A time-frequency transmission system that downloads and distributes data simultaneously at any location in the transmission optical path

Abstract

The present invention discloses a time-frequency transmission system that downloads and distributes at any position in a transmission optical path at the same time, uses an IQ mixer to obtain the transmission phase delay of an optical fiber link, and feedback controls the optical delay line to maintain the stability of the optical fiber link length, thereby realizing the stable transmission of the time-frequency synchronization signal. In addition, a time-frequency synchronization signal distribution module is designed using a dual circulator structure to realize the download of the time-frequency synchronization signal at any node in the optical fiber link, thereby meeting the clock synchronization requirements of modern electronic equipment for collaborative work between multiple devices within a long distance.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical fiber communication and time-frequency synchronization, and in particular relates to a time-frequency transmission system for simultaneous downloading and distribution at any position in a transmission optical path over a long distance. Background Art

[0002] High synchronization is a core requirement of modern electronic equipment. In timing systems, distributed measurement and control systems, integrated telepathy technology and network systems, the accuracy and stability of time and frequency synchronization will directly affect the core performance of the system. In order to ensure the stability of electronic equipment operation, atomic clocks are widely used in electronic equipment due to their high stability. However, long-term frequency stability drift will occur between two or more atomic clocks working independently for a long time, and multiple atomic clocks will also greatly increase the system cost, limiting its application scenarios. Therefore, the time-frequency synchronization signal is distributed to each target end through the time-frequency transmission system with high quality, low loss and indiscriminate distribution to complete the time-frequency synchronization of the entire system, which will greatly improve the accuracy and level of people's observation of targets such as the earth and deep space, and contribute to national defense and the national economy. Summary of the invention

[0003] In order to solve the above technical problems, the present invention proposes a time-frequency transmission system for simultaneous downloading and distribution at any position in the transmission optical path, so as to solve the problems existing in the above prior art.

[0004] To achieve the above object, the present invention provides a time-frequency transmission system for simultaneous downloading and distribution at any position in a transmission optical path, comprising:

[0005] A local transmission optical path stabilization module and a remote time-frequency synchronization signal downloading module, wherein the local transmission optical path stabilization module and the remote time-frequency synchronization signal downloading module are connected via an optical fiber;

[0006] The local transmission optical path stabilization module includes a laser, a Mach-Zehnder intensity modulator, a first optical circulator, a second optical circulator, a first photoelectric converter, a first electric amplifier, a first bandpass filter, an IQ mixer, a microwave power splitter, a first low-pass filter, a second low-pass filter, an ARM processor, an optical delay line, a long optical fiber, and an optical fiber amplifier;

[0007] Wherein the laser and the microwave power divider are both connected to the Mach-Zehnder intensity modulator to perform optical carrier modulation on the time-frequency synchronization signal, the Mach-Zehnder intensity modulator, the first optical circulator, the optical delay line, and the long optical fiber are connected in sequence, the first optical circulator is connected in sequence to the first photoelectric converter, the first electrical amplifier, and the first bandpass filter, the microwave power divider is connected to the local oscillator port of the IQ mixer, and the first bandpass filter is connected to the radio frequency port of the IQ mixer; the I-channel output end and the Q-channel output end of the IQ mixer are respectively connected to the first low-pass filter and the second low-pass filter, the first low-pass filter and the second low-pass filter are connected to the ARM processor, and the ARM processor is connected to the optical delay line; the ARM processor is used to feedback control the optical delay line according to the transmission optical path phase delay jitter of the electrical signal input to the ARM processor;

[0008] The second port and the third port of the second optical circulator are connected via an optical fiber amplifier;

[0009] The remote end time and frequency synchronization signal download module includes a third optical circulator, a first optical coupler, a fourth optical circulator, a second optical coupler, a second photoelectric converter, a second electrical amplifier, a second band-pass filter, a third photoelectric converter, a third electrical amplifier, a third band-pass filter, a first mixer, and a fourth band-pass filter;

[0010] The end of the long optical fiber is connected to the third optical circulator and the first optical coupler in sequence, the first output end of the first optical coupler is connected to the fourth optical circulator, and the fourth optical circulator is connected to the second optical circulator; the second optical circulator is connected to the second optical coupler, and the first output end of the second optical coupler is connected to the third optical circulator; the second output end of the first optical coupler is connected to the second photoelectric converter, the second electrical amplifier and the second band-pass filter in sequence, and the second output end of the second optical coupler is connected to the third photoelectric converter, the third electrical amplifier and the third band-pass filter in sequence; the second band-pass filter and the third band-pass filter are both connected to the first mixer, and the first mixer is connected to the fourth band-pass filter to output a time-frequency synchronization signal.

[0011] Optionally, the remote-end time-frequency synchronization signal download module is inserted at any position on the long optical fiber.

[0012] Optionally, the remote-end time-frequency synchronization signal download module is inserted at several positions on the long optical fiber.

[0013] Optionally, the optical fiber amplifier is an erbium-doped optical fiber amplifier.

[0014] Optionally, in the local transmission optical path stabilization module, the forward propagation of the optical signal after the time-frequency synchronization signal is modulated by the optical carrier passes through the first optical circulator, the optical delay line, the long optical fiber, the third optical circulator, the first optical coupler, the fourth optical circulator and the second optical circulator in sequence, and the propagation direction of the optical signal is adjusted by the second optical circulator.

[0015] Optionally, in the local transmission optical path stabilization module, the backward propagation of the optical signal after the time-frequency synchronization signal is modulated by the optical carrier passes through the second optical circulator, the second optical coupler, the third optical circulator, the long optical fiber, the optical delay line and the first optical circulator in sequence, and is successively photoelectrically converted, amplified and filtered through the first photoelectric converter, the first electrical amplifier and the first bandpass filter to be transmitted to the RF port of the IQ mixer.

[0016] Optionally, the first mixer performs frequency combining processing in frequency mixing.

[0017] Compared with the prior art, the present invention has the following advantages and technical effects:

[0018] (1) The time-frequency transmission system implemented by the present invention for simultaneous downloading and distribution at any position in the transmission optical path is not affected by the nonlinearity of the device itself.

[0019] (2) The present invention uses an IQ mixer to obtain the phase delay of the transmission optical path, and can use the I-path and Q-path outputs of the IQ mixer to accurately solve the current signal phase difference, effectively avoiding the angle resolution error caused by optical power jitter during the transmission process.

[0020] (3) The present invention can realize the download of time-frequency synchronization signals at any node in the optical fiber link, and the time-frequency synchronization signal downloading modules at each remote end are independent of each other without crosstalk, and the download of the time-frequency synchronization signal is independent of the stable control process of the transmission optical path, so the system has high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0022] Figure 1 A schematic diagram of the structure of a time-frequency transmission system for simultaneous downloading and distribution at any location in a transmission optical path according to an embodiment of the present invention;

[0023] Among them, 1. laser, 2. Mach-Zehnder intensity modulator, 3. first optical circulator, 4. second optical circulator, 5. first photoelectric converter, 6. first electric amplifier, 7. first bandpass filter, 8. IQ mixer, 9. microwave power divider, 10. first low-pass filter, 11. second low-pass filter, 12. ARM processor, 13. optical delay line, 14. long optical fiber, 15. erbium-doped fiber amplifier, 16. third optical circulator, 17. first optical coupler, 18. fourth optical circulator, 19. second optical coupler, 20. second photoelectric converter, 21. second electric amplifier, 22. second bandpass filter, 23. third photoelectric converter, 24. third electric amplifier, 25. third bandpass filter, 26. first mixer, 27. fourth bandpass filter. DETAILED DESCRIPTION

[0024] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0026] like Figure 1 As shown, the present invention provides a time-frequency transmission system that downloads and distributes at any position in the transmission optical path at the same time, uses an IQ mixer 8 to obtain the transmission phase delay of the optical fiber link, and feedback controls the optical delay line 13 to maintain the stability of the optical fiber link length, thereby realizing the stable transmission of the time-frequency synchronization signal. In addition, a dual circulator structure is used to design a time-frequency synchronization signal distribution module to realize the download of the time-frequency synchronization signal at any node in the optical fiber link, thereby meeting the clock synchronization requirements of modern electronic devices for the coordinated work of multiple devices within a long distance. The optical fiber link is close to Figure 1 It is represented as a long optical fiber 4.

[0027] The time-frequency transmission system for simultaneous downloading and distribution at any position in the transmission optical path includes a local transmission optical path stabilization module and a remote time-frequency synchronization signal downloading module connected through optical fiber on the optical fiber link.

[0028] The local transmission optical path stabilization module is responsible for completing the control of the phase delay of the transmission optical path, and the remote end is responsible for downloading the time-frequency synchronization signal at any position of the transmission optical path.

[0029] The remote-end time-frequency synchronization signal download module can be inserted at any position of the transmission optical path, i.e., the long optical fiber 14, and supports simultaneous downloading at any multiple positions.

[0030] Specifically, the local transmission optical path stabilization module includes the following optical and electronic devices: a laser 1, a Mach-Zehnder intensity modulator 2, a first optical circulator 3, a second optical circulator 4, a first photoelectric converter 5, a first electrical amplifier 6, a first bandpass filter 7, an IQ mixer 8, a microwave power divider 9, a first low-pass filter 10, a second low-pass filter 11, an ARM processor 12, an optical delay line 13, a long optical fiber 14, and an erbium-doped fiber amplifier 15.

[0031] Among them, the time-frequency synchronization signal is divided into two paths through the microwave power divider 9, wherein one output end of the microwave power divider 9 is connected to the microwave input end of the Mach-Zehnder intensity modulator 2; the output end of the laser 1 is connected to the optical output end of the Mach-Zehnder intensity modulator 2, the Mach-Zehnder intensity modulator 2 modulates one path of the time-frequency synchronization signal onto an optical carrier or an optical signal, and outputs it through the output end of the Mach-Zehnder intensity modulator 2, the output end of the Mach-Zehnder intensity modulator 2 is connected to the first port of the first optical circulator 3, and the second port of the first optical circulator 3 is connected to the optical delay line 13, the optical delay line 13 is connected to the long optical fiber 14, and the optical signal is transmitted to the long optical fiber 14 for forward light transmission; wherein the forward and backward directions are relative to the laser 1, and on the optical path, the light transmission direction gradually away from the local end is the forward direction, and the light transmission direction gradually approaching the local end is the backward direction.

[0032] The forward optical signal is transmitted in the long optical fiber 14 to the second optical circulator 4, inputted at the first port of the second optical circulator 4, and outputted at the second port of the second optical circulator 4. An erbium-doped fiber amplifier 15 is connected between the second port and the third port of the second optical circulator 4. The optical signal outputted from the second port of the second optical circulator 4 is amplified by the erbium-doped fiber amplifier 15, and retransmitted to the third port of the second optical circulator 4, and outputted at the first port of the second optical circulator 4, thereby starting the transmission of the backward light.

[0033] The backward optical signal is transmitted to the long optical fiber 14, and returns to the second port of the first optical circulator 3 through the long optical fiber 14 and the optical delay line 13, and is output at the third port of the first optical circulator 3. The third port of the first optical circulator 3 is connected to the input end of the first photoelectric converter 5. The first photoelectric converter 5 converts the optical signal into an electrical signal. The output end of the first photoelectric converter 5 is connected to the input end of the first electrical amplifier 6. The output end of the first electrical amplifier 6 is connected to the input end of the first bandpass filter 7. The output end of the first bandpass filter 7 is connected to the radio frequency port of the IQ mixer 8; the other output end of the microwave power divider 9 is connected to the local oscillator port of the IQ mixer 8. The IQ mixer 8 converts the time-frequency synchronization signal input from the local oscillator port and the carrier signal input from the radio frequency port into a frequency synchronization signal. The backward optically converted electrical signal with a phase delay in the transmission optical path is mixed, and the mixed signal is output through the output port. The output port of the IQ mixer 8 includes an I-channel output end and a Q-channel output end, which are respectively connected to a first low-pass filter 10 and a second low-pass filter 11. The output ends of the first low-pass filter 10 and the second low-pass filter 11 are connected to an ARM processor 12. The mixed signal is filtered by the first low-pass filter 10 and the second low-pass filter 11, respectively, to obtain a corresponding DC component signal, which is input into the ARM processor 12. The ARM processor 12 analyzes and processes the above DC component signal, and the output end of the ARM processor 12 is connected to an optical delay line 13 through a control line to feedback control the optical delay line 13.

[0034] Specifically, the remote-end time and frequency synchronization signal download module includes the following optical and electronic devices: a third optical circulator 16, a first optical coupler 17, a fourth optical circulator 18, a second optical coupler 19, a second photoelectric converter 20, a second electrical amplifier 21, a second bandpass filter 22, a third photoelectric converter 23, a third electrical amplifier 24, a third bandpass filter 25, a first mixer 26, and a fourth bandpass filter 27.

[0035] Wherein, during the transmission of the forward optical signal, the transmission end of the long optical fiber 14 is connected to the first port of the third optical circulator 16 to transmit the forward optical signal to the first port of the third optical circulator 16, and outputs it through the second port of the third optical circulator 16, the second port of the third optical circulator 16 is connected to the input end of the first optical coupler 17, the first output end of the first optical coupler 17 is connected to the first port of the fourth optical circulator 18, and the forward optical signal is output through the second port of the fourth optical circulator 18, the second port of the fourth optical circulator 18 is connected to the first port of the second optical circulator 4 to input the forward optical signal into the first port of the second optical circulator 4, under the adjustment of the optical signal by the second optical circulator 4 in the above-mentioned local end transmission optical path stabilization module, the optical signal is output at the first port of the second optical circulator 4, and the transmission of the backward light starts;

[0036] During the backward optical transmission process, the first port of the second optical circulator 4 is connected to the second port of the fourth optical circulator 18, and the backward optical signal is transmitted back to the first port of the second optical circulator 4. The third port of the second optical circulator 4 is connected to the input end of the second optical coupler 19. The first output end of the second optical coupler 19 is connected to the third port of the third optical circulator 16, and the backward optical signal is transmitted back to the third optical circulator 16, and transmitted through the first port of the third optical circulator 16 to the long optical fiber 14, so that the backward optical signal is transmitted back to the first optical circulator 3;

[0037] The second output end of the first optical coupler 17 is connected to the input end of the second photoelectric converter 20, the output end of the second photoelectric converter 20 is connected to the input end of the second electrical amplifier 21, and the output end of the second electrical amplifier 21 is connected to the input end of the first mixer 26 through the second bandpass filter 22;

[0038] The second output end of the second optical coupler 19 is connected to the input end of the third photoelectric converter 23, the output end of the third photoelectric converter 23 is connected to the input end of the third electrical amplifier 24, and the output end of the third electrical amplifier 24 is connected to the other input end of the first mixer 26 through the third bandpass filter 25;

[0039] The first mixer 26 performs mixing processing on the electrical signals after the above two-way photoelectric conversion, amplification and filtering, and filters the mixed electrical signals through the fourth bandpass filter 27 to obtain the final output time-frequency synchronization signal.

[0040] like Figure 1 As shown, the above technical solution is described in detail, specifically:

[0041] The time-frequency transmission system for simultaneous downloading and distribution at any position in a transmission optical path provided by the present invention is composed of a local transmission optical path stabilization module and a remote time-frequency synchronization signal downloading module.

[0042] The local transmission optical path stabilization module includes the following optical and electronic devices: a laser 1, a Mach-Zehnder intensity modulator 2, a first optical circulator 3, a second optical circulator 4, a first photoelectric converter 5, a first electrical amplifier 6, a first bandpass filter 7, an IQ mixer 8, a microwave power divider 9, a first low-pass filter 10, a second low-pass filter 11, an ARM processor 12, an optical delay line 13, a long optical fiber 14, and an erbium-doped fiber amplifier 15.

[0043] The above optical and electronic devices are used to form a time-frequency transmission optical path stabilization module. The time-frequency synchronization signal is first divided into two paths through a microwave power divider 9, one of which enters the local oscillator port of the IQ mixer 8; the other path modulates the time-frequency synchronization signal onto an optical carrier through a Mach-Zehnder intensity modulator 2, and then couples into the long optical fiber 14 through the first optical circulator 3 to start the transmission of the forward light. After the time-frequency synchronization signal is transmitted along the long optical fiber 14 to the second optical circulator 4 at the end, the optical signal is amplified by the erbium-doped fiber amplifier 15, and then returns to the long optical fiber 14 through the second optical circulator 4 again to start the transmission of the backward light. After the backward light reaches the first optical circulator 3, it is photoelectrically converted, filtered, and amplified by the first photoelectric converter 5, the first electrical amplifier 6, and the first bandpass filter 7, and then enters the radio frequency port of the IQ mixer 8. After the IQ mixer 8 mixes the backward optical signal carrying the phase delay of the transmission optical path with the time-frequency synchronization signal, the first low-pass filter 10 and the second low-pass filter 11 are used to filter the output signal, and the DC component is taken to connect to the ARM processor 12. According to the voltage value of the output signal of the IQ mixer 8 collected, the ARM processor 12 averages the results of continuous multiple sampling of the IQ channel voltage value, divides them, and takes the inverse tangent transformation to obtain the current transmission optical path phase delay jitter. Then, the ARM processor 12 subtracts the set optical path phase delay fixed value from the calculated optical path phase delay jitter value to obtain the current optical path phase delay error, and uses the PID control algorithm to feedback control the optical delay line 13 according to the current optical path phase delay error to maintain the stability of the transmission optical path length.

[0044] The remote-end time-frequency synchronization signal download module includes the following optical and electronic devices: a third optical circulator 16, a first optical coupler 17, a fourth optical circulator 18, a second optical coupler 19, a second photoelectric converter 20, a second electrical amplifier 21, a second band-pass filter 22, a third photoelectric converter 23, a third electrical amplifier 24, a third band-pass filter 25, a first mixer 26, and a fourth band-pass filter 27.

[0045] The above optical and electronic devices are used to form a time-frequency synchronization signal download module. The forward transmission light reaches the first optical coupler 17 through the third optical circulator 16 and is divided into two paths. One path is completed by the second photoelectric converter 20, the second electrical amplifier 21, and the second bandpass filter 22 to complete the photoelectric conversion, filtering, and amplification before entering the intermediate frequency end of the first mixer 26; the other path continues to be transmitted along the long optical fiber 14 after passing through the fourth optical circulator 18.

[0046] After reaching the second optical circulator 4, it returns to the transmission optical path and continues to be transmitted as backward light. After passing through the fourth optical circulator 18 and the second optical coupler 19, the backward light is divided into two paths, one of which passes through the third optical circulator 16 and continues to be transmitted along the optical fiber to complete the backward light transmission process and participate in the feedback process at the local end; the other path is completed by the third photoelectric converter 23, the third electrical amplifier 24, and the third bandpass filter 25. After completing photoelectric conversion, filtering, and amplification, it enters the first mixer 26, the local oscillator end and the intermediate frequency end signal are mixed, and then filtered by the fourth bandpass filter 27 to obtain a phase-stable time-frequency synchronization signal.

[0047] At the same time, the present invention also proposes a method for remote synchronization using the above-mentioned time-frequency transmission system for simultaneous downloading and distribution at any position in the transmission optical path, the steps are as follows:

[0048] Step 1: The local time-frequency synchronization signal is divided into two paths after passing through the first microwave power divider 9: one path participates in the modulation of the Mach-Zehnder intensity modulator 2, and the other path enters the IQ mixer 8;

[0049] Step 2: The forward optical signal emitted by the laser 1 passes through the Mach-Zehnder intensity modulator 2, the first optical circulator 3, the optical delay line 13, the long optical fiber 14, the third optical circulator 16, the first optical coupler 17, the fourth optical circulator 18, the second optical circulator 4, and the erbium-doped fiber amplifier 15 in sequence, and then is coupled into the transmission optical path again, so as to form a transmission of the backward light in the transmission optical path;

[0050] Step 3: After the backward optical signal is coupled into the transmission optical path from the second optical circulator 4, it passes through the fourth optical circulator 18, the second optical coupler 19, the third optical circulator 16, the long optical fiber 14, the optical delay line 13, and the first optical circulator 3 in sequence, and is converted into an electrical signal by the first photoelectric converter 5, and then enters the IQ mixer 8 after passing through the first electrical amplifier 6 and the first bandpass filter 7;

[0051] Step 4: The IQ mixer 8 mixes the input signal, and its I-channel and Q-channel outputs are respectively connected to the first low-pass filter 10 and the second low-pass filter 11, and the DC signal component carrying the phase delay information of the transmission optical path is extracted, and the ARM processor 12 completes the acquisition and processing, and the feedback control optical delay line 13 completes the control of the transmission optical path length;

[0052] Step 5: The forward light is divided into two paths after passing through the first optical coupler 17. One path continues to be connected to the fourth optical circulator 18 for subsequent transmission, and the other path is converted into an electrical signal by the second photoelectric converter 20, and is connected to the first mixer 26 after passing through the second electrical amplifier 21 and the second bandpass filter 22;

[0053] Step 6: The backward light is divided into two paths after passing through the second optical coupler 19. One path continues to be connected to the third optical circulator 16 for subsequent transmission, and the other path is converted into an electrical signal by the third photoelectric converter 23, and is connected to the first mixer 26 after passing through the third electrical amplifier 24 and the third bandpass filter 25.

[0054] Step 7: The first mixer 26 mixes the two signals carrying the forward optical path phase delay information and the backward optical path phase delay information and takes the combined frequency thereof through the fourth bandpass filter 27 to obtain a phase-stable time-frequency synchronization signal at the remote end.

[0055] The present invention discloses a time-frequency transmission system for downloading and distributing at any position in a transmission optical path at the same time. The system uses optical and electronic devices such as a laser 1, a Mach-Zehnder intensity modulator 2, an optical circulator, an optical coupler, a photoelectric converter, and an electric amplifier to form a local end responsible for controlling the phase delay of the transmission optical path and a remote end responsible for downloading a time-frequency synchronization signal at any position. The signal carrying the phase delay of the transmission optical path is mixed by an IQ mixer 8 and its difference frequency is taken to obtain the phase jitter information of the transmission optical path, and then the optical delay line 13 is feedback-controlled to maintain the stability of the phase delay of the transmission optical path. In addition, the remote-end time-frequency synchronization download module uses the combination of an optical circulator and a coupler to realize the simultaneous distribution and downloading of the time-frequency synchronization signal at any position in the transmission optical path, and the phases of the time-frequency synchronization signals received by each remote end are highly stable.

[0056] Compared with the prior art, the beneficial effects of the present invention are:

[0057] (1) The time-frequency transmission system implemented by the present invention for simultaneous downloading and distribution at any position in the transmission optical path is not affected by the nonlinearity of the device itself.

[0058] (2) The present invention uses the IQ mixer 8 to obtain the phase delay of the transmission optical path, and can use the I-path and Q-path outputs of the IQ mixer 8 to accurately solve the current signal phase difference, effectively avoiding the angle resolution error caused by optical power jitter during the transmission process.

[0059] (3) The present invention can realize the download of time-frequency synchronization signals at any node in the optical fiber link, and the time-frequency synchronization signal downloading modules at each remote end are independent of each other without crosstalk, and the download of the time-frequency synchronization signal is independent of the stable control process of the transmission optical path, so the system has high stability.

[0060] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A time-frequency transmission system for simultaneous downloading and distribution at any location in a transmission optical path, characterized in that: include: A local transmission optical path stabilization module and a remote time-frequency synchronization signal downloading module, wherein the local transmission optical path stabilization module and the remote time-frequency synchronization signal downloading module are connected via an optical fiber; The local transmission optical path stabilization module includes a laser, a Mach-Zehnder intensity modulator, a first optical circulator, a second optical circulator, a first photoelectric converter, a first electric amplifier, a first bandpass filter, an IQ mixer, a microwave power splitter, a first low-pass filter, a second low-pass filter, an ARM processor, an optical delay line, a long optical fiber, and an optical fiber amplifier; Wherein the laser and the microwave power divider are both connected to the Mach-Zehnder intensity modulator to perform optical carrier modulation on the time-frequency synchronization signal, the Mach-Zehnder intensity modulator, the first optical circulator, the optical delay line, and the long optical fiber are connected in sequence, the first optical circulator is connected in sequence to the first photoelectric converter, the first electrical amplifier, and the first bandpass filter, the microwave power divider is connected to the local oscillator port of the IQ mixer, and the first bandpass filter is connected to the radio frequency port of the IQ mixer; the I-channel output end and the Q-channel output end of the IQ mixer are respectively connected to the first low-pass filter and the second low-pass filter, the first low-pass filter and the second low-pass filter are connected to the ARM processor, and the ARM processor is connected to the optical delay line; the IQ mixer is used to perform difference frequency analysis processing on the input signal, and the ARM processor is used to feedback control the optical delay line according to the transmission optical path phase delay difference reflected by the electrical signal input to the ARM processor; The second port and the third port of the second optical circulator are connected via an optical fiber amplifier; The remote end time and frequency synchronization signal download module includes a third optical circulator, a first optical coupler, a fourth optical circulator, a second optical coupler, a second photoelectric converter, a second electrical amplifier, a second band-pass filter, a third photoelectric converter, a third electrical amplifier, a third band-pass filter, a first mixer, and a fourth band-pass filter; The end of the long optical fiber is connected to the third optical circulator and the first optical coupler in sequence, the first output end of the first optical coupler is connected to the fourth optical circulator, and the fourth optical circulator is connected to the second optical circulator; the second optical circulator is connected to the second optical coupler, and the first output end of the second optical coupler is connected to the third optical circulator; the second output end of the first optical coupler is connected to the second photoelectric converter, the second electrical amplifier and the second band-pass filter in sequence, and the second output end of the second optical coupler is connected to the third photoelectric converter, the third electrical amplifier and the third band-pass filter in sequence; the second band-pass filter and the third band-pass filter are both connected to the first mixer, and the first mixer is connected to the fourth band-pass filter to output a time-frequency synchronization signal.

2. The system according to claim 1, characterized in that The remote end time and frequency synchronization signal downloading module is inserted at any position on the long optical fiber.

3. The system according to claim 1, characterized in that The remote-end time-frequency synchronization signal downloading module is inserted at several positions on the long optical fiber.

4. The system according to claim 1, characterized in that The optical fiber amplifier adopts an erbium-doped optical fiber amplifier.

5. The system according to claim 1, characterized in that In the local transmission optical path stabilization module, the forward propagation of the optical signal after the time-frequency synchronization signal is modulated by the optical carrier passes through the first optical circulator, the optical delay line, the long optical fiber, the third optical circulator, the first optical coupler, the fourth optical circulator and the second optical circulator in sequence, and the propagation direction of the optical signal is adjusted by the second optical circulator.

6. The system according to claim 1, characterized in that In the local transmission optical path stabilization module, the backward propagation of the optical signal after the time-frequency synchronization signal is modulated by the optical carrier passes through the second optical circulator, the second optical coupler, the third optical circulator, the long optical fiber, the optical delay line and the first optical circulator in sequence, and is successively transmitted to the RF port of the IQ mixer through the first optical-to-electrical converter, the first electrical amplifier and the first bandpass filter for optical-to-electrical conversion, amplification and filtering.

7. The system according to claim 1, characterized in that The first mixer performs frequency mixing and extracts the combined frequency through the fourth bandpass filter to obtain a time-frequency synchronization signal.

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