A relay system and method for optical fiber optical frequency transfer with automatic phase locking

Abstract

The present application relates to the technical field of optical frequency transfer, and particularly relates to a relay system and method for realizing automatic phase locking of optical fiber optical frequency transfer, which comprises: an optical fiber beam splitter for splitting signal light into two parts; an acousto-optic modulator for frequency shifting; a relay laser for generating regenerative laser; a photodetector for beat frequency between signal light and regenerative laser; a signal processing and discrimination locking unit for processing beat frequency signals and discriminating whether to lock at a target frequency; a control unit for maintaining the locking state of the regenerative laser when it is discriminated that the frequency of the regenerative laser is locked; and outputting the locked regenerative laser to the next optical fiber link after frequency shifting by a third acousto-optic modulator; and the specific method is to realize automatic frequency locking and relocking of the regenerative laser through double beat frequency signal discrimination and feedback control, and to ensure stable relay of optical frequency signals. The present application improves the long-term stability and reliability of the relay system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical frequency transfer technology, and in particular to a relay system and method for realizing automatic phase locking of optical fiber optical frequency transfer. BACKGROUND

[0002] With the performance of optical clocks entering the 10-18 level, optical frequency transmission technology based on optical fiber becomes the key to realize high-precision distributed applications. However, in long-distance direct transmission, the attenuation of the optical fiber itself will cause the signal-to-noise ratio to decrease, and the control bandwidth of the noise compensation system is limited by the link delay. Although the relay station using regenerative lasers can solve the above problems, it can amplify the signal and suppress the noise of the link in segments, but such relay stations are usually deployed in unattended field rooms, which have a fatal flaw: once the phase locking state between the regenerative laser and the transferred signal light is lost due to environmental interference, the system cannot automatically recover. This loss of lock not only causes the interruption of high-precision optical frequency signal transfer, but also has the risk of false locking of the regenerative laser to stray light during the relocking process, thereby seriously affecting the long-term stable operation of the system. Therefore, designing a regenerative optical relay system that can realize automatic and reliable phase locking and avoid false locking to ensure zero frequency shift has become a core problem that needs to be solved to promote the practicality of optical frequency transfer technology. SUMMARY

[0003] The present application provides a relay system and method for realizing automatic phase locking of optical fiber optical frequency transfer, which solves the problem that the existing optical fiber optical frequency transfer relay station cannot automatically recover after losing lock in an unattended environment, causing signal transmission interruption and affecting long-term stable operation.

[0004] The purpose of the present application can be achieved by the following technical solutions:

[0005] The first aspect of the present application provides a relay system for realizing automatic phase locking of optical fiber optical frequency transfer, comprising:

[0006] A receiving unit for receiving input signal light and dividing the input signal light into first signal light and discrimination reference light;

[0007] A relay laser for generating a regenerative laser;

[0008] A first acousto-optic modulator for frequency shifting the regenerative laser;

[0009] A first photodetector for receiving the first signal light after frequency shifting and the regenerative laser after frequency shifting by the first acousto-optic modulator, and generating a first beat frequency signal;

[0010] a second photodetector configured to receive the reference light and the regenerated laser light after frequency shifting by the first AOM, and generate a second beat signal;

[0011] a signal processing and discrimination locking unit configured to process the first beat signal and the second beat signal, obtain a first voltage signal and a second voltage signal, and discriminate whether the frequency of the regenerated laser light is locked to the target frequency according to the first voltage signal and the second voltage signal;

[0012] a control unit configured to maintain the locking state of the regenerated laser light when it is discriminated that the frequency of the regenerated laser light is locked, and output the locked regenerated laser light after frequency shifting by a third AOM to a next fiber link.

[0013] Further, the receiving unit comprises a first fiber coupler, a second fiber coupler, a third fiber coupler, a second AOM, a first DDS and a first partially reflective Faraday rotator mirror.

[0014] The first fiber coupler is configured to divide the input signal light into a first path signal light and a reference light; the second AOM is configured to perform frequency shifting on the first path signal light; the first DDS is configured to generate a stable digital signal for driving the second AOM; the first partially reflective Faraday rotator mirror is configured to rotate the polarization direction of the light signal by Faraday effect, for controlling and adjusting the polarization state of the light signal; the second fiber coupler is configured to combine the first path signal light after frequency shifting and the regenerated laser light after frequency shifting by the first AOM; and the third fiber coupler is configured to combine the reference light and the regenerated laser light after frequency shifting by the first AOM.

[0015] Further, the driving frequency of the second AOM , the frequency of the first beat signal and the driving frequency of the third AOM satisfy the following relationship: so that the net frequency shift introduced by the relay system is zero.

[0016] Further, the signal processing and discrimination locking unit comprises a first signal processing unit, a second signal processing unit and a discrimination locking unit.

[0017] The first signal processing unit comprises a first band-pass filter, a first frequency-to-voltage converter and a power divider; the center frequency of the first band-pass filter is , for filtering the first beat signal; the first frequency-to-voltage converter is used for converting the filtered first beat signal into a first voltage signal; the power divider is used for dividing the filtered first beat signal into two paths, one of which is sent to the first phase detector, and the other of which is sent to the first frequency-to-voltage converter;

[0018] The second signal processing unit comprises a second band-pass filter and a second frequency-to-voltage converter; the center frequency of the second band-pass filter is , for filtering the second beat signal; wherein, is the driving frequency of the second acousto-optic modulator; the second frequency-to-voltage converter is used for converting the filtered second beat signal into a second voltage signal;

[0019] The discrimination locking unit comprises a master control chip, which is used for receiving the first voltage signal and the second voltage signal, and determining whether the frequency of the regenerated laser is locked to the target frequency when both of them reach the peak value at the same time , wherein is the frequency of the input signal light.

[0020] Further, the control unit comprises a first phase detector, a first PID controller, a second PID controller, a second direct digital frequency synthesizer, a relay laser, an optical isolator, and a first acousto-optic modulator;

[0021] The first phase detector is used for generating an error signal according to the phase difference between the filtered first beat signal and a first radio frequency reference signal, which is denoted as a first error signal;

[0022] The first PID controller is used for controlling the relay laser to perform slow and large-range frequency coarse adjustment according to the first error signal;

[0023] The second PID controller is used for controlling the second direct digital frequency synthesizer to set the driving frequency of the first acousto-optic modulator according to the first error signal, so as to realize fast and small-range frequency fine adjustment and compensate for the fast phase noise introduced by the optical fiber;

[0024] The second direct digital frequency synthesizer generates a stable digital signal for driving the first acousto-optic modulator;

[0025] The optical isolator only allows light to pass in one direction and prevents reflected light from returning, for protecting the relay laser and stabilizing the system.

[0026] Further, a sending unit is further included, which comprises a second partially reflective Faraday rotator mirror, a third photodetector, a third acousto-optic modulator, a sixth fiber splitter, and a servo control system;

[0027] The second partial reflection Faraday rotating mirror is arranged in an output light path of the third acousto-optic modulator, and is used for reflecting part of the output light as local reference light;

[0028] The third photoelectric detector is used for receiving the optical signal reflected from the next link and performing beat frequency with the local reference light to obtain a third beat frequency signal;

[0029] The third acousto-optic modulator is used for performing frequency shift processing on the locked regenerative laser;

[0030] The sixth optical fiber beam splitter is used for sending one path to the third photoelectric detector as the local reference light, and sending another path to the next link N+1 through the second partial reflection Faraday rotating mirror and then through the third acousto-optic modulator;

[0031] The servo control system comprises a third band-pass filter, a second phase detector, a third PID controller and a third direct digital frequency synthesizer, and is used for generating a compensation signal according to the output signal of the third photoelectric detector, and driving the third acousto-optic modulator or a dedicated phase modulator to suppress the link phase noise;

[0032] The third band-pass filter is used for filtering the third beat frequency signal;

[0033] The second phase detector is used for generating an error signal according to the phase difference between the filtered third beat frequency signal and a second radio frequency reference signal, and the error signal is recorded as a second error signal;

[0034] The third PID controller is used for controlling the third direct digital frequency synthesizer according to the second error signal to set the driving frequency of the first acousto-optic modulator, so as to realize fast and small-range frequency fine adjustment and compensate the fast phase noise introduced by the optical fiber.

[0035] The second aspect of the present application provides a kind of optical fiber optical frequency transfer method for realizing automatic phase locking, comprising:

[0036] The input signal light is split to obtain first signal light and discrimination reference light;

[0037] The first signal light is frequency-shifted to obtain beat frequency reference light;

[0038] The PZT voltage scanning of regenerative laser is opened, the frequency of regenerative laser is adjusted, so that it beats frequency with the first beat frequency signal and the second beat frequency signal is generated with the beat frequency reference light and the discrimination reference light;

[0039] The first beat frequency signal and the second beat frequency signal are processed to obtain first voltage signal and second voltage signal, and whether the frequency of the regenerative laser is locked at target frequency is discriminated according to the first voltage signal and the second voltage signal.

[0040] When the lock is determined, the PZT voltage scanning is closed, the lock state is maintained, and the regenerated laser after frequency shift is output to the next optical fiber link;

[0041] The lock state is continuously monitored, and when the lock is detected, the frequency adjustment and lock steps are automatically re-executed.

[0042] Further, the first beat frequency signal and the second beat frequency signal are processed to obtain a first voltage signal and a second voltage signal, and whether the frequency of the regenerated laser is locked to the target frequency is determined according to the first voltage signal and the second voltage signal, including:

[0043] The first beat frequency signal is filtered through a band-pass filter with a center frequency of , and is converted into a first voltage signal;

[0044] The second beat frequency signal is filtered through a band-pass filter with a center frequency of , and is converted into a second voltage signal;

[0045] It is judged whether the first voltage signal and the second voltage signal reach the peak value at the same time; if yes, it is determined that the frequency is locked to , wherein is the frequency of the input signal light.

[0046] Further, it further includes a link phase noise suppression step:

[0047] The regenerated laser is output to the light reflection of the next optical fiber link as a local reference light;

[0048] The optical signal output from the local transmitting unit to the next link and reflected back by the next station relay receiving unit is received, and the reflected optical signal is beat with the local reference light to detect the phase noise introduced by the link;

[0049] According to the detected phase noise, a compensation signal is generated to feedback compensate the phase of the output light.

[0050] The third aspect of the present application provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the computer program to realize the optical fiber optical frequency transfer method for automatic phase locking.

[0051] Compared with the prior art, the beneficial effects of the present application are: splitting the input signal light to obtain first signal light and discrimination reference light; providing an optical basis for subsequent double-path frequency discrimination; frequency-shifting the first signal light to obtain beat frequency reference light; converting the optical phase-locked problem to the radio frequency domain which is easy to process; adjusting the frequency of the regenerated laser to make it beat with the beat frequency reference light to generate a first beat frequency signal and beat with the discrimination reference light to generate a second beat frequency signal; simultaneously generating key signals for frequency locking and false discrimination prevention; processing the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and discriminating whether the frequency of the regenerated laser is locked to the target frequency according to the first voltage signal and the second voltage signal; accurately and reliably confirming that the regenerated laser is locked at the correct frequency; when it is discriminated that it is locked, maintaining the locked state and outputting the locked regenerated laser after frequency shifting to the next optical fiber link; realizing signal regeneration and amplification and segmented suppression of link noise; continuously monitoring the locked state, and when a loss of lock is detected, automatically re-executing the frequency adjustment and locking steps; ensuring that the system can operate stably for a long time in an unattended environment; the present application improves the long-term stability and reliability of the relay system; solves the problem that the existing optical fiber optical frequency transfer relay station cannot automatically recover after losing lock in an unattended environment, resulting in interruption of signal transmission and affecting long-term stable operation. BRIEF DESCRIPTION OF DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0053] Figure 1 A module flowchart of a relay system for realizing automatic phase-locked optical fiber optical frequency transfer is provided for the present application.

[0054] Figure 2 A regenerated laser automatic locking flowchart is provided.

[0055] Figure 1 The various reference signs in the drawings are: 1, receiving unit; 2, first signal processing unit; 3, second signal processing unit; 4, discrimination locking unit; 5, control unit; 6, sending unit. DETAILED DESCRIPTION

[0056] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0057] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented in an order other than that illustrated or described herein. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0058] In view of the problems in the background art, a relay system and method for realizing automatic phase-locked optical fiber optical frequency transfer are designed, which has important practical significance.

[0059] As shown in Figure 1 The first aspect of the present application is to provide a relay system for realizing automatic phase-locked optical fiber optical frequency transfer, comprising:

[0060] The receiving unit 1 is used for receiving the input signal light and dividing the input signal light into first path signal light and discrimination reference light;

[0061] The relay laser is used for generating a regenerated laser;

[0062] The first acousto-optic modulator AOM1 is used for frequency shifting processing on the regenerated laser;

[0063] The first photodetector PD1 is used for receiving the first path signal light after frequency shifting and the regenerated laser after frequency shifting by the first acousto-optic modulator AOM1, and generating a first beat frequency signal;

[0064] The second photodetector PD2 is used for receiving the discrimination reference light and the regenerated laser after frequency shifting by the first acousto-optic modulator AOM1, and generating a second beat frequency signal;

[0065] The signal processing and discrimination locking unit is configured to process the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and to discriminate whether the frequency of the regenerated laser is locked to a target frequency according to the first voltage signal and the second voltage signal.

[0066] The control unit 5 is configured to maintain the locking state of the regenerated laser when it is determined that the frequency of the regenerated laser is locked, and to output the locked regenerated laser to a next optical fiber link after frequency shifting by a third acousto-optic modulator AOM3.

[0067] The receiving unit 1 comprises a first optical fiber beam splitter OC1, a second optical fiber beam splitter OC2, a third optical fiber beam splitter OC3, a second acousto-optic modulator AOM2, a first direct digital frequency synthesizer DDS1, and a first partially reflective Faraday mirror PFM1.

[0068] The first optical fiber beam splitter OC1 is configured to split the input signal light into first path signal light and discrimination reference light. The second acousto-optic modulator AOM2 is configured to perform frequency shifting processing on the first path signal light. The first direct digital frequency synthesizer DDS1 is configured to generate a stable digital signal for driving the second acousto-optic modulator AOM2. The first partially reflective Faraday mirror PFM1 is configured to rotate the polarization direction of the optical signal by Faraday effect, for controlling and adjusting the polarization state of the optical signal. The second optical fiber beam splitter OC2 is configured to combine the frequency-shifted first path signal light with the regenerated laser after frequency shifting by the first acousto-optic modulator AOM1. The third optical fiber beam splitter OC3 is configured to combine the discrimination reference light with the regenerated laser after frequency shifting by the first acousto-optic modulator AOM1.

[0069] The fourth optical fiber beam splitter OC4 is configured to split the regenerated laser after frequency shifting by the first acousto-optic modulator AOM1, and send one path to the second optical fiber beam splitter OC2 and another path to a fifth optical fiber beam splitter OC5.

[0070] The fifth optical fiber beam splitter OC5 is configured to split the regenerated laser sent by the fourth optical fiber beam splitter OC4, and send one path to the third optical fiber beam splitter OC3 and another path to a sixth optical fiber beam splitter OC6.

[0071] The driving frequency of the second acousto-optic modulator AOM2 The frequency of the first beat frequency signal And the driving frequency of the third acousto-optic modulator AOM3 Satisfy the following relationship: So that the net frequency shift introduced by the relay system is zero.

[0072] The signal processing and discrimination locking unit comprises a first signal processing unit 2, a second signal processing unit 3 and a discrimination locking unit 4.

[0073] The first signal processing unit 2 comprises a first band-pass filter BPF1, a first frequency-to-voltage converter PDT1 and a power divider PC1; the first band-pass filter BPF1 has a center frequency of , and is used for filtering the first beat frequency signal; the first frequency-to-voltage converter PDT1 is used for converting the filtered first beat frequency signal into a first voltage signal; and the power divider PC1 is used for dividing the filtered first beat frequency signal into two paths, one of which is sent to the first phase discriminator PFD1, and the other of which is sent to the first frequency-to-voltage converter PDT1.

[0074] The second signal processing unit 3 comprises a second band-pass filter BPF2 and a second frequency-to-voltage converter PDT2; the second band-pass filter BPF2 has a center frequency of , and is used for filtering the second beat frequency signal; wherein is the driving frequency of the second acousto-optic modulator AOM2; and the second frequency-to-voltage converter PDT2 is used for converting the filtered second beat frequency signal into a second voltage signal.

[0075] The discrimination locking unit 4 comprises a master chip, which is used for receiving the first voltage signal and the second voltage signal, and determining whether the frequency of the regenerated laser has been locked to the target frequency when both of them reach the peak value at the same time. , wherein is the frequency of the input signal light.

[0076] The control unit 5 comprises a first phase discriminator PFD1, a first PID controller PID1, a second PID controller PID2, a second direct digital frequency synthesizer DDS2, a relay laser, an optical isolator ISO1 and a first acousto-optic modulator AOM1.

[0077] The first phase discriminator PFD1 is used for generating an error signal according to the phase difference between the filtered first beat frequency signal and a first radio frequency reference signal RF1, which is denoted as a first error signal.

[0078] The first PID controller PID1 is used for controlling the relay laser to perform slow and large-range frequency coarse adjustment according to the first error signal.

[0079] The second PID controller PID2 is used for controlling the second direct digital frequency synthesizer DDS2 to set the driving frequency of the first acousto-optic modulator AOM1 according to the first error signal, so as to realize fast and small-range frequency fine adjustment and compensate for the fast phase noise introduced by the optical fiber.

[0080] The second direct digital frequency synthesizer DDS2 generates a stable digital signal for driving the first acousto-optic modulator AOM1;

[0081] The optical isolator ISO1 only allows light to pass in one direction and prevents reflected light from returning, for protecting the relay laser and stabilizing the system.

[0082] The relay system for realizing automatic phase-locked optical fiber optical frequency transfer further comprises a sending unit 6, which comprises a second partially reflective Faraday rotating mirror PFM2, a third photodetector PD3, a third acousto-optic modulator AOM3, a sixth optical fiber coupler OC6 and a servo control system.

[0083] The second partially reflective Faraday rotating mirror PFM2 is arranged in the output light path of the third acousto-optic modulator AOM3, for reflecting part of the output light as a local reference light;

[0084] The third photodetector PD3 is used for receiving the light signal reflected from the next link and beating with the local reference light to obtain a third beat signal;

[0085] The third acousto-optic modulator AOM3 is used for frequency shifting the locked regenerative laser;

[0086] The sixth optical fiber coupler OC6 is used for sending one path to the third photodetector PD3 as a local reference light, and sending another path through the second partially reflective Faraday rotating mirror PFM2 and then through the third acousto-optic modulator AOM3 to the next link N+1;

[0087] The servo control system comprises a third band-pass filter BPF3, a second phase detector PFD2, a third PID controller PID3 and a third direct digital frequency synthesizer DDS3, which are used for generating a compensation signal according to the output signal of the third photodetector PD3, driving the third acousto-optic modulator AOM3 or a dedicated phase modulator, so as to suppress the link phase noise;

[0088] The third band-pass filter BPF3 is used for filtering the third beat signal;

[0089] The second phase detector PFD2 is used for generating an error signal according to the phase difference between the filtered third beat signal and a second radio frequency reference signal RF2, which is recorded as a second error signal;

[0090] The third PID controller PID3 is used for controlling the third direct digital frequency synthesizer DDS3 according to the second error signal to set the driving frequency of the first acousto-optic modulator AOM1, so as to realize fast and small-range frequency fine adjustment and compensate for the fast phase noise introduced by the optical fiber.

[0091] Thus far, the present embodiment is completed.

[0092] wherein, Figure 1The English full names of each symbol are as follows: OC1 is the English full name of Optical Coupler 1, OC2 is the English full name of Optical Coupler 2, OC3 is the English full name of Optical Coupler 3, OC4 is the English full name of Optical Coupler 4, OC5 is the English full name of Optical Coupler 5, OC6 is the English full name of Optical Coupler 6, AOM1 is the English full name of Acousto-Optic Modulator 1, AOM2 is the English full name of Acousto-Optic Modulator 2, AOM3 is the English full name of Acousto-Optic Modulator 3, PFM1 is the English full name of First Partially Reflective Faraday Mirror, PFM2 is the English full name of Second Partially Reflective Faraday Mirror, PD1 is the English full name of Photodetector 1, PD2 is the English full name of Photodetector 2, PD3 is the English full name of Photodetector 3, BPF1 is the English full name of Band-Pass Filter 1, BPF2 is the English full name of Band-Pass Filter 2, BPF3 is the English full name of Band-Pass Filter 3, PC1 is the English full name of Power Combiner 1, PDT1 is the English full name of Pulse Density-to-Tension Converter 1, PDT2 is the English full name of Pulse Density-to-Tension Converter 2, RF1 is the English full name of Radio Frequency Reference Signal 1, RF2 is the English full name of Radio Frequency Reference Signal 2, PID1 is the English full name of Proportional-Integral-Derivative Controller 1, PID2 is the English full name of Proportional-Integral-Derivative Controller 2, PID3 is the English full name of Proportional-Integral-Derivative Controller 3, DDS1 is the English full name of Direct Digital Synthesizer 1, DDS2 is the English full name of Direct Digital Synthesizer 2, DDS3 is the English full name of Direct Digital Synthesizer 3,ISO1 is the full name of Isolator 1, PFD1 is the full name of Phase-Frequency Detector 1, and PFD2 is the full name of Phase-Frequency Detector 2.

[0093] The second aspect of the present application is to provide a method for realizing automatic phase-locked optical fiber optical frequency transfer, comprising the following steps:

[0094] Split the input signal light to obtain a first signal light and a discrimination reference light;

[0095] Frequency shift the first signal light to obtain a beat frequency reference light;

[0096] Turn on the PZT (Piezoelectric Transducer) voltage scan of the regenerative laser to adjust the frequency of the regenerative laser, so that it beats with the beat frequency reference light to generate a first beat frequency signal, and beats with the discrimination reference light to generate a second beat frequency signal;

[0097] Process the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and determine whether the frequency of the regenerative laser is locked to the target frequency according to the first voltage signal and the second voltage signal;

[0098] When it is determined that it is locked, turn off the PZT voltage scan to maintain the locked state, and output the locked regenerative laser after frequency shift to the next optical fiber link;

[0099] Continuously monitor the locked state, and automatically re-execute the frequency adjustment and locking steps when a loss of lock is detected. The automatic locking process of the regenerative laser is shown in Figure 2 .

[0100] Among them, processing the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and determining whether the frequency of the regenerative laser is locked to the target frequency according to the first voltage signal and the second voltage signal, comprises:

[0101] Filter the first beat frequency signal through a band-pass filter with a center frequency of , and convert it into a first voltage signal;

[0102] Filter the second beat frequency signal through a band-pass filter with a center frequency of , and convert it into a second voltage signal;

[0103] Determine whether the first voltage signal and the second voltage signal reach the peak value at the same time; if so, it is determined that the frequency is locked to .

[0104] The method for realizing automatic phase locking of optical fiber optical frequency transfer, characterized in further comprising a link phase noise suppression step:

[0105] The regenerated laser output is reflected as local reference light by the next optical fiber link;

[0106] The optical signal output from the local transmitting unit 6 to the next link and reflected back by the next relay station receiving unit is received, and the reflected back optical signal is beat with the local reference light to detect the link-induced phase noise;

[0107] A compensation signal is generated according to the detected phase noise to feedback compensate the phase of the output light.

[0108] Thus far, the embodiment is completed.

[0109] The third aspect of the present application provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor realizes a method for realizing automatic phase locking of optical fiber optical frequency transfer when executing the computer program.

[0110] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can take the form of a computer program product implemented on one or more computer-usable storage media (including, but not limited to, disk storage, optical storage, etc.) containing computer-usable program code.

[0111] The present application is described with reference to flowcharts and / or block diagrams of the method, system, and computer program product according to the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of flows and / or blocks in the flowcharts and / or block diagrams can be realized by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device that implements the functions specified in the flowcharts and / or block diagrams. Figure 1 The device that realizes the functions specified in one flow or multiple flows and / or blocks Figure 1 The device that realizes the functions specified in one flow or multiple flows and / or blocks

[0112] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flow Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or multiple blocks.

[0113] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flow Figure 1 one or more flows and / or blocks Figure 1 one or more blocks or multiple blocks.

[0114] Finally, it should be noted that the above-mentioned embodiments are merely used to illustrate the technical solutions of the present application, rather than limiting the same. Although the present application has been described in detail with reference to the above-mentioned embodiments, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced equivalently, and any modification or replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the present application.

Claims

1. A relay system for automatic phase-locked optical frequency transmission, characterized in that, include: The receiving unit is used to receive the input signal light and divide the input signal light into a first signal light and a discrimination reference light. Relay lasers are used to generate regenerated lasers; A first acousto-optic modulator is used to perform frequency shifting processing on the regenerated laser; The first photodetector is used to receive the first signal light after frequency shifting and the regenerated laser after frequency shifting by the first acousto-optic modulator, and to generate the first beat frequency signal. The second photodetector is used to receive the discrimination reference light and the regenerated laser after frequency shifting by the first acousto-optic modulator, and to generate a second beat frequency signal; The signal processing and discrimination locking unit is used to process the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and to determine whether the frequency of the regenerated laser is locked to the target frequency based on the first voltage signal and the second voltage signal. The control unit is used to maintain the locked state of the regenerated laser when it is determined that the frequency of the regenerated laser is locked; and to output the locked regenerated laser to the next fiber optic link after frequency shifting by the third acousto-optic modulator.

2. The relay system for automatic phase-locked optical frequency transmission according to claim 1, characterized in that, The receiving unit includes a first fiber optic beam splitter, a second fiber optic beam splitter, a third fiber optic beam splitter, a second acousto-optic modulator, a first direct digital frequency synthesizer, and a first partially reflective Faraday rotator. The first fiber beam splitter is used to split the input signal light into a first signal light and a discrimination reference light; the second acousto-optic modulator performs frequency shifting processing on the first signal light; the first direct digital frequency synthesizer generates a stable digital signal to drive the second acousto-optic modulator; the first partially reflective Faraday rotating mirror rotates the polarization direction of the optical signal through the Faraday effect to control and adjust the polarization state of the optical signal. The second fiber beam splitter is used to combine the first signal light after frequency shifting and the regenerated laser after frequency shifting by the first acousto-optic modulator. The third fiber beam splitter is used to combine the discrimination reference light and the regenerated laser after frequency shifting by the first acousto-optic modulator.

3. A relay system for automatic phase-locked optical frequency transmission in fiber optics according to claim 2, characterized in that, The driving frequency of the second acousto-optic modulator The frequency of the first beat frequency signal and the driving frequency of the third acousto-optic modulator The following relationship must be satisfied: This is to ensure that the net frequency shift introduced by the relay system is zero.

4. A relay system for automatic phase-locked optical frequency transmission in fiber optics according to claim 2, characterized in that, The signal processing and discrimination locking unit includes a first signal processing unit, a second signal processing unit, and a discrimination locking unit; The first signal processing unit includes a first bandpass filter, a first frequency-to-voltage converter, and a power divider; the center frequency of the first bandpass filter is... The first frequency converter is used to filter the first beat frequency signal, and the first frequency-to-voltage converter is used to convert the filtered first beat frequency signal into a first voltage signal; the power divider is used to split the filtered first beat frequency signal into two paths, one path is sent to the first phase detector, and the other path is sent to the first frequency-to-voltage converter. The second signal processing unit includes a second bandpass filter and a second frequency-to-voltage converter; the center frequency of the second bandpass filter is... , used to filter the second beat frequency signal; wherein, The driving frequency of the second acoustic-optic modulator; the second frequency-to-voltage converter is used to convert the filtered second beat frequency signal into a second voltage signal; The discrimination and locking unit includes a main control chip, which receives the first voltage signal and the second voltage signal, and determines whether the frequency of the regenerated laser has been locked to the target frequency when both reach their peak values ​​simultaneously. ,in The frequency of the input signal light.

5. A relay system for automatic phase-locked optical frequency transmission according to claim 4, characterized in that, The control unit includes a first phase detector, a first PID controller, a second PID controller, a second direct digital frequency synthesizer, a relay laser, an optical isolator, and a first acousto-optic modulator. The first phase detector is used to generate an error signal based on the phase difference between the filtered first beat frequency signal and the first radio frequency reference signal, denoted as the first error signal; The first PID controller is used to control the relay laser to perform slow, wide-range coarse frequency adjustment based on the first error signal; The second PID controller is used to control the second direct digital frequency synthesizer according to the first error signal to set the driving frequency of the first acousto-optic modulator, thereby achieving fast, small-range frequency fine-tuning and compensating for the fast phase noise introduced by the optical fiber; The second direct digital frequency synthesizer generates a stable digital signal to drive the first acousto-optic modulator; The optical isolator allows light to pass through in only one direction and prevents reflected light from returning, thus protecting the relay laser and stabilizing the system.

6. A relay system for automatic phase-locked optical frequency transmission in fiber optics according to claim 1, characterized in that, It also includes a transmitting unit, which comprises a second part of a reflecting Faraday rotator, a third photodetector, a third acousto-optic modulator, a sixth fiber optic beam splitter, and a servo control system; The second part of the reflective Faraday rotator is disposed in the output optical path of the third acousto-optic modulator and is used to reflect part of the output light as a local reference light; The third photodetector is used to receive the optical signal reflected back from the next link segment and beat it with the local reference light to obtain a third beat frequency signal; The third acousto-optic modulator is used to perform frequency shifting on the locked regenerated laser. The sixth fiber beam splitter is used to send one path to the third photodetector as a local reference light, and the other path passes through the second part of the Faraday rotator mirror and then through the third acousto-optic modulator to be incident into the next link N+1. The servo control system includes a third bandpass filter, a second phase detector, a third PID controller, and a third direct digital frequency synthesizer, used to generate a compensation signal based on the output signal of the third photodetector, and drive the third acousto-optic modulator or a dedicated phase modulator to suppress link phase noise. The third bandpass filter is used to filter the third beat frequency signal; The second phase detector is used to generate an error signal based on the phase difference between the filtered third beat frequency signal and the second radio frequency reference signal, denoted as the second error signal; The third PID controller is used to control the third direct digital frequency synthesizer according to the second error signal to set the driving frequency of the first acousto-optic modulator, thereby achieving fast, small-range frequency fine-tuning and compensating for the fast phase noise introduced by the optical fiber.

7. A method for achieving automatic phase-locked optical frequency transfer, characterized in that, A relay system for automatic phase-locked optical frequency transmission using fiber optics as described in any one of claims 1-6, comprising the following steps: The input signal light is split into two beams to obtain the first signal light and the discrimination reference light; The first signal light is frequency-shifted to obtain the beat frequency reference light; PZT voltage scanning of the regenerated laser is activated, and the frequency of the regenerated laser is adjusted so that it beats the beat frequency reference light to generate a first beat frequency signal, and beats the beat frequency reference light to generate a second beat frequency signal. The first beat frequency signal and the second beat frequency signal are processed to obtain a first voltage signal and a second voltage signal, and the frequency of the regenerated laser is determined to be locked to the target frequency based on the first voltage signal and the second voltage signal. When it is determined that the laser is locked, the PZT voltage scan is turned off, the locked state is maintained, and the regenerated laser after locking is frequency shifted and output to the next fiber optic link. It continuously monitors the lock status and automatically re-executes the frequency adjustment and locking steps when a loss of lock is detected.

8. A fiber optic frequency transfer method for achieving automatic phase-locked loop according to claim 7, characterized in that, The step of processing the first beat frequency signal and the second beat frequency signal to obtain a first voltage signal and a second voltage signal, and determining whether the frequency of the regenerated laser is locked to the target frequency based on the first voltage signal and the second voltage signal, includes: The first beat frequency signal is passed through a center frequency of The bandpass filter filters the signal and converts it into a first voltage signal; The second beat frequency signal is passed through a center frequency of The bandpass filter filters the signal and converts it into a second voltage signal; Determine whether the first voltage signal and the second voltage signal reach their peak values ​​simultaneously; if so, determine that the frequency is locked at [frequency value]. ,in The frequency of the input signal light.

9. A fiber optic frequency transfer method for achieving automatic phase-locked loop according to claim 7, characterized in that, It also includes a link phase noise suppression step: The light reflected from the regenerated laser output to the next fiber optic link is used as the local reference light. The system receives optical signals that are output from the local transmitting unit to the next link segment and reflected back by the next relay receiving unit, and performs frequency matching between the reflected optical signals and the local reference light to detect phase noise introduced by the link. A compensation signal is generated based on the detected phase noise to provide feedback compensation for the phase of the output light.

10. An electronic device, characterized in that, The method includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor, when executing the computer program, implements the fiber optic frequency transfer method for automatic phase-locking as described in any one of claims 7-9.

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