High demodulation accuracy phi-otdr system and demodulation method based on 1-bit quantization bit number

Abstract

The application discloses a high demodulation precision Phi-OTDR system based on 1bit quantization bit number, which comprises a laser, a pulse generator, an acousto-optic modulator, a first coupler, a second coupler, an erbium-doped fiber amplifier, a circulator, a sensing optical fiber, a balanced detector, a comparator, a timer and a processor; the comparator quantizes beat frequency signals with a value greater than 0 as 1 and quantizes beat frequency signals less than or equal to 0 as 0; the timer collects quantized signals output by the comparator, observes the jumping moment of signal 0 and signal 1, and obtains a digital signal corresponding to a beat frequency signal of each period by dividing the time interval of two jumping moments by a clock period; the processor analyzes the digital signal output by the timer, analyzes the phase change value of a corresponding period according to the encoding information of each period digital signal, and completes the reconstruction of the disturbance signal. The application can reduce the data volume of the system and improve the data processing speed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical fiber sensing, and particularly relates to a high demodulation precision Φ-OTDR system and a demodulation method based on 1bit quantization bits. BACKGROUND

[0002] A distributed optical fiber sensing system takes an entire optical fiber as an information sensing medium and a transmission medium to realize non-blind area detection of the entire optical fiber. As a branch of distributed optical fiber sensing technology, a phase-sensitive optical time-domain reflectometer (Φ-OTDR) is widely applied to vibration signal monitoring due to its high sensitivity and fast response speed. Since the Φ-OTDR system is sensitive to phase changes, the change in the phase of an optical signal caused by a disturbance signal can be demodulated to reconstruct the amplitude, phase, frequency and other information of the disturbance signal with high fidelity. However, the Φ-OTDR system will introduce a large amount of original data in actual application, which not only consumes huge computing power but also puts forward extremely high requirements for storage devices.

[0003] The high and low of the quantization bits directly determines the size of the data amount received and processed by the system. Higher quantization bits can accurately reconstruct external disturbance signals, but will bring problems such as large data processing amount and high cost. The document “Data Reduction in Phase-Sensitive OTDR with Ultra-Low Sampling Resolution and Undersampling Techniques” proposes that the data amount of the system can be reduced by using undersampling technology and 1bit quantization bits instead of 8bit quantization bits, reducing 128MB data within 268.44ms to 1.6MB; the document “Ultra-low sampling resolution technique for heterodyne phase-OTDR based distributed acoustics sensing” proves through experiments that the external disturbance signal can still be successfully reconstructed after 1bit quantization of the intermediate frequency signal. However, the above researches do not overcome the low phase discrimination accuracy of the Φ-OTDR system caused by 1bit quantization. In addition, the current demodulation method mainly used by the Φ-OTDR system has large data operation amount and low efficiency. SUMMARY

[0004] The technical problems solved by the present application: In view of the problem of large system data volume in the existing distributed optical fiber vibration sensing system, a high demodulation accuracy Φ-OTDR system and a demodulation method based on 1bit quantization bits are provided, which can reduce the data volume of the system, improve the data processing speed, and provide a path for the realization of a low-cost Φ-OTDR system.

[0005] Technical scheme

[0006] A high demodulation accuracy Φ-OTDR system based on 1bit quantization bits, the high demodulation accuracy Φ-OTDR system comprises a laser, a pulse generator, an acousto-optic modulator, a first coupler, a second coupler, an erbium-doped fiber amplifier, a circulator, a sensing optical fiber, a balanced detector, a comparator, a timer and a processor.

[0007] The continuous narrow linewidth laser output by the laser is divided into reference light and probe light after passing through the first coupler; the probe light becomes pulsed light after being modulated by the acousto-optic modulator, and the pulsed light is optically amplified by the erbium-doped fiber amplifier and transmitted along the circulator to the sensing optical fiber; the backscattered Rayleigh scattering light signal generated along the sensing optical fiber is transmitted to the second coupler through the circulator; and the backscattered Rayleigh scattering light signal received by the second coupler is mixed with the reference light to form two coherent light signals; the balanced detector converts the two coherent light signals into electrical signals, and the electrical signals are converted into beat frequency signals with a mean value of 0V after bandpass filtering;

[0008] The pulse generator simultaneously applies a trigger signal to the timer and the acousto-optic modulator, so that the timing of the timer and the acousto-optic modulator is synchronized;

[0009] The bandwidth of the comparator is greater than the frequency of the beat frequency signal, the comparator receives the beat frequency signal from the balanced detector, quantizes the beat frequency signal with a value greater than 0 as 1, and quantizes the beat frequency signal less than or equal to 0 as 0; the timer collects the quantized signal output by the comparator, observes the jump time of the signal 0 and the signal 1, and obtains the digital signal corresponding to the beat frequency signal of each period by dividing the time interval of the two jump times by the clock period; the processor analyzes the digital signal output by the timer, analyzes the phase change value φ t of the corresponding period according to the encoding information of each period digital signal, and completes the reconstruction of the disturbance signal.

[0010] Further, the reference voltage value of the comparator is the voltage value V REF representing 0 of the intermediate frequency signal, the upper threshold voltage is V TH+ , the lower threshold voltage is V TH_ , and the threshold width is ΔV=V TH+ -V TH- .

[0011] Further, the electrical signal output by the balanced detector is represented as:

[0012] I(t)∝A R cos(Δωt+φ t -φ0)

[0013] wherein A R is the amplitude of the signal, Δω is the frequency shift of the probe light applied by the acousto-optic modulator, φ t is the phase change value caused by the external disturbance signal, and φ0 is the initial phase of the signal.

[0014] When the ratio of the system sampling rate f s to the frequency f w of the intermediate frequency signal is n, there are n sampling points in one period of the intermediate frequency signal, and the values at the n sampling points are quantized by the comparator to 1 bit and represented as:

[0015]

[0016] wherein when t>0, the value of the ε(t) function is 1, and when t≤0, the value of the ε(t) function is 0.

[0017] Further, the ratio n of the system sampling rate f s to the frequency f w of the intermediate frequency signal is an odd number.

[0018] Further, the processor stores an encoding-phase correspondence table, and the encoding-phase correspondence table is used to represent the relationship between the encoding value of the digital signal and the phase change value φ t caused by the external disturbance; when the amplitude of the disturbance signal is 0-2π, the processor analyzes the phase change value φ t by querying the encoding-phase correspondence table to reconstruct the external disturbance signal; and when the amplitude of the disturbance signal is greater than 2π, the processor restores the real amplitude of the signal by using a phase unwrapping algorithm.

[0019] Further, the phase discrimination accuracy of the high demodulation accuracy Φ-OTDR system is:

[0020]

[0021] wherein φ R is the phase discrimination accuracy of the system, f s is the sampling rate of the system, f w is the frequency of the intermediate frequency signal, and n is the ratio of the system sampling rate f s to the frequency f w of the intermediate frequency signal.

[0022] In a second aspect, the application discloses a demodulation method of a high demodulation precision Φ-OTDR system based on 1bit quantization bits, and the method comprises the following steps:

[0023] The continuous narrow linewidth laser output by the laser is divided into reference light and probe light, the probe light becomes pulsed light after being modulated by an acousto-optic modulator, and the pulsed light is optically amplified by an erbium-doped fiber amplifier and transmitted to a sensing optical fiber along a circulator; the backscattered Rayleigh scattering light signals generated by the sensing optical fiber along the line and the reference light are mixed to form two coherent light signals;

[0024] The two coherent light signals are converted into electrical signals by a balanced detector, and the electrical signals are converted into beat frequency signals with a mean value of 0V after bandpass filtering; the beat frequency signals with a value greater than 0 are quantized as 1, and the beat frequency signals with a value less than or equal to 0 are quantized as 0;

[0025] A timer is used to collect the quantized signals, and the jumping moments of the signals 0 and 1 are observed, and the time interval between the two jumping moments is divided by the clock period to obtain the digital signal corresponding to the beat frequency signal of each period; the timing of the timer and the acousto-optic modulator is synchronized;

[0026] The digital signals output by the timer are analyzed, and the phase change value φ of each period is analyzed according to the encoding information of the digital signals of each period t , and the reconstruction of the disturbance signal is completed.

[0027] Further, the duty cycle of the output signal of the comparator is 50% by setting the hysteresis range of the comparator.

[0028] Further, the electrical signal output by the balanced detector is represented as:

[0029] I(t)∝A R cos(Δωt+φ t -φ0)

[0030] wherein A R is the amplitude of the signal, Δω is the frequency shift of the probe light applied by the acousto-optic modulator, φ t is the phase change value caused by the external disturbance signal, and φ0 is the initial phase of the signal;

[0031] When the ratio of the sampling rate f s of the system to the frequency f w of the intermediate frequency signal is n, there are n sampling points in one period of the intermediate frequency signal, and the values at the n sampling points are quantized by the comparator as 1bit, and are represented as:

[0032]

[0033] Wherein, when t>0, the value of epsilon(t) function is 1, when t<=0, the value of epsilon(t) function is 0.

[0034] Further, when the amplitude of the disturbance signal is at 0~2pi, the phase change value phi is obtained by inquiring the code-phase corresponding table t , the code-phase corresponding table is used to represent the relationship between the code value composed of the digital signal and the phase change value phi caused by the external disturbance t ; when the amplitude of the disturbance signal is greater than 2pi, the processor restores the real amplitude of the signal by using the phase unwrapping algorithm.

[0035] Beneficial effects:

[0036] Firstly, the high demodulation precision Phi-OTDR system and demodulation method based on 1bit quantization bits of the application use the comparator to quantize the data collected by the system in real time, and use the comparator and the timer to replace the data acquisition card, which greatly reduces the data amount of the system, improves the data processing speed of the system and reduces the cost of the system.

[0037] Secondly, the high demodulation precision Phi-OTDR system and demodulation method based on 1bit quantization bits of the application propose a phase demodulation method suitable for 1bit system. s For a signal with a data amount of M rows and N columns, taking IQ demodulation as an example, 2*M*N multiplication operations and M*N division operations are required, and then low-pass filtering is performed to obtain the phase change, while using the demodulation method only needs to perform M*N / n comparisons to obtain the phase change, wherein n is the ratio of the system sampling rate f w to the intermediate frequency signal frequency. Therefore, the demodulation method reduces the data operation amount and improves the demodulation efficiency on the premise of demodulating the phase.

[0038] Thirdly, the high demodulation precision Phi-OTDR system and demodulation method based on 1bit quantization bits of the application can improve the phase discrimination precision of the system by increasing the sampling rate of the system, and in the case of 1bit quantization, a super-high sampling rate of several hundred times the intermediate frequency signal frequency can be used to sample the signal to compensate for the lack of system phase discrimination precision caused by 1bit quantization.

[0039] Fourthly, the high demodulation precision Phi-OTDR system and demodulation method based on 1bit quantization bits of the application uses a hysteresis comparator to improve the stability of the output signal and the anti-interference ability of the system. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is the structure diagram of the high demodulation precision Phi-OTDR system based on 1bit quantization bits of the application.

[0041] Figure 2 is a demodulation method flow chart of the high demodulation accuracy Φ-OTDR system based on 1bit quantization bit number of the application;

[0042] Figure 3 is a schematic diagram for improving the stability of the output signal through a comparator;

[0043] Figure 4 is a schematic diagram of a coding and demodulation method suitable for a 1bit quantization system;

[0044] Figure 5 is a schematic diagram of sampling and reconstructing a disturbance signal with an amplitude of 2π using a sampling rate of 2.5GHz for an intermediate frequency signal with a frequency of 20MHz. DETAILED DESCRIPTION

[0045] The following examples enable those skilled in the art to more fully understand the present application, but in no way limit the present application.

[0046] The application discloses a high demodulation accuracy Φ-OTDR system based on 1bit quantization bit number, which comprises a laser, a pulse generator, an acousto-optic modulator, a first coupler, a second coupler, an erbium-doped fiber amplifier, a circulator, a sensing optical fiber, a balanced detector, a comparator, a timer and a processor.

[0047] The continuous narrow linewidth laser output by the laser is divided into reference light and probe light after passing through the first coupler; the probe light becomes pulsed light after being modulated by the acousto-optic modulator, the pulsed light is optically amplified by the erbium-doped fiber amplifier and transmitted along the circulator to the sensing optical fiber, the backscattered Rayleigh scattering light signal generated by the sensing optical fiber along the line is transmitted to the second coupler through the circulator, and the backscattered Rayleigh scattering light signal received by the second coupler is mixed with the reference light to form two coherent light signals; the balanced detector converts the two coherent light signals into electrical signals, and the electrical signals become beat frequency signals with a mean value of 0V after bandpass filtering.

[0048] The pulse generator simultaneously applies a trigger signal to the timer and the acousto-optic modulator, so that the timing of the timer and the acousto-optic modulator is synchronized, the influence of random noise can be effectively suppressed, the consistency of the signal is ensured, and the phase discrimination accuracy is improved.

[0049] The bandwidth of the comparator is greater than the frequency of the beat signal, the comparator receives the beat signal from the balanced detector, and quantizes the beat signal value greater than 0 as 1 and the beat signal value less than or equal to 0 as 0. The reference voltage value of the comparator is set to 0V, since the signal received by the comparator can be regarded as a sinusoidal signal, the hysteresis range of the comparator is set so that the duty cycle of the output signal of the comparator is 50%, so that even if the value of the input signal near the zero crossing point fluctuates due to noise, the comparator can still output the correct signal, improving the stability of the output signal and the anti-interference ability of the system.

[0050] The data acquisition function is completed by a timer driven by a high-frequency clock, and the frequency clock is the sampling rate of the system. Since the output signal of the comparator only contains 0 and 1, the quantized signal output by the comparator can be collected by the timer, and the jump time of signal 0 and signal 1 is observed. The time interval between the two jump times is divided by the clock period to obtain the digital signal corresponding to the beat signal in each period; the processor analyzes the digital signal output by the timer, and analyzes the phase change value φ t of the corresponding period according to the encoding information of each period digital signal to complete the reconstruction of the disturbance signal.

[0051] The reference voltage value of the comparator is the voltage value V REF representing 0 of the intermediate frequency signal, the upper threshold voltage is V TH+ , and the lower threshold voltage is V TH_ . The threshold width is ΔV=V TH+ -V TH- .

[0052] The electrical signal received by the comparator output from the balanced detector can be represented as:

[0053] I(t)∝A R cos(Δωt+φ t -φ0)

[0054] Where A R is the amplitude of the signal, Δω is the frequency shift applied to the probe light by the acousto-optic modulator, φ t is the phase change caused by the external disturbance signal, and φ0 is the initial phase of the signal.

[0055] When the ratio of the sampling rate f s of the system to the frequency f w of the intermediate frequency signal is n, there are n sampling points in one period of the signal, and the values at these n sampling points are quantized by the comparator to 1 bit, which can be represented as:

[0056]

[0057] Wherein, the function of epsilon (t) is 1 when t>0, and 0 when t<=0. When the amplitude of the disturbance signal is between 0 and 2pi, different amplitudes of the disturbance signal make the phi t Different, and thus the n encoding values composed of digital signals 0 and 1 are different, so that an encoding-phase correspondence table can be obtained, and the phase change phi t caused by external disturbance can be obtained according to the n encoding values, and finally the reconstruction of the external disturbance signal is realized in the processor. When the amplitude of the disturbance signal is greater than 2pi, the signal true amplitude can be restored by using a phase unwrapping algorithm.

[0058] The phase discrimination accuracy of the system is related to the sampling rate of the system and the frequency of the intermediate frequency signal, and the formula of the phase discrimination accuracy of the system is:

[0059]

[0060] Wherein, phi R is the phase discrimination accuracy of the system, f s is the sampling rate of the system, f w is the frequency of the intermediate frequency signal, and n is the ratio of the sampling rate f s of the system to the frequency f w of the intermediate frequency signal. The greater the ratio of the sampling rate of the system to the frequency of the intermediate frequency signal, the higher the phase discrimination accuracy of the system. From the formula of the phase discrimination accuracy of the system, it can be seen that the deficiency of the 1bit phi-OTDR system in phase discrimination accuracy can be compensated by increasing the sampling rate f s of the system, so that the disturbance signal can be accurately reconstructed by using a super-high sampling rate of several hundred times the frequency of the intermediate frequency signal.

[0061] In addition, from the formula of the phase discrimination accuracy of the system, it can be seen that when the ratio n is odd, the phase discrimination accuracy of the system is twice that when the ratio n is even, the phase discrimination accuracy is higher, the image of the phase change phi t is more accurate, and the external disturbance signal can be more accurately reconstructed, so the present application is more suitable for the case where the ratio of the sampling rate f s of the system to the frequency f w of the intermediate frequency signal is odd.

[0062] Examples

[0063] Referring to Figure 1 , the high demodulation accuracy phi-OTDR system in the example comprises a laser, a pulse generator, an acousto-optic modulator, a coupler 1, a coupler 2, an erbium-doped fiber amplifier, a circulator, a sensing optical fiber, a balanced detector, a comparator, a timer, and a processor.

[0064] A laser outputs narrow-linewidth continuous light (1530nm, 10nm linewidth) to coupler 1. Coupler 1 has a splitting ratio of 10:90, dividing the optical signal into 10% reference light and 90% probe light. The probe light is modulated by an acousto-optic modulator into pulsed light with a 20MHz frequency shift. The probe pulsed light enters an erbium-doped fiber amplifier to amplify the optical signal, and then is injected into the sensing fiber along port a of a circulator. The pulsed light continuously generates backscattered Rayleigh light along the sensing fiber. The backscattered Rayleigh light is transmitted to coupler 2 through ports b and c of the circulator. Coupler 2 receives the reference light and the backscattered Rayleigh light signals, mixes them to form a coherent optical signal, and splits the coherent optical signal into two signals according to a 50:50 splitting ratio, which are then transmitted to a balanced detector. The balanced detector converts the optical signal into an electrical signal, and after bandpass filtering, sends the resulting beat frequency signal to a comparator. After the comparator quantizes the signal by 1 bit, a timer driven by a high-frequency clock converts the quantized signal output by the comparator into a digital signal. The digital signal is then transmitted to the processor for display to obtain the current phase change value φ. t The system's sampling rate is 2.5 GHz, which is 125 times the intermediate frequency signal frequency.

[0065] See Figure 2 The specific process of the demodulation method for the high demodulation accuracy Φ-OTDR system based on 1 bit quantization in this example includes:

[0066] Step 1: Connect the sensing fiber to the Φ-OTDR system, and connect it to the vibration event box at a specific location on the sensing fiber. The vibration event box outputs a 2π-amplitude sinusoidal signal, which is applied to the sensing fiber as an external disturbance signal. Real-time dynamic acquisition of the signal is performed to obtain the intermediate frequency signal along the fiber.

[0067] Step 2: The comparator receives the real-time intermediate frequency signal and performs 1-bit quantization on the signal. Simultaneously, the comparator... Figure 3 The method shown ensures the stability of the output signal and improves the system's anti-interference capability;

[0068] Step 3: Use a high-frequency clock to drive the quantized signal output by the comparator to convert it into a digital signal;

[0069] Step 4: The processor receives the digital signal and follows... Figure 4 The current phase change value φ is determined in the manner shown. t , received Figure 5 The reconstructed signal is shown. Because the ratio of the system sampling rate to the intermediate frequency signal frequency is 125, according to the formula...

[0070]

[0071] Therefore, the phase detection accuracy φ of the system at this time is... R Very high Thus φ is obtained t The image of φ is very accurate, and the disturbance signal with a disturbance amplitude of 2π can be reconstructed with high accuracy finally.

[0072] The above is only the preferred embodiment of the present application, the protection scope of the present application is not limited to the above-mentioned examples, all technical solutions belonging to the idea of the present application are within the protection scope of the present application. It should be pointed out that, for ordinary skilled in the art, some improvements and refinements without departing from the principles of the present application, should be considered as the protection scope of the present application.

Claims

1. A high demodulation accuracy Φ-OTDR system based on 1bit quantization bit number, characterized in that, The high demodulation precision Φ-OTDR system comprises a laser, a pulse generator, an acousto-optic modulator, a first coupler, a second coupler, an erbium-doped fiber amplifier, a circulator, a sensing optical fiber, a balanced detector, a comparator, a timer and a processor. The continuous narrow linewidth laser output by the laser is divided into reference light and probe light after passing through the first coupler; the probe light becomes pulsed light after being modulated by the acousto-optic modulator, and the pulsed light is optically amplified by the erbium-doped fiber amplifier and transmitted to the sensing optical fiber along the circulator; the backscattered Rayleigh scattering light signals generated by the sensing optical fiber along the line are transmitted to the second coupler through the circulator, and the backscattered Rayleigh scattering light signals received by the second coupler are mixed with the reference light to form two coherent light signals; the balanced detector converts the two coherent light signals into electrical signals, and the electrical signals are band-pass filtered into beat frequency signals with a mean value of 0 V. The pulse generator simultaneously applies a trigger signal to the timer and the acousto-optic modulator to synchronize the timing of the timer and the acousto-optic modulator. The bandwidth of the comparator is greater than the frequency of the beat signal, the comparator receives the beat signal from the balanced detector, quantizes the beat signal with voltage value greater than 0 as 1, and quantizes the beat signal less than or equal to 0 as 0; the timer collects the quantized signal output by the comparator, observes the jump time of the signal 0 and the signal 1, and obtains the digital signal corresponding to the beat signal of each period by dividing the time interval of the two jump times by the clock period; the processor analyzes the digital signal output by the timer, analyzes the phase change value Φ of the corresponding period according to the encoding information of each period digital signal, and completes the reconstruction of the disturbance signal. t ​ 2. The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number according to claim 1, characterized in that, The reference voltage value of the comparator is the voltage value V REF representing 0 of the intermediate frequency signal TH+ The upper threshold voltage is V TH- The lower threshold voltage is V TH+ The threshold width is ΔV = V TH- -V 3.The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number of claim 1, wherein, The electrical signal output by the balanced detector is represented as: I(t) ∝ A R cos(Δωt + Φ t -Φ0) where A R is the amplitude of the signal, Δω is the frequency shift imposed on the probe light by the acousto-optic modulator, Φ t is the phase change value due to the effect of the external disturbance signal, and Φ0 is the initial phase of the signal. When the system sampling rate f s With the frequency f of the intermediate frequency signal w When the ratio is n, there are n sampling points within one period of the intermediate frequency signal. The values ​​at these n sampling points are quantized by a comparator using 1 bit and represented as: wherein the value of the ε(t) function is 1 when t>0, and the value of the ε(t) function is 0 when t≤0. 4.The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number of claim 1, wherein, The system sampling rate f s The ratio n of the frequency f w of the intermediate frequency signal to the frequency f of the input signal is an odd number. 5.The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number of claim 1, wherein, The processor stores an encoding-phase correspondence table, which is used to represent the relationship between the encoding value of the digital signal and the phase change value Φ caused by the external disturbance t When the amplitude of the disturbance signal is between 0 and 2π, the processor analyzes the phase change value Φ by querying the encoding-phase correspondence table t When the amplitude of the disturbance signal is greater than 2π, the processor restores the real amplitude of the signal by using a phase unwrapping algorithm. 6.The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number of claim 1, wherein, The phase discrimination accuracy of the high demodulation precision Φ-OTDR system is: where Φ R is the phase discrimination accuracy of the system, f s is the system sampling rate, f w is the frequency of the intermediate frequency signal, and n is the ratio of the system sampling rate f s to the frequency f w of the intermediate frequency signal.

7. A demodulation method of a high demodulation accuracy Φ-OTDR system based on 1 bit quantization bit number, characterized in that, The demodulation method comprises the following steps: The continuous narrow linewidth laser output by the laser is divided into reference light and probe light, the probe light becomes pulsed light after being modulated by the acousto-optic modulator, and the pulsed light is optically amplified by the erbium-doped fiber amplifier and transmitted to the sensing optical fiber along the circulator; the backscattered Rayleigh scattering light signals generated by the sensing optical fiber along the line are mixed with the reference light to form two coherent light signals; The two coherent light signals are converted into electrical signals by the balanced detector, and the electrical signals are band-pass filtered into beat frequency signals with a mean value of 0 V; the beat frequency signals with a voltage value greater than 0 are quantized as 1, and the beat frequency signals with a voltage value less than or equal to 0 are quantized as 0; The quantized signals are collected by the timer, the jump time of the signals 0 and the signals 1 is observed, and the time interval between the two jump times is divided by the clock period to obtain the digital signal corresponding to each period of the beat frequency signal; the timing of the timer and the acousto-optic modulator is synchronized; The digital signal output by the timer is analyzed to obtain the phase change value Φ of each cycle according to the encoding information of the digital signal of each cycle t , and the reconstruction of the disturbance signal is completed. 8.The high demodulation accuracy Φ-OTDR system based on 1-bit quantization bit number of claim 7, wherein, The duty cycle of the output signal of the comparator is set to 50% by setting the hysteresis range of the comparator. 9.The demodulation method of the 1-bit quantization bit number based high demodulation accuracy Φ-OTDR system according to claim 7, wherein, The electrical signal output by the balanced detector is represented as: I(t)∝A R cos(Δωt+Φ t -Φ0) where A R is the amplitude of the signal, Δω is the frequency shift imposed on the probe light by the acousto-optic modulator, Φ t is the phase change value due to the effect of the external disturbance signal, and Φ0is the initial phase of the signal. When the system sampling rate f s With the frequency f of the intermediate frequency signal w When the ratio is n, there are n sampling points within one period of the intermediate frequency signal. The values ​​at these n sampling points are quantized by a comparator using 1 bit and represented as: wherein the value of the ε(t) function is 1 when t>0, and the value of the ε(t) function is 0 when t≤0.

10. The demodulation method of the 1-bit quantization bit number based high demodulation accuracy Φ-OTDR system according to claim 7, wherein, When the amplitude of the disturbance signal is between 0 and 2π, the phase change value Φ is obtained by querying the encoding-phase correspondence table t The external disturbance signal is reconstructed; the encoding-phase correspondence table is used to represent the relationship between the encoding value of the digital signal composition and the phase change value Φ caused by the external disturbance t When the amplitude of the disturbance signal is greater than 2π, the processor restores the real amplitude of the signal by using a phase unwrapping algorithm.

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