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CN119805902A - A laser time transfer system and method based on high-speed pseudo code - Google Patents

A laser time transfer system and method based on high-speed pseudo code Download PDF

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Publication number
CN119805902A
CN119805902A CN202411972624.XA CN202411972624A CN119805902A CN 119805902 A CN119805902 A CN 119805902A CN 202411972624 A CN202411972624 A CN 202411972624A CN 119805902 A CN119805902 A CN 119805902A
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laser
frequency
optical
transfer system
laser time
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王国永
卢樟健
郑先安
吉欣
杨克元
贺玉玲
姚鑫
刘洋
徐连军
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Xian Institute of Space Radio Technology
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Xian Institute of Space Radio Technology
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
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Abstract

本发明公开了一种基于高速伪码的激光时间传递系统及方法，利用光梳实现了普通窄线宽激光器锁定到原子钟参考频率上，使光载波更稳定更准确；采用与原子钟同源的激光载波搭载高速伪码实现时间的传递，通过在FPGA内实现码片级粗延迟并使用延迟线实现优于1个码片精延迟两种方案相结合实现高精度的码相关测量。传递的高速伪码能够实现时间的传递和比对，是空间高精度原子钟比对的有效途径，满足新型原子钟时频传递比对需求，适于工业上的使用与推广。

The present invention discloses a laser time transfer system and method based on high-speed pseudo-code, which uses an optical comb to lock a common narrow-linewidth laser to an atomic clock reference frequency, making the optical carrier more stable and accurate; a laser carrier with the same source as the atomic clock is used to carry a high-speed pseudo-code to realize time transfer, and a high-precision code correlation measurement is realized by combining the two schemes of realizing a coarse delay at the chip level in an FPGA and realizing a fine delay better than 1 chip using a delay line. The transmitted high-speed pseudo-code can realize the transfer and comparison of time, which is an effective way to compare high-precision atomic clocks in space, meets the requirements of time-frequency transfer and comparison of new atomic clocks, and is suitable for industrial use and promotion.

Description

Laser time transfer system and method based on high-speed pseudo code
Technical Field
The invention belongs to the field of time frequency, and particularly relates to a laser time transfer system and method based on high-speed pseudo codes.
Background
In recent years, the frequency stability and uncertainty of the novel atomic clock are greatly improved, the second-level frequency stability of the microwave atomic clock reaches 10 -13 orders of magnitude, the day frequency stability reaches 10 -16 orders of magnitude, and the integrating sphere atomic clock is carried in a Chinese space station.
The second-order frequency stability of the optical atomic clock reaches 10 -15 orders of magnitude, and the frequency stability and uncertainty reach 10 -18 orders of magnitude. The traditional space time-frequency transmission link is generally a microwave time-frequency transmission link and a time transmission link based on laser pulse flight time measurement, the additional instability of the second-level time-frequency transmission is 10 -11～10-12 orders of magnitude, the additional instability of the natural time-frequency transmission is 10 -15～10-16 orders of magnitude, and the requirement of novel atomic clock time-frequency transmission comparison cannot be met.
Disclosure of Invention
The invention aims to provide a laser time transfer system and method based on high-speed pseudo codes, which are used for solving the problems that the short-term precision of time-frequency transfer of a space time-frequency transfer link in the prior art is insufficient and the time-frequency transfer comparison requirement of a novel atomic clock cannot be met.
In order to solve the technical problems, the invention adopts the following technical scheme:
The laser time transfer system based on the high-speed pseudo code comprises a laser time-frequency transfer system, wherein the laser time-frequency transfer system comprises an atomic clock, an optical comb frequency synthesis unit, two narrow linewidth lasers, two modulation modules, an amplifier, a digital signal processing unit, two optical phase-locked loops, an acousto-optic frequency shifter, two groups of delay lines, a coherent receiving module and a laser receiving and transmitting terminal;
the atomic clock comprises a plurality of microwave atomic clocks and optical clocks;
the optical comb frequency comprehensive unit comprises an optical comb, an optical comb locking unit and an optical generating microwave unit;
The optical comb locking unit comprises a photoelectric detector, a mixer, a loop filter, a voltage-controlled crystal oscillator and an acousto-optic frequency shifter;
the digital signal processing unit comprises an FPGA chip, a frequency integrated circuit and an AD;
The coherent receiving module comprises a 90-degree optical mixer and two balance detectors;
The laser time-frequency transmission systems are two groups of first laser time-frequency transmission systems and second laser time-frequency transmission systems which are respectively configured on different satellites, and the first laser time-frequency transmission systems and the second laser time-frequency transmission systems are symmetrical in structure and identical in function.
The invention also has the following characteristics:
Further, the wavelength difference between the first laser time-frequency transmission system and the second laser time-frequency transmission system is more than or equal to 0.8nm.
Further, the sampling rate of the AD is more than or equal to twice the code rate;
The FPGA chip comprises a high-speed data transmission interface.
The laser time transmission method based on the high-speed pseudo code is based on the laser time transmission system based on the high-speed pseudo code, and comprises the following steps of:
Step 1, for a first laser time-frequency transmission system, locking an optical comb of an optical comb frequency synthesis unit onto an atomic clock;
Step 2, for a first laser time-frequency transmission system, locking a narrow linewidth laser to an optical comb of an optical comb frequency synthesis unit;
Step 3, the first laser time-frequency transmission system generates a clock for generating pseudo codes and a clock for AD sampling through the optical comb frequency synthesis unit, generates the pseudo codes in multiple paths in parallel in the FPGA chip, modulates data on the pseudo codes to generate baseband signals, and outputs the multiple paths of baseband signals to the modulation module after parallel-serial conversion, and the modulation module modulates and amplifies the signals and then sends the signals to the laser receiving and transmitting terminal;
Step4, obtaining error signals of local laser and received laser by using two branch signals output by a coherent receiving module of the first laser time-frequency transmission system, inputting the error signals into two optical phase-locked loops, and realizing optical carrier synchronization by the two-stage phase-locked loops;
Step 5, the received light signal output by the laser receiving and transmitting terminal of the first laser time-frequency transmission system and the local laser signal output by the modulation module and delayed by the delay line are connected to the coherent receiving module, so as to complete coherent receiving and data demodulation;
Step 6, the digital signal processing unit of the first laser time-frequency transmission system is used for carrying out the chip-level multipath parallel code correlation processing, and the pseudo code signal output by the digital signal processing unit is delayed through a delay line to realize code synchronization;
step 7, the same operation as the first laser time-frequency transmission system in the steps 1-6 is adopted for the second laser time-frequency transmission system;
And 8, collecting a one-way time delay measured value from the first laser time-frequency transmission system to the second laser time-frequency transmission system and a one-way time delay measured value from the second laser time-frequency transmission system to the first laser time-frequency transmission system, calculating to obtain clock differences of the two atomic clocks, and finishing comparison of the two atomic clocks.
Further, step 2 comprises the following sub-steps:
Step 21, an optical frequency comb signal in an optical comb frequency synthesis unit of a first laser time-frequency transmission system and an optical frequency signal output by a narrow linewidth laser are connected to a photoelectric detector to obtain a radio frequency signal;
Step 22, the radio frequency signals are connected into a mixer together with the output signals of the atomic clock after frequency division, and the mixed signals are connected into a loop filter;
step 23, the signal output by the loop filter is connected to the voltage-controlled crystal oscillator, and the output signal of the voltage-controlled crystal oscillator is connected to the acousto-optic frequency shifter;
and step 24, adjusting parameters of a loop filter, and locking the narrow linewidth laser of the first laser time-frequency transmission system on an optical comb of the optical comb frequency synthesis unit after the loop is stable.
Further, step 3 comprises the following sub-steps:
Step 31, generating a pseudo code generating clock and an AD sampling clock by using an optical comb signal by using an optical generation microwave module in an optical comb frequency synthesis unit;
Step 32, the frequency synthesis circuit in the digital signal processing unit divides the clock generating the pseudo code into clocks which can be used by the FPGA chip in the digital signal processing unit, takes the clocks as reference, drives multiple paths of parallel generation of the pseudo code in the FPGA chip, modulates data on the pseudo code and generates a baseband signal;
Step 33, performing parallel-to-serial conversion on the generated multipath baseband signals in the FPGA chip, and outputting the baseband signals through a high-speed interface of the FPGA chip;
And step 34, the baseband signal is sent to a modulation module, modulated and amplified by the modulation module, modulated on light, amplified and sent to a laser receiving and transmitting terminal.
Further, in step 4, two branch signals of the coherent receiving module are respectively generated by two balance detectors inside the coherent receiving module;
the piezoelectric ceramic port of the narrow linewidth laser is adjusted by one optical phase-locked loop, so that the large-range slow tuning of the laser signal is realized, and meanwhile, the small-range fast tuning of the laser signal is realized by the other optical phase-locked loop, so that the optical carrier synchronization is finally realized.
In step 5, the optical signal output by the laser receiving and transmitting terminal and the local laser signal output by the modulator and delayed by the delay line are connected to a 90-degree optical mixer in the coherent receiving module;
the 90-degree optical mixer outputs four paths of optical signals of 0 degree, 90 degree, 180 degree and 270 degree;
wherein, 0 DEG and 180 DEG optical signals are connected into one balance detector, and 90 DEG and 270 DEG optical signals are connected into the other balance detector, thus realizing coherent receiving and data demodulation.
In step 6, the output signal of the coherent receiving module of the first laser time-frequency transmission system enters the digital signal processing unit to perform chip-level multipath parallel code correlation processing, and then two groups of delay lines are used for respectively delaying pseudo code signals output by the digital signal processing unit to realize code synchronization;
The two groups of delay lines are divided into an optical delay line and an electric delay line, the optical delay line delays an optical signal output by the modulation module, and the electric delay line delays an electric signal output by the digital signal processing unit.
In step 8, when the digital signal processing units of the first laser time-frequency transmission system and the second laser time-frequency transmission system find the maximum correlation peak value, adding the corresponding delay adjustment quantity of the chip level in the FPGA chip and the adjustment quantity of the delay line, so as to obtain the unidirectional delay value from the first laser time-frequency transmission system to the second laser time-frequency transmission system and the unidirectional delay value from the second laser time-frequency transmission system to the first laser time-frequency transmission system;
Then, according to the measured one-way time delay value delta T AB from the first laser time-frequency transmission system to the second laser time-frequency transmission system and the measured one-way time delay value delta T BA from the second laser time-frequency transmission system to the first laser time-frequency transmission, calculating the clock difference delta T of the two atomic clocks by using the following formula:
ΔT=(ΔTBA-ΔTAB)/2-ΔTL
where Δt L represents the error value of the link non-reciprocity error and the device delay error.
Compared with the prior art, the invention has the following technical effects:
The laser time transmission system and the method based on the high-speed pseudo code realize that a common narrow linewidth laser is locked to the atomic clock reference frequency by utilizing an optical comb, so that an optical carrier wave is more stable and accurate, realize time transmission by adopting a laser carrier wave carrying the high-speed pseudo code (the code rate is more than or equal to 1 Gcps) which is homologous to the atomic clock, and realize code correlation measurement with high precision by combining two schemes of realizing chip-level coarse delay in an FPGA and realizing fine delay superior to 1 chip by using a delay line. The transmitted high-speed pseudo code can realize time transmission and comparison, is an effective way for space high-precision atomic clock comparison, meets the time-frequency transmission comparison requirement of a novel atomic clock, and is suitable for industrial use and popularization.
Drawings
FIG. 1 is a block diagram of a laser time transfer system based on high speed pseudocode in one embodiment of the invention.
Detailed Description
All the components in the present invention are known in the art unless otherwise specified. For example, a 90 ° optical mixer is used as a known conventional 90 ° optical mixer.
All operations in the present invention, unless specified otherwise, all employ methods known in the art. For example, in step 24, the loop filter parameters are adjusted using methods known in the art.
The following specific embodiments of the present application are provided, and it should be noted that the present application is not limited to the following specific embodiments, and all equivalent changes made on the basis of the technical scheme of the present application fall within the protection scope of the present application.
The laser time transfer system based on the high-speed pseudo code comprises a laser time-frequency transfer system, wherein the laser time-frequency transfer system comprises an atomic clock, an optical comb frequency synthesis unit, two narrow linewidth lasers, two modulation modules, an amplifier, a digital signal processing unit, two optical phase-locked loops, an acousto-optic frequency shifter, two groups of delay lines, a coherent receiving module and a laser receiving and transmitting terminal;
As shown in fig. 1, the first laser time-frequency transmission system includes an atomic clock 1, an optical comb frequency synthesis unit 1, a narrow linewidth laser 1, a modulation module 1, an amplifier 1, a digital signal processing unit 1, an optical phase-locked loop 2, a narrow linewidth laser 2, an acousto-optic frequency shifter 1, a modulation module 2, a delay line 1, a delay line 2, a coherent receiving module 1 and a laser receiving and transmitting terminal 1;
The second laser time-frequency transmission system comprises an atomic clock 2, an optical comb frequency synthesis unit 2, a narrow linewidth laser 3, a modulation module 3, an amplifier 2, a digital signal processing unit 2, an optical phase-locked loop 3, an optical phase-locked loop 4, a narrow linewidth laser 4, an acousto-optic frequency shifter 2, a modulation module 4, a delay line 3, a delay line 4, a coherent receiving module 2 and a laser receiving and transmitting terminal 2.
It should be noted that, the components in the laser time-frequency transmission system and the connection manner between the components are all known in the prior art, and those skilled in the art know how to connect the components, and the connection relationship between the components does not belong to the content discussed in this embodiment, and will not be described again.
The laser time-frequency transmission system is mainly used for completing the functions of modulation and demodulation, transmission and reception and signal processing, and the working principle of the laser time-frequency transmission system is further described below by combining specific components.
The atomic clock comprises various microwave atomic clocks and optical clocks, and is used for providing a frequency reference source for a laser time-frequency transmission system, wherein the atomic clock comprises common microwave atomic clocks such as a hydrogen clock, a cesium clock, a rubidium clock, a mercury ion clock, an integrating sphere clock and the like according to conventional selection, and can also comprise optical atomic clocks such as a strontium atomic optical clock, an aluminum ion optical clock, a calcium ion optical clock and the like, so as to provide a frequency reference source for the laser time-frequency transmission system.
The optical comb frequency synthesis unit comprises an optical comb, an optical comb locking unit and an optical generating microwave unit, wherein the optical comb, the optical comb locking unit and the optical generating microwave unit are all known units in the prior art, and the connection relationship is known in the prior art and is not repeated.
The optical comb locking unit comprises a photoelectric detector, a mixer, a loop filter, a voltage-controlled crystal oscillator and an acousto-optic frequency shifter.
The optical comb locking unit is used for locking the narrow linewidth laser on the optical comb, locking the optical comb of the optical comb frequency integrating unit on the atomic clock, providing a needed high-frequency signal for the digital signal processing unit, generating a clock of pseudo codes and an AD sampling clock;
The digital signal processing unit comprises an FPGA chip, a frequency integrated circuit and an AD;
The frequency integrated circuit and the AD of the FPGA chip are all known in the prior art, and the connection relation between the FPGA chip and the frequency integrated circuit and the AD is known in the prior art.
The function of the components within the digital signal processing unit is further described in connection with the specific components below:
The FPGA chip can generate pseudo codes in multiple paths in parallel, modulate data on the pseudo codes, generate time reference signals, and output multiple paths of baseband signals to the modulation module after serial-parallel conversion;
the modulation module is used for modulating and amplifying the received signals and then sending the signals to the laser receiving and transmitting terminal;
The coherent receiving module comprises a 90-degree optical mixer and two balance detectors;
The coherent receiving module can output branch signals, can obtain error signals of local laser and received laser according to the branch signals, and can realize optical carrier synchronization through two stages of optical phase-locked loops by inputting the error signals into the two optical phase-locked loops.
The coherent receiving module can also perform coherent receiving and separating optical signals and electric signals;
Furthermore, the laser time-frequency transmission systems are two groups of first laser time-frequency transmission systems and second laser time-frequency transmission systems which are respectively configured on different satellites, and the first laser time-frequency transmission systems and the second laser time-frequency transmission systems are symmetrical in structure and identical in function.
The FPGA chip comprises a high-speed data transmission interface, and the arrangement is the optimal scheme from the aspect of actual use requirement, so that the working efficiency is improved in actual use.
The laser time transmission method based on the high-speed pseudo code is based on the laser time transmission system based on the high-speed pseudo code, and comprises the following steps of:
Step 1, for a first laser time-frequency transmission system, locking an optical comb of an optical comb frequency synthesis unit onto an atomic clock;
Step 2, for a first laser time-frequency transmission system, locking a narrow linewidth laser to an optical comb of an optical comb frequency synthesis unit;
Step 3, the first laser time-frequency transmission system generates a clock for generating pseudo codes and a clock for AD sampling through the optical comb frequency synthesis unit, generates the pseudo codes in multiple paths in parallel in the FPGA chip, modulates data on the pseudo codes to generate baseband signals, and outputs the multiple paths of baseband signals to the modulation module after parallel-serial conversion, and the modulation module modulates and amplifies the signals and then sends the signals to the laser receiving and transmitting terminal;
Step4, obtaining error signals of local laser and received laser by using two branch signals output by a coherent receiving module of the first laser time-frequency transmission system, inputting the error signals into two optical phase-locked loops, and realizing optical carrier synchronization by the two-stage phase-locked loops;
Step 5, the received light signal output by the laser receiving and transmitting terminal of the first laser time-frequency transmission system and the local laser signal output by the modulation module and delayed by the delay line are connected to the coherent receiving module, so as to complete coherent receiving and data demodulation;
Step 6, the digital signal processing unit of the first laser time-frequency transmission system is used for carrying out the chip-level multipath parallel code correlation processing, and the pseudo code signal output by the digital signal processing unit is delayed through a delay line to realize code synchronization;
step 7, the same operation as the first laser time-frequency transmission system in the steps 1-6 is adopted for the second laser time-frequency transmission system;
And 8, collecting a one-way time delay measured value from the first laser time-frequency transmission system to the second laser time-frequency transmission system and a one-way time delay measured value from the second laser time-frequency transmission system to the first laser time-frequency transmission system, calculating to obtain clock differences of the two atomic clocks, and finishing comparison of the two atomic clocks.
Further, step 2 comprises the following sub-steps:
Step 21, an optical frequency comb signal in an optical comb frequency synthesis unit of a first laser time-frequency transmission system and an optical frequency signal output by a narrow linewidth laser are connected to a photoelectric detector to obtain a radio frequency signal;
Step 22, the radio frequency signals are connected into a mixer together with the output signals of the atomic clock after frequency division, and the mixed signals are connected into a loop filter;
step 23, the signal output by the loop filter is connected to the voltage-controlled crystal oscillator, and the output signal of the voltage-controlled crystal oscillator is connected to the acousto-optic frequency shifter;
and step 24, adjusting parameters of a loop filter, and locking the narrow linewidth laser of the first laser time-frequency transmission system on an optical comb of the optical comb frequency synthesis unit after the loop is stable.
Further, step 3 comprises the following sub-steps:
Step 31, generating a pseudo code generating clock and an AD sampling clock by using an optical comb signal by using an optical generation microwave module in an optical comb frequency synthesis unit;
Step 32, the frequency synthesis circuit in the digital signal processing unit divides the clock generating the pseudo code into clocks which can be used by the FPGA chip in the digital signal processing unit, takes the clocks as reference, drives multiple paths of parallel generation of the pseudo code in the FPGA chip, modulates data on the pseudo code and generates a baseband signal;
Step 33, performing parallel-to-serial conversion on the generated multipath baseband signals in the FPGA chip, and outputting the baseband signals through a high-speed interface of the FPGA chip;
And step 34, the baseband signal is sent to a modulation module, modulated and amplified by the modulation module, modulated on light, amplified and sent to a laser receiving and transmitting terminal.
In step 4, two branch signals of the coherent receiving module are respectively generated by two balance detectors inside the coherent receiving module, wherein the output signal of the optical delay line is used as the local laser of the coherent receiving module, and the output signal of the laser receiving and transmitting terminal is used as the receiving laser of the coherent receiving module.
The piezoelectric ceramic port of the narrow linewidth laser is adjusted by an optical phase-locked loop to realize large-range slow tuning of the laser signal, and meanwhile, the other acousto-optic frequency shifter is adjusted by the optical phase-locked loop to realize small-range fast tuning of the laser signal, so that the frequency and the phase of the local laser signal are consistent with those of the received optical signal, and homodyne reception is realized.
In step 5, the optical signal output by the laser receiving and transmitting terminal and the local laser signal output by the modulator and delayed by the delay line are connected to a 90-degree optical mixer in the coherent receiving module;
the 90-degree optical mixer outputs four paths of optical signals of 0 degree, 90 degree, 180 degree and 270 degree;
wherein, 0 DEG and 180 DEG optical signals are connected into one balance detector, and 90 DEG and 270 DEG optical signals are connected into the other balance detector, thus realizing coherent receiving and data demodulation.
Further, in step 6, the delay lines are divided into two groups, namely an optical delay line and an electrical delay line, the optical delay line delays the optical signal output by the modulation module, and the electrical delay line delays the electrical signal output by the digital signal processing unit.
In step 8, when the digital signal processing units of the first laser time-frequency transmission system and the second laser time-frequency transmission system find the maximum correlation peak value, adding the corresponding delay adjustment quantity of the chip level in the FPGA chip and the adjustment quantity of the delay line, so as to obtain the unidirectional delay value from the first laser time-frequency transmission system to the second laser time-frequency transmission system and the unidirectional delay value from the second laser time-frequency transmission system to the first laser time-frequency transmission system;
Then, according to the measured one-way time delay value delta T AB from the first laser time-frequency transmission system to the second laser time-frequency transmission system and the measured one-way time delay value delta T BA from the second laser time-frequency transmission system to the first laser time-frequency transmission, calculating the clock difference delta T of the two atomic clocks by using the following formula:
ΔT=(ΔTBA-ΔTAB)/2-ΔTL
Where Δt L represents the error value of the link non-reciprocity error and the device delay error. The error values of the link non-reciprocity error and the device delay error can be obtained through calculation by a conventional method in the field.

Claims (10)

1.一种基于高速伪码的激光时间传递系统，其特征在于，包括激光时频传递系统，所述的激光时频传递系统包括原子钟、光梳频率综合单元、两个窄线宽激光器、两个调制模块、放大器、数字信号处理单元、两个光锁相环、声光移频器、两组延迟线、相干接收模块和激光收发终端；1. A laser time transfer system based on high-speed pseudo code, characterized in that it includes a laser time-frequency transfer system, wherein the laser time-frequency transfer system includes an atomic clock, an optical comb frequency synthesis unit, two narrow linewidth lasers, two modulation modules, an amplifier, a digital signal processing unit, two optical phase-locked loops, an acousto-optic frequency shifter, two groups of delay lines, a coherent receiving module and a laser transceiver terminal; 所述原子钟包括多种微波原子钟和光钟；The atomic clocks include various microwave atomic clocks and optical clocks; 所述的光梳频率综合单元包括光梳、光梳锁定单元和光生微波单元；The optical comb frequency synthesis unit comprises an optical comb, an optical comb locking unit and an optically generated microwave unit; 所述的光梳锁定单元包含光电探测器、混频器、环路滤波器、压控晶振和声光移频器；The optical comb locking unit comprises a photodetector, a mixer, a loop filter, a voltage-controlled crystal oscillator and an acousto-optic frequency shifter; 所述的数字信号处理单元包括FPGA芯片、频率综合电路和AD；The digital signal processing unit includes an FPGA chip, a frequency synthesis circuit and an AD; 所述的相干接收模块包含90°光混频器和两个平衡探测器；The coherent receiving module comprises a 90° optical mixer and two balanced detectors; 所述的激光时频传递系统有两组，分别为配置于不同卫星的第一激光时频传递系统和第二激光时频传递系统；所述的第一激光时频传递系统与第二激光时频传递系统结构对称且功能相同。The laser time-frequency transfer system has two groups, namely a first laser time-frequency transfer system and a second laser time-frequency transfer system configured on different satellites; the first laser time-frequency transfer system and the second laser time-frequency transfer system have symmetrical structures and the same functions. 2.如权利要求1所述的基于高速伪码的激光时间传递系统，其特征在于，所述的第一激光时频传递系统和第二激光时频传递系统的波长差≥0.8nm。2. The laser time transfer system based on high-speed pseudocode as described in claim 1 is characterized in that the wavelength difference between the first laser time-frequency transfer system and the second laser time-frequency transfer system is ≥0.8nm. 3.如权利要求1所述的基于高速伪码的激光时间传递系统，其特征在于，所述的AD的采样率≥两倍码速率；3. The laser time transfer system based on high-speed pseudo-code as claimed in claim 1, characterized in that the sampling rate of the AD is ≥ twice the code rate; 所述的FPGA芯片包括高速数据传输接口。The FPGA chip includes a high-speed data transmission interface. 4.一种基于高速伪码的激光时间传递方法，该方法基于权利要求1-3所述的基于高速伪码的激光时间传递系统，其特征在于，包括以下步骤：4. A laser time transfer method based on high-speed pseudo-code, the method is based on the laser time transfer system based on high-speed pseudo-code according to claims 1-3, characterized in that it comprises the following steps: 步骤1，对于第一激光时频传递系统，将光梳频率综合单元的光梳锁定到原子钟上；Step 1: for the first laser time-frequency transfer system, lock the optical comb of the optical comb frequency synthesis unit to the atomic clock; 步骤2，对于第一激光时频传递系统，将窄线宽激光器锁定到光梳频率综合单元的光梳上；Step 2: for the first laser time-frequency transfer system, lock the narrow linewidth laser to the optical comb of the optical comb frequency synthesis unit; 步骤3，令第一激光时频传递系统通过光梳频率综合单元生成产生伪码的时钟以及AD采样的时钟，在FPGA芯片中多路并行生成伪码，并在伪码上调制数据，生成基带信号，多路基带信号进行并串转换后输出至调制模块，调制模块将信号调制并放大后发送至激光收发终端；Step 3, the first laser time-frequency transmission system generates a clock for generating a pseudo code and a clock for AD sampling through an optical comb frequency synthesis unit, generates pseudo codes in parallel in multiple channels in the FPGA chip, modulates data on the pseudo codes, generates baseband signals, and outputs the multiple baseband signals to the modulation module after parallel-to-serial conversion. The modulation module modulates and amplifies the signals and sends them to the laser transceiver terminal; 步骤4，使用第一激光时频传递系统的相干接收模块输出的两个支路信号得到本地激光和接收激光的误差信号，将误差信号输入两个光锁相环，通过两级锁相环实现光载波同步；Step 4, using the two branch signals output by the coherent receiving module of the first laser time-frequency transfer system to obtain the error signal of the local laser and the receiving laser, inputting the error signal into two optical phase-locked loops, and realizing the optical carrier synchronization through the two-stage phase-locked loop; 步骤5，将第一激光时频传递系统激光收发终端输出的接收光信号和调制模块输出并经延迟线延迟后的本地激光信号均接入相干接收模块，完成相干接收和数据解调；Step 5, connecting the received optical signal output by the laser transceiver terminal of the first laser time-frequency transmission system and the local laser signal output by the modulation module and delayed by the delay line to the coherent receiving module to complete coherent reception and data demodulation; 步骤6，使用第一激光时频传递系统的数字信号处理单元进行码片级的多路并行码相关处理，并通过延迟线将数字信号处理单元输出的伪码信号进行延迟，实现码同步；Step 6, using the digital signal processing unit of the first laser time-frequency transfer system to perform chip-level multi-channel parallel code correlation processing, and delaying the pseudo code signal output by the digital signal processing unit through a delay line to achieve code synchronization; 步骤7，对第二激光时频传递系统采取步骤1-6中与第一激光时频传递系统相同的操作；Step 7, performing the same operations as those of the first laser time-frequency transfer system in steps 1-6 on the second laser time-frequency transfer system; 步骤8，收集从第一激光时频传递系统到第二激光时频传递系统的单向时延测量值和第二激光时频传递系统到第一激光时频传递系统的单向时延测量值，计算获得两个原子钟的钟差，完成两个原子钟的比对。Step 8, collect the one-way delay measurement values from the first laser time-frequency transfer system to the second laser time-frequency transfer system and the one-way delay measurement values from the second laser time-frequency transfer system to the first laser time-frequency transfer system, calculate the clock difference between the two atomic clocks, and complete the comparison of the two atomic clocks. 5.如权利要求4所述的基于高速伪码的激光时间传递方法，其特征在于，步骤2包括以下分步骤：5. The laser time transfer method based on high-speed pseudo code as claimed in claim 4, characterized in that step 2 comprises the following sub-steps: 步骤21，将第一激光时频传递系统光梳频率综合单元内部的光学频率梳信号与窄线宽激光器输出的光频信号接入光电探测器，得到射频信号；Step 21, connecting the optical frequency comb signal inside the optical comb frequency synthesis unit of the first laser time-frequency transfer system and the optical frequency signal output by the narrow linewidth laser to a photodetector to obtain a radio frequency signal; 步骤22，将射频信号分频后与原子钟的输出信号共同接入混频器，将混频后的信号接入环路滤波器；Step 22, dividing the RF signal and the output signal of the atomic clock and connecting them to a mixer, and connecting the mixed signal to a loop filter; 步骤23，将环路滤波器输出的信号接入压控晶振，并将压控晶振的输出信号接入声光移频器；Step 23, connecting the signal output by the loop filter to a voltage-controlled crystal oscillator, and connecting the output signal of the voltage-controlled crystal oscillator to an acousto-optic frequency shifter; 步骤24，调整环路滤波器参数，待环路稳定后将第一激光时频传递系统的窄线宽激光器锁定在光梳频率综合单元的光梳上。Step 24, adjust the loop filter parameters, and after the loop is stable, lock the narrow linewidth laser of the first laser time-frequency transfer system onto the optical comb of the optical comb frequency synthesis unit. 6.如权利要求5所述的基于高速伪码的激光时间传递方法，其特征在于，步骤3包括以下分步骤：6. The laser time transfer method based on high-speed pseudo code according to claim 5, characterized in that step 3 comprises the following sub-steps: 步骤31，使用光梳频率综合单元内部的光生微波模块将光梳信号生成产生伪码的时钟和AD采样的时钟；Step 31, using the optical microwave module inside the optical comb frequency synthesis unit to generate a pseudo code clock and an AD sampling clock from the optical comb signal; 步骤32，数字信号处理单元中的频率综合电路将产生伪码的时钟分频为数字信号处理单元中FPGA芯片能够使用的时钟，以该时钟为参考，在FPGA芯片内部驱动多路并行生成伪码，并在伪码上调制数据，生成基带信号；Step 32, the frequency synthesis circuit in the digital signal processing unit divides the clock for generating the pseudo code into a clock that can be used by the FPGA chip in the digital signal processing unit, and uses the clock as a reference to drive multiple channels to generate pseudo codes in parallel inside the FPGA chip, and modulates data on the pseudo codes to generate baseband signals; 步骤33，在FPGA芯片中将生成的多路基带信号进行并串转换，通过FPGA芯片的高速接口输出基带信号；Step 33, performing parallel-to-serial conversion on the generated multi-channel baseband signals in the FPGA chip, and outputting the baseband signals through the high-speed interface of the FPGA chip; 步骤34，将基带信号送到调制模块，经调制模块调制和放大后将基带信号调制到光上，调制信号经放大后发送到激光收发终端。Step 34, the baseband signal is sent to the modulation module, and after being modulated and amplified by the modulation module, the baseband signal is modulated onto light, and the modulated signal is amplified and sent to the laser transceiver terminal. 7.如权利要求5所述的基于高速伪码的激光时间传递方法，其特征在于，步骤4中，相干接收模块的两个支路信号由相干接收模块内部的两个平衡探测器分别产生；7. The laser time transfer method based on high-speed pseudo-code as claimed in claim 5, characterized in that in step 4, the two branch signals of the coherent receiving module are respectively generated by two balanced detectors inside the coherent receiving module; 采用一个光锁相环调整窄线宽激光器的压电陶瓷端口，实现对激光信号的大范围慢速调谐；同时采用另一个光锁相环调声光移频器，实现对激光信号的小范围快速调谐，最终实现光载波同步。An optical phase-locked loop is used to adjust the piezoelectric ceramic port of the narrow-linewidth laser to achieve large-range slow tuning of the laser signal; at the same time, another optical phase-locked loop is used to adjust the acousto-optic frequency shifter to achieve small-range fast tuning of the laser signal, ultimately achieving optical carrier synchronization. 8.如权利要求5所述的基于高速伪码的激光时间传递方法，其特征在于，步骤5中，将激光收发终端输出的光信号与调制器输出经延迟线延迟的本地激光信号接入相干接收模块中的90°光混频器；8. The laser time transfer method based on high-speed pseudo code as claimed in claim 5, characterized in that in step 5, the optical signal output by the laser transceiver terminal and the local laser signal output by the modulator delayed by the delay line are connected to the 90° optical mixer in the coherent receiving module; 令90°光混频器输出0°、90°、180°和270°四路光信号；The 90° optical mixer is made to output four optical signals of 0°, 90°, 180° and 270°; 其中0°和180°的光信号接入一个平衡探测器，90°、270°的光信号接入另一个平衡探测器，实现相干接收和数据解调。The optical signals at 0° and 180° are connected to a balanced detector, and the optical signals at 90° and 270° are connected to another balanced detector to achieve coherent reception and data demodulation. 9.如权利要求5所述的基于高速伪码的激光时间传递方法，其特征在于，步骤6中，使用第一激光时频传递系统的相干接收模块输出信号进入数字信号处理单元进行码片级的多路并行码相关处理，再利用两组延迟线分别将数字信号处理单元输出的伪码信号进行延迟，实现码同步；9. The laser time transfer method based on high-speed pseudo-code as claimed in claim 5, characterized in that in step 6, the coherent receiving module output signal of the first laser time-frequency transfer system is used to enter the digital signal processing unit for chip-level multi-path parallel code correlation processing, and then two groups of delay lines are used to delay the pseudo-code signals output by the digital signal processing unit respectively to achieve code synchronization; 其中，两组延迟线分为光延迟线和电延迟线，光延迟线延迟调制模块输出的光信号，电延迟线延迟数字信号处理单元输出的电信号。The two groups of delay lines are divided into optical delay lines and electrical delay lines. The optical delay lines delay the optical signal output by the modulation module, and the electrical delay lines delay the electrical signal output by the digital signal processing unit. 10.如权利要求5所述的基于高速伪码的激光时间传递方法，其特征在于，步骤8中，当第一激光时频传递系统和第二激光时频传递系统各自的数字信号处理单元找到最大相关峰值时，将对应的FPGA芯片内部码片级的时延调整量和延迟线的调整量相加，即可获得从第一激光时频传递系统到第二激光时频传递系统的单向时延值以及从第二激光时频传递系统到第一激光时频传递系统的单向时延值；10. The laser time transfer method based on high-speed pseudo-code as described in claim 5 is characterized in that, in step 8, when the respective digital signal processing units of the first laser time-frequency transfer system and the second laser time-frequency transfer system find the maximum correlation peak, the corresponding delay adjustment amount at the internal chip level of the FPGA chip and the adjustment amount of the delay line are added together to obtain the one-way delay value from the first laser time-frequency transfer system to the second laser time-frequency transfer system and the one-way delay value from the second laser time-frequency transfer system to the first laser time-frequency transfer system; 接着，根据测量的第一激光时频传递系统到第二激光时频传递系统的单向时延值ΔTAB以及第二激光时频传递系统到第一激光时频传递的单向时延测量值ΔTBA，使用下式，计算两个原子钟的钟差ΔT：Next, the clock difference ΔT between the two atomic clocks is calculated using the following formula based on the measured one-way delay ΔT AB from the first laser time-frequency transfer system to the second laser time-frequency transfer system and the measured one-way delay ΔT BA from the second laser time-frequency transfer system to the first laser time-frequency transfer system: ΔT＝(ΔTBA-ΔTAB)/2-ΔTL ΔT=(ΔT BA -ΔT AB )/2-ΔT L 其中，ΔTL表示链路非互易性误差和设备时延误差的误差值。Wherein, ΔT L represents the error value of link non-reciprocity error and device delay error.
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