Optical time domain reflection system based on reference optical fiber phase compensation and demodulation method

Abstract

The invention provides an optical time domain reflection system and demodulation method based on reference optical fiber phase compensation, and the system comprises a signal generator, a distributed feedback laser, a semiconductor optical fiber amplifier, a first amplifier, a circulator, a second amplifier, a wave filter, a detector, a reference optical fiber, and an optical fiber to be measured. A continuous laser signal of the distributed feedback laser is converted into a pulse optical signal through the semiconductor optical fiber amplifier and is amplified through the first amplifier; the amplified pulse optical signal enters a second port of the circulator through a first port of the circulator and sequentially enters a reference optical fiber and an optical fiber to be detected, and an optical fiber Rayleigh scattering signal enters a third port of the circulator through the second port and sequentially passes through a second amplifier and a filter to be detected; and the detector obtains Rayleigh interference spectrums of the reference optical fiber and the optical fiber to be detected according to the filtered scattering signals. According to the invention, the technical problem of insufficient measurement precision caused by the influence of light source phase drift on the traditional phase-OTDR system can be solved.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to an optical time domain reflection system and a demodulation method based on reference optical fiber phase compensation. Background Art

[0002] Distributed fiber optic sensing technology has been used in large-scale infrastructure, geological disasters, geophysical exploration, the Internet of Things and other fields. This research has significant economic and scientific research value. Distributed fiber optic sensing technology mainly uses the nonlinear effects in optical fibers, including Rayleigh scattering, Brillouin scattering and Raman scattering, to form various types of distributed fiber optic sensing demodulation systems, with distributed fiber optic sensing monitoring capabilities in different scenarios. For high-sensitivity dynamic strain measurement, the optical time domain reflectometry (OTDR) system based on the Rayleigh scattering effect is one of the best measurement solutions.

[0003] The traditional phase-OTDR system uses a narrow linewidth high coherence light source to generate pulsed light and directly detects the interference intensity between the backward Rayleigh scattered signals in the pulse. Due to the random distribution of scattering points in the optical fiber, the interference signal has a jagged irregular shape. When the external environment and system remain unchanged, the interference pattern remains unchanged and is repeatable; when the external temperature or strain changes, the optical path between the scattering points changes, causing the phase of the scattered light to change, affecting the interference intensity at the disturbance position. However, the traditional phase-OTDR with direct signal intensity detection can only be used for qualitative measurement, for intrusion, positioning, speed and vibration monitoring, and cannot obtain the change in temperature and strain. Further research found that the main reason for the change in interference intensity is the change in the phase difference of the scattered light. Therefore, the phase change can be determined by phase demodulation and frequency compensation schemes to achieve quantitative measurement of temperature and strain. In the past decade, phase-OTDR for high-sensitivity quantitative measurement has been widely studied. The main technologies include interferometer demodulation, heterodyne coherent detection, frequency sweeping schemes and chirped pulses, which have achieved high-resolution strain / temperature measurement at the nanostrain and millikelvin levels.

[0004] The high-sensitivity phase-OTDR demodulation system provides an effective solution for acoustic wave detection such as seismic waves and geological exploration. However, due to its high sensitivity, it places higher requirements on the stability of the measurement system. The phase drift of the light source system (including wavelength, initial phase, etc.) is one of the main sources of error, resulting in a decrease in the absolute accuracy of the measurement. In 2018, German researchers conducted experiments and found that the measurement deviation caused by 24-hour laser phase drift was 120 nanostrain or 13.4 millikelvin (Liehr S, Sven Münzenberger, Krebber K. Wavelength-scanning coherent OTDR for dynamic high strain resolution sensing [J]. Optics Express, 2018, 26 (8): 10573). The error caused by jitter is about two orders of magnitude higher than the system resolution. Therefore, the laser phase drift seriously affects the system performance. The cost of ultra-stable light sources is high, and it is still difficult to ensure the absolute stability of the wavelength / phase of the light source for a long time. Therefore, the high-sensitivity phase-OTDR measurement results are more reported in simulation tests under laboratory conditions. The practical application of engineering still needs to solve the problem of light source wavelength drift. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0006] According to one aspect of the present invention, an optical time domain reflection system based on reference fiber phase compensation is provided, and the optical time domain reflection system comprises: a signal generator, a distributed feedback laser, a semiconductor fiber amplifier, a first amplifier, a circulator, a second amplifier, a filter, a detector, a reference fiber and a fiber to be tested, wherein the signal generator drives and controls the distributed feedback laser and the semiconductor fiber amplifier respectively; the continuous laser signal of the distributed feedback laser is converted into a pulsed light signal by the semiconductor fiber amplifier and amplified by the first amplifier; the amplified pulsed light signal enters the second port of the circulator through the first port of the circulator, and successively enters the reference fiber and the fiber to be tested; the fiber Rayleigh scattering signal enters the third port of the circulator through the second port, and then passes through the second amplifier and the filter in sequence, and the detector obtains the Rayleigh interference spectrum of the reference fiber and the fiber to be tested according to the filtered scattering signal.

[0007] Furthermore, the reference optical fiber is placed in a constant temperature environment and is in a relaxed state.

[0008] Furthermore, the length of the reference optical fiber is at least twice the spatial resolution of the system, and the middle section of the reference optical fiber is used as the phase compensation monitoring area.

[0009] Furthermore, the measured length of the optical fiber to be measured is the difference between the system measurement distance and the length of the reference optical fiber.

[0010] Furthermore, both the first amplifier and the second amplifier are erbium-doped fiber amplifiers.

[0011] Furthermore, the optical time domain reflectometry system also includes an acquisition card, which is connected to the signal generator and the detector respectively.

[0012] Furthermore, the signal generator synchronously drives the acquisition card to achieve synchronization of light source wavelength scanning, pulse modulation and signal acquisition.

[0013] According to another aspect of the present invention, a demodulation method of an optical time domain reflectometry system based on reference fiber phase compensation is provided. The demodulation method of the optical time domain reflectometry system uses the optical time domain reflectometry system based on reference fiber phase compensation as described above to realize phase demodulation.

[0014] Furthermore, the demodulation method of the optical time domain reflection system includes: obtaining the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested respectively based on the optical time domain reflection system based on the reference optical fiber phase compensation as described above; obtaining the phase change of the reference optical fiber and the optical fiber to be tested according to the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested; subtracting the phase change of the optical fiber to be tested from the phase change of the reference optical fiber, and completing the demodulation of the optical time domain reflection system based on the difference.

[0015] Furthermore, a cross-correlation operation is performed based on the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested to obtain the phase changes of the reference optical fiber and the optical fiber to be tested.

[0016] By applying the technical solution of the present invention, an optical time domain reflection system and a demodulation method based on reference optical fiber phase compensation are provided. The optical time domain reflection system obtains the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested respectively by setting the reference optical fiber and the optical fiber to be tested in series. The system phase drift can be obtained in real time through the reference optical fiber to compensate for the phase change of the optical fiber to be tested, avoiding demodulating the light source phase jitter into temperature / strain changes, achieving high-precision and high-sensitivity temperature / strain demodulation, and effectively improving the environmental adaptability of the phase-OTDR system and enhancing its engineering usability. Compared with the prior art, the technical solution of the present invention can solve the technical problem in the prior art that the traditional phase-OTDR system is affected by the light source phase drift, resulting in insufficient measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The included drawings are used to provide a further understanding of the embodiments of the present invention, which constitute a part of the specification, are used to illustrate the embodiments of the present invention, and together with the text description, explain the principles of the present invention. Obviously, the drawings in the following description are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1 A schematic diagram showing the working principle of an optical time domain reflectometry system based on reference fiber phase compensation provided according to a specific embodiment of the present invention is shown;

[0019] Figure 2 A Rayleigh interference spectrum diagram of an optical fiber to be tested provided according to a specific embodiment of the present invention is shown;

[0020] Figure 3 A reference optical fiber Rayleigh interference spectrum diagram provided according to a specific embodiment of the present invention is shown;

[0021] Figure 4 Shows Figure 3 A partial enlarged schematic diagram of . DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0024] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present invention. Meanwhile, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, and therefore, once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0025] like Figure 1 As shown, according to a specific embodiment of the present invention, an optical time domain reflection system based on reference fiber phase compensation is provided, and the optical time domain reflection system includes: a signal generator, a distributed feedback laser (DFBLaser), a semiconductor fiber amplifier (SOA), a first amplifier, a circulator, a second amplifier, a filter, a detector, a reference fiber and a fiber to be tested, the signal generator drives and controls the distributed feedback laser and the semiconductor fiber amplifier respectively; the continuous laser signal of the distributed feedback laser is converted into a pulsed light signal by the semiconductor fiber amplifier and amplified by the first amplifier; the amplified pulsed light signal enters the second port of the circulator through the first port of the circulator, and enters the reference fiber and the fiber to be tested successively, and the fiber Rayleigh scattering signal enters the third port of the circulator through the second port, and then passes through the second amplifier and the filter in sequence, and the detector obtains the Rayleigh interference spectrum of the reference fiber and the fiber to be tested according to the filtered scattering signal.

[0026] By applying this configuration, an optical time domain reflectometry system based on reference fiber phase compensation is provided. The optical time domain reflectometry system obtains the Rayleigh interference spectra of the reference fiber and the fiber to be tested respectively by setting the reference fiber and the fiber to be tested in series. The system phase drift can be obtained in real time through the reference fiber to compensate for the phase change of the fiber to be tested, avoiding demodulating the light source phase jitter into temperature / strain changes, achieving high-precision and high-sensitivity temperature / strain demodulation, and effectively improving the environmental adaptability of the phase-OTDR system and enhancing its engineering availability.

[0027] Furthermore, in the present invention, the signal generator controls the driving voltage of the distributed feedback laser, and the driving voltage is proportional to the laser modulation current. The correspondence between the modulation current and the wavelength can be obtained by obtaining the current-wavelength curve through advance testing and calibration, and the laser linear scanning can be achieved by pre-calibrating the voltage curve.

[0028] In addition, the signal generator provides a driving pulse signal for the semiconductor optical fiber amplifier.

[0029] Furthermore, in the present invention, the reference optical fiber can be placed in a constant temperature environment and in a relaxed state. By placing the reference optical fiber in a constant temperature environment and in a relaxed state, the influence of external temperature and strain can be isolated. The length of the reference optical fiber can be at least twice the spatial resolution of the system, and the middle section is used as the phase compensation monitoring area.

[0030] As a specific embodiment of the present invention, both the first amplifier and the second amplifier can be erbium-doped fiber amplifiers. The first amplifier amplifies the peak power of the pulse light to the order of hundreds of milliwatts, and the second amplifier amplifies the scattered signal to the order of microwatts.

[0031] Furthermore, the filter may adopt an adjustable optical filter to filter out the spontaneous radiation noise signal.

[0032] In addition, in the present invention, the configurable optical time domain reflectometry system also includes an acquisition card, which is connected to the signal generator and the detector respectively, and the acquisition card records the electrical signal converted by the detector. The signal generator synchronously drives the acquisition card to realize the synchronization of light source wavelength scanning, pulse modulation and signal acquisition.

[0033] In the present invention, the key parameters of the optical time domain reflectometry system based on reference fiber phase compensation include spatial resolution, measurement distance and measurement time, etc. The pulse width determines the spatial resolution of the phase-OTDR system, and the time interval between pulses determines the measurement distance of the system. The measurement length of the optical fiber to be measured should be the system measurement distance minus the reference fiber length; the time interval between pulses and the number of frequency scans determine the measurement time of the system.

[0034] The optical time domain reflectometry system based on reference fiber phase compensation of the present invention uses a reference fiber to measure the phase drift of the phase-OTDR system in real time and synchronously corrects the measurement result of the optical fiber to be measured. Compared with the existing swept-frequency phase-OTDR measurement system, it can improve the measurement accuracy of the system and has the following advantages:

[0035] 1) The optical time domain reflectometry system of the present invention can achieve high-precision and high-sensitivity temperature / strain measurement. The system phase drift is obtained in real time by using a reference optical fiber to compensate for the phase change of the optical fiber to be measured, thereby avoiding demodulating the light source phase jitter into temperature / strain changes, achieving high-precision and high-sensitivity temperature / strain demodulation, and reducing the long-term measurement error by two orders of magnitude;

[0036] 2) The optical time domain reflectometry system of the present invention has a high anti-interference ability. The light source of the phase-OTDR system is usually a DFB fiber laser. When the laser temperature changes or the driving current jitters, the wavelength of the light source will change. The present invention can effectively improve the environmental adaptability of the phase-OTDR demodulation system and enhance its engineering usability by compensating the phase of the reference optical fiber in real time;

[0037] 3) The optical time domain reflectometry system of the present invention does not increase the complexity of the hardware system and is applicable to all types of phase-OTDR systems, including interferometer demodulation, heterodyne coherent detection, frequency sweeping schemes and chirped pulse schemes, etc. The reference optical fiber can be connected in series with the optical fiber to be tested, and the hardware complexity of the phase-OTDR system will not be increased.

[0038] According to another aspect of the present invention, a demodulation method of an optical time domain reflectometry system based on reference fiber phase compensation is provided. The demodulation method of the optical time domain reflectometry system uses the optical time domain reflectometry system based on reference fiber phase compensation as described above to realize phase demodulation.

[0039] Furthermore, in the present invention, the demodulation method of the optical time domain reflection system based on the reference fiber phase compensation includes: obtaining the Rayleigh interference spectra of the reference fiber and the optical fiber to be tested respectively based on the optical time domain reflection system based on the reference fiber phase compensation as described above; obtaining the phase change of the reference fiber and the optical fiber to be tested according to the Rayleigh interference spectra of the reference fiber and the optical fiber to be tested; subtracting the phase change of the optical fiber to be tested from the phase change of the reference fiber, and completing the demodulation of the optical time domain reflection system based on the difference.

[0040] As a specific embodiment of the present invention, the phase changes of the reference optical fiber and the optical fiber to be tested can be obtained by performing cross-correlation calculation based on the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested.

[0041] In the present invention, the phase change of the reference optical fiber is the system phase drift, and the phase change of the optical fiber to be measured is the phase change caused by temperature / strain and light source jitter. The phase change of the optical fiber to be measured is subtracted from the phase change of the reference optical fiber to obtain a demodulation result that eliminates the influence of the system, thereby avoiding demodulating the system phase jitter into a temperature / strain measurement value, and improving the measurement accuracy of the phase-OTDR system.

[0042] In the swept-frequency phase-OTDR system, the change in optical frequency is used to compensate for the phase change caused by the external environment, that is, the phase change is determined by the frequency shift of the Rayleigh interference spectrum. R (t,Δv) is the superposition of N signals within a half-width pulse, and the following one-dimensional pulse response model is used for analysis:

[0043]

[0044] Among them, r i is the reflectivity of the i-th scattering point; E0 is the incident light field intensity; α is the fiber loss; τ i is the time delay of the i-th scattering point, that is, the time from incident to detector reception, τ i =2nz i / c, c is the speed of light in vacuum; z i The position of the i-th scattering point, n is the refractive index of the optical fiber; v0 is the carrier frequency of the laser; Δv is the change compared to the frequency of the first pulse light; τ d is the pulse width; rect() is the pulse function,

[0045] The detector output power is the square of the modulus of the measured superimposed signal, which can be divided into two parts, the DC component and the AC component:

[0046] I(t,Δv)=|E R (t,Δv)| 2 =I DC +I AC

[0047]

[0048]

[0049] DC Component I DC It is the linear superposition of the signal strength of each scattering point. However, the DC component is meaningless for interferometric phase measurement, and an AC detection scheme is usually used to filter out the DC component. AC middle represents the phase difference between the i-th scattering point and the k-th scattering point, τ k is the time delay of the kth scattering point, The AC component makes the intensity of the Rayleigh scattering signal jagged, that is, the intensity fluctuates, and is sensitive to phase changes caused by external temperature and strain. m The phase change caused by the strain change Δε and the temperature change ΔT is compensated to restore the Rayleigh interference spectrum, wherein the relative movement of the Rayleigh interference spectrum can determine the frequency shift through the cross-correlation algorithm.

[0050]

[0051] Among them, K ε is the strain coefficient; Δτ ik is the time difference change between the i-th scattering point and the k-th scattering point; τ ik is the time difference between the i-th scattering point and the k-th scattering point; K Tis the temperature coefficient.

[0052] The change in light frequency Δv m It includes both the phase change caused by temperature and strain and the jitter of the system phase, which causes system measurement errors. The high-precision optical time domain reflectometry based on phase compensation of the present invention is used to obtain the phase change Δv caused by temperature / strain and light source jitter using the Rayleigh interference spectrum of the optical fiber to be measured. m , the phase change Δv caused by the light source jitter is demodulated by the reference fiber, and the difference Δv is calculated. m -Δv, real-time difference compensation eliminates the influence of system phase jitter, avoids demodulating system phase jitter into temperature / strain measurement values, and realizes high-precision temperature / strain measurement of phase-OTDR system.

[0053] The demodulation method of the optical time domain reflectometry system of the present invention uses a reference optical fiber to measure the phase change of the phase-OTDR system in real time, synchronously corrects the measurement result of the phase-OTDR optical fiber to be tested, and compensates for the measurement deviation caused by the phase change of the light source. Through the reference optical fiber phase measurement, the system phase drift is obtained in real time, avoiding the influence of the traditional phase-OTDR phase noise and long-term light source drift, compensating the temperature / strain measurement result of the optical fiber to be tested, and avoiding the influence of the wavelength fluctuation of the system light source, achieving high-precision and high-sensitivity measurement, with strong robustness and high engineering practicality.

[0054] In order to further understand the present invention, the following Figures 1 to 4 The demodulation method of the optical time domain reflectometry system based on reference optical fiber phase compensation of the present invention is described in detail.

[0055] The demodulation method of the optical time domain reflectometry system based on reference optical fiber phase compensation of the present invention adopts the following method: Figure 1 The optical time domain reflectometry system shown in the figure realizes phase demodulation. First, the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested are obtained respectively; and the phase changes of the reference optical fiber and the optical fiber to be tested are obtained by performing cross-correlation operation based on the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested. Figure 2 The Rayleigh interference spectrum of the optical fiber under test is shown. The relative shift of the spectrum is caused by temperature / strain and system phase jitter. Figure 3 The Rayleigh interference spectrum of the reference optical fiber is shown in Figure 1, and the partially enlarged image is shown in Figure 2. Figure 4 As shown, the relative shift of the spectrum is caused by the system phase jitter.

[0056] The demodulation of the optical time domain reflectometry system is completed by subtracting the phase change of the optical fiber to be tested from the phase change of the reference optical fiber.

[0057] In summary, the present invention provides an optical time domain reflection system and a demodulation method based on reference optical fiber phase compensation. The optical time domain reflection system obtains the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested respectively by setting the reference optical fiber and the optical fiber to be tested in series. The system phase drift can be obtained in real time through the reference optical fiber to compensate for the phase change of the optical fiber to be tested, thereby avoiding demodulating the phase jitter of the light source into the temperature / strain change, realizing high-precision and high-sensitivity temperature / strain demodulation, and being able to effectively improve the environmental adaptability of the phase-OTDR system and enhance its engineering availability.

[0058] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An optical time domain reflectometry system based on reference fiber phase compensation, characterized in that: The optical time domain reflection system comprises: a signal generator, a distributed feedback laser, a semiconductor fiber amplifier, a first amplifier, a circulator, a second amplifier, a filter, a detector, a reference fiber and a fiber to be tested. The signal generator drives and controls the distributed feedback laser and the semiconductor fiber amplifier respectively; the continuous laser signal of the distributed feedback laser is converted into a pulsed light signal by the semiconductor fiber amplifier and amplified by the first amplifier; the amplified pulsed light signal enters the second port of the circulator through the first port of the circulator, and successively enters the reference fiber and the fiber to be tested; the fiber Rayleigh scattering signal enters the third port of the circulator through the second port, and then passes through the second amplifier and the filter in sequence; the detector obtains the Rayleigh interference spectrum of the reference fiber and the fiber to be tested according to the filtered scattering signal.

2. The optical time domain reflectometry system based on reference fiber phase compensation according to claim 1, characterized in that: The reference optical fiber is placed in a constant temperature environment and is in a relaxed state.

3. The optical time domain reflectometry system based on reference fiber phase compensation according to claim 1, characterized in that: The length of the reference optical fiber is at least twice the spatial resolution of the system, and the middle section of the reference optical fiber is used as a phase compensation monitoring area.

4. The optical time domain reflectometry system based on reference fiber phase compensation according to any one of claims 1 to 3, characterized in that: The measured length of the optical fiber to be tested is the difference between the system measurement distance and the length of the reference optical fiber.

5. The optical time domain reflectometry system based on reference fiber phase compensation according to claim 1, characterized in that: The first amplifier and the second amplifier both use erbium-doped fiber amplifiers.

6. The optical time domain reflectometry system based on reference fiber phase compensation according to any one of claims 1 to 4, characterized in that: The optical time domain reflectometry system further includes an acquisition card, which is connected to the signal generator and the detector respectively.

7. The optical time domain reflectometry system based on reference fiber phase compensation according to claim 6, characterized in that: The signal generator synchronously drives the acquisition card to realize synchronization of light source wavelength scanning, pulse modulation and signal acquisition.

8. A demodulation method for an optical time domain reflectometry system based on reference fiber phase compensation, characterized in that: The demodulation method of the optical time domain reflectometry system uses the optical time domain reflectometry system based on reference optical fiber phase compensation as described in any one of claims 1 to 7 to realize phase demodulation.

9. The demodulation method of the optical time domain reflectometry system based on reference fiber phase compensation according to claim 8, characterized in that: The demodulation method of the optical time domain reflectometry system comprises: Acquire Rayleigh interference spectra of the reference fiber and the fiber to be tested respectively based on the optical time domain reflectometry system based on reference fiber phase compensation as described in any one of claims 1 to 7; Acquiring phase changes of the reference optical fiber and the optical fiber to be tested according to the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested; The phase change of the optical fiber to be tested is subtracted from the phase change of the reference optical fiber, and the demodulation of the optical time domain reflectometry system is completed based on the difference.

10. The demodulation method of an optical time domain reflectometry system based on reference fiber phase compensation according to claim 9, characterized in that: A cross-correlation operation is performed based on the Rayleigh interference spectra of the reference optical fiber and the optical fiber to be tested to obtain the phase changes of the reference optical fiber and the optical fiber to be tested.

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