Distributed optical fiber long-distance detection device based on stimulated Brillouin optical time domain reflection principle

Abstract

The invention relates to the technical field of optical fiber sensing, in particular to a distributed optical fiber long-distance detection device based on a stimulated Brillouin optical time domain reflection principle, which is characterized in that a light source module generates continuous light, a light pulse modulation module modulates the continuous light into light pulses with specific pulse width and repetition frequency, and the light pulses are amplified by a light amplification module; and a to-be-measured long-distance optical fiber is injected through the optical fiber coupler module. Brillouin scattering light generated in the optical fiber is processed by the optical filtering and circulating module and then is converted into an electric signal by the optical detection module, the electric signal is amplified, filtered and the like by the signal amplification and conditioning module, and analog-to-digital conversion and data analysis are performed by the data acquisition and processing module; and finally, the control and display module is used for controlling the whole device and displaying a measurement result. The detection precision and resolution of the Brillouin scattering signal are remarkably improved, the temperature and strain distribution along the optical fiber can be accurately measured, and therefore the problem that an existing detection device is low in precision is solved.

Description

Technical Field

[0001] The invention relates to the field of optical fiber sensing technology, in particular to a distributed optical fiber long-distance detection device based on the stimulated Brillouin light time-domain reflection principle. Background Art

[0002] With the continuous advancement of various large-scale infrastructure construction, such as bridges, tunnels, power transmission lines, oil and gas pipelines, etc., the demand for structural health monitoring is growing. Distributed fiber optic sensing technology has become a very promising monitoring method due to its unique advantages, such as the ability to achieve long-distance continuous monitoring, anti-electromagnetic interference, and corrosion resistance.

[0003] Distributed fiber optic sensing technology based on the principle of stimulated Brillouin optical time-domain reflectometry injects pulsed light into the optical fiber and uses the correlation between the frequency of Brillouin scattered light and the temperature and strain state of the optical fiber to achieve distributed measurement of physical parameters along the optical fiber.

[0004] However, there are many technical difficulties in actual long-distance detection applications. For example, optical signals will suffer severe attenuation during long-distance transmission, resulting in extremely weak Brillouin scattering signals that are difficult to accurately detect and analyze; at the same time, due to the influence of factors such as dispersion, nonlinear effects, and environmental noise of long-distance optical fibers, the measurement accuracy and resolution are greatly limited. Some existing detection devices are difficult to meet the needs of actual engineering for high-precision, high-reliability distributed optical fiber sensing in terms of long-distance detection performance. Summary of the invention

[0005] The purpose of the present invention is to provide a distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflectometry principle, aiming to solve the problem of low accuracy of existing detection devices.

[0006] To achieve the above-mentioned purpose, the present invention provides a distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflectometry principle, comprising a light source module, an optical pulse modulation module, an optical amplification module, an optical fiber coupler module, a long-distance optical fiber to be measured, an optical filtering and circulation module, an optical detection module, a signal amplification and conditioning module, a data acquisition and processing module, and a control and display module, wherein the light source module, the optical pulse modulation module, the optical amplification module, the optical fiber coupler module, the long-distance optical fiber to be measured, the optical filtering and circulation module, the optical detection module, the signal amplification and conditioning module, and the data acquisition and processing module are connected in sequence, and are respectively connected to the control and display module;

[0007] The light source module is used to generate continuous light with high stability and narrow line width;

[0008] The optical pulse modulation module is used to modulate continuous light into optical pulses with specific pulse width and repetition frequency;

[0009] The optical amplification module is used to amplify the optical pulses to ensure sufficient optical power to support long-distance transmission;

[0010] The optical fiber coupler module is used to efficiently couple optical pulses into the long-distance optical fiber to be tested;

[0011] The long-distance optical fiber to be measured is used as a sensing medium to sense the temperature and strain along the line;

[0012] The optical filtering and recycling module is used to filter out stray light and guide the Brillouin scattered light back to the detection module;

[0013] The optical detection module is used to convert the Brillouin scattered light signal into an electrical signal;

[0014] The signal amplification and conditioning module is used to amplify and filter the electrical signal;

[0015] The data acquisition and processing module is used to perform analog-to-digital conversion and data analysis on the signal;

[0016] The control and display module is used to control the entire device and display the measurement results.

[0017] Wherein, the light source module includes a distributed feedback laser unit, a temperature control unit, a current driving unit, an optical power monitoring unit and a wavelength monitoring unit, and the temperature control unit, the current driving unit, the optical power monitoring unit and the wavelength monitoring unit are respectively connected to the distributed feedback laser unit;

[0018] The distributed feedback laser unit is used to generate continuous light with a central wavelength of 1550.12nm and a line width of less than 3kHz, and an output power of 20mW;

[0019] The temperature control unit is used to ensure that the wavelength stability of the laser output light is better than 0.01 pm / °C;

[0020] The current driving unit is used to ensure that the power stability of the laser output light is better than 0.01dB / h;

[0021] The optical power monitoring unit is used to monitor the output power of the laser in real time;

[0022] The wavelength monitoring unit is used to monitor the output wavelength of the laser in real time.

[0023] The optical pulse modulation module includes a pulse generator unit, an electro-optical modulator unit, a modulation drive unit, a pulse shaping unit and a pulse synchronization unit.

[0024] The pulse generator unit is connected to the modulation drive unit, the modulation drive unit and the pulse shaping unit are respectively connected to the electro-optical modulator unit, and the pulse synchronization unit is connected to the pulse generator unit and the electro-optical modulator unit;

[0025] The pulse generator unit is used to generate an electrical pulse signal with a pulse width of 500ns and a repetition frequency of 500kHz;

[0026] The electro-optic modulator unit is used to convert the electrical pulse signal generated by the pulse generator into an optical pulse signal, with an extinction ratio greater than 35dB and an insertion loss less than 4dB;

[0027] The modulation driving unit is used to provide a stable driving signal for the electro-optic modulator;

[0028] The pulse shaping unit is used to shape the modulated optical pulse to optimize the rising edge and falling edge characteristics of the pulse;

[0029] The pulse synchronization unit is used to ensure the synchronization of the pulse signal with subsequent modules.

[0030] Wherein, the optical amplification module comprises a semiconductor optical amplifier unit and an erbium-doped fiber amplifier unit, and the semiconductor optical amplifier unit is connected to the erbium-doped fiber amplifier unit;

[0031] The semiconductor optical amplifier unit is used to preliminarily amplify the optical pulse signal with a gain of 15dB;

[0032] The erbium-doped fiber amplifier unit is used to further amplify the pre-amplified optical pulses, with a maximum output power of up to 23dBm.

[0033] The optical fiber coupler module comprises a polarization-maintaining optical fiber coupler unit, a polarization state control unit, a coupling efficiency monitoring unit and an insertion loss compensation unit, and the polarization state control unit, the coupling efficiency monitoring unit and the insertion loss compensation unit are respectively connected to the polarization-maintaining optical fiber coupler unit;

[0034] The polarization-maintaining fiber coupler unit is used to have a coupling efficiency greater than 90% and an insertion loss less than 0.05 dB;

[0035] The polarization state control unit is used to ensure the stability of the polarization state of light and improve the intensity and quality of the Brillouin scattering signal;

[0036] The coupling efficiency monitoring unit is used to monitor the coupling efficiency in real time to ensure efficient coupling;

[0037] The insertion loss compensation unit is used to compensate for the insertion loss during the coupling process and optimize signal transmission.

[0038] Wherein, the optical filtering and circulation module comprises an optical filter unit and an optical circulator unit, and the optical filter unit and the optical circulator unit are connected;

[0039] The optical filter unit is used to filter out the pump light and other stray light transmitted in the optical fiber, and only allow the Brillouin scattered light to pass through, and the central wavelength matches the Brillouin scattered light;

[0040] The optical circulator unit is used to guide the filtered Brillouin scattered light back to the optical detection module, with an insertion loss of less than 0.03 dB and an isolation of more than 30 dB.

[0041] Wherein, the optical detection module includes an avalanche photodiode unit, a temperature management unit, a detection efficiency monitoring unit, a noise suppression unit and a signal preprocessing unit, and the temperature management unit, the detection efficiency monitoring unit, the noise suppression unit and the signal preprocessing unit are respectively connected to the avalanche photodiode unit;

[0042] The avalanche photodiode unit is used to efficiently convert weak Brillouin scattered light signals into electrical signals;

[0043] The temperature management unit is used to stabilize the operating temperature of the avalanche photodiode unit at about 30°C, reduce the noise level, and improve the signal-to-noise ratio;

[0044] The detection efficiency monitoring unit is used to monitor the detection efficiency of the APD in real time to ensure its performance;

[0045] The noise suppression unit is used to reduce the dark current and noise of the avalanche photodiode unit and improve the detection accuracy;

[0046] The signal preprocessing unit is used to perform preliminary processing on the converted electrical signal to optimize the signal quality.

[0047] The distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflection principle of the present invention comprises a light source module, an optical pulse modulation module, an optical amplification module, an optical fiber coupler module, a long-distance optical fiber to be measured, an optical filtering and circulation module, an optical detection module, a signal amplification and conditioning module, a data acquisition and processing module and a control and display module. The light source module, the optical pulse modulation module, the optical amplification module, the optical fiber coupler module, the long-distance optical fiber to be measured, the optical filtering and circulation module, the optical detection module, the signal amplification and conditioning module and the data acquisition and processing module are connected in sequence and are respectively connected to the control and display module; the light source module is used to generate continuous light with high stability and narrow line width; the optical pulse modulation module is used to modulate the continuous light into a signal having a ... The optical pulse has a specific pulse width and repetition frequency; the optical amplification module is used to amplify the optical pulse to ensure sufficient optical power to support long-distance transmission; the optical fiber coupler module is used to efficiently couple the optical pulse into the long-distance optical fiber to be measured; the long-distance optical fiber to be measured is used as a sensing medium to sense the temperature and strain along the line; the optical filtering and circulation module is used to filter out stray light and guide the Brillouin scattered light back to the detection module; the optical detection module is used to convert the Brillouin scattered light signal into an electrical signal; the signal amplification and conditioning module is used to amplify and filter the electrical signal; the data acquisition and processing module is used to perform analog-to-digital conversion and data analysis on the signal; the control and display module is used to realize the control of the entire device and the display of the measurement results. The light source module generates continuous light, and the optical pulse modulation module modulates it into an optical pulse with a specific pulse width and repetition frequency. After amplification by the optical amplification module, it is injected into the long-distance optical fiber to be measured through the optical fiber coupler module. The Brillouin scattered light generated in the optical fiber is processed by the optical filtering and circulation module, converted into an electrical signal by the optical detection module, and then amplified and filtered by the signal amplification and conditioning module, and the analog-to-digital conversion and data analysis are performed by the data acquisition and processing module, and finally the control and display module realizes the control of the entire device and the display of the measurement results. The detection accuracy and resolution of the Brillouin scattering signal are significantly improved, and the temperature and strain distribution along the optical fiber can be accurately measured, thereby solving the problem of low accuracy of existing detection devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The present invention is further illustrated by means of the non-limiting examples given in the accompanying drawings.

[0049] Figure 1 It is a schematic diagram of a distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflection principle of the present invention.

[0050] Figure 2 is a schematic diagram of a light source module.

[0051] Figure 3 is a schematic diagram of the optical pulse modulation module.

[0052] Figure 4 is a schematic diagram of an optical amplifier module.

[0053] Figure 5 is a schematic diagram of a fiber optic coupler module.

[0054] Figure 6 It is a schematic diagram of the optical filtering and recycling module.

[0055] Figure 7 is a schematic diagram of the light detection module.

[0056] In the figure: 1-light source module, 2-optical pulse modulation module, 3-optical amplification module, 4-optical fiber coupler module, 5-long-distance optical fiber to be tested, 6-optical filtering and circulation module, 7-optical detection module, 8-signal amplification and conditioning module, 9-data acquisition and processing module, 10-control and display module, 11-distributed feedback laser unit, 12-temperature control unit, 13-current driving unit, 14-optical power monitoring unit, 15-wavelength monitoring unit, 21-pulse generator unit, 22-electro-optical modulator unit, 23-modulation drive unit, 24-pulse shaping unit, 25-pulse synchronization unit, 31-semiconductor optical amplifier unit, 32-erbium-doped fiber amplifier unit, 41-polarization-maintaining fiber coupler unit, 42-polarization state control unit, 43-coupling efficiency monitoring unit, 44-insertion loss compensation unit, 61-optical filter unit, 62-optical circulator unit, 71-avalanche photodiode unit, 72-temperature management unit, 73-detection efficiency monitoring unit, 74-noise suppression unit, 75-signal preprocessing unit. DETAILED DESCRIPTION

[0057] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0058] See also Figures 1 to 7The present invention provides a distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflectometry principle, comprising a light source module 1, an optical pulse modulation module 2, an optical amplification module 3, an optical fiber coupler module 4, a long-distance optical fiber to be measured 5, an optical filtering and circulation module 6, an optical detection module 7, a signal amplification and conditioning module 8, a data acquisition and processing module 9 and a control and display module 10, wherein the light source module 1, the optical pulse modulation module 2, the optical amplification module 3, the optical fiber coupler module 4, the long-distance optical fiber to be measured 5, the optical filtering and circulation module 6, the optical detection module 7, the signal amplification and conditioning module 8 and the data acquisition and processing module 9 are connected in sequence and are respectively connected to the control and display module 10;

[0059] The light source module 1 is used to generate continuous light with high stability and narrow line width;

[0060] The optical pulse modulation module 2 is used to modulate continuous light into optical pulses with specific pulse width and repetition frequency;

[0061] The optical amplification module 3 is used to amplify the optical pulses to ensure sufficient optical power to support long-distance transmission;

[0062] The optical fiber coupler module 4 is used to efficiently couple the optical pulse into the long-distance optical fiber 5 to be tested;

[0063] The long-distance optical fiber 5 to be measured is used as a sensing medium to sense the temperature and strain along the line;

[0064] The optical filtering and recycling module 6 is used to filter out stray light and guide the Brillouin scattered light back to the detection module;

[0065] The optical detection module 7 is used to convert the Brillouin scattered light signal into an electrical signal;

[0066] The signal amplification and conditioning module 8 is used to amplify and filter the electrical signal;

[0067] The data acquisition and processing module 9 is used to perform analog-to-digital conversion and data analysis on the signal;

[0068] The control and display module 10 is used to control the entire device and display the measurement results.

[0069] In this embodiment, the light source module 1 adopts a distributed feedback laser (DFB) with high stability and narrow line width as the light source, and the central wavelength of its output light is 1550.12nm, the line width is less than 3kHz, and the output power is 20mW. It is equipped with a high-precision temperature control unit 12 and a current driving unit 13 to ensure the wavelength stability and power stability of the laser output light. The wavelength stability is better than 0.01pm / ℃, and the power stability is better than 0.01dB / h. The optical pulse modulation module 2 includes an electro-optic modulator (EOM) and a pulse generator. The pulse generator generates an electrical pulse signal with a pulse width of 500ns and a repetition frequency of 500kHz, and drives the electro-optic modulator to pulse modulate the continuous light output by the light source module 1 to obtain an optical pulse signal with the desired pulse characteristics. The extinction ratio of the electro-optic modulator is greater than 35dB, and the insertion loss is less than 4dB to ensure the quality and modulation efficiency of the optical pulse. The optical amplifier module 3 adopts a two-stage amplification structure. The first stage is a pre-amplifier, which uses a semiconductor optical amplifier (SOA) to preliminarily amplify the optical pulse signal with a gain of 15dB to increase the power level of the optical pulse so that it can effectively stimulate Brillouin scattering in long-distance optical fibers. The second stage is a power amplifier, which uses an erbium-doped fiber amplifier (EDFA) to further amplify the pre-amplified optical pulse. The maximum output power can reach 23dBm, ensuring sufficient optical power during long-distance transmission and good gain flatness. The optical fiber coupler module 4 uses a polarization-maintaining optical fiber coupler with high coupling efficiency and low insertion loss to efficiently couple the optical pulse signal output by the optical amplifier module 3 into the long-distance optical fiber 5 to be tested. The coupling efficiency is greater than 90%, and the insertion loss is less than 0.05dB. At the same time, the polarization state stability of the light is guaranteed to improve the intensity and quality of the Brillouin scattering signal. The long-distance optical fiber 5 to be measured uses a single-mode optical fiber with low loss and high strain sensitivity as a sensing optical fiber, and its length can reach 100km. In the wavelength range of 1526-1565nm, the attenuation coefficient of the optical fiber is less than 0.18dB / km. The coating layer of the optical fiber is made of special materials, has good environmental resistance, and can adapt to various complex monitoring environments, such as high temperature, high humidity, strong acid and alkali, etc. The optical filtering and circulation module 6 is located at the end of the long-distance optical fiber 5 to be measured, and includes an optical filter and an optical circulator. The optical filter is used to filter out the pump light and other stray light transmitted in the optical fiber, and only allows Brillouin scattered light to pass, and its central wavelength matches the central wavelength of the Brillouin scattered light. The optical circulator guides the filtered Brillouin scattered light back to the optical detection module 7, which improves the utilization rate of the Brillouin scattered light and reduces the detection threshold of the system. The insertion loss of the circulator is less than 0.03dB, and the isolation is greater than 30dB. The light detection module 7 uses a highly sensitive avalanche photodiode (APD) as a light detector, which can efficiently convert weak Brillouin scattered light signals into electrical signals.It is equipped with a precise temperature control circuit to stabilize the operating temperature of the APD at around 30°C to ensure the stability and reliability of its performance, reduce the noise level and improve the signal-to-noise ratio. The signal amplification and conditioning module 8 includes a preamplifier and a bandpass filter. The preamplifier performs low-noise amplification on the electrical signal output by the light detection module 7 to increase the signal strength without introducing too much noise. The bandpass filter is used to filter out low-frequency noise and high-frequency interference in the electrical signal, which can effectively improve the signal quality, enhance the signal-to-noise ratio, and provide a high-quality signal source for subsequent data acquisition and processing. The data acquisition part of the data acquisition and processing module 9 adopts a high-speed, high-precision analog-to-digital converter (ADC), which can quickly and accurately convert the amplified and conditioned analog electrical signal into a digital signal, ensuring the real-time and accurate acquisition of the Brillouin scattered light signal. The data processing part uses a digital signal processor (DSP) or a field programmable gate array (FPGA) as the core processor, and has a built-in signal processing algorithm based on the principle of stimulated Brillouin optical time-domain reflection. It can perform fast Fourier transform (FFT), spectrum analysis, frequency shift calculation and other processing on the collected digital signals. According to the linear relationship between Brillouin frequency shift and temperature and strain, the temperature and strain values ​​at each position along the optical fiber are accurately calculated. The algorithm takes into account the influence of factors such as dispersion, nonlinear effects and noise of optical signals during long-distance transmission, and improves the accuracy and resolution of measurement through real-time calibration and compensation of measurement data. At the same time, it has a data storage function and can store a large amount of measurement data and historical data, which is convenient for subsequent data query and analysis. The control and display module 10 uses a microcontroller (MCU) as the control core, and realizes the precise control and coordination of each part such as the light source module 1, the optical pulse modulation module 2, the optical amplification module 3, the optical detection module 7, the signal amplification and conditioning module 8 and the data acquisition and processing module 9 through programming. The control parameters include the output power, wavelength, pulse modulation parameters, amplifier gain, optical detector operating voltage, ADC sampling parameters, etc. of the laser. Through the preset control program and communication interface, the entire detection device can be automatically and intelligently controlled. It is equipped with a display screen and operation buttons. The display screen can display the temperature, strain distribution curve, measurement parameters, device working status and alarm information along the optical fiber in real time. The operation buttons are used to set measurement parameters, start and stop measurement, view historical data, etc., which is convenient for users to use and operate and realize human-computer interaction.

[0070] The light source module 1 generates continuous light, which is modulated into a light pulse with a specific pulse width and repetition frequency by the light pulse modulation module 2. After being amplified by the light amplifier module 3, it is injected into the long-distance optical fiber 5 to be measured through the fiber coupler module 4. The Brillouin scattered light generated in the optical fiber is processed by the optical filtering and circulation module 6, converted into an electrical signal by the light detection module 7, and then amplified and filtered by the signal amplification and conditioning module 8. The data acquisition and processing module performs analog-to-digital conversion and data analysis, and finally the control and display module 10 realizes the control of the entire device and the display of the measurement results. The detection accuracy and resolution of the Brillouin scattering signal are significantly improved, and the temperature and strain distribution along the optical fiber can be accurately measured, thereby solving the problem of low accuracy of the existing detection device.

[0071] Further, the light source module 1 includes a distributed feedback laser unit 11, a temperature control unit 12, a current driving unit 13, an optical power monitoring unit 14 and a wavelength monitoring unit 15, and the temperature control unit 12, the current driving unit 13, the optical power monitoring unit 14 and the wavelength monitoring unit 15 are respectively connected to the distributed feedback laser unit 11;

[0072] The distributed feedback laser unit 11 is used to generate continuous light with a central wavelength of 1550.12nm and a line width of less than 3kHz, and an output power of 20mW;

[0073] The temperature control unit 12 is used to ensure that the wavelength stability of the laser output light is better than 0.01 pm / °C;

[0074] The current driving unit 13 is used to ensure that the power stability of the laser output light is better than 0.01dB / h;

[0075] The optical power monitoring unit 14 is used to monitor the output power of the laser in real time;

[0076] The wavelength monitoring unit 15 is used to monitor the output wavelength of the laser in real time.

[0077] In this embodiment, the distributed feedback laser unit 11 generates continuous light with a central wavelength of 1550.12nm, a line width of less than 3kHz, and an output power of 20mW; the temperature control unit 12 is used to ensure that the wavelength stability of the laser output light is better than 0.01pm / ℃; the current driving unit 13 is used to ensure that the power stability of the laser output light is better than 0.01dB / h; the optical power monitoring unit 14 is used to monitor the output power of the laser in real time; the wavelength monitoring unit 15 is used to monitor the output wavelength of the laser in real time.

[0078] Furthermore, the optical pulse modulation module 2 includes a pulse generator unit 21, an electro-optical modulator unit 22, a modulation drive unit 23, a pulse shaping unit 24 and a pulse synchronization unit 25.

[0079] The pulse generator unit 21 is connected to the modulation drive unit 23, the modulation drive unit 23 and the pulse shaping unit 24 are respectively connected to the electro-optical modulator unit 22, and the pulse synchronization unit 25 is connected to the pulse generator unit 21 and the electro-optical modulator unit 22;

[0080] The pulse generator unit 21 is used to generate an electrical pulse signal with a pulse width of 500ns and a repetition frequency of 500kHz;

[0081] The electro-optical modulator unit 22 is used to convert the electrical pulse signal generated by the pulse generator into an optical pulse signal, with an extinction ratio greater than 35dB and an insertion loss less than 4dB;

[0082] The modulation driving unit 23 is used to provide a stable driving signal for the electro-optic modulator;

[0083] The pulse shaping unit 24 is used to shape the modulated optical pulse to optimize the rising edge and falling edge characteristics of the pulse;

[0084] The pulse synchronization unit 25 is used to ensure the synchronization of the pulse signal with subsequent modules.

[0085] In this embodiment, the pulse generator unit 21 generates an electrical pulse signal with a pulse width of 500ns and a repetition frequency of 500kHz; the electro-optical modulator unit 22 converts the electrical pulse signal generated by the pulse generator into an optical pulse signal with an extinction ratio greater than 35dB and an insertion loss less than 4dB; the modulation drive unit 23 provides a stable drive signal for the electro-optical modulator; the pulse shaping unit 24 shapes the modulated optical pulse to optimize the rising and falling edge characteristics of the pulse; and the pulse synchronization unit 25 ensures the synchronization of the pulse signal with subsequent modules.

[0086] Further, the optical amplification module 3 includes a semiconductor optical amplifier unit 31 and an erbium-doped fiber amplifier unit 32, and the semiconductor optical amplifier unit 31 is connected to the erbium-doped fiber amplifier unit 32;

[0087] The semiconductor optical amplifier unit 31 is used to preliminarily amplify the optical pulse signal, with a gain of 15 dB;

[0088] The erbium-doped fiber amplifier unit 32 is used to further amplify the pre-amplified optical pulses, and the maximum output power can reach 23 dBm.

[0089] In this embodiment, the semiconductor optical amplifier unit 31 is used to preliminarily amplify the optical pulse signal with a gain of 15 dB; the erbium-doped fiber amplifier unit 32 is used to further amplify the pre-amplified optical pulse, with a maximum output power of up to 23 dBm.

[0090] Further, the optical fiber coupler module 4 includes a polarization-maintaining optical fiber coupler unit 41, a polarization state control unit 42, a coupling efficiency monitoring unit 43 and an insertion loss compensation unit 44, and the polarization state control unit 42, the coupling efficiency monitoring unit 43 and the insertion loss compensation unit 44 are respectively connected to the polarization-maintaining optical fiber coupler unit 41;

[0091] The polarization-maintaining fiber coupler unit 41 is used for coupling efficiency greater than 90% and insertion loss less than 0.05 dB;

[0092] The polarization state control unit 42 is used to ensure the stability of the polarization state of light and improve the intensity and quality of the Brillouin scattering signal;

[0093] The coupling efficiency monitoring unit 43 is used to monitor the coupling efficiency in real time to ensure efficient coupling;

[0094] The insertion loss compensation unit 44 is used to compensate for the insertion loss during the coupling process and optimize signal transmission.

[0095] In this embodiment, the coupling efficiency of the polarization-maintaining fiber coupler is greater than 90%, and the insertion loss is less than 0.05 dB; the polarization state control unit 42 ensures the stability of the polarization state of light and improves the intensity and quality of the Brillouin scattering signal; the coupling efficiency monitoring unit 43 monitors the coupling efficiency in real time to ensure efficient coupling; the insertion loss compensation unit 44 compensates for the insertion loss in the coupling process to optimize signal transmission.

[0096] Further, the optical filtering and circulation module 6 comprises an optical filter unit 61 and an optical circulator unit 62, and the optical filter unit 61 and the optical circulator unit 62 are connected;

[0097] The optical filter unit 61 is used to filter out the pump light and other stray light transmitted in the optical fiber, and only allow the Brillouin scattered light to pass through, and the central wavelength matches the Brillouin scattered light;

[0098] The optical circulator unit 62 is used to guide the filtered Brillouin scattered light back to the optical detection module 7, with an insertion loss of less than 0.03 dB and an isolation greater than 30 dB.

[0099] In this embodiment, the optical filter unit 61 filters out the pump light and other stray light transmitted in the optical fiber, and only allows the Brillouin scattered light to pass, and the central wavelength matches the Brillouin scattered light; the optical circulator unit 62 guides the filtered Brillouin scattered light back to the optical detection module 7, with an insertion loss of less than 0.03dB and an isolation of more than 30dB.

[0100] Further, the optical detection module 7 includes an avalanche photodiode unit 71, a temperature management unit 72, a detection efficiency monitoring unit 73, a noise suppression unit 74 and a signal preprocessing unit 75, and the temperature management unit 72, the detection efficiency monitoring unit 73, the noise suppression unit 74 and the signal preprocessing unit 75 are respectively connected to the avalanche photodiode unit 71;

[0101] The avalanche photodiode unit 71 is used to efficiently convert weak Brillouin scattered light signals into electrical signals;

[0102] The temperature management unit 72 is used to stabilize the operating temperature of the avalanche photodiode unit 71 at about 30° C., reduce the noise level, and improve the signal-to-noise ratio;

[0103] The detection efficiency monitoring unit 73 is used to monitor the detection efficiency of the APD in real time to ensure its performance;

[0104] The noise suppression unit 74 is used to reduce the dark current and noise of the avalanche photodiode unit 71 and improve the detection accuracy;

[0105] The signal preprocessing unit 75 is used to perform preliminary processing on the converted electrical signal to optimize the signal quality.

[0106] In this embodiment, the avalanche photodiode unit 71 efficiently converts weak Brillouin scattered light signals into electrical signals; the temperature management unit 72 stabilizes the operating temperature of the avalanche photodiode unit 71 at about 30°C, reduces the noise level, and improves the signal-to-noise ratio; the detection efficiency monitoring unit 73 monitors the detection efficiency of the APD in real time to ensure its performance; the noise suppression unit 74 reduces the dark current and noise of the avalanche photodiode unit 71 to improve the detection accuracy; the signal preprocessing unit 75 performs preliminary processing on the converted electrical signal to optimize the signal quality.

[0107] What is disclosed above is only one or more preferred embodiments of the present application, and cannot be used to limit the scope of rights of the present application. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and equivalent changes made according to the claims of the present application are still within the scope covered by the present application.

Claims

1. A distributed optical fiber long-distance detection device based on the stimulated Brillouin optical time-domain reflectometry principle, characterized in that: It includes a light source module, an optical pulse modulation module, an optical amplification module, an optical fiber coupler module, a long-distance optical fiber to be measured, an optical filtering and circulation module, an optical detection module, a signal amplification and conditioning module, a data acquisition and processing module, and a control and display module. The light source module, the optical pulse modulation module, the optical amplification module, the optical fiber coupler module, the long-distance optical fiber to be measured, the optical filtering and circulation module, the optical detection module, the signal amplification and conditioning module, and the data acquisition and processing module are connected in sequence and are respectively connected to the control and display module; The light source module is used to generate continuous light with high stability and narrow line width; The optical pulse modulation module is used to modulate continuous light into optical pulses with specific pulse width and repetition frequency; The optical amplification module is used to amplify the optical pulses to ensure sufficient optical power to support long-distance transmission; The optical fiber coupler module is used to efficiently couple optical pulses into the long-distance optical fiber to be tested; The long-distance optical fiber to be measured is used as a sensing medium to sense the temperature and strain along the line; The optical filtering and recycling module is used to filter out stray light and guide the Brillouin scattered light back to the detection module; The optical detection module is used to convert the Brillouin scattered light signal into an electrical signal; The signal amplification and conditioning module is used to amplify and filter the electrical signal; The data acquisition and processing module is used to perform analog-to-digital conversion and data analysis on the signal; The control and display module is used to control the entire device and display the measurement results.

2. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The light source module comprises a distributed feedback laser unit, a temperature control unit, a current driving unit, an optical power monitoring unit and a wavelength monitoring unit, wherein the temperature control unit, the current driving unit, the optical power monitoring unit and the wavelength monitoring unit are respectively connected to the distributed feedback laser unit; The distributed feedback laser unit is used to generate continuous light with a central wavelength of 1550.12nm and a line width of less than 3kHz, and an output power of 20mW; The temperature control unit is used to ensure that the wavelength stability of the laser output light is better than 0.01 pm / °C; The current driving unit is used to ensure that the power stability of the laser output light is better than 0.01dB / h; The optical power monitoring unit is used to monitor the output power of the laser in real time; The wavelength monitoring unit is used to monitor the output wavelength of the laser in real time.

3. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The optical pulse modulation module includes a pulse generator unit, an electro-optical modulator unit, a modulation drive unit, a pulse shaping unit and a pulse synchronization unit. The pulse generator unit is connected to the modulation drive unit, the modulation drive unit and the pulse shaping unit are respectively connected to the electro-optical modulator unit, and the pulse synchronization unit is connected to the pulse generator unit and the electro-optical modulator unit; The pulse generator unit is used to generate an electrical pulse signal with a pulse width of 500ns and a repetition frequency of 500kHz; The electro-optic modulator unit is used to convert the electrical pulse signal generated by the pulse generator into an optical pulse signal, with an extinction ratio greater than 35dB and an insertion loss less than 4dB; The modulation driving unit is used to provide a stable driving signal for the electro-optic modulator; The pulse shaping unit is used to shape the modulated optical pulse to optimize the rising edge and falling edge characteristics of the pulse; The pulse synchronization unit is used to ensure the synchronization of the pulse signal with the subsequent modules.

4. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The optical amplification module comprises a semiconductor optical amplifier unit and an erbium-doped fiber amplifier unit, and the semiconductor optical amplifier unit is connected to the erbium-doped fiber amplifier unit; The semiconductor optical amplifier unit is used to preliminarily amplify the optical pulse signal with a gain of 15dB; The erbium-doped fiber amplifier unit is used to further amplify the pre-amplified optical pulses, with a maximum output power of up to 23dBm.

5. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The optical fiber coupler module comprises a polarization-maintaining optical fiber coupler unit, a polarization state control unit, a coupling efficiency monitoring unit and an insertion loss compensation unit, wherein the polarization state control unit, the coupling efficiency monitoring unit and the insertion loss compensation unit are respectively connected to the polarization-maintaining optical fiber coupler unit; The polarization-maintaining fiber coupler unit is used to have a coupling efficiency greater than 90% and an insertion loss less than 0.05 dB; The polarization state control unit is used to ensure the stability of the polarization state of light and improve the intensity and quality of the Brillouin scattering signal; The coupling efficiency monitoring unit is used to monitor the coupling efficiency in real time to ensure efficient coupling; The insertion loss compensation unit is used to compensate for the insertion loss during the coupling process and optimize signal transmission.

6. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The optical filtering and circulation module comprises an optical filter unit and an optical circulator unit, wherein the optical filter unit and the optical circulator unit are connected; The optical filter unit is used to filter out the pump light and other stray light transmitted in the optical fiber, and only allow the Brillouin scattered light to pass through, and the central wavelength matches the Brillouin scattered light; The optical circulator unit is used to guide the filtered Brillouin scattered light back to the optical detection module, with an insertion loss of less than 0.03 dB and an isolation of more than 30 dB.

7. The distributed optical fiber long-distance detection device based on stimulated Brillouin optical time-domain reflectometry principle as claimed in claim 1, characterized in that: The optical detection module includes an avalanche photodiode unit, a temperature management unit, a detection efficiency monitoring unit, a noise suppression unit and a signal preprocessing unit, wherein the temperature management unit, the detection efficiency monitoring unit, the noise suppression unit and the signal preprocessing unit are respectively connected to the avalanche photodiode unit; The avalanche photodiode unit is used to efficiently convert weak Brillouin scattered light signals into electrical signals; The temperature management unit is used to stabilize the operating temperature of the avalanche photodiode unit at about 30°C, reduce the noise level, and improve the signal-to-noise ratio; The detection efficiency monitoring unit is used to monitor the detection efficiency of the APD in real time to ensure its performance; The noise suppression unit is used to reduce the dark current and noise of the avalanche photodiode unit and improve the detection accuracy; The signal preprocessing unit is used to perform preliminary processing on the converted electrical signal to optimize the signal quality.

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