Optical fiber phase stabilizing device and method

Abstract

The invention provides an optical fiber phase stabilization device and method, and the device comprises a crystal oscillator, a power divider, an optical module, a phase comparison time delay control module, an optical fiber beam splitter, an optical switch, and a first circulator, the crystal oscillator is used for transmitting a signal source, and inputting the signal source into the power divider; the power divider is used for dividing the electric signal into two paths, one path is input into the optical module, and the other path is input into the phase comparison time delay control module; the output end of the optical module is connected with the optical fiber beam splitter, and the input end of the optical module is connected with the optical switch; the optical fiber beam splitter is used for dividing an optical signal output from the optical module into two paths, one path is input into the first circulator, and the other path is input into the optical switch; the phase comparison time delay control module receives two paths of different optical signals through an optical switch. According to the invention, the problem that the optical fiber length measurement control precision is affected due to the fact that the electro-optical modulation device and the photoelectric detection device both have certain slow phase drift in the current high-precision optical fiber length change measurement process can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision optical fiber phase stabilization, and more specifically, to a sub-ps level optical fiber phase stabilization device and method. Background Art

[0002] Fiber optic phase stabilization technology is widely used in the fields of time-frequency transmission, satellite measurement and control, and coherent signal transmission. Among them, multiple optical pulse signals need to be synchronized after being transmitted to the remote end through optical fiber. Since the length of multiple optical fibers changes differently with environmental conditions such as temperature, the optical pulse signals output by the optical fiber can no longer maintain synchronization. Therefore, it is necessary to measure the change in the length of the optical fiber and perform feedback control to achieve optical fiber.

[0003] At present, a relatively simple method for high-precision measurement of optical fiber length changes is to modulate the electrical signal onto light and transmit it to the far end through the optical fiber; after the far end is looped back to the near end through a circulator and other devices, the electrical signal is detected by a photodetector. By performing phase comparison between the detected electrical signal and the original electrical signal, accurate measurement of the change in optical fiber length can be achieved. Since both the electro-optical modulation device and the photodetection device have a certain slow phase drift, the control accuracy of the optical fiber length measurement is affected.

[0004] In order to solve the above problems, the present invention provides a new optical fiber phase stabilization device and method. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a fiber optic phase stabilization device and method to solve the current high-precision measurement of fiber length changes due to the presence of a certain phase slow drift in both the electro-optical modulation device and the photoelectric detection device, which affects the control accuracy of the fiber length measurement.

[0006] The present invention provides an optical fiber phase stabilization device, comprising a crystal resonator, a power divider, an optical module connected to the power divider and a phase comparison delay control module, an optical fiber beam splitter and an optical switch connected to the optical module, and a first circulator connected to the optical fiber beam splitter and the optical switch, wherein:

[0007] The crystal resonator is used to send out a signal source and input it into the power divider;

[0008] The power divider is used to divide the electrical signal emitted by the signal source into two paths, wherein one path of the electrical signal is input into the optical module, and the other path of the electrical signal is input into the phase comparison delay control module;

[0009] The output end of the optical module is connected to the optical fiber splitter, and the input end of the optical module is connected to the optical switch;

[0010] The optical fiber beam splitter is used to split the optical signal output from the optical module into two paths, wherein one optical signal is input into the first circulator, and the other optical signal is input into the optical switch;

[0011] The phase comparison delay control module receives two different optical signals through the optical switch.

[0012] In addition, a preferred solution is that filters are provided in the optical module and the phase comparison delay control module, wherein:

[0013] The filter is used to filter the optical signal output from the optical module to form a sinusoidal electrical signal, and input the signal into the phase comparison delay control module.

[0014] In addition, a preferred solution is that the optical module includes an electro-optic modulator and a photodetector, wherein:

[0015] The electro-optic modulator is used to adjust and process the electrical signal input to the optical module to generate an optical signal, and output the optical signal to the optical fiber splitter;

[0016] The photoelectric detector is used to detect and amplify the optical signal input to the optical module, and output it to the filter.

[0017] In addition, a preferred solution is that the optical fiber phase stabilization device further includes a first wavelength division multiplexer and an adjustable optical delay line, wherein:

[0018] The first wavelength division multiplexer is connected to the first circulator and the adjustable optical delay line respectively, and is located between the first circulator and the adjustable optical delay line.

[0019] In addition, a preferred solution is that the optical fiber phase stabilization device further includes an external long optical fiber, a second wavelength division multiplexer, and a second circulator connected in sequence, wherein:

[0020] The external long optical fiber is connected to the adjustable optical delay line, and the adjustable optical delay line is located between the first wavelength division multiplexer and the external long optical fiber.

[0021] In addition, a preferred solution is that the first circulator, the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, and the second circulator are connected in sequence to form a round-trip loop of the optical signal.

[0022] The present invention also provides an optical fiber phase stabilization method, which uses the above optical fiber phase stabilization device to achieve phase stabilization, and the method comprises:

[0023] The electrical signal emitted by the signal source is divided into two paths by a power divider, one of the electrical signals is input into the optical module, and the other electrical signal is input into the phase comparison delay control module as an input electrical signal;

[0024] The optical module processes the input electrical signal to generate an optical signal, and inputs the optical signal into the optical fiber splitter;

[0025] The optical signal is divided into two paths by the optical fiber beam splitter, wherein one optical signal is a near-ground signal and the other optical signal is a far-ground signal;

[0026] Controlling the optical switch to receive the near-ground signal and the far-ground signal respectively through the phase comparison delay control module, and inputting the received near-ground signal and the far-ground signal respectively into the optical module;

[0027] Amplifying the near-ground signal and the far-ground signal respectively through the optical module;

[0028] The near-ground signal and the far-ground signal after amplification are filtered respectively, and input into the phase comparison delay control module;

[0029] Processing the input electrical signal, the filtered near-ground signal, and the filtered far-ground signal through the phase comparison delay control module to obtain phase differences of the near-ground signal and the far-ground signal relative to the input electrical signal respectively;

[0030] The change in optical fiber length is determined according to the difference between the phase difference between the far-ground signal and the input electrical signal and the phase difference between the near-ground signal and the input electrical signal.

[0031] In addition, a preferred solution is that the near-ground signal is directly input into the optical switch from the optical fiber beam splitter;

[0032] The remote signal enters the first circulator from the optical fiber splitter, passes through the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, the second circulator in sequence, and then returns from the second circulator to the first circulator, and then enters the optical switch.

[0033] In addition, a preferred solution is that controlling the optical switch to receive the near-ground signal and the far-ground signal respectively through the phase comparison delay control module comprises the following steps:

[0034] When the optical switch is controlled by the phase comparison delay control module to receive the ground proximity signal, the ground proximity signal is input to the optical module;

[0035] When the optical switch is controlled by the phase comparison delay control module to receive the remote signal, the remote signal is input to the optical module.

[0036] In addition, a preferred solution is that when the ground proximity signal is input to the optical module,

[0037] The optical module detects and amplifies the ground proximity signal, converts the ground proximity signal from an optical signal into an electrical signal, and inputs the electrical signal into a filter;

[0038] The near-ground signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module;

[0039] The phase difference between the near-ground signal and the input electrical signal is measured by the phase comparison delay control module.

[0040] In addition, a preferred solution is that when the remote signal is input to the optical module,

[0041] The remote signal is detected and amplified by the optical module, and the remote signal is converted from an optical signal into an electrical signal, and input into a filter;

[0042] The remote signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module;

[0043] The phase difference between the remote signal and the input electrical signal is measured by the phase comparison delay control module.

[0044] In addition, a preferred solution is to use the difference between the phase difference between the remote signal and the input electrical signal and the phase difference between the near-ground signal and the input electrical signal as the measurement result of the change in optical fiber length; wherein,

[0045] The measurement result includes information on the change in length of the external long optical fiber. The adjustable optical fiber delay line is controlled by the measurement result, and the change in optical fiber length is compensated to achieve stability of the optical fiber length.

[0046] It can be seen from the above technical solutions that the optical fiber phase stabilization device and method provided by the present invention switches between the local short optical fiber loopback signal (near-ground signal) of the photodetector in the optical module and the loopback signal (far-ground signal) from the long optical fiber through the optical path transmission process. The phase difference between the received filtered electrical signal (sine wave) and the input electrical signal is measured by the phase comparison delay control module. By making a difference between the phase difference during the far-ground loopback and the phase difference during the near-ground loopback, the slow phase drift of the signal during electro-optical modulation and the slow phase drift of the signal during photoelectric detection filtering are completely eliminated. The change in the phase difference before and after the optical switch switching only contains the information of the change in optical fiber length, and this signal is used to control the adjustable optical fiber delay line to achieve the purpose of stabilizing the optical fiber length. By using optical devices with smaller drift (optical fiber splitters and optical switches) to eliminate the influence of electrical devices with larger drift (electro-optical modulators, photodetectors, and filters), a sub-ps level stable optical fiber length is achieved.

[0047] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] By referring to the following description and claims in conjunction with the accompanying drawings, and with a more comprehensive understanding of the present invention, other objects and results of the present invention will become more apparent and easier to understand. In the accompanying drawings:

[0049] Figure 1 is a schematic diagram of an optical fiber phase stabilization device according to an embodiment of the present invention;

[0050] Figure 2 Schematic diagram of the process of the optical fiber phase stabilization method according to an embodiment of the present invention.

[0051] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0052] In the following description, for the purpose of illustration, in order to provide a comprehensive understanding of one or more embodiments, many specific details are set forth. However, it is apparent that these embodiments may also be implemented without these specific details. In other examples, for ease of describing one or more embodiments, known structures and devices are shown in the form of block diagrams.

[0053] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0054] In response to the aforementioned problems that in the current high-precision measurement of optical fiber length changes, both the electro-optical modulation device and the photoelectric detection device have a certain phase slow drift, which affects the control accuracy of the optical fiber length measurement, the present invention proposes an optical fiber phase stabilization device and method.

[0055] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0056] In order to illustrate the structure of the optical fiber phase stabilization device provided by the present invention, Figure 1 The structure of the optical fiber phase stabilizing device according to an embodiment of the present invention is shown.

[0057] like Figure 1 As shown, the optical fiber phase stabilization device provided by the present invention includes a crystal oscillator, a power divider, an optical module and a phase comparison delay control module connected to the power divider, an optical fiber splitter and an optical switch connected to the optical module, and a first circulator connected to the optical fiber splitter and the optical switch, wherein the crystal oscillator is used to emit a signal source and input it into the power divider; the power divider is used to divide the electrical signal emitted by the signal source into two paths, wherein one path of electrical signal is input into the optical module, and the other path of electrical signal is input into the phase comparison delay control module; the output end of the optical module is connected to the optical fiber splitter, and the input end of the optical module is connected to the optical switch; the optical fiber splitter is used to divide the optical signal output from the optical module into two paths, wherein one path of optical signal is input into the first circulator, and the other path of optical signal is input into the optical switch; the phase comparison delay control module receives two different optical signals through the optical switch.

[0058] In the present invention, by adding optical fiber splitters and optical switches in the optical path, optical devices with smaller drift (optical fiber splitters and optical switches) are used to eliminate the influence of electrical devices with larger drift (electro-optical modulators and photodetectors and filters in optical modules), thereby achieving sub-ps level stable optical fiber length.

[0059] In an embodiment of the present invention, filters are provided in the optical module and the phase comparison delay control module, and the filters are used to filter the optical signal output from the optical module to form a sinusoidal electrical signal and input it into the phase comparison delay control module.

[0060] The optical module includes an electro-optical modulator and a photodetector, wherein the electro-optical modulator is used to adjust and process the electrical signal input to the optical module to generate an optical signal, and output it to the optical fiber splitter; the photodetector is used to detect and amplify the optical signal input to the optical module, and output it to the filter.

[0061] The optical fiber phase stabilization device further includes a first wavelength division multiplexer, an adjustable optical delay line, an external long optical fiber, a second wavelength division multiplexer, and a second circulator, wherein the first wavelength division multiplexer is respectively connected to the first circulator and the adjustable optical delay line, and is located between the first circulator and the adjustable optical delay line; the external long optical fiber is connected to the adjustable optical delay line, and the adjustable optical delay line is located between the first wavelength division multiplexer and the external long optical fiber. The first circulator, the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, and the second circulator are connected in sequence to form a round-trip loop of the optical signal.

[0062] exist Figure 1 In the embodiment shown, the sine wave signal output by the 100MHz crystal oscillator is divided into two signals by the power divider, one of which is connected to the phase comparison delay control module, and the other is connected to the optical module. The optical module sends out the modulated signal of the input signal. The modulated optical signal is divided into two paths by the optical fiber splitter, and one optical signal S1 is output to the optical switch. The other optical signal is output to the external long optical fiber after passing through the first circulator, the first wavelength division multiplexer, and the adjustable optical delay line; after passing through the long optical fiber, the optical signal is output to the remote second wavelength division multiplexer and the second circulator, and the optical signal is looped back, and after passing through the second circulator and the second wavelength division multiplexer, it returns to the external long optical fiber. After passing through the long optical fiber, the optical signal is output to the adjustable optical delay line, the first wavelength division multiplexer, and the first circulator. The first circulator outputs the looped optical signal S2 to the optical switch. The change in the length of the long optical fiber caused by the environment causes the delay of the optical signal to change, which is ultimately reflected in the phase change of the S2 modulation signal.

[0063] Based on the above optical fiber phase stabilization device, the present invention also provides an optical fiber phase stabilization method. Figure 2 The flowchart of the optical fiber phase stabilization method according to an embodiment of the present invention is shown.

[0064] like Figure 2 As shown, the optical fiber phase stabilization method provided by the present invention comprises:

[0065] S110: Splitting the electrical signal emitted by the signal source into two paths through a power splitter, inputting one of the electrical signals into an optical module, and inputting the other electrical signal as an input electrical signal into a phase comparison delay control module;

[0066] S120: Processing the input electrical signal through the optical module to generate an optical signal, and inputting the optical signal into the optical fiber splitter;

[0067] S130: Splitting the optical signal into two paths through the optical fiber splitter, wherein one optical signal is a near-ground signal and the other optical signal is a far-ground signal;

[0068] S140: Control the optical switch to receive the near-ground signal and the far-ground signal respectively through the phase comparison delay control module, and input the received near-ground signal and the far-ground signal to the optical module respectively;

[0069] S150: Amplifying the near-ground signal and the far-ground signal respectively by using the optical module;

[0070] S160: filtering the near-ground signal and the far-ground signal after amplification respectively, and inputting the amplified near-ground signal and the far-ground signal into the phase comparison delay control module;

[0071] S170: Processing the input electrical signal, the filtered near-ground signal, and the filtered far-ground signal through the phase comparison delay control module to obtain phase differences of the near-ground signal and the far-ground signal relative to the input electrical signal, respectively;

[0072] S180: Determine the change in optical fiber length according to the difference between the phase difference between the far-ground signal and the input electrical signal and the phase difference between the near-ground signal and the input electrical signal.

[0073] In step S130, the near-ground signal is directly input into the optical switch from the optical fiber splitter; the far-ground signal enters the first circulator from the optical fiber splitter, and then passes through the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, the second circulator in sequence, and then returns from the second circulator to the first circulator, and then inputs into the optical switch.

[0074] In step S140, controlling the optical switch to receive the near-ground signal and the far-ground signal respectively through the phase comparison delay control module includes the following steps:

[0075] When the phase comparison and delay control module is used to control the optical switch to receive the near-ground signal, the near-ground signal is input to the optical module; when the phase comparison and delay control module is used to control the optical switch to receive the far-ground signal, the far-ground signal is input to the optical module.

[0076] Among them, when the near-ground signal is input into the optical module, the near-ground signal is detected and amplified by the optical module, and the near-ground signal is converted from an optical signal into an electrical signal and input into the filter; the near-ground signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module; the phase difference between the near-ground signal and the input electrical signal is measured by the phase comparison delay control module.

[0077] Among them, when the remote signal is input to the optical module, the remote signal is detected and amplified by the optical module, and the remote signal is converted from an optical signal to an electrical signal and input into the filter; the remote signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module; the phase difference between the remote signal and the input electrical signal is measured by the phase comparison delay control module.

[0078] The difference between the phase difference between the remote signal and the input electrical signal and the difference between the phase difference between the near-ground signal and the input electrical signal is used as the measurement result of the change in the optical fiber length. This measurement result contains information about the change in the length of the long optical fiber, which is used to control the optical fiber delay line, compensate for the change in the optical fiber length, and achieve the purpose of stabilizing the optical fiber length.

[0079] In an embodiment of the present invention, the phase comparison delay control module controls the optical switch to a near-ground signal receiving state, at which time the optical signal S1 is input into the optical module; the electrical signal output by the photodetector of the optical module after amplification is converted into a sine wave signal after low-pass filtering, and is input into the phase comparison delay control module to measure the phase difference ps10 relative to the input signal S0.

[0080] Among them, the phase comparison delay control module controls the optical switch to the remote signal receiving state. At this time, the optical signal S2 is input into the optical module. The electrical signal output by the photodetector in the optical module after amplification is converted into a sine wave signal after low-pass filtering and input into the phase comparison delay control module to measure the phase difference ps20 relative to the input signal S0. ps20 contains the information of the change of the long optical fiber length, which can be used to control the optical fiber delay line, compensate for the change of the optical fiber length, and achieve the purpose of stabilizing the optical fiber length.

[0081] The phase comparison delay control module has the ability to measure the phase difference with an accuracy better than sub-ps in the short and long term. Since both the electro-optic modulator and the photodetector have a certain slow phase drift, the optoelectronic module contains such a device, and the filter also has a certain slow phase drift, so ps20 may have a slow phase drift of several ps, more than ten ps, or even tens of ps that is unrelated to the change in the length of the optical fiber. The above slow phase drift in ps20 and ps10 all contain the same value. Since the optical signal S1 is a signal looped back near the ground, ps10 does not contain any information about the change in the length of the long optical fiber. The value of ps20-ps10 is used as the measurement result of the change in the length of the optical fiber, which completely eliminates the influence of the phase drift of the electro-optic modulator, photodetector, and filter. Light passes through optical devices such as optical fiber splitters and optical switches at a speed close to the speed of light, which is an ultra-high-speed device compared to electrical devices. The delay change is only related to the change in the size of the device, and the change is usually much less than 1ps. Electrical devices are electrons moving inside the device, and the speed is much slower than the speed of light. It is normal to have a large delay change due to environmental changes or device aging. Therefore, the present invention uses devices such as optical fiber beam splitters and optical switches with smaller phase drift to eliminate the influence of large phase drift of electro-optic modulators, photoelectric detectors, and filters.

[0082] It can be seen from the above embodiments that the optical fiber phase stabilization device and method provided by the present invention switches between the local short optical fiber loopback signal (near-ground signal) of the photodetector in the optical module and the loopback signal from the far-ground through the long optical fiber (far-ground signal) by adding an optical fiber splitter and an optical switch during the optical path transmission. The phase difference between the received filtered electrical signal (sine wave) and the input electrical signal is measured by the phase comparison delay control module. By making a difference between the phase difference during the far-ground loopback and the phase difference during the near-ground loopback, the slow drift of the signal phase during electro-optical modulation and the slow drift of the signal phase during photoelectric detection filtering are completely eliminated. The change in the phase difference before and after the optical switch switching only contains the information of the change in the optical fiber length. This signal is used to control the adjustable optical fiber delay line to achieve the purpose of stabilizing the optical fiber length.

[0083] The optical fiber phase stabilization device and method according to the present invention are described above by way of example with reference to the accompanying drawings. However, those skilled in the art should understand that various improvements can be made to the optical fiber phase stabilization device and method according to the present invention without departing from the content of the present invention. Therefore, the protection scope of the present invention should be determined by the content of the attached claims.

Claims

1. An optical fiber phase stabilization device, characterized in that: It includes a crystal resonator, a power divider, an optical module connected to the power divider and a phase comparison delay control module, an optical fiber splitter and an optical switch connected to the optical module, and a first circulator connected to the optical fiber splitter and the optical switch, wherein: The crystal resonator is used to send out a signal source and input it into the power divider; The power divider is used to divide the electrical signal emitted by the signal source into two paths, wherein one path of the electrical signal is input into the optical module, and the other path of the electrical signal is input into the phase comparison delay control module; The output end of the optical module is connected to the optical fiber splitter, and the input end of the optical module is connected to the optical switch; The optical fiber beam splitter is used to split the optical signal output from the optical module into two paths, wherein one optical signal is input into the first circulator, and the other optical signal is input into the optical switch; The phase comparison delay control module receives two different optical signals through the optical switch.

2. The optical fiber phase stabilization device according to claim 1, characterized in that: The optical module and the phase comparison delay control module are provided with filters, wherein: The filter is used to filter the electrical signal output from the optical module to form a sinusoidal electrical signal, and input the signal into the phase comparison delay control module.

3. The optical fiber phase stabilization device according to claim 2, characterized in that: The optical module includes an electro-optic modulator and a photodetector, wherein: The electro-optic modulator is used to adjust and process the electrical signal input to the optical module to generate an optical signal, and output the optical signal to the optical fiber splitter; The photoelectric detector is used to detect and amplify the optical signal input to the optical module to generate an electrical signal, and output the electrical signal to the filter.

4. The optical fiber phase stabilization device according to claim 1, characterized in that: The optical fiber phase stabilization device also includes a first wavelength division multiplexer and an adjustable optical delay line, wherein: The first wavelength division multiplexer is connected to the first circulator and the adjustable optical delay line respectively, and is located between the first circulator and the adjustable optical delay line.

5. The optical fiber phase stabilization device according to claim 4, characterized in that: The optical fiber phase stabilization device also includes an external long optical fiber, a second wavelength division multiplexer, and a second circulator connected in sequence, wherein: The external long optical fiber is connected to the adjustable optical delay line, and the adjustable optical delay line is located between the first wavelength division multiplexer and the external long optical fiber.

6. The optical fiber phase stabilization device according to claim 5, characterized in that: The first circulator, the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, and the second circulator are connected in sequence to form a round-trip loop of the optical signal.

7. A method for stabilizing optical fiber phase, characterized in that: Phase stabilization is achieved by using the optical fiber phase stabilization device according to any one of claims 1 to 6, the method comprising: The electrical signal emitted by the signal source is divided into two paths by a power divider, one of the electrical signals is input into the optical module, and the other electrical signal is input into the phase comparison delay control module as an input electrical signal; The optical module processes the input electrical signal to generate an optical signal, and inputs the optical signal into the optical fiber splitter; The optical signal is divided into two paths by the optical fiber beam splitter, wherein one optical signal is a near-ground signal and the other optical signal is a far-ground signal; Controlling the optical switch to receive the near-ground signal and the far-ground signal respectively through the phase comparison delay control module, and inputting the received near-ground signal and the far-ground signal respectively into the optical module; Amplifying the near-ground signal and the far-ground signal respectively through the optical module; The near-ground signal and the far-ground signal after amplification are filtered respectively, and input into the phase comparison delay control module; Processing the input electrical signal, the filtered near-ground signal, and the filtered far-ground signal through the phase comparison delay control module to obtain phase differences of the near-ground signal and the far-ground signal relative to the input electrical signal respectively; The change in optical fiber length is determined according to the difference between the phase difference between the far-ground signal and the input electrical signal and the phase difference between the near-ground signal and the input electrical signal.

8. The optical fiber phase stabilization method according to claim 7, characterized in that: The ground proximity signal is directly input into the optical switch from the optical fiber beam splitter; The remote signal enters the first circulator from the optical fiber splitter, passes through the first wavelength division multiplexer, the adjustable optical delay line, the external long optical fiber, the second wavelength division multiplexer, the second circulator in sequence, and then returns from the second circulator to the first circulator, and then enters the optical switch.

9. The optical fiber phase stabilization method according to claim 7, characterized in that: The method of controlling the optical switch to receive the near-ground signal and the far-ground signal respectively by the phase comparison delay control module comprises the following steps: When the optical switch is controlled by the phase comparison delay control module to receive the ground proximity signal, the ground proximity signal is input to the optical module; When the optical switch is controlled by the phase comparison delay control module to receive the remote signal, the remote signal is input to the optical module.

10. The optical fiber phase stabilization method according to claim 9, characterized in that: When the ground proximity signal is input to the optical module, The optical module detects and amplifies the ground proximity signal, converts the ground proximity signal from an optical signal into an electrical signal, and inputs the electrical signal into a filter; The near-ground signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module; The phase difference between the near-ground signal and the input electrical signal is measured by the phase comparison delay control module.

11. The optical fiber phase stabilization method according to claim 10, characterized in that: When the remote signal is input to the optical module, The remote signal is detected and amplified by the optical module, and the remote signal is converted from an optical signal into an electrical signal, and input into a filter; The remote signal converted into an electrical signal is filtered by the filter and input into the phase comparison delay control module; The phase difference between the remote signal and the input electrical signal is measured by the phase comparison delay control module.

12. The optical fiber phase stabilization method according to claim 11, characterized in that: The difference between the phase difference between the remote signal and the input electrical signal and the phase difference between the near-ground signal and the input electrical signal is used as the measurement result of the change in optical fiber length; wherein, The measurement result includes information on the change in length of the external long optical fiber. The adjustable optical fiber delay line is controlled by the measurement result, and the change in optical fiber length is compensated to achieve stability of the optical fiber length.

Images