Dynamically adjustable double-channel BOTDR polarization fading suppression device

Abstract

The invention provides a dynamically adjustable dual-path BOTDR (Brillouin Optical Time Domain Reflectometer) polarization fading suppression device, and belongs to the technical field of BOTDR polarization fading suppression devices. In order to solve the technical problems that a scrambler has working frequency harmonic noise and a single polarization controller cannot ensure an optimal coherent result, the adopted technical scheme is as follows: the output end of a first path of optical fiber input interface is connected to the input end a of a polarized light beam splitter; the output end b of the polarized light beam splitter is connected to the input end a of the electric control light delay line; the c output end of the electric control light delay line is connected to the a input end of the electric control polarization controller; an output end c of the electric control polarization controller is connected to an input end b of the polarized light beam combiner; the output end a of the polarized light beam combiner is connected to the input end of the first optical fiber output interface; the c output end of the polarized light beam splitter is connected to the c input end of the polarized light beam combiner; the power supply anode input end is connected to the a anode input end of the power supply interface; the BOTDR polarization fading suppression method is applied to BOTDR polarization fading suppression.

Description

Technical Field

[0001] This invention provides a dynamically adjustable dual-channel BOTDR polarization fading suppression device, belonging to the technical field of BOTDR polarization fading suppression devices. Background Technology

[0002] Distributed fiber optic sensing technology, exemplified by Brillouin optical time domain reflectometers (BOTDR), has been widely studied due to its advantages in long-distance and large-scale monitoring. Using optical fiber as both the sensing and transmission medium, it can simultaneously acquire temporal and spatial information of the measured physical quantity, finding wide application in fields such as oil and gas pipeline monitoring, bridge and building monitoring. However, distributed fiber optic sensing systems are prone to polarization fading, which can degrade system performance, including spatial resolution and measurement accuracy. Furthermore, coherent detection BOTDR systems are polarization sensitive and susceptible to polarization fading. Polarization fading occurs because the inhomogeneity of the internal structure of a single-mode fiber or the presence of external perturbations causes birefringence of the light, resulting in random changes in the polarization state of the light. During coherent detection, the coherence between the signal light and the reference light continuously changes, leading to significant fluctuations in the signal-to-noise ratio of the sensing signal. This reduces the demodulation accuracy of the sensing system and may even prevent the system from demodulating external signals from the reflected light, severely impacting the accuracy and reliability of the fiber optic sensing system. Therefore, suppressing polarization fading is crucial for improving the measurement accuracy of coherent detection BOTDR systems.

[0003] Currently, active polarizers or polarization controllers are generally used in BOTDR systems to mitigate polarization fading. The mechanism of active polarizers in suppressing polarization fading involves driving several piezoelectric ceramics with voltages of different frequencies to compress the optical fiber, causing the single-mode fiber to rapidly change the polarization state of the light. This results in the overall effect of the polarized light losing its polarization characteristics for a certain period. However, this polarization scrambling method easily introduces operating frequency noise and harmonic noise. Polarization controllers can adjust the polarization state of the light to a fixed state; however, due to the birefringence effect in standard single-mode fiber, the polarization states of both the input pulse signal and the backscattered signal are affected. The birefringence effect varies for backscattered light generated at different locations, resulting in different final polarization states. Therefore, using a single polarization controller cannot guarantee optimal coherence results.

[0004] Therefore, it is necessary to design a dynamically adjustable dual-channel BOTDR polarization fading suppression device that combines piezoelectric ceramics and a polarization controller. In addition, the system can evaluate the polarization fading suppression effect in real time based on the root mean square error of the feedback sensing signal, and dynamically adjust the operating frequency of the piezoelectric ceramics, the polarization controller, and the length of the optical delay line to solve the problems of unstable polarization fading suppression effect and high-frequency noise. This ensures that the system measurement is more stable and reliable, making the BOTDR sensing system closer to real practical products and generating significant economic and social value. Summary of the Invention

[0005] To address the technical problems existing in the background art, the present invention adopts the following technical solution: A dynamically adjustable dual-channel BOTDR polarization fading suppression device is provided, comprising a first fiber optic input interface, a polarization beam splitter, an electrically controlled optical delay line, an electrically controlled polarization controller, a polarization beam combiner, a first fiber optic output interface, an electrically controlled optical delay line communication interface, an electrically controlled polarization controller control unit, a power interface, a linear voltage regulator module, a central processing unit, a first digital-to-analog converter (DAC), a second DAC, a third DAC, a fourth DAC, a first operational amplifier, a second operational amplifier, a third operational amplifier, a fourth operational amplifier, a first piezoelectric ceramic, a second piezoelectric ceramic, a third piezoelectric ceramic, a fourth piezoelectric ceramic, a second fiber optic input interface, a second fiber optic output interface, a positive power input terminal, a negative power input terminal, an analog-to-digital converter (ADC), and an ADC input interface, wherein: The output of the first fiber optic input interface is connected to input port a of the polarization beamsplitter; the output port b of the polarization beamsplitter is connected to input port a of the electrically controlled optical delay line; the output port c of the electrically controlled optical delay line is connected to input port a of the electrically controlled polarization controller; the output port c of the electrically controlled polarization controller is connected to input port b of the polarization beam combiner; the output port a of the polarization beam combiner is connected to input port a of the first fiber optic output interface; and the output port c of the polarization beamsplitter is connected to input port c of the polarization beam combiner. The positive input terminal of the power supply is connected to the positive input terminal a of the power interface; the negative input terminal of the power supply is connected to the negative input terminal b of the power interface; the output terminal c of the power interface is connected to the input terminal a of the linear regulator module. The output terminal b of the linear voltage regulator module is connected to the input terminal a of the first operational amplifier; The output terminal b of the linear voltage regulator module is connected to the input terminal a of the second operational amplifier; The output terminal b of the linear voltage regulator module is connected to the input terminal a of the third operational amplifier; The output terminal b of the linear regulator module is connected to the input terminal a of the fourth operational amplifier; The output terminal C of the linear voltage regulator module is connected to the input terminal A of the first digital-to-analog converter; The output terminal C of the linear voltage regulator module is connected to the input terminal A of the second digital-to-analog converter; The output terminal C of the linear voltage regulator module is connected to the input terminal A of the third digital-to-analog converter; The output terminal C of the linear voltage regulator module is connected to the input terminal A of the fourth digital-to-analog converter; The output terminal d of the linear voltage regulator module is connected to the input terminal a of the central processing unit; The e-output terminal of the linear regulator module is connected to the a-input terminal of the analog-to-digital converter; The g output terminal of the central processing unit is connected to the input terminal of the electronically controlled optical delay line communication interface; the output terminal of the electronically controlled optical delay line communication interface is connected to the b input terminal of the electronically controlled optical delay line. The h output terminal of the central processing unit is connected to the input terminal of the electronically controlled polarization controller control unit; the output terminal of the electronically controlled polarization controller control unit is connected to the b input terminal of the electronically controlled polarization controller. The c output terminal of the central processing unit is connected to the b input terminal of the first digital-to-analog converter; The d output terminal of the central processing unit is connected to the b input terminal of the second digital-to-analog converter; The e-output terminal of the central processing unit is connected to the b-input terminal of the third digital-to-analog converter; The f output terminal of the central processing unit is connected to the b input terminal of the fourth digital-to-analog converter; The C output terminal of the first digital-to-analog converter is connected to the B input terminal of the first operational amplifier; The output terminal (c) of the second digital-to-analog converter is connected to the input terminal (b) of the second operational amplifier; The c output terminal of the third digital-to-analog converter is connected to the b input terminal of the third operational amplifier; The c output terminal of the fourth digital-to-analog converter is connected to the b input terminal of the fourth operational amplifier; The c output terminal of the first operational amplifier is connected to the a input terminal of the first piezoelectric ceramic. The output terminal (C) of the second operational amplifier is connected to the input terminal (A) of the second piezoelectric ceramic. The c output terminal of the third operational amplifier is connected to the a input terminal of the third piezoelectric ceramic. The c output terminal of the fourth operational amplifier is connected to the a input terminal of the fourth piezoelectric ceramic. The output of the second optical fiber input interface is connected to the b input of the first piezoelectric ceramic; the c output of the first piezoelectric ceramic is connected to the b input of the second piezoelectric ceramic; the c output of the second piezoelectric ceramic is connected to the b input of the third piezoelectric ceramic; the c output of the third piezoelectric ceramic is connected to the b input of the fourth piezoelectric ceramic; and the c output of the fourth piezoelectric ceramic is connected to the input of the second optical fiber output interface. The output terminal of the analog-to-digital converter input interface is connected to the b input terminal of the analog-to-digital converter; the c output terminal of the analog-to-digital converter is connected to the b input terminal of the central processing unit.

[0006] It also includes a narrow-linewidth laser, a first fiber coupler, and an optical pulse modulator. In use, the narrow-linewidth laser emits a continuous narrow-linewidth laser with a center wavelength of 1550nm, which is input to the a-input terminal of the first fiber coupler. The first fiber coupler splits the narrow-linewidth laser into two paths, 90% and 10%, where: 90% of the laser light is used as reference light and outputs to the input of the first fiber optic input interface via the output (C) terminal of the first fiber optic coupler. 10% of the laser light is used as probe light and output to the input of the optical pulse modulator via the output terminal b of the first fiber coupler.

[0007] It also includes a signal acquisition and processing unit. When in use, the signal acquisition and processing unit processes the acquired signal to obtain the Brillouin center frequency curve, calculates the root mean square error of the Brillouin center frequency curve, and sends it to the central processing unit through the analog-to-digital converter input interface and analog-to-digital converter.

[0008] The central processing unit determines the effectiveness of the system's polarization fading suppression based on the received root mean square error signal. It changes the output frequencies of the first, second, third, and fourth digital-to-analog converters, communicates with the electrically controlled optical delay line via the communication interface, changes the length of the optical delay line, and then electrically compresses the electrically controlled polarization controller via the control unit to change the polarization state of the light, thereby achieving the optimal polarization fading suppression effect.

[0009] The present invention has the following advantages over the prior art: I. This invention utilizes an active-driven piezoelectric ceramic and a polarization controller to construct a hybrid dual-path polarization fading suppression device, which can effectively alleviate the operating frequency noise caused by the piezoelectric ceramic's operating frequency limitation and the inability of a single polarization controller to guarantee optimal coherence results. This ensures the reliability and accuracy of the system's measurements. II. This invention introduces a feedback mechanism, using the root mean square error of the returned sensor signal, which is then converted from analog to digital and fed into the central processing unit for real-time evaluation of polarization fading suppression. It can dynamically adjust the operating frequency of the piezoelectric ceramic and simultaneously adjust the optical delay line length and polarization controller. The system can optimize polarization fading suppression based on real-time feedback, providing optimal polarization control, thereby improving the system's adaptability and measurement accuracy. Third, this invention employs a dual-path structure, which can be placed separately in the reference and probe paths of a BOTDR system, enhancing the stability and reliability of polarization fading suppression. In practical applications, single-path or dual-path usage can be flexibly selected according to system requirements. Attached Figure Description

[0010] The present invention will be further described below with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the dual-channel BOTDR polarization fading suppression device of the present invention; Figure 2 This is a schematic diagram of the dual-channel BOTDR polarization fading suppression device of the present invention in the BOTDR system usage state; In the diagram, 1 is the first fiber optic input interface, 2 is the polarization beam splitter, 3 is the electrically controlled optical delay line, 4 is the electrically controlled polarization controller, 5 is the polarization beam combiner, 6 is the first fiber optic output interface, 7 is the electrically controlled optical delay line communication interface, 8 is the electrically controlled polarization controller control unit, 9 is the power interface, 10 is the linear voltage regulator module, 11 is the central processing unit, 12 is the first digital-to-analog converter, 13 is the second digital-to-analog converter, 14 is the third digital-to-analog converter, 15 is the fourth digital-to-analog converter, 16 is the first operational amplifier, 17 is the second operational amplifier, 18 is the third operational amplifier, 19 is the fourth operational amplifier, 20 is the first piezoelectric ceramic, 21 is the second piezoelectric ceramic, and 22 is the third piezoelectric ceramic. 23 is the fourth piezoelectric ceramic, 24 is the second fiber optic input interface, 25 is the second fiber optic output interface, 26 is the positive power input terminal, 27 is the negative power input terminal, 28 is the analog-to-digital converter, 29 is the analog-to-digital converter input interface, 30 is the 1550nm narrow linewidth laser, 31 is the first fiber optic coupler, 32 is the optical pulse modulator, 33 is the pulsed optical amplifier, 34 is the fiber under test, 35 is the continuous optical amplifier, 36 is the circulator, 37 is the voltage source, 38 is the second fiber optic coupler, 39 is the photodetector, 40 is the mixer, 41 is the microwave source, 42 is the low-noise amplifier, 43 is the bandpass filter, 44 is the detector, and 45 is the signal acquisition and processing unit. Detailed Implementation

[0011] This invention addresses the technical problems of harmonic noise at the operating frequency in conventional polarization scramblers and the inability of a single polarization controller to guarantee optimal coherence results. It proposes a dynamically adjustable dual-path BOTDR polarization fading suppression device. By using four piezoelectric ceramics with different operating frequencies, the rapid change in the polarization state of the single-mode fiber is combined with the polarization controller to achieve dual-path polarization fading suppression. Simultaneously, the root mean square error of the received sensor signal is used to quantify the system's polarization fading suppression effect. The operating frequency of the piezoelectric ceramics is dynamically changed, and the length of the optical delay line and the polarization controller are adjusted synchronously to achieve the optimal polarization fading suppression effect, thereby improving the measurement reliability and accuracy of the BOTDR system.

[0012] like Figure 1 As shown, to achieve the above technical solution, the present invention provides a dynamically adjustable dual-channel BOTDR polarization fading suppression device, comprising: a first fiber optic input interface 1, a polarization beam splitter 2, an electrically controlled optical delay line 3, an electrically controlled polarization controller 4, a polarization beam combiner 5, a first fiber optic output interface 6, an electrically controlled optical delay line communication interface 7, an electrically controlled polarization controller control unit 8, a power interface 9, a linear voltage regulator module 10, a central processing unit 11, a first digital-to-analog converter 12, a second digital-to-analog converter 13, a third digital-to-analog converter 14, a fourth digital-to-analog converter 15, a first operational amplifier 16, a second operational amplifier 17, a third operational amplifier 18, a fourth operational amplifier 19, a first piezoelectric ceramic 20, a second piezoelectric ceramic 21, a third piezoelectric ceramic 22, a fourth piezoelectric ceramic 23, a second fiber optic input interface 24, a second fiber optic output interface 25, a positive power input terminal 26, a negative power input terminal 27, an analog-to-digital converter 28, and an analog-to-digital converter input interface 29, wherein: The output of the first fiber optic input interface 1 is connected to input a of polarization beamsplitter 2; the output b of polarization beamsplitter 2 is connected to input a of electrically controlled optical delay line 3; the output c of electrically controlled optical delay line 3 is connected to input a of electrically controlled polarization controller 4; the output c of electrically controlled polarization controller 4 is connected to input b of polarization beam combiner 5; the output a of polarization beam combiner 5 is connected to input of the first fiber optic output interface 6; and the output c of polarization beamsplitter 2 is connected to input c of polarization beam combiner 5. The positive input terminal 26 of the power supply is connected to the positive input terminal a of the power interface 9; the negative input terminal 27 of the power supply is connected to the negative input terminal b of the power interface 9; and the output terminal c of the power interface 9 is connected to the input terminal a of the linear regulator module 10. The output terminal b of the linear voltage regulator module 10 is connected to the input terminal a of the first operational amplifier 16; The output terminal b of the linear voltage regulator module 10 is connected to the input terminal a of the second operational amplifier 17; The output terminal b of the linear voltage regulator module 10 is connected to the input terminal a of the third operational amplifier 18; The output terminal b of the linear voltage regulator module 10 is connected to the input terminal a of the fourth operational amplifier 19; The c output terminal of the linear voltage regulator module 10 is connected to the a input terminal of the first digital-to-analog converter 12; The c output terminal of the linear voltage regulator module 10 is connected to the a input terminal of the second digital-to-analog converter 13; The output terminal (c) of the linear voltage regulator module 10 is connected to the input terminal (a) of the third digital-to-analog converter 14; The output terminal (c) of the linear voltage regulator module 10 is connected to the input terminal (a) of the fourth digital-to-analog converter 15. The output terminal d of the linear voltage regulator module 10 is connected to the input terminal a of the central processing unit 11; The e-output terminal of the linear voltage regulator module 10 is connected to the a-input terminal of the analog-to-digital converter 28; The g output terminal of the central processing unit 11 is connected to the input terminal of the electrically controlled optical delay line communication interface 7; the output terminal of the electrically controlled optical delay line communication interface 7 is connected to the b input terminal of the electrically controlled optical delay line 3. The h output terminal of the central processing unit 11 is connected to the input terminal of the electrically controlled polarization controller control unit 8; the output terminal of the electrically controlled polarization controller control unit 8 is connected to the b input terminal of the electrically controlled polarization controller 4. The c output terminal of the central processing unit 11 is connected to the b input terminal of the first digital-to-analog converter 12; The d output terminal of the central processing unit 11 is connected to the b input terminal of the second digital-to-analog converter 13; The e-output terminal of the central processing unit 11 is connected to the b-input terminal of the third digital-to-analog converter 14; The f output terminal of the central processing unit 11 is connected to the b input terminal of the fourth digital-to-analog converter 15; The C output terminal of the first digital-to-analog converter 12 is connected to the B input terminal of the first operational amplifier 16; The output terminal (c) of the second digital-to-analog converter 13 is connected to the input terminal (b) of the second operational amplifier 17; The c output terminal of the third digital-to-analog converter 14 is connected to the b input terminal of the third operational amplifier 18; The c output terminal of the fourth digital-to-analog converter 15 is connected to the b input terminal of the fourth operational amplifier 19; The c-output terminal of the first operational amplifier 16 is connected to the a-input terminal of the first piezoelectric ceramic 20; The output terminal (c) of the second operational amplifier 17 is connected to the input terminal (a) of the second piezoelectric ceramic 21; The c output terminal of the third operational amplifier 18 is connected to the a input terminal of the third piezoelectric ceramic 22; The c output terminal of the fourth operational amplifier 19 is connected to the a input terminal of the fourth piezoelectric ceramic 23; The output of the second optical fiber input interface 24 is connected to the b input of the first piezoelectric ceramic 20; the c output of the first piezoelectric ceramic 20 is connected to the b input of the second piezoelectric ceramic 21; the c output of the second piezoelectric ceramic 21 is connected to the b input of the third piezoelectric ceramic 22; the c output of the third piezoelectric ceramic 22 is connected to the b input of the fourth piezoelectric ceramic 23; and the c output of the fourth piezoelectric ceramic 23 is connected to the input of the second optical fiber output interface 25. The output of the analog-to-digital converter input interface 29 is connected to the b input of the analog-to-digital converter 28; the c output of the analog-to-digital converter 28 is connected to the b input of the central processing unit 11.

[0013] like Figure 2 The diagram shown illustrates the structure of the dynamically adjustable dual-channel BOTDR polarization fading suppression device of the present invention in use within a BOTDR system. The system also includes a 1550nm narrow-linewidth laser 30, a first fiber coupler 31, an optical pulse modulator 32, a pulsed optical amplifier 33, an optical fiber under test 34, a continuous optical amplifier 35, a circulator 36, a voltage source 37, a second fiber coupler 38, a photodetector 39, a mixer 40, a microwave source 41, a low-noise amplifier 42, a bandpass filter 43, a detector 44, and a signal acquisition and processing unit 45. The specific control method is as follows: The 1550nm narrow-linewidth laser 30 emits a continuous narrow-linewidth laser with a center wavelength of 1550nm, which is input to the a input terminal of the first fiber coupler 31. The first fiber coupler 31 splits the narrow-linewidth laser into two paths: 90% and 10%. The 90% laser, used as a reference light, is output through the c output terminal of the first fiber coupler 31 to the input terminal of the first fiber input interface 1. The 10% laser, used as a probe light, is output through the b output terminal of the first fiber coupler 31 to the input terminal of the optical pulse modulator 32. The optical pulse modulator 32 modulates the laser into pulsed light, which is then connected to the output terminal of the optical pulse modulator 32. The pulsed light is amplified at the input of the pulsed light amplifier 33. The amplified pulsed light is then input to the first loop (a) of the circulator 36 via the output of the pulsed light amplifier 33, and then enters the first loop (b) of the circulator 36 via the second loop (b). The pulsed light enters the first loop (a) of the fiber under test 34 and generates spontaneous Brillouin scattering. The Brillouin scattered light is output from the first loop (a) of the fiber under test 34 to the second loop (b) of the circulator 36, and then output from the third loop (c) of the circulator 36 to the input of the continuous light amplifier 35 for continuous light amplification. The amplified continuous light is then input from the output of the continuous light amplifier 35 to the input of the second fiber input interface 24. The 12V voltage output terminal 'a' of the voltage source 37 is connected to the positive input terminal 26 of the power supply, and the ground output terminal 'b' of the voltage source 37 is connected to the negative input terminal 27 of the power supply. The positive input terminal 26 of the power supply is connected to the input terminal 'a' of the power interface 9, and the negative input terminal 27 of the power supply is connected to the input terminal 'b' of the power interface 9. The output terminal 'c' of the power interface 9 is connected to the input terminal 'a' of the linear voltage regulator module 10. The linear voltage regulator module 10 converts the 12V voltage from the voltage source into various different voltages. The output terminal 'b' of the linear voltage regulator module 10 is connected to the input terminals 'a' of the first operational amplifier 16, the second operational amplifier 17, the third operational amplifier 18, and the fourth operational amplifier 19, respectively. The c output terminal is connected to the a input terminal of the first digital-to-analog converter 12, the a input terminal of the second digital-to-analog converter 13, the a input terminal of the third digital-to-analog converter 14, and the a input terminal of the fourth digital-to-analog converter 15, respectively; the d output terminal of the linear regulator module 10 is connected to the a input terminal of the central processing unit 11; the e output terminal of the linear regulator module 10 is connected to the a input terminal of the analog-to-digital converter 28; the c, d, e, and f output terminals of the central processing unit 11 are connected to the b input terminals of the first digital-to-analog converter 12, the second digital-to-analog converter 13, the third digital-to-analog converter 14, and the fourth digital-to-analog converter 15, respectively, to control the first digital-to-analog converter 12, the second digital-to-analog converter 13, the third digital-to-analog converter 14, and the fourth digital-to-analog converter 15. Digital-to-analog converter 14 and fourth digital-to-analog converter 15 generate four voltage signals of different frequencies. These four voltage signals are output from the C output terminals of the first digital-to-analog converter 12, the second digital-to-analog converter 13, the third digital-to-analog converter 14, and the fourth digital-to-analog converter 15 to the B input terminals of the first operational amplifier 16, the second operational amplifier 17, the third operational amplifier 18, and the fourth operational amplifier 19, respectively. The four voltage signals are amplified by these amplifiers. The amplified four voltage signals are then input to the A input terminal of the first piezoelectric ceramic 20. The input terminals of the first, second, third, and fourth piezoelectric ceramics 21, 22, and 23 are connected to drive the four piezoelectric ceramics to extrude optical fiber at different frequencies, thereby rapidly changing the polarization state of the light. The output terminal of the central processing unit 11 is connected to the input terminal of the electrically controlled optical delay line communication interface 7, and the output terminal of the electrically controlled optical delay line communication interface 7 is connected to the input terminal of the electrically controlled optical delay line 3, which can adjust the length of the electrically controlled optical delay line. The output terminal of the central processing unit 11 is connected to the input terminal of the electrically controlled polarization controller control unit 8, and the output terminal of the electrically controlled polarization controller control unit 8 is connected to the input terminal of the electrically controlled polarization controller 4, which can control the extrusion polarization controller to change the polarization state of the light.

[0014] The spontaneously scattered light from the second fiber input interface 24 passes through the first piezoelectric ceramic 20, the second piezoelectric ceramic 21, the third piezoelectric ceramic 22, and the fourth piezoelectric ceramic 23 to the second fiber output interface 25. The four piezoelectric ceramics compress the single-mode fiber at different frequencies, causing the spontaneously scattered light to rapidly change its polarization state. It then enters the second fiber output interface 25 and is input to the b-input terminal of the second fiber coupler 38. 90% of the laser light, used as a reference light, enters the first fiber input interface 1 and is input to the a-input terminal of the polarization beamsplitter 2. The b-output terminal of the polarization beamsplitter 2 is connected to the a-input terminal of the electrically controlled optical delay line 3. The c-output terminal of the electrically controlled optical delay line 3 is connected to the a-input terminal of the electrically controlled polarization controller 4. The c-output terminal of the electrically controlled polarization controller 4 is connected to the b-input terminal of the polarization beam combiner 5. The c-output terminal of the polarization beamsplitter 2 is connected to the polarization beam combiner. The polarization states of the light at input c of optical coupler 5, input b of optical coupler 5, and input c of optical coupler 5 are different. After coherence by optical coupler 5, a reference light with an approximately circular polarization state is obtained. This reference light is input from output a of optical coupler 5 to the first fiber optic output interface 6 and output from the first fiber optic output interface 6 to input a of second fiber optic coupler 38. The reference light with an approximately circular polarization state and the spontaneously scattered light with a rapidly changing polarization state are input to input a of second fiber optic coupler 38 and input b of second fiber optic coupler 38, respectively. After coherence by second fiber optic coupler 38, the coherent light is output from output c of second fiber optic coupler 38 to input of photodetector 39. The coherent light signal undergoes photoelectric conversion by photodetector 39. Due to the frequency limitation of photodetector, the final output frequency is close to 10.An 8GHz self-generated frequency-shifted electrical signal is converted and input from the output of photodetector 39 to input a of mixer 40. The output of microwave source 41 is connected to input b of mixer 40. The output signal of microwave source is mixed with the signal converted by photodetector in mixer 40, and a mixed signal close to 700MHz is output. This mixed signal is input from output c of mixer 40 to input of low-noise amplifier 42. After amplification by low-noise amplifier 42, the amplified signal is input from output of low-noise amplifier 42 to input of bandpass filter 43. After filtering at a center frequency of 700MHz, the filtered signal is input from output of bandpass filter 43 to input of detector 44. After power detection by detector 44, the detected signal is input from output of detector 44 to signal acquisition and processing unit 45. Signal acquisition and processing unit 45 processes the acquired signal. The received signal is processed to obtain the Brillouin center frequency curve. The root mean square error (RMSE) of the Brillouin center frequency curve is calculated and input to the analog-to-digital converter (ADC) input interface 29. From the ADC input interface 29, the signal is input to the b input terminal of the ADC 28. After analog-to-digital conversion by the ADC 28, the signal is output from the c output terminal of the ADC 28 to the b input terminal of the central processing unit (CPU) 11. The CPU 11 judges the effectiveness of the system's polarization fading suppression based on the feedback RMSE signal and changes the output frequencies of the first digital-to-analog converter (DAC) 12, the second DAC 13, the third DAC 14, and the fourth DAC 15. Communication is established with the electrically controlled optical delay line 3 via the electrically controlled optical delay line communication interface 7 to change the length of the optical delay line. The electrically controlled polarization controller 4 is electrically compressed via the electrically controlled polarization controller control unit 8 to change the polarization state of the light, thereby achieving the optimal polarization fading suppression effect.

[0015] The dynamically adjustable dual-channel BOTDR polarization fading suppression device provided by this invention aims to suppress polarization fading in BOTDR systems. It primarily utilizes a combination of piezoelectric ceramics and a polarization controller for dual-channel polarization suppression, addressing the noise defects at the operating frequency of the piezoelectric ceramics and the inability of a single polarization controller to guarantee optimal coherence results. Furthermore, the device can determine the polarization fading suppression effect in real time by receiving the root mean square error of the feedback sensor signal. By adjusting the operating frequency of the piezoelectric ceramics, the length of the optical delay line, and the polarization controller, the optimal polarization fading suppression effect can be achieved, making the BOTDR system measurement more stable and reliable, and improving the system's measurement accuracy.

[0016] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamically adjustable dual-channel BOTDR polarization fading suppression device, characterized in that: The system includes a first fiber optic input interface (1), a polarization beam splitter (2), an electrically controlled optical delay line (3), an electrically controlled polarization controller (4), a polarization beam combiner (5), a first fiber optic output interface (6), an electrically controlled optical delay line communication interface (7), an electrically controlled polarization controller control unit (8), a power interface (9), a linear voltage regulator module (10), a central processing unit (11), a first digital-to-analog converter (12), a second digital-to-analog converter (13), a third digital-to-analog converter (14), a fourth digital-to-analog converter (15), a first operational amplifier (16), a second operational amplifier (17), a third operational amplifier (18), a fourth operational amplifier (19), a first piezoelectric ceramic (20), a second piezoelectric ceramic (21), a third piezoelectric ceramic (22), a fourth piezoelectric ceramic (23), a second fiber optic input interface (24), a second fiber optic output interface (25), a positive power input terminal (26), a negative power input terminal (27), an analog-to-digital converter (28), and an analog-to-digital converter input interface (29), wherein: The output end of the first fiber optic input interface (1) is connected to the a input end of the polarization beam splitter (2); the b output end of the polarization beam splitter (2) is connected to the a input end of the electrically controlled optical delay line (3); the c output end of the electrically controlled optical delay line (3) is connected to the a input end of the electrically controlled polarization controller (4); the c output end of the electrically controlled polarization controller (4) is connected to the b input end of the polarization beam combiner (5); the a output end of the polarization beam combiner (5) is connected to the input end of the first fiber optic output interface (6); the c output end of the polarization beam splitter (2) is connected to the c input end of the polarization beam combiner (5). The positive input terminal (26) of the power supply is connected to the positive input terminal a of the power interface (9); the negative input terminal (27) of the power supply is connected to the negative input terminal b of the power interface (9); the output terminal c of the power interface (9) is connected to the input terminal a of the linear regulator module (10); The output terminal b of the linear voltage regulator module (10) is connected to the input terminal a of the first operational amplifier (16); The output terminal b of the linear voltage regulator module (10) is connected to the input terminal a of the second operational amplifier (17); The b output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the third operational amplifier (18); The output terminal b of the linear voltage regulator module (10) is connected to the input terminal a of the fourth operational amplifier (19); The c output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the first digital-to-analog converter (12); The c output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the second digital-to-analog converter (13); The c output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the third digital-to-analog converter (14); The c output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the fourth digital-to-analog converter (15); The d output terminal of the linear voltage regulator module (10) is connected to the a input terminal of the central processing unit (11); The e-output terminal of the linear regulator module (10) is connected to the a-input terminal of the analog-to-digital converter (28); The g output terminal of the central processing unit (11) is connected to the input terminal of the electronically controlled optical delay line communication interface (7); the output terminal of the electronically controlled optical delay line communication interface (7) is connected to the b input terminal of the electronically controlled optical delay line (3); The h output terminal of the central processing unit (11) is connected to the input terminal of the electric polarization controller control unit (8); the output terminal of the electric polarization controller control unit (8) is connected to the b input terminal of the electric polarization controller (4); The c output terminal of the central processing unit (11) is connected to the b input terminal of the first digital-to-analog converter (12); The d output terminal of the central processing unit (11) is connected to the b input terminal of the second digital-to-analog converter (13); The e-output terminal of the central processing unit (11) is connected to the b-input terminal of the third digital-to-analog converter (14); The f output terminal of the central processing unit (11) is connected to the b input terminal of the fourth digital-to-analog converter (15); The c output terminal of the first digital-to-analog converter (12) is connected to the b input terminal of the first operational amplifier (16); The c output terminal of the second digital-to-analog converter (13) is connected to the b input terminal of the second operational amplifier (17); The c output terminal of the third digital-to-analog converter (14) is connected to the b input terminal of the third operational amplifier (18); The c output terminal of the fourth digital-to-analog converter (15) is connected to the b input terminal of the fourth operational amplifier (19); The c output terminal of the first operational amplifier (16) is connected to the a input terminal of the first piezoelectric ceramic (20); The c output terminal of the second operational amplifier (17) is connected to the a input terminal of the second piezoelectric ceramic (21); The c output terminal of the third operational amplifier (18) is connected to the a input terminal of the third piezoelectric ceramic (22); The c output terminal of the fourth operational amplifier (19) is connected to the a input terminal of the fourth piezoelectric ceramic (23); The output of the second optical fiber input interface (24) is connected to the b input of the first piezoelectric ceramic (20); the c output of the first piezoelectric ceramic (20) is connected to the b input of the second piezoelectric ceramic (21); the c output of the second piezoelectric ceramic (21) is connected to the b input of the third piezoelectric ceramic (22); the c output of the third piezoelectric ceramic (22) is connected to the b input of the fourth piezoelectric ceramic (23); and the c output of the fourth piezoelectric ceramic (23) is connected to the input of the second optical fiber output interface (25). The output of the analog-to-digital converter input interface (29) is connected to the b input of the analog-to-digital converter (28); the c output of the analog-to-digital converter (28) is connected to the b input of the central processing unit (11).

2. The dynamically adjustable dual-channel BOTDR polarization fading suppression device according to claim 1, characterized in that: It also includes a narrow linewidth laser (30), a first fiber coupler (31), and an optical pulse modulator (32). In use, the narrow linewidth laser (30) emits a continuous narrow linewidth laser with a center wavelength of 1550nm, which is input to the a input end of the first fiber coupler (31). The first fiber coupler (31) splits the narrow linewidth laser into two paths, 90% and 10%, of which: 90% of the laser light is used as reference light and is output from the c output end of the first fiber coupler (31) to the input end of the first fiber input interface (1). 10% of the laser light is used as probe light and output to the input of the optical pulse modulator (32) via the output of the first fiber coupler (31).

3. The dynamically adjustable dual-channel BOTDR polarization fading suppression device according to claim 2, characterized in that: It also includes a signal acquisition and processing unit (45). When in use, the signal acquisition and processing unit (45) processes the acquired signal to obtain the Brillouin center frequency curve, calculates the root mean square error of the Brillouin center frequency curve, and sends it to the central processing unit (11) through the analog-to-digital converter input interface (29) and the analog-to-digital converter (28).

4. The dynamically adjustable dual-channel BOTDR polarization fading suppression device according to claim 3, characterized in that: The central processing unit (11) judges the quality of the system's polarization fading suppression effect based on the received root mean square error signal. By changing the output frequency of the first digital-to-analog converter (12), the second digital-to-analog converter (13), the third digital-to-analog converter (14), and the fourth digital-to-analog converter (15), it communicates with the electrically controlled optical delay line (3) through the electrically controlled optical delay line communication interface (7), changes the length of the optical delay line, and electrically squeezes the electrically controlled polarization controller (4) through the electrically controlled polarization controller control unit (8) to change the polarization state of the light, so as to achieve the optimal polarization fading suppression effect.

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