber optical frequency transmission transmitter;
sending an optical frequency signal output by an optical fiber optical frequency transmission transmitter and an optical signal from a laser to a first wavelength division multiplexer, sending the optical signal to a first demodulation and decoding module by the first wavelength division multiplexer, combining the optical signals from the optical fiber optical frequency transmission transmitter and a first circulator into one beam, and sending the beam into an optical fiber link;
the first demodulation decoding module is used for demodulating and decoding the optical signal into a time signal, the time signal is sent to the time difference measuring module, the difference value between the time signal from the atomic clock and the time signal of the first demodulation decoding module is measured and sent to the coding modulation module;
a signal of the first femtosecond optical comb, a time signal of an atomic clock and a real-time measured value of the time difference measuring module are coded and modulated by a coding modulation module and then are sent to the laser;
the laser modulates the signal from the code modulation module on the laser with fixed wavelength and sends the laser into the first circulator;
combining the optical signal from the optical fiber optical frequency transmission receiver and the optical signal of the second circulator into a beam by a second wavelength division multiplexer, and sending the optical signal into the optical fiber optical frequency transmission receiver and the second circulator;
sending the received signal of the second wavelength division multiplexer to the beam splitter through the second circulator, and sending the optical signal from the beam splitter to the second wavelength division multiplexer;
the optical fiber optical frequency transmission receiver sends the output optical frequency signal to a second femtosecond optical comb and a user, the second femtosecond optical comb converts the optical frequency signal into a microwave signal, one path of the microwave signal is sent to the time signal generation module, and the other path of the microwave signal is output to the user;
and demodulating and decoding the signal from the beam splitter into a time signal and a real-time round-trip link time difference value through a second demodulation and decoding module, sending the time signal to the time signal generation module to calculate a time compensation amount according to the demodulated time signal difference value, compensating the time signal and outputting the time signal to a user.
6. The transfer method of claim 5, wherein the optical signal from the first circulator is converted into an electrical signal by the first photodetector and sent to the first demodulation and decoding module; the second photoelectric detector converts the optical signal into an electric signal and sends the electric signal to the second demodulation and decoding module, the optical amplification module amplifies the received signal of the second circulator and sends the amplified signal to the beam splitter, and the optical signal is output to the second photoelectric detector and the second circulator according to the beam splitting ratio.
7. The method of claim 5Characterized in that the first femtosecond optical comb and the ultrastable optical module jointly convert the frequency reference signal into lambda 1 Optical frequency signal of wave band, laser emitting wavelength is lambda 2 The wavelength channel of the first wavelength division multiplexer is lambda 1 And λ 2 For passing the light from the fiber-optic frequency transmitter at a wavelength λ 1 And the optical signal from the first circulator has a wavelength lambda 2 The optical signals are combined into a beam and sent into the optical fiber link, and simultaneously the optical signals from the optical fiber link are received, and the wavelength from the optical fiber optical frequency transmission receiver is lambda 1 Sending the optical signal into an optical fiber optical frequency transmission transmitter to transmit the optical signal with the wavelength of lambda 2 Is fed into the first circulator.
8. The delivery method as claimed in claim 5, wherein the time signal generation module is configured to generate a 1PPS time signal according to a difference of the demodulated 1PPS time signal
Calculating the time compensation amount required by the time signal generation module
And compensating the 1PPS time signal and outputting the signal to a user.
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