A fiber phase compensator for suppressing system error of laser frequency drift

Abstract

The application discloses a kind of optical fiber phase compensators for inhibiting laser frequency drift system error, optical fiber phase compensator is the optical fiber phase compensator of two equal-arm length optical fiber interferometers sharing an interference arm, one optical fiber interferometer measures the transmission delay variation amount on optical fiber cable that phase detection error generated by inhibiting laser frequency drift, another local optical fiber interferometer measures the transmission delay variation amount caused by temperature drift of shared interference arm, and corrects the transmission delay variation amount detection error on optical fiber cable caused by temperature variation of reference arm of optical fiber interferometer.

Description

Technical Field

[0001] This invention relates to fiber optic time-frequency transmission technology, and more particularly to a fiber optic phase-stabilized transmission device based on an equal-arm fiber optic interferometer to suppress the detection error of fiber optic transmission delay variation caused by laser frequency drift. Specifically, it is a fiber optic phase compensator that suppresses laser frequency drift system error and can achieve accurate detection and compensation of transmission delay variation on optical fiber cables. Background Technology

[0002] Optical fiber is a crucial carrier for high-precision time and frequency transmission. Environmental noise along the transmission path can degrade the quality of high-precision time and frequency signals, necessitating proactive control measures for fiber optic time and frequency transmission. A fiber optic phase compensator based on the fiber optic interferometer fringe counting method achieves a resolution of λ / 4 for detecting changes in fiber transmission delay. Due to the extremely short wavelength of the laser, its detection resolution reaches the order of 1 fs, theoretically enabling femtosecond-level stable phase compensation accuracy.

[0003] However, the phase changes detected by the fiber interferometer include changes in fiber transmission delay caused by temperature and vibration, as well as phase changes caused by laser frequency drift. The phase changes caused by laser frequency drift become a systematic error in the detection of fiber transmission delay changes, and this systematic error reaches 26 fs / (km·MHz). Currently, the short-term frequency stability of commercial narrow-linewidth lasers is about 10MHz@100s. Due to changes in operating temperature, the laser center frequency will also experience larger frequency drifts of hundreds of MHz to tens of GHz, which will seriously reduce the phase compensation accuracy of the fiber phase compensator.

[0004] Using an equal-arm fiber interferometer can suppress the phase drift detection error caused by laser frequency drift, but it also introduces the phase drift detection error caused by reference arm temperature drift, which reduces the accuracy of detecting the delay change of the transmission optical cable. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a fiber optic phase compensator for suppressing laser frequency drift system errors. This fiber optic phase compensator employs two equal-arm fiber optic interferometers sharing a single interferometer arm. It can measure the transmission delay variation on the fiber optic cable after suppressing the phase detection error caused by laser frequency drift, and can correct the transmission delay variation error caused by temperature drift of the reference arm of the equal-arm fiber optic interferometer. This enables accurate detection and compensation of transmission delay variations on the fiber optic cable.

[0006] The technical solution to achieve the objective of this invention is:

[0007] A fiber optic phase compensator for suppressing laser frequency drift system errors includes a narrow-linewidth laser, a first 3×3 fiber coupler, a second 3×3 fiber coupler, a first wavelength division multiplexer, a phase compensation module, a first fiber optic cable L1, a second wavelength division multiplexer, a first Faraday magnetic rotating mirror, a first 1×2 fiber coupler, a second fiber segment L2, a second Faraday magnetic rotating mirror, a fiber isolator ISO, a fiber optic circulator CIR, a third fiber segment L3, a third Faraday magnetic rotating mirror, a first photodetector PD-1, a second photodetector PD-2, a third photodetector PD-3, a fourth photodetector PD-4, and a control module, wherein:

[0008] A first 3×3 fiber coupler, a first wavelength division multiplexer (WDM), a phase compensation module, a first fiber optic cable L1, a second WDM, and a first Faraday magnetic rotating mirror are sequentially connected. Simultaneously, the first 3×3 fiber coupler, together with a first 1×2 fiber coupler, a second fiber segment L2, and a second Faraday magnetic rotating mirror, constitute a first fiber interferometer. A narrow-linewidth laser outputs laser light into port 1 of the first 3×3 fiber coupler, splitting it into three beams that are output from ports 4, 5, and 6 respectively. The optical path of the measuring arm of the first fiber interferometer is as follows: the laser output from port 4 of the first 3×3 fiber coupler enters the transmission end of the first WDM; the laser output from the common end of the first WDM passes through the phase compensation module to the first fiber optic cable L1, entering the common end of the second WDM; and the laser output from the transmission end of the second WDM enters the first Faraday magnetic rotating mirror. The first Faraday magnetic rotating mirror reflects the laser back to port 4 of the first 3×3 fiber coupler. The reference arm optical path of the first fiber interferometer is as follows: the output of port 5 of the first 3×3 fiber coupler is connected to port 1 of the first 1×2 fiber coupler and output through port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflecting back to port 5 of the first 3×3 fiber coupler. The first fiber interferometer is a Michelson fiber interferometer. The lasers of the measuring arm and the reference arm of the first fiber interferometer are coherent in the first 3×3 fiber coupler. The output interference signals enter the first photodetector PD-1 and the second photodetector PD-2 through ports 2 and 3 of the first 3×3 fiber coupler, respectively. The first photodetector PD-1 and the second photodetector PD-2 are connected to the control module. The control module demodulates the phase change of the first fiber interferometer.

[0009] The first connection method for constructing the second fiber optic interferometer is as follows: a first 3×3 fiber optic coupler, a first 1×2 fiber optic coupler, a second fiber segment L2, and a second Faraday magnetic rotating mirror are connected sequentially. Simultaneously, the first 3×3 fiber optic coupler, a fiber optic circulator CIR, a third fiber segment L3, and a third Faraday magnetic rotating mirror are connected sequentially. Furthermore, the first 1×2 fiber optic coupler, a fiber optic isolator ISO, and the second 3×3 fiber optic coupler are connected, and the fiber optic circulator CIR is connected to the second 3×3 fiber optic coupler, together forming the second fiber optic interferometer. The optical path of the measuring arm of the second fiber optic interferometer is as follows: the output from port 5 of the first 3×3 fiber optic coupler is connected to port 1 of the first 1×2 fiber optic coupler and output from port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflected back to the first 1×2 fiber optic coupler; the output from port 2 of the first 1×2 fiber optic coupler is connected to port 4 of the second 3×3 fiber optic coupler via the fiber optic isolator ISO. The optical path of the reference arm of the second fiber optic interferometer is as follows: the output from port 6 of the first 3×3 fiber optic coupler... The output signal is connected to port 1 of the fiber optic circulator (CIR) and output through port 2. It then passes through the third fiber segment L3 to the third Faraday magnetic rotating mirror and is reflected back to port 2 of the CIR. The output signal is connected to port 5 of the second 3×3 fiber coupler through port 3 of the CIR. The second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers of the measuring arm and the reference arm of the second fiber interferometer are coherent within the second 3×3 fiber coupler. The output interference signals enter the third photodetector PD-3 and the fourth photodetector PD-4 through ports 1 and 2 of the second 3×3 fiber coupler, respectively. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module. The control module demodulates the phase change of the second fiber interferometer. Based on the phase change of the first fiber interferometer and the phase change of the second fiber interferometer, the control module calculates the fiber delay change on the measuring arm of the first fiber interferometer and controls the phase compensation module to provide feedback compensation for the fiber delay change on the measuring arm of the first fiber interferometer.

[0010] The second connection method for the second fiber optic interferometer is as follows: the laser output from the narrow-linewidth laser is input to port 1 of the second 1×2 fiber optic coupler and split into two outputs: one output is connected from port 2 of the second 1×2 fiber optic coupler to port 1 of the first 3×3 fiber optic coupler, and the other output is connected from port 3 of the second 1×2 fiber optic coupler to port 1 of the second 3×3 fiber optic coupler. The optical path of the measuring arm of the second fiber optic interferometer is as follows: the output from port 2 of the second 1×2 fiber optic coupler is connected to port 1 of the first 3×3 fiber optic coupler, output from port 5 of the first 3×3 fiber optic coupler, connected to port 1 of the first 1×2 fiber optic coupler, and output from port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflected back to the first 1×2 fiber optic coupler, and output from port 2 of the first 1×2 fiber optic coupler, passing through the fiber isolator ISO to the second Faraday magnetic rotating mirror. The optical path of the reference arm of the second fiber interferometer is as follows: the laser from the measuring arm of the second fiber interferometer is output from the 3-port of the second 1×2 fiber coupler, connected to the 1-port of the second 3×3 fiber coupler, output from the 5-port of the second 3×3 fiber coupler, reaches the third Faraday magnetic rotating mirror via the third fiber segment L3, and is reflected back to the 5-port of the second 3×3 fiber coupler. At this time, the second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers of the measuring arm and the reference arm of the second fiber interferometer are coherent in the second 3×3 fiber coupler. The output interference signals enter the third photodetector PD-3 and the fourth photodetector PD-4 from the 2-port and 3-port of the second 3×3 fiber coupler, respectively. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module to demodulate the phase change of the second fiber interferometer.

[0011] The service signal transmission path is as follows: the service signal modulation input terminal is input through the reflection end of the first wavelength division multiplexer and output through the common end of the first wavelength division multiplexer, then through the phase compensation module and the first optical fiber cable L1, and finally input through the common end of the second wavelength division multiplexer and output through the reflection end of the second wavelength division multiplexer to the service signal photoelectric receiving end.

[0012] The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer, and the fiber delay of the measuring arm of the first fiber interferometer is equal to the fiber delay of the reference arm of the first fiber interferometer. The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer. That is, except for the common part consisting of the pigtail at the common end output of the first wavelength division multiplexer, the phase compensation module, the first fiber optic cable L1, and the pigtail at the common end of the second wavelength division multiplexer, the sum of the fiber lengths of the service signal output pigtail and the reflection pigtail of the first wavelength division multiplexer is equal to the sum of the fiber lengths of the transmission pigtail of the first wavelength division multiplexer and the 4-port pigtail of the first 3×3 fiber coupler. The first fiber interferometer is an equal-arm fiber interferometer, thus ensuring that the phase change detected by the first fiber interferometer does not include the phase change caused by laser frequency drift. The second wavelength division multiplexer... The sum of the fiber lengths of the transmission end pigtail and the pigtail of the first Faraday reflector is equal to the sum of the fiber lengths of the reflection end pigtail of the second wavelength division multiplexer and the service signal photoelectric receiver pigtail. The fiber delay of the first fiber interferometer measuring arm is twice the fiber delay from the output of port 4 of the first 3×3 fiber coupler, the input of the transmission end of the first wavelength division multiplexer, the output of the common end of the first wavelength division multiplexer, through the phase compensation module, the first fiber optic cable L1, the input of the common end of the second wavelength division multiplexer, the output of the transmission end of the second wavelength division multiplexer, to the first Faraday magnetic rotating reflector. The fiber delay of the first fiber interferometer reference arm is twice the fiber delay from the output of port 5 of the first 3×3 fiber coupler, through the input of port 1 of the first 1×2 fiber coupler, the output of port 3 of the first 1×2 fiber coupler, through the second fiber segment L2, to the second Faraday magnetic rotating reflector.

[0013] The fiber delay of the first fiber interferometer reference arm is equal to the fiber delay of the second fiber interferometer measurement arm. This is simplified to mean that, except for the common part from the output of the first 1×2 fiber coupler port 3 through the second fiber segment L2 to the second Faraday magnetic rotating mirror, the sum of the fiber lengths of the pigtails of the first 3×3 fiber coupler port 5 and the first 1×2 fiber coupler port 1 is equal to the sum of the fiber lengths of the pigtails of the first 1×2 fiber coupler port 2, the fiber isolator ISO input pigtail, the fiber isolator ISO output pigtail, and the second 3×3 fiber coupler port 4.

[0014] The fiber delay of the second fiber interferometer measuring arm is equal to the fiber delay of the second fiber interferometer reference arm. This can be simplified to the sum of the lengths of the pigtails at ports 5 of the first 3×3 fiber coupler, 1 of the first 1×2 fiber coupler, twice the length of the pigtail at port 3 of the first 1×2 fiber coupler, the pigtail at port 2 of the first 1×2 fiber coupler, the pigtail at the input of the fiber isolator ISO, the pigtail at the output of the fiber isolator ISO, and the pigtail at port 4 of the second 3×3 fiber coupler, and the first 3×3 fiber coupler reference arm's fiber delay. The sum of the lengths of the pigtails at ports 6 and 1 of the fiber optic coupler, twice the lengths of the pigtails at ports 2 and 3 of the fiber optic coupler, and the pigtails at ports 5 of the second 3×3 fiber optic coupler is equal. The lengths of the pigtails at the second and third Faraday magnetic rotating mirrors are equal. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

[0015] When the second fiber optic interferometer adopts the second connection method, the sum of the fiber lengths of the pigtail at port 2 of the second 1×2 fiber coupler and the pigtail at port 1 of the first 3×3 fiber coupler is equal to the sum of the fiber lengths of the pigtail at port 3 of the second 1×2 fiber coupler and the pigtail at port 1 of the second 3×3 fiber coupler. The sum of the fiber lengths of the pigtail at port 5 of the first 3×3 fiber coupler and the pigtail at port 1 of the first 1×2 fiber coupler is equal to the sum of the fiber lengths of the pigtail at port 2 of the first 1×2 fiber coupler, the input pigtail of the fiber isolator ISO, the output pigtail of the fiber isolator ISO, and the pigtail at port 4 ... The sum of the fiber lengths of the pigtails at ports 1 and 2 of the first 1×2 fiber coupler, the pigtail at port 2 of the first 1×2 fiber coupler, the pigtail at the input end of the fiber isolator ISO, the pigtail at the output end of the fiber isolator ISO, and the pigtail at port 4 of the second 3×3 fiber coupler is equal to twice the fiber length of the pigtail at port 5 of the second 3×3 fiber coupler. The fiber length of the pigtail of the second Faraday magnetic rotating mirror is equal to the fiber length of the pigtail of the third Faraday magnetic rotating mirror. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

[0016] Except for the second fiber segment L2 or the third fiber segment L3, the optical fibers of the pigtails of other optical devices, the optical fibers of the phase compensation module, and the optical fibers of the first optical fiber cable L1 are all single-mode optical fibers with the same refractive index and the same temperature drift delay change system.

[0017] The first 3×3 fiber optic coupler and the second 3×3 fiber optic coupler have ports 1, 2 and 3 on the same side with no order requirement, and ports 4, 5 and 6 on the same side with no order requirement.

[0018] The second fiber segment L2, the third fiber segment L3, the first 3×3 fiber coupler, the second 3×3 fiber coupler, the first 1×2 fiber coupler, the second Faraday magnetic rotating mirror, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror operate in the same temperature environment, and the pigtail lengths of the first 3×3 fiber coupler, the second 3×3 fiber coupler, the first 1×2 fiber coupler, the second Faraday magnetic rotating mirror, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror, in addition to matching the equal length requirement, do not exceed one meter.

[0019] The second fiber segment L2 and the third fiber segment L3 have the following relationship:

[0020] The fiber length of the second fiber segment L2 is D1 and the refractive index is n1. The fiber length of the third fiber segment L3 is D2 and the refractive index is n2. Therefore, D1×n1=D2×n2.

[0021] The fiber delay temperature drift coefficient of the third fiber segment L3 is A(tp) times that of the second fiber segment L2. A(tp) is a function of temperature, and A(tp)≠1. The delay temperature drift coefficient is the amount of delay change caused by a unit length of fiber under a unit temperature change, and the unit is ps / (km·℃), as shown in formula (1):

[0022]

[0023] The phase change detected by the first fiber interferometer per unit time is dN1 / dt, and the phase change detected by the second fiber interferometer per unit time is dN2 / dt. The real-time transmission delay change dN / dt that the phase compensation module needs to compensate is shown in formula (2):

[0024]

[0025] Where N1, N2, and N are the number of cycles of the coherent signal output by the fiber optic interferometer.

[0026] This technical solution addresses the problem of significant transmission delay variation detection errors caused by frequency drift of the coherent light source in existing fiber optic phase compensators. It employs a fiber optic phase compensator using two equal-length fiber optic interferometers sharing a common interferometer arm. One interferometer measures the transmission delay variation on the fiber optic cable after suppressing the phase detection error caused by laser frequency drift, while the other local interferometer measures the transmission delay variation caused by temperature drift of the shared interferometer arm, thus correcting the detection error of transmission delay variation on the fiber optic cable.

[0027] This technical solution uses two equal-arm fiber interferometers sharing a common interferometer arm to measure the transmission delay variation on the fiber optic cable after suppressing the phase detection error caused by laser frequency drift. It also corrects the transmission delay variation error caused by temperature drift of the reference arm of the equal-arm fiber interferometer, thereby achieving accurate detection and compensation of the transmission delay variation on the fiber optic cable.

[0028] This fiber optic phase compensator uses two equal-arm fiber optic interferometers sharing a common interferometer arm. It can measure the transmission delay variation on the fiber optic cable after suppressing the phase detection error caused by laser frequency drift, and can correct the transmission delay variation error caused by temperature drift of the reference arm of the equal-arm fiber optic interferometer. It can achieve accurate detection and compensation of the transmission delay variation on the fiber optic cable. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the compensator principle when the second fiber optic interferometer is connected in the first way in the embodiment.

[0030] Figure 2 This is a schematic diagram of the compensator principle when the second fiber optic interferometer is connected in the second embodiment.

[0031] In the diagram, 3×3-1. First 3×3 fiber optic coupler; 3×3-2. Second 3×3 fiber optic coupler; WDM-1. First wavelength division multiplexer; L1. First fiber optic cable; WDM-2. Second wavelength division multiplexer; FRM-1. First Faraday magnetic rotating mirror; 1×2-1. First 1×2 fiber optic coupler; L2. Second fiber segment; FRM-2. Second Faraday magnetic rotating mirror; ISO. Fiber optic isolator; CIR. Fiber optic circulator; L3. Third fiber segment; FRM-3. Third Faraday magnetic rotating mirror; PD-1. First photodetector; PD-2. Second photodetector; PD-3. Third photodetector; PD-4. Fourth photodetector. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this is not intended to limit the scope of the invention.

[0033] Example:

[0034] A fiber optic phase compensator for suppressing laser frequency drift system errors includes a narrow-linewidth laser, a first 3×3 fiber coupler 3×3-1, a second 3×3 fiber coupler 3×3-2, a first wavelength division multiplexer (WDM-1), a phase compensation module, a first optical fiber cable L1, a second WDM-2, a first Faraday magnetic rotating mirror (FRM-1), a first 1×2 fiber coupler 1×2-1, a second fiber segment L2, a second Faraday magnetic rotating mirror (FRM-2), an optical fiber isolator (ISO), an optical fiber circulator (CIR), a third fiber segment L3, a third Faraday magnetic rotating mirror (FRM-3), a first photodetector (PD-1), a second photodetector (PD-2), a third photodetector (PD-3), a fourth photodetector (PD-4), and a control module, wherein:

[0035] The first 3×3 fiber coupler 3×3-1, the first wavelength division multiplexer (WDM-1), the phase compensation module, the first optical fiber cable L1, the second wavelength division multiplexer (WDM-2), and the first Faraday magnetic rotating mirror (FRM-1) are sequentially connected. Simultaneously, the first 3×3 fiber coupler 3×3-1 is also sequentially connected with the first 1×2 fiber coupler 1×2-1, the second optical fiber segment L2, and the second Faraday magnetic rotating mirror (FRM-2) to collectively form the first fiber interferometer. The laser output from the narrow-linewidth laser is input into the first... A 3×3 fiber optic coupler (3×3-1) has its port 1 split into three beams, outputting from ports 4, 5, and 6 respectively. The optical path of the measuring arm of the first fiber optic interferometer is as follows: the laser output from port 4 of the first 3×3 fiber optic coupler (3×3-1) is connected to the transmission end of the first wavelength division multiplexer (WDM-1). The laser output from the common end of the first WDM-1 passes through the phase compensation module to the first fiber optic cable L1, which connects to the common end of the second WDM-2. The laser output from the common end of the second WDM-2... The laser output from the transmission end is fed into the first Faraday magnetic rotating mirror FRM-1 and reflected back to port 4 of the first 3×3 fiber coupler 3×3-1. The optical path of the reference arm of the first fiber interferometer is as follows: the output of port 5 of the first 3×3 fiber coupler 3×3-1 is fed into port 1 of the first 1×2 fiber coupler 1×2-1 and output through port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror FRM-2 and reflected back to port 5 of the first 3×3 fiber coupler 3×3-1. The first fiber interferometer is a Michelson fiber interferometer. The lasers of the measuring arm and the reference arm of the first fiber interferometer are coherent within the first 3×3 fiber coupler 3×3-1. The output interference signals enter the first photodetector PD-1 and the second photodetector PD-2 through ports 2 and 3 of the first 3×3 fiber coupler 3×3-1, respectively. The first photodetector PD-1 and the second photodetector PD-2 are connected to the control module, and the control module demodulates the phase change of the first fiber interferometer.

[0036] The first connection method for constructing the second fiber optic interferometer in this example is as follows: Figure 1 As shown, the first 3×3 fiber coupler 3×3-1, the first 1×2 fiber coupler 1×2-1, the second fiber segment L2, and the second Faraday magnetic rotating mirror FRM-2 are connected in sequence. Simultaneously, the first 3×3 fiber coupler 3×3-1, the fiber circulator CIR, the third fiber segment L3, and the third Faraday magnetic rotating mirror FRM-3 are connected in sequence. Furthermore, the first 1×2 fiber coupler 1×2-1, the fiber isolator ISO, and the second 3×3 fiber coupler 3×3-2 are connected, and the fiber circulator CIR is connected to the second 3×3 fiber coupler 3×3-2. Together, they form the second fiber optic interferometer. The optical path of the measuring arm of the second fiber optic interferometer is as follows: the output of port 5 of the first 3×3 fiber coupler 3×3-1 is connected to port 1 of the first 1×2 fiber coupler 1×2-1 and outputs through port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror FRM-2 and reflected back to the first 1×2 fiber coupler 1×2-1; the output of port 2 of the first 1×2 fiber coupler 1×2-1 is connected to port 4 of the second 3×3 fiber coupler 3×3-2 through the fiber isolator ISO; the optical path of the reference arm of the second fiber optic interferometer is as follows. The output of the first 3×3 fiber coupler 3×3-1 is connected to port 1 of the fiber optic circulator CIR and output through port 2. It then travels through the third fiber segment L3 to the third Faraday magnetic rotating mirror FRM-3 and is reflected back to port 2 of the fiber optic circulator CIR. Finally, it is connected from port 3 of the fiber optic circulator CIR to port 5 of the second 3×3 fiber coupler 3×3-2. The second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers from the measuring arm and reference arm of the second fiber interferometer are coherent within the second 3×3 fiber coupler 3×3-2. The output interference signals are respectively... Ports 1 and 2 of the second 3×3 fiber coupler 3×3-2 are connected to the third photodetector PD-3 and the fourth photodetector PD-4. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module. The control module demodulates the phase change of the second fiber interferometer. The control module calculates the fiber delay change on the measuring arm of the first fiber interferometer based on the phase change of the first fiber interferometer and the phase change of the second fiber interferometer, and controls the phase compensation module to provide feedback compensation for the fiber delay change on the measuring arm of the first fiber interferometer.

[0037] The second connection method for constructing the second fiber optic interferometer in this example is as follows: Figure 2As shown, the narrow linewidth laser output is connected to port 1 of the second 1×2 fiber coupler 1×2-2 and split into two outputs: one output is connected from port 2 of the second 1×2 fiber coupler 1×2-2 to port 1 of the first 3×3 fiber coupler 3×3-1, and the other output is connected from port 3 of the second 1×2 fiber coupler 1×2-2 to port 1 of the second 3×3 fiber coupler 3×3-2. The optical path of the measuring arm of the second fiber interferometer is as follows: the output from port 2 of the second 1×2 fiber coupler 1×2-2 is connected to port 1 of the first 3×3 fiber coupler 3×3-1, and the output from port 5 of the first 3×3 fiber coupler 3×3-1 is connected to the first 1×2 fiber coupler 1×2-1. The optical path of the reference arm of the second fiber interferometer is as follows: the output from port 1 and port 3 of the first 1×2 fiber coupler 1×2-1 is connected to port 1 of the second 3×3 fiber coupler 3×3-2 via the second fiber segment L2 and then reflected back to the first 1×2 fiber coupler 1×2-1. The output from port 2 of the first 1×2 fiber coupler 1×2-1 is connected to port 4 of the second 3×3 fiber coupler 3×3-2 via the fiber isolator ISO. The three Faraday magnetic rotating mirror FRM-3 reflects the light back to port 5 of the second 3×3 fiber coupler 3×3-2. At this time, the second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers of the measuring arm and the reference arm of the second fiber interferometer are coherent within the second 3×3 fiber coupler 3×3-2. The output interference signals enter the third photodetector PD-3 and the fourth photodetector PD-4 through ports 2 and 3 of the second 3×3 fiber coupler 3×3-2, respectively. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module to demodulate the phase change of the second fiber interferometer.

[0038] In this example, the service signal transmission path is as follows: the service signal modulation input terminal is input through the reflection terminal of the first wavelength division multiplexer (WDM-1) and output through the common terminal of the first wavelength division multiplexer (WDM-1), then through the phase compensation module and the first optical fiber cable L1, and finally input through the common terminal of the second wavelength division multiplexer (WDM-2) and output through the reflection terminal of the second wavelength division multiplexer (WDM-2) to the service signal photoelectric receiving terminal.

[0039] The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer, and the fiber delay of the measuring arm of the first fiber interferometer is equal to the fiber delay of the reference arm of the first fiber interferometer. The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer. That is, except for the common part consisting of the output pigtail of the common end of the first wavelength division multiplexer (WDM-1), the phase compensation module, the first optical fiber cable L1, and the common end pigtail of the second wavelength division multiplexer (WDM-2), the sum of the fiber lengths of the service signal output pigtail and the reflection pigtail of the first wavelength division multiplexer (WDM-1) is equal to the sum of the fiber lengths of the transmission pigtail of the first wavelength division multiplexer (WDM-1) and the 4-port pigtail of the first 3×3 fiber coupler 3×3-1. The first fiber interferometer is an equal-arm fiber interferometer, thus ensuring that the phase change detected by the first fiber interferometer does not include the phase change caused by laser frequency drift. The transmission pigtail of the second wavelength division multiplexer (WDM-2) and the first Faraday reflector F... The sum of the fiber lengths of the RM-1 pigtail is equal to the sum of the fiber lengths of the pigtails at the reflection end of the second wavelength division multiplexer (WDM-2) and the service signal photoelectric receiver end. The fiber delay of the first fiber interferometer measuring arm is as follows: from the output of the 4 ports of the first 3×3 fiber coupler 3×3-1, the input of the transmission end of the first wavelength division multiplexer (WDM-1), the output of the common end of the first wavelength division multiplexer (WDM-1), through the phase compensation module, the first fiber optic cable L1, and the input of the common end of the second wavelength division multiplexer (WDM-2). The fiber delay between the output of the transmission end of the second wavelength division multiplexer (WDM-2) and the first Faraday reflector (FRM-1) is twice the fiber delay. The fiber delay of the reference arm of the first fiber interferometer is twice the fiber delay between the output of the 5th port of the first 3×3 fiber coupler (3×3-1), the input of the 1st port of the first 1×2 fiber coupler (1×2-1), the output of the 3rd port of the first 1×2 fiber coupler (1×2-1), and the second fiber segment L2 to the second Faraday magnetic rotating reflector (FRM-2).

[0040] The fiber delay of the first fiber interferometer reference arm is equal to the fiber delay of the second fiber interferometer measurement arm. This can be simplified to the fact that, except for the common part from the 3-port output of the first 1×2 fiber coupler 1×2-1 through the second fiber segment L2 to the second Faraday magnetic rotating mirror FRM-2, the sum of the fiber lengths of the 5-port pigtail of the first 3×3 fiber coupler 3×3-1 and the 1-port pigtail of the first 1×2 fiber coupler 1×2-1 is equal to the sum of the fiber lengths of the 2-port pigtail of the first 1×2 fiber coupler 1×2-1, the ISO input pigtail of the fiber isolator, the ISO output pigtail of the fiber isolator, and the 4-port pigtail of the second 3×3 fiber coupler 3×3-2.

[0041] The fiber delay of the second fiber interferometer measuring arm is equal to the fiber delay of the second fiber interferometer reference arm. This can be simplified to the sum of the lengths of the following: the 5-port pigtail of the first 3×3 fiber coupler 3×3-1; the 1-port pigtail of the first 1×2 fiber coupler 1×2-1; twice the length of the 3-port pigtail of the first 1×2 fiber coupler 1×2-1; the 2-port pigtail of the first 1×2 fiber coupler 1×2-1; the input pigtail of the fiber isolator ISO; the output pigtail of the fiber isolator ISO; and the 4-port pigtail of the second 3×3 fiber coupler 3×3-2. This sum is equal to the length of the first... The sum of the lengths of the 6-port pigtail of the 3×3 fiber coupler 3×3-1, the 1-port pigtail of the fiber circulator, twice the length of the 2-port pigtail of the fiber circulator, the 3-port pigtail of the fiber circulator, and the 5-port pigtail of the second 3×3 fiber coupler 3×3-2 is equal. The lengths of the pigtails of the second Faraday magnetic rotating mirror FRM-2 and the third Faraday magnetic rotating mirror FRM-3 are equal. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

[0042] When the second fiber optic interferometer adopts the second connection method, the following conditions must be met: the sum of the fiber lengths of the 2-port pigtail of the second 1×2 fiber coupler 1×2-2 and the 1-port pigtail of the first 3×3 fiber coupler 3×3-1 is equal to the sum of the fiber lengths of the 3-port pigtail of the second 1×2 fiber coupler 1×2-2 and the 1-port pigtail of the second 3×3 fiber coupler 3×3-2; the sum of the fiber lengths of the 5-port pigtail of the first 3×3 fiber coupler 3×3-1 and the 1-port pigtail of the first 1×2 fiber coupler 1×2-1 is equal to the sum of the fiber lengths of the 2-port pigtail of the first 1×2 fiber coupler 1×2-1, the input pigtail of the fiber isolator ISO, the output pigtail of the fiber isolator ISO, and the 4-port pigtail of the second 3×3 fiber coupler 3×3-2; the first 3×3 fiber coupler 3×3... The sum of the fiber lengths of the following components is equal to twice the length of the 5-port pigtail of the first 1×2 fiber coupler 1×2-1, the 1-port pigtail of the first 1×2 fiber coupler 1×2-1, the 2-port pigtail of the first 1×2 fiber coupler 1×2-1, the input pigtail of the fiber isolator ISO, the output pigtail of the fiber isolator ISO, and the 4-port pigtail of the second 3×3 fiber coupler 3×3-2. The fiber length of the second Faraday magnetic rotating mirror pigtail is equal to the fiber length of the third Faraday magnetic rotating mirror pigtail. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

[0043] Except for the second fiber segment L2 or the third fiber segment L3, the optical fibers of the pigtails of other optical devices, the optical fibers of the phase compensation module, and the optical fibers of the first optical fiber cable L1 are all single-mode optical fibers with the same refractive index and the same temperature drift delay change system.

[0044] The first 3×3 fiber optic coupler 3×3-1 and the second 3×3 fiber optic coupler 3×3-2 have ports 1, 2 and 3 on the same side and there is no order requirement. Ports 4, 5 and 6 are on the same side and there is no order requirement.

[0045] The second fiber segment L2, the third fiber segment L3, the first 3×3 fiber coupler 3×3-1, the second 3×3 fiber coupler 3×3-2, the first 1×2 fiber coupler 1×2-1, the second Faraday magnetic rotating mirror FRM-2, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror FRM-3 operate in the same temperature environment, and the pigtail lengths of the first 3×3 fiber coupler 3×3-1, the second 3×3 fiber coupler 3×3-2, the first 1×2 fiber coupler 1×2-1, the second Faraday magnetic rotating mirror FRM-2, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror FRM-3, in addition to matching the length requirement, do not exceed one meter.

[0046] The second fiber segment L2 and the third fiber segment L3 have the following relationship:

[0047] The fiber length of the second fiber segment L2 is D1 and the refractive index is n1. The fiber length of the third fiber segment L3 is D2 and the refractive index is n2. Therefore, D1×n1=D2×n2.

[0048] The fiber delay temperature drift coefficient of the third fiber segment L3 is A(tp) times that of the second fiber segment L2. A(tp) is a function of temperature, and A(tp)≠1. The delay temperature drift coefficient is the amount of delay change caused by a unit length of fiber under a unit temperature change, and the unit is ps / (km·℃), as shown in formula (1):

[0049]

[0050] The phase change detected by the first fiber interferometer per unit time is dN1 / dt, and the phase change detected by the second fiber interferometer per unit time is dN2 / dt. The real-time transmission delay change dN / dt that the phase compensation module needs to compensate is shown in formula (2):

[0051]

[0052] Where N1, N2, and N are the number of cycles of the coherent signal output by the fiber optic interferometer.

Claims

1. A fiber optic phase compensator for suppressing laser frequency drift system errors, characterized in that, The system includes a narrow-linewidth laser, a first 3×3 fiber coupler, a second 3×3 fiber coupler, a first wavelength division multiplexer, a phase compensation module, a first fiber optic cable L1, a second wavelength division multiplexer, a first Faraday magnetic rotator, a first 1×2 fiber coupler, a second fiber segment L2, a second Faraday magnetic rotator, a fiber isolator ISO, a fiber optic circulator CIR, a third fiber segment L3, a third Faraday magnetic rotator, a first photodetector PD-1, a second photodetector PD-2, a third photodetector PD-3, a fourth photodetector PD-4, and a control module, wherein: A first 3×3 fiber coupler, a first wavelength division multiplexer (WDM), a phase compensation module, a first fiber optic cable L1, a second WDM, and a first Faraday magnetic rotating mirror are sequentially connected. Simultaneously, the first 3×3 fiber coupler, together with a first 1×2 fiber coupler, a second fiber segment L2, and a second Faraday magnetic rotating mirror, constitute a first fiber interferometer. A narrow-linewidth laser outputs laser light into port 1 of the first 3×3 fiber coupler, splitting it into three beams that are output from ports 4, 5, and 6 respectively. The optical path of the measuring arm of the first fiber interferometer is as follows: the laser output from port 4 of the first 3×3 fiber coupler enters the transmission end of the first WDM; the laser output from the common end of the first WDM passes through the phase compensation module to the first fiber optic cable L1, entering the common end of the second WDM; and the laser output from the transmission end of the second WDM enters the first Faraday magnetic rotating mirror. The first Faraday magnetic rotating mirror reflects the laser back to port 4 of the first 3×3 fiber coupler. The reference arm optical path of the first fiber interferometer is as follows: the output of port 5 of the first 3×3 fiber coupler is connected to port 1 of the first 1×2 fiber coupler and output through port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflecting back to port 5 of the first 3×3 fiber coupler. The first fiber interferometer is a Michelson fiber interferometer. The lasers of the measuring arm and the reference arm of the first fiber interferometer are coherent in the first 3×3 fiber coupler. The output interference signals enter the first photodetector PD-1 and the second photodetector PD-2 through ports 2 and 3 of the first 3×3 fiber coupler, respectively. The first photodetector PD-1 and the second photodetector PD-2 are connected to the control module. The control module demodulates the phase change of the first fiber interferometer. The first connection method for constructing the second fiber optic interferometer is as follows: a first 3×3 fiber optic coupler, a first 1×2 fiber optic coupler, a second fiber segment L2, and a second Faraday magnetic rotating mirror are connected sequentially. Simultaneously, the first 3×3 fiber optic coupler, a fiber optic circulator CIR, a third fiber segment L3, and a third Faraday magnetic rotating mirror are connected sequentially. Furthermore, the first 1×2 fiber optic coupler, a fiber optic isolator ISO, and the second 3×3 fiber optic coupler are connected, and the fiber optic circulator CIR is connected to the second 3×3 fiber optic coupler, together forming the second fiber optic interferometer. The optical path of the measuring arm of the second fiber optic interferometer is as follows: the output from port 5 of the first 3×3 fiber optic coupler is connected to port 1 of the first 1×2 fiber optic coupler and output from port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflected back to the first 1×2 fiber optic coupler; the output from port 2 of the first 1×2 fiber optic coupler is connected to port 4 of the second 3×3 fiber optic coupler via the fiber optic isolator ISO. The optical path of the reference arm of the second fiber optic interferometer is as follows: the output from port 6 of the first 3×3 fiber optic coupler... The output signal is connected to port 1 of the fiber optic circulator (CIR) and output through port 2. It then passes through the third fiber segment L3 to the third Faraday magnetic rotating mirror and is reflected back to port 2 of the CIR. The output signal is connected to port 5 of the second 3×3 fiber coupler through port 3 of the CIR. The second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers of the measuring arm and the reference arm of the second fiber interferometer are coherent within the second 3×3 fiber coupler. The output interference signals enter the third photodetector PD-3 and the fourth photodetector PD-4 through ports 1 and 2 of the second 3×3 fiber coupler, respectively. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module. The control module demodulates the phase change of the second fiber interferometer. Based on the phase change of the first fiber interferometer and the phase change of the second fiber interferometer, the control module calculates the fiber delay change on the measuring arm of the first fiber interferometer and controls the phase compensation module to provide feedback compensation for the fiber delay change on the measuring arm of the first fiber interferometer. The second connection method for the second fiber optic interferometer is as follows: the laser output from the narrow-linewidth laser is input to port 1 of the second 1×2 fiber optic coupler and split into two outputs: one output is connected from port 2 of the second 1×2 fiber optic coupler to port 1 of the first 3×3 fiber optic coupler, and the other output is connected from port 3 of the second 1×2 fiber optic coupler to port 1 of the second 3×3 fiber optic coupler. The optical path of the measuring arm of the second fiber optic interferometer is as follows: the output from port 2 of the second 1×2 fiber optic coupler is connected to port 1 of the first 3×3 fiber optic coupler, output from port 5 of the first 3×3 fiber optic coupler, connected to port 1 of the first 1×2 fiber optic coupler, and output from port 3, passing through the second fiber segment L2 to the second Faraday magnetic rotating mirror and reflected back to the first 1×2 fiber optic coupler, and output from port 2 of the first 1×2 fiber optic coupler, passing through the fiber isolator ISO to the second Faraday magnetic rotating mirror. The optical path of the reference arm of the second fiber interferometer is as follows: the laser from the measuring arm of the second fiber interferometer is output from the 3-port of the second 1×2 fiber coupler, connected to the 1-port of the second 3×3 fiber coupler, output from the 5-port of the second 3×3 fiber coupler, reaches the third Faraday magnetic rotating mirror via the third fiber segment L3, and is reflected back to the 5-port of the second 3×3 fiber coupler. At this time, the second fiber interferometer is a Mach-Zehnder fiber interferometer. The lasers of the measuring arm and the reference arm of the second fiber interferometer are coherent in the second 3×3 fiber coupler. The output interference signals enter the third photodetector PD-3 and the fourth photodetector PD-4 from the 2-port and 3-port of the second 3×3 fiber coupler, respectively. The third photodetector PD-3 and the fourth photodetector PD-4 are connected to the control module to demodulate the phase change of the second fiber interferometer. The service signal transmission path is as follows: the service signal modulation input terminal is input through the reflection end of the first wavelength division multiplexer and output through the common end of the first wavelength division multiplexer, then through the phase compensation module and the first optical fiber cable L1, and finally input through the common end of the second wavelength division multiplexer and output through the reflection end of the second wavelength division multiplexer to the service signal photoelectric receiving end.

2. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer, and the fiber delay of the measuring arm of the first fiber interferometer is equal to the fiber delay of the reference arm of the first fiber interferometer. The fiber length for transmitting the service signal is equal to the fiber length of the measuring arm of the first fiber interferometer. That is, except for the common part consisting of the pigtail at the common end output of the first wavelength division multiplexer, the phase compensation module, the first optical fiber cable L1, and the pigtail at the common end of the second wavelength division multiplexer, the sum of the fiber lengths of the service signal output pigtail and the reflection pigtail of the first wavelength division multiplexer is equal to the sum of the fiber lengths of the transmission pigtail of the first wavelength division multiplexer and the 4-port pigtail of the first 3×3 fiber coupler. The sum of the fiber lengths of the transmission pigtail of the second wavelength division multiplexer and the pigtail of the first Faraday reflector is equal to the sum of the fiber lengths of the second wavelength division multiplexer. The sum of the fiber lengths of the pigtails at the reflector end of the multiplexer and the photoelectric receiver end of the service signal is equal. The fiber delay of the first fiber interferometer measuring arm is twice the fiber delay from the output of port 4 of the first 3×3 fiber coupler, the input of the transmission end of the first wavelength division multiplexer, the output of the common end of the first wavelength division multiplexer, through the phase compensation module, the first fiber optic cable L1, the input of the common end of the second wavelength division multiplexer, the output of the transmission end of the second wavelength division multiplexer, to the first Faraday magnetic rotating mirror. The fiber delay of the first fiber interferometer reference arm is twice the fiber delay from the output of port 5 of the first 3×3 fiber coupler, through the input of port 1 of the first 1×2 fiber coupler, the output of port 3 of the first 1×2 fiber coupler, through the second fiber segment L2 to the second Faraday magnetic rotating mirror.

3. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The fiber delay of the first fiber interferometer reference arm is equal to the fiber delay of the second fiber interferometer measurement arm. This is simplified to mean that, except for the common part from the output of the first 1×2 fiber coupler port 3 through the second fiber segment L2 to the second Faraday magnetic rotating mirror, the sum of the fiber lengths of the pigtails of the first 3×3 fiber coupler port 5 and the first 1×2 fiber coupler port 1 is equal to the sum of the fiber lengths of the pigtails of the first 1×2 fiber coupler port 2, the fiber isolator ISO input pigtail, the fiber isolator ISO output pigtail, and the second 3×3 fiber coupler port 4.

4. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The fiber delay of the second fiber interferometer measuring arm is equal to the fiber delay of the second fiber interferometer reference arm. This can be simplified to the sum of the lengths of the pigtails at ports 5 of the first 3×3 fiber coupler, 1 of the first 1×2 fiber coupler, twice the length of the pigtail at port 3 of the first 1×2 fiber coupler, the pigtail at port 2 of the first 1×2 fiber coupler, the pigtail at the input of the fiber isolator ISO, the pigtail at the output of the fiber isolator ISO, and the pigtail at port 4 of the second 3×3 fiber coupler, and the first 3×3 fiber coupler reference arm's fiber delay. The sum of the lengths of the pigtails at ports 6 and 1 of the fiber optic coupler, twice the lengths of the pigtails at ports 2 and 3 of the fiber optic coupler, and the pigtails at ports 5 of the second 3×3 fiber optic coupler is equal. The lengths of the pigtails at the second and third Faraday magnetic rotating mirrors are equal. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

5. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, When the second fiber optic interferometer adopts the second connection method, the sum of the fiber lengths of the pigtail at port 2 of the second 1×2 fiber coupler and the pigtail at port 1 of the first 3×3 fiber coupler is equal to the sum of the fiber lengths of the pigtail at port 3 of the second 1×2 fiber coupler and the pigtail at port 1 of the second 3×3 fiber coupler. The sum of the fiber lengths of the pigtail at port 5 of the first 3×3 fiber coupler and the pigtail at port 1 of the first 1×2 fiber coupler is equal to the sum of the fiber lengths of the pigtail at port 2 of the first 1×2 fiber coupler, the input pigtail of the fiber isolator ISO, the output pigtail of the fiber isolator ISO, and the pigtail at port 4 ... The sum of the fiber lengths of the pigtails at ports 1 and 2 of the first 1×2 fiber coupler, the pigtail at port 2 of the first 1×2 fiber coupler, the pigtail at the input end of the fiber isolator ISO, the pigtail at the output end of the fiber isolator ISO, and the pigtail at port 4 of the second 3×3 fiber coupler is equal to twice the fiber length of the pigtail at port 5 of the second 3×3 fiber coupler. The fiber length of the pigtail of the second Faraday magnetic rotating mirror is equal to the fiber length of the pigtail of the third Faraday magnetic rotating mirror. The length of the second fiber segment L2 is D1, and the refractive index of the fiber core is n1. The length of the third fiber segment L3 is D2, and the refractive index of the fiber core is n2. Therefore, D1×n1=D2×n2.

6. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, Except for the second fiber segment L2 or the third fiber segment L3, the optical fibers of the pigtails of other optical devices, the optical fibers of the phase compensation module, and the optical fibers of the first optical fiber cable L1 are all single-mode optical fibers with the same refractive index and the same temperature drift delay change system.

7. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The first 3×3 fiber optic coupler and the second 3×3 fiber optic coupler have ports 1, 2 and 3 on the same side with no order requirement, and ports 4, 5 and 6 on the same side with no order requirement.

8. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The second fiber segment L2, the third fiber segment L3, the first 3×3 fiber coupler, the second 3×3 fiber coupler, the first 1×2 fiber coupler, the second Faraday magnetic rotating mirror, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror operate in the same temperature environment, and the pigtail lengths of the first 3×3 fiber coupler, the second 3×3 fiber coupler, the first 1×2 fiber coupler, the second Faraday magnetic rotating mirror, the fiber isolator ISO, the fiber circulator CIR, and the third Faraday magnetic rotating mirror, in addition to matching the equal length requirement, do not exceed one meter.

9. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The second fiber segment L2 and the third fiber segment L3 have the following relationship: The fiber length of the second fiber segment L2 is D1 and the refractive index is n1. The fiber length of the third fiber segment L3 is D2 and the refractive index is n2. Therefore, D1×n1=D2×n2. The fiber delay temperature drift coefficient of the third fiber segment L3 is A(tp) times that of the second fiber segment L2. A(tp) is a function of temperature. The delay temperature drift coefficient is the amount of delay change caused by a unit length of fiber under a unit temperature change, and the unit is ps / (km·℃), as shown in formula (1):

10. The fiber optic phase compensator for suppressing laser frequency drift system errors according to claim 1, characterized in that, The phase change detected by the first fiber interferometer per unit time is dN1 / dt, and the phase change detected by the second fiber interferometer per unit time is dN2 / dt. The real-time transmission delay change dN / dt that the phase compensation module needs to compensate is shown in formula (2): Where N1, N2, and N are the number of cycles of the coherent signal output by the fiber optic interferometer.

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