Method, system and equipment for improving performance of BOTDR (Brillouin Optical Time Domain Reflectometer) system and storage medium

Abstract

The invention discloses a method, system and device for improving BOTDR system performance and a storage medium, and relates to the technical field of optical fiber sensing, and the method comprises the steps: using a single narrow linewidth laser to output light, dividing the light into three paths through an optocoupler, carrying out the shunting processing, carrying out the light splitting processing of a Brillouin scattering signal returned by a to-be-measured optical fiber, and obtaining a Brillouin scattering signal; after being divided into two paths, different beat frequency interference operations are respectively carried out; processing the high-frequency beat frequency electric signal to obtain a Brillouin frequency shift obtained through beat frequency demodulation of a reference optical fiber signal and a Brillouin frequency shift obtained through direct beat frequency demodulation of local light; according to different temperature and stress change conditions, results demodulated by different light paths are judged and processed; according to the invention, the performance of the Brillouin optical time domain reflection system can be effectively improved; the reference light frequency is stabilized, and measurement errors are reduced; the frequency sweeping range is widened, and various monitoring requirements are met; the radio frequency design is simplified, and the signal amplification stability is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing technology, and in particular to a method, system, device and storage medium for improving the performance of a BOTDR system. BACKGROUND

[0002] In modern industry, infrastructure monitoring, and scientific research, there is an increasing demand for high-precision, distributed measurement of temperature and stress. Distributed optical fiber sensing technology has become a key means to achieve such measurements due to its long-range, continuous monitoring, and resistance to electromagnetic interference. Among them, Brillouin optical time domain reflectometry (BOTDR) technology, as an important distributed optical fiber sensing technology, uses the Brillouin scattering effect in optical fiber to obtain temperature and stress information along the length of the optical fiber by detecting the Brillouin frequency shift. It has shown great application potential in large-scale structure health monitoring, energy pipeline safety detection, and other fields.

[0003] However, the existing BOTDR technology still faces many problems to be solved in practical application. Currently, the reference fiber heterodyne detection technology is one of the commonly used demodulation methods in BOTDR systems. This technology uses a reference fiber to generate stable stimulated Brillouin scattering light as a reference signal, which is frequency-mixed with the backscattered Brillouin light of the measured fiber to extract the Brillouin frequency shift. However, this method has obvious limitations. On the one hand, the frequency stability of the reference light is poor, and small fluctuations in the length, temperature, or stress state of the reference fiber will cause changes in the Brillouin frequency shift of the reference light, thereby affecting the accuracy and reliability of the measurement. On the other hand, the frequency shift of the reference light itself is fixed, and the frequency-mixing range is limited, making it difficult to cover a wide range of Brillouin frequency shift bandwidth, and unable to meet the measurement requirements of large-scale temperature or stress changes in some complex environments. At the same time, the microwave heterodyne scheme is also a commonly used demodulation technology in BOTDR systems. This scheme mixes the Brillouin scattering light with a local oscillator light to down-convert the high-frequency Brillouin frequency shift signal to a lower frequency for subsequent signal processing. However, this scheme requires a highly selective filter during direct down-conversion. Due to the high frequency and narrow bandwidth of the Brillouin frequency shift signal, a high-performance filter is needed to suppress the image frequency and spurious signals, which not only increases the complexity and cost of the radio frequency design, but also poses a high challenge to the performance of the filter. In addition, stable amplification of high-frequency small signals is also a major problem faced by the microwave heterodyne scheme. In the high-frequency band, signals are easily affected by noise and interference, and the gain and linearity of the amplifier are difficult to guarantee, resulting in a decrease in measurement accuracy. SUMMARY

[0004] In view of the above problems, the present application is proposed.

[0005] Therefore, the present application solves the technical problem that the existing BOTDR technology has many deficiencies in demodulation accuracy, frequency stability, sweep flexibility and radio frequency design complexity, and cannot meet the requirements of high accuracy, high stability and wide range measurement in practical applications.

[0006] To solve the above technical problems, the present application provides the following technical solutions.

[0007] In a first aspect, the present application provides a method for improving the performance of a BOTDR system, comprising:

[0008] The output light of a single narrow linewidth laser is split into three paths by an optical coupler, and different processing is performed on each path to generate different types of signals.

[0009] After the split processing, the Brillouin scattering signals returned from the fiber under test are split into two paths, and different beat frequency interference operations are performed on the two paths.

[0010] The high-frequency beat frequency electrical signal is mixed, down-converted, spectrum-transformed and curve-fitted to obtain the Brillouin frequency shift demodulated by the reference fiber signal beat frequency.

[0011] The high-frequency beat frequency electrical signal is processed by a secondary down-conversion radio frequency receiving module to realize linear sweep coverage of the Brillouin frequency shift, and the Brillouin frequency shift demodulated by the local light direct beat frequency is obtained.

[0012] Based on the Brillouin frequency shift demodulated by the reference fiber signal beat frequency and the Brillouin frequency shift demodulated by the local light direct beat frequency, the results demodulated by different optical paths are judged and processed according to different temperature and stress changes.

[0013] As a preferred scheme of the method for improving the performance of the BOTDR system, wherein:

[0014] The Brillouin frequency shift demodulated by the reference fiber signal beat frequency and the Brillouin frequency shift demodulated by the local light direct beat frequency are used to judge and process the results demodulated by different optical paths according to different temperature and stress changes, including:

[0015] Different dynamic thresholds are set to judge the temperature and strain values demodulated by different optical paths; when the dynamic threshold-based judgment is a regular temperature or stress measurement, the cumulative average method is used to process the detection results of the two-path interference signal outputs; when the temperature or stress is rapidly changing and large based on the dynamic threshold judgment, only the beat frequency signal generated by the microwave heterodyne detection optical path is demodulated; when the temperature or stress is changing weakly based on the dynamic threshold judgment, only the beat frequency signal generated by the reference fiber heterodyne detection optical path is demodulated.

[0016] The beneficial effects of the preferred technical solution are: by setting different dynamic thresholds, different optical path demodulation results are processed according to different temperature and stress changes. When measuring the temperature or stress, the cumulative average method is used, which can effectively reduce the measurement error and improve the accuracy and stability of the measurement; when the temperature or stress changes rapidly and greatly, only the beat frequency signal generated by the microwave heterodyne detection light path is demodulated, which can quickly respond to the rapid change and capture the data in time; when the temperature or stress changes slightly, only the beat frequency signal generated by the reference fiber heterodyne detection light path is demodulated, which can fully utilize the high sensitivity characteristics of the light path and accurately detect the slight change, thereby comprehensively improving the measurement performance and adaptability of the BOTDR system in different environments.

[0017] As a preferred method for improving the performance of the BOTDR system, wherein:

[0018] The high-frequency beat frequency electrical signal is processed by the double-down-conversion radio frequency receiving module to realize linear sweep coverage of the Brillouin frequency shift, and the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light includes:

[0019] The beat frequency signal is first mixed with the first local oscillator signal in the first mixer to output an intermediate frequency signal; the intermediate frequency signal passes through a narrow-band intermediate frequency filter and is amplified in amplitude by a low-noise intermediate frequency amplifier; the intermediate frequency signal is secondly mixed with the second local oscillator signal to output a low-frequency signal, and the linear sweep coverage of the Brillouin frequency shift is realized by controlling the frequency synthesizer.

[0020] As a preferred method for improving the performance of the BOTDR system, wherein:

[0021] The high-frequency beat frequency electrical signal is processed by the double-down-conversion radio frequency receiving module to realize linear sweep coverage of the Brillouin frequency shift, and the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light also includes:

[0022] The baseband signal enters the data acquisition card after removing high-frequency spurs by a low-pass filter, the time-domain signal collected is subjected to frequency spectrum transformation, and the Brillouin frequency shift is extracted by Lorenz curve fitting.

[0023] As a preferred method for improving the performance of the BOTDR system, wherein:

[0024] The single narrow line width laser output light is divided into three paths by an optical coupler, and different signals of different categories are generated by different processing, which includes:

[0025] The first path is injected into the measured optical fiber through a pulse modulator to generate a backward spontaneous Brillouin scattering signal; the second path is injected into a reference optical fiber through a circulator to excite stable stimulated Brillouin scattering as reference light for high signal-to-noise ratio beat frequency; and the third path is directly used as reference light to interfere with the backward Brillouin scattering light to generate beat frequency signal light.

[0026] The beneficial effects of the preferred technical solution are that the single narrow linewidth laser output light is divided into three paths for different processing, and different types of signals can be efficiently generated. The first path is injected into the measured optical fiber through a pulse modulator to generate a backward spontaneous Brillouin scattering signal, which can be used to obtain the actual state information of the measured optical fiber; the second path is injected into a reference optical fiber through a circulator to excite stable stimulated Brillouin scattering as reference light for high signal-to-noise ratio beat frequency, which provides a stable and reliable reference signal for subsequent beat frequency operation, and improves the quality and signal-to-noise ratio of the beat frequency signal; and the third path is directly used as reference light to interfere with the backward Brillouin scattering light to generate beat frequency signal light, which enriches the signal acquisition method, helps to analyze and process the Brillouin scattering signal from multiple angles, and improves the measurement capability and accuracy of the system.

[0027] As a preferred scheme of the method for improving the performance of the BOTDR system, wherein:

[0028] After the splitting processing, the Brillouin scattering signal returned from the measured optical fiber is split and processed, and after being split into two paths, different beat frequency interference operations are performed on the two paths respectively, including:

[0029] The Brillouin scattering signal is split into two paths by a splitter, one of which is subjected to beat frequency interference with local reference light on a photodetector to output a high-frequency beat frequency electrical signal, and the other of which is used to obtain the Brillouin frequency shift difference between the reference optical fiber and the backward scattering light.

[0030] As a preferred scheme of the method for improving the performance of the BOTDR system, wherein:

[0031] The high-frequency beat frequency electrical signal is subjected to mixing, down-conversion, spectrum transformation and curve fitting to obtain the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal, including:

[0032] The high-frequency beat frequency electrical signal is mixed with a low-frequency local oscillator source and then down-converted to baseband; the time-domain signal is subjected to fast Fourier transform to obtain a frequency spectrum, and the Brillouin frequency shift is extracted through Lorentz curve fitting.

[0033] The beneficial effects of the preferred technical solutions are that the high-frequency beat frequency electrical signal is down-converted to baseband after mixing with a low-frequency local oscillator, which can convert the high-frequency signal into a low-frequency signal that is easier to process, thereby reducing the difficulty and complexity of subsequent processing. The time-domain signal is subjected to fast Fourier transform to obtain a frequency spectrum, which can convert the time-domain signal to the frequency domain, facilitating observation and analysis of the frequency components of the signal. The Brillouin frequency shift can be extracted by Lorenz curve fitting, which can more accurately determine the value of the Brillouin frequency shift from the frequency spectrum, thereby improving the accuracy and precision of the measurement, and optimizing the measurement performance of the BOTDR system for temperature and strain.

[0034] In a second aspect, the present application provides a system for improving the performance of a BOTDR system, comprising:

[0035] A laser branching module is used to split the output light of a single narrow-linewidth laser into three paths through an optical coupler, and different processing is performed on each path to generate different types of signals.

[0036] A scattering light beat frequency module is used to split the Brillouin scattering signal returned from the measured optical fiber into two paths after branching processing, and different beat frequency interference operations are performed on each path.

[0037] A reference frequency shift demodulation module is used to mix, down-convert, spectrum transform, and curve fit the high-frequency beat frequency electrical signal to obtain the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal.

[0038] A local frequency shift demodulation module is used to process the high-frequency beat frequency electrical signal using a secondary down-conversion radio frequency receiving module to achieve linear sweep coverage of the Brillouin frequency shift, and obtain the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light.

[0039] A result judgment processing module is used to judge and process the results obtained by demodulation of different optical paths based on the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal and the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light according to different temperature and stress changes.

[0040] In a third aspect, the present application provides an electronic device, comprising:

[0041] A memory and a processor.

[0042] The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions. When the one or more programs are executed by the one or more processors, the one or more processors implement the method for improving the performance of a BOTDR system as described in the present application.

[0043] In a fourth aspect, the present application provides a computer readable storage medium storing computer executable instructions, which, when executed by a processor, implement the method for improving performance of a BOTDR system.

[0044] The present application has the following advantages: The present application combines reference fiber heterodyne detection and secondary down-conversion microwave processing technology, effectively solves many problems of the existing Brillouin optical time domain reflectometer (BOTDR) system, and has significant advantages in practical applications. In terms of reference fiber heterodyne detection, one of the light outputs of a single narrow linewidth laser is injected into a reference fiber through a circulator to excite stable stimulated Brillouin scattering as reference light, high signal-to-noise ratio beat frequency is achieved, and the frequency stability of the reference light is improved. This makes the system effectively reduce the measurement error caused by unstable reference light frequency shift in actual measurement, improves the accuracy of temperature and stress measurement, and can be widely used in health monitoring of large infrastructure such as bridges and dams to ensure their safe operation. The secondary down-conversion microwave processing technology solves the problem of the microwave heterodyne scheme. This technology step-by-step down-converts the original high-frequency beat signal, reduces the requirement for filter selectivity, and simplifies the radio frequency design. At the same time, step-by-step amplification of the signal reduces the design difficulty of the amplifier, improves the overall gain and dynamic response capability of the system. This is of great significance in temperature and stress monitoring of oil pipelines, which can accurately detect the state change of the pipeline under different environments and timely discover potential safety hazards. According to different dynamic thresholds, the temperature and strain values demodulated by different light paths can be judged and different processing methods can be used. Whether it is regular measurement or facing rapid and large changes, weak changes in temperature or stress, the system measurement error can be effectively reduced to meet the measurement requirements in complex environments, such as providing reliable technical support for real-time monitoring of aircraft structures in the field of aerospace. BRIEF DESCRIPTION OF DRAWINGS

[0045] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0046] Figure 1 is the overall flowchart of the method for improving performance of a BOTDR system provided by the present application. DETAILED DESCRIPTION

[0047] In order to make the above objectives, characteristics and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should fall within the scope of protection of the present application.

[0048] Embodiment 1, refer to Figure 1 For the first embodiment of the present application, the embodiment provides a method for improving the performance of a BOTDR system, comprising:

[0049] S1: using single narrow linewidth laser output light, dividing into three paths through optical coupling, and respectively performing different processing to generate different types of signals;

[0050] S2: after the branch processing, performing optical splitting processing on the Brillouin scattering signal returned in the optical fiber to be measured, and respectively performing different beat frequency interference operations after being divided into two paths;

[0051] S3: performing mixing, down-conversion, spectrum transformation and curve fitting on the high-frequency beat frequency electrical signal to obtain the Brillouin frequency shift obtained by beat frequency demodulation through the reference optical fiber signal;

[0052] S4: processing the high-frequency beat frequency electrical signal using a second down-conversion radio frequency receiving module to realize linear sweep coverage of the Brillouin frequency shift, and obtaining the Brillouin frequency shift obtained by direct beat frequency demodulation through the local light;

[0053] S5: based on the Brillouin frequency shift obtained by beat frequency demodulation through the reference optical fiber signal and the Brillouin frequency shift obtained by direct beat frequency demodulation through the local light, judging and processing the results demodulated by different optical paths according to different temperature and stress changes.

[0054] It should be noted that through steps S1-S5, the microwave heterodyne demodulation system and the reference optical fiber demodulation system are combined, and the second down-conversion radio frequency receiving is used in the microwave heterodyne demodulation system. The advantages and disadvantages of the microwave heterodyne demodulation and the reference optical fiber demodulation system are combined, and the processing of the two paths is proposed to improve the accuracy and range of demodulation.

[0055] Embodiment 2, refer to Figure 1 For an embodiment of the present application, based on the previous embodiment, a method for improving the performance of a BOTDR system is provided, comprising:

[0056] In the present embodiment, the step S1 of using single narrow linewidth laser output light, dividing into three paths through optical coupling, and respectively performing different processing to generate different types of signals comprises:

[0057] The light output by the single narrow-linewidth laser is split into three paths by an optical coupler: the first path enters the test optical fiber via a pulse modulator, and the test optical fiber generates a backscattered Brillouin scattering signal; the second path enters a reference optical fiber via a circulator to excite a stable stimulated Brillouin scattering (SBS) as a reference light for realizing high signal-to-noise ratio beat frequency; and the third path directly serves as a reference light for interference with the backscattered Brillouin scattering light to generate beat frequency signal light. This step generates the backscattered Brillouin scattering signal of the test optical fiber, the stimulated Brillouin scattering reference light of the reference optical fiber, the reference light for interference, and the beat frequency signal light.

[0058] In this embodiment, after the splitting processing in step S2, the Brillouin scattering signal returned in the test optical fiber is subjected to light splitting processing and split into two paths, and different beat frequency interference operations are performed on the two paths respectively.

[0059] The Brillouin scattering signal is split into two paths by a light splitter. One of the two paths is subjected to beat frequency interference with a local reference light on a photodetector to output a high-frequency beat frequency electrical signal, and the other path is used to obtain a Brillouin frequency shift difference between the reference optical fiber and the backscattered light.

[0060] This step generates the high-frequency beat frequency electrical signal and the Brillouin frequency shift difference between the reference optical fiber and the backscattered light.

[0061] In another possible implementation, when the two paths are split and subjected to different beat frequency interference operations, a plurality of local lights with specific wavelengths can also be used to perform beat frequency interference with the Brillouin scattering signal on the photodetector. These local lights with multiple wavelengths can be generated by a multi-wavelength laser, and each wavelength corresponds to a different frequency.

[0062] One beat frequency operation can simultaneously obtain beat frequency information of multiple frequency points, which is equivalent to analyzing the Brillouin scattering signal in different frequency dimensions. This helps to more comprehensively understand the frequency characteristics of the Brillouin scattering signal, and is very useful for measurements in complex environments or scenarios requiring high-precision frequency analysis. For example, when measuring an optical fiber with multiple temperature or strain distributions, multi-wavelength beat frequency can capture the Brillouin frequency shift information corresponding to different regions.

[0063] In another possible implementation, when the two paths are split and subjected to different beat frequency interference operations, the second Brillouin scattering signal can not be directly compared with a single reference optical fiber, but can be compared with backscattered lights of a plurality of reference optical fibers with different known characteristics (such as different lengths, different temperatures, or different strain preset values) respectively, to obtain a plurality of Brillouin frequency shift differences.

[0064] The plurality of reference optical fibers provides more reference standards, which can more accurately calibrate and determine the actual state of the optical fiber to be measured. By comprehensively analyzing the plurality of Brillouin frequency shift differences, measurement errors can be reduced, and the accuracy and reliability of the measurement can be improved. For example, when measuring long-distance optical fibers, using a plurality of reference optical fibers at different positions can more accurately reflect the temperature and strain changes at different positions of the optical fiber.

[0065] In the embodiment, the Brillouin frequency shift obtained by the reference fiber signal beat frequency demodulation obtained by the mixing, down-conversion, spectrum transformation and curve fitting of the high-frequency beat frequency electrical signal in the above step S3 includes:

[0066] The high-frequency beat frequency electrical signal is mixed with the low-frequency local oscillator source and then down-converted to the baseband, which is convenient for data acquisition card acquisition. The time domain signal collected is subjected to fast Fourier transform to obtain the frequency spectrum, and the Brillouin frequency shift is extracted through Lorentz curve fitting.

[0067] In the embodiment, the high-frequency beat frequency electrical signal is processed by the secondary down-conversion radio frequency receiving module in the above step S4, the linear sweep coverage of the Brillouin frequency shift is realized, and the Brillouin frequency shift obtained by the local light direct beat frequency demodulation includes:

[0068] The beat frequency signal is mixed with the first local oscillator signal (fixed frequency, such as 10.7GHz) in the first mixer (in a multi-stage mixing system, the mixer used for the first mixing operation), and the intermediate frequency signal (IF1) is output. The intermediate frequency signal passes through a narrow-band intermediate frequency filter and is amplified in amplitude by a low-noise intermediate frequency amplifier. The intermediate frequency signal is mixed with the second local oscillator signal (generated by a low-frequency high-precision frequency synthesizer, adjustable) for the second time, and a low-frequency (baseband) signal is output. The linear sweep coverage of the Brillouin frequency shift is realized by controlling the frequency synthesizer. The baseband signal passes through a low-pass filter to remove high-frequency spurs and enters a data acquisition card. The collected time domain signal is subjected to spectrum transformation by an FFT algorithm, and the Brillouin frequency shift is extracted by Lorentz curve fitting.

[0069] In another possible implementation, the frequency of the first local oscillator signal can be set to 10.6GHz. In the BOTDR system, the received Brillouin beat frequency signal generally has a frequency in the range of 10-11GHz. The first local oscillator signal with a frequency of 10.6GHz is mixed with the beat frequency signal in the first mixer.

[0070] The frequency range of the intermediate frequency signal (IF1) generated after mixing is 0-400MHz (|10-10.6| |10-10.6| GHz- |11-10.6| |11-10.6| GHz). The relatively narrow intermediate frequency range allows the narrow-band intermediate frequency filter to more accurately filter signals, further reducing noise interference. At the same time, the lower intermediate frequency frequency makes the amplification process more stable for the low-noise intermediate frequency amplifier, effectively reducing signal distortion and improving signal quality.

[0071] The second local oscillator signal can be a signal adjustable in the range of 100-300MHz generated by a low-frequency high-precision frequency synthesizer. The first mixed intermediate frequency signal (IF1) has a frequency range of 0-400MHz, which is mixed with the second local oscillator signal for the second time.

[0072] By adjusting the frequency of the second local oscillator signal, linear sweep coverage of the Brillouin frequency shift can be flexibly achieved. For example, when IF1 is 200MHz, if the second local oscillator signal is set to 150MHz, the low-frequency (baseband) signal frequency after mixing is 50MHz; if IF1 is 350MHz, adjust the second local oscillator signal to 300MHz, and the baseband signal after mixing is 50MHz. This can further reduce the signal frequency to a range that is very suitable for data acquisition card processing, enhancing the precision and flexibility of the system for Brillouin frequency shift detection.

[0073] In another possible implementation, the first local oscillator signal can be set to a frequency of 10.8GHz. Given that the Brillouin beat signal frequency received by the BOTDR system is usually in the range of 10-11GHz, the first mixing is performed with the first local oscillator signal of 10.8GHz.

[0074] The frequency range of the intermediate frequency signal (IF1) generated after mixing is 0-200MHz (|10-10.8| |10-10.8| GHz- |11-10.8| |11-10.8| GHz). The extremely narrow intermediate frequency range allows the narrow-band intermediate frequency filter to more efficiently remove noise and interference, and the low-noise intermediate frequency amplifier can work more stably, reducing signal fluctuations and distortion, providing high-quality intermediate frequency signals for subsequent signal processing.

[0075] The second local oscillator signal can be a signal adjustable in the range of 50-150MHz generated by a low-frequency high-precision frequency synthesizer. The first mixed intermediate frequency signal (IF1) has a frequency range of 0-200MHz, which is mixed with the second local oscillator signal for the second time.

[0076] By precisely adjusting the frequency of the second local oscillator signal, linear sweep coverage of the Brillouin frequency shift can be achieved in detail. For example, when IF1 is 120 MHz, if the second local oscillator signal is set to 100 MHz, the low frequency (baseband) signal frequency obtained after mixing is 20 MHz; if IF1 is 180 MHz, the second local oscillator signal is adjusted to 150 MHz, and a 30 MHz baseband signal is obtained after mixing. This setting can reduce the signal frequency to a very low range, greatly improving the signal acquisition accuracy of the data acquisition card, thereby improving the accuracy of temperature and strain measurement of the entire BOTDR system.

[0077] In another possible implementation, linear sweep coverage of the Brillouin frequency shift can also be achieved by combining the optical heterodyne method with a tunable laser: the optical heterodyne method is to mix the reference light and the signal light, and to change the frequency of the reference light to achieve the sweep of the Brillouin frequency shift.

[0078] Specifically, a tunable laser is used as a reference light source, and the frequency of the output reference light can be precisely adjusted within a certain range. The reference light and the signal light carrying the Brillouin frequency shift information are mixed in an optical mixer.

[0079] By controlling the driving current or temperature of the tunable laser and other parameters, the output frequency changes according to a predetermined linear law, thereby achieving linear sweep coverage of the Brillouin frequency shift.

[0080] The mixed optical signal is converted into an electrical signal, which is amplified, filtered, and processed into a data acquisition card, and then the FFT algorithm is used for frequency spectrum analysis and Lorentz curve fitting to extract the Brillouin frequency shift.

[0081] This method directly adjusts the frequency in the optical domain, avoiding some noise and distortion problems in the radio frequency processing process, and can achieve high-precision sweep coverage.

[0082] In another possible implementation, linear sweep coverage of the Brillouin frequency shift can also be achieved by the scanning method of an acousto-optic modulator (AOM): the acousto-optic modulator can modulate the frequency of the input light by changing the frequency of the radio frequency signal applied thereto.

[0083] Specifically, the input light is divided into two paths, one of which is injected into the optical fiber as probe light, and the other of which is used as local oscillator light. The local oscillator light is frequency-modulated by the acousto-optic modulator.

[0084] A linearly varying radio frequency signal is generated and applied to the acousto-optic modulator, so that the frequency of the local oscillator light changes according to a linear law.

[0085] The probe light carrying the Brillouin frequency shift information returned from the optical fiber is mixed with the frequency-modulated local light in an optical mixer, and after being converted into an electrical signal, subsequent processing is performed.

[0086] The acousto-optic modulator has fast response speed and can realize fast frequency scanning, and is suitable for application scenarios requiring fast measurement.

[0087] In the embodiment, the Brillouin frequency shifts obtained by the reference fiber signal beat frequency demodulation and the Brillouin frequency shifts obtained by the local light direct beat frequency demodulation in the step S5 are used to judge and process the results obtained by the different optical paths according to different temperature and stress changes, including:

[0088] Different dynamic thresholds are set to judge the temperature and strain values obtained by the different optical paths. In the conventional temperature or stress measurement, the cumulative average method is used to process the detection results of the two-way interference signal outputs; when the temperature or stress changes rapidly and greatly, only the beat frequency signal generated by the microwave heterodyne detection optical path is demodulated; when the temperature or stress changes slightly, only the beat frequency signal generated by the reference fiber heterodyne detection optical path is demodulated, so as to obtain more accurate Brillouin frequency shifts after processing, which are used to realize the distributed temperature or stress measurement along the optical fiber.

[0089] In another possible implementation, when different dynamic thresholds are set, multiple threshold levels can be set for each scenario. For example, a relatively narrow threshold range can be set for normal conditions; different levels of thresholds are set according to the change rate for slow change conditions; a higher threshold is set for rapid change and large change conditions to trigger emergency response; a lower sensitive threshold is set for slight change conditions.

[0090] In another possible implementation, when different dynamic thresholds are set, each threshold can be associated with a specific processing method. For example, when the measurement value is within the normal threshold range, regular recording and monitoring are performed; when the slow change threshold is exceeded, the measurement frequency is increased; when the rapid change or large change threshold is exceeded, an alarm is immediately issued and an emergency processing program is started.

[0091] Embodiment 3, the above is a schematic scheme of the method for improving the performance of the BOTDR system of the embodiment. It should be noted that the technical scheme of the system for improving the performance of the BOTDR system belongs to the same concept as the technical scheme of the method for improving the performance of the BOTDR system described above. The technical scheme of the system for improving the performance of the BOTDR system in the embodiment is not described in detail, and can be referred to the description of the technical scheme of the method for improving the performance of the BOTDR system.

[0092] The embodiment also provides a system for improving the performance of the BOTDR system, including:

[0093] A laser branching module is used to branch the light output by a single narrow-linewidth laser into three paths by an optical coupler, and different processes are performed on the three paths to generate different types of signals.

[0094] A scattered light frequency modulation module is used to perform light splitting on the Brillouin scattering signal returned from the fiber under test after branching, and different frequency mixing operations are performed on the two paths after splitting.

[0095] A reference frequency shift demodulation module is used to mix, down-convert, spectrum transform and curve fit the high-frequency beat signal to obtain the Brillouin frequency shift obtained by reference fiber signal beat demodulation.

[0096] A local frequency shift demodulation module is used to process the high-frequency beat signal by using a twice down-converted RF receiving module to realize linear sweep coverage of the Brillouin frequency shift, and obtain the Brillouin frequency shift obtained by local light direct beat demodulation.

[0097] A result judgment processing module is used to judge and process the results obtained by different optical paths according to different temperature and stress changes based on the Brillouin frequency shift obtained by reference fiber signal beat demodulation and the Brillouin frequency shift obtained by local light direct beat demodulation.

[0098] The embodiment also provides an electronic device suitable for the method for improving the performance of the BOTDR system, which comprises:

[0099] A memory and a processor; the memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions to realize the method for improving the performance of the BOTDR system proposed in the above embodiment.

[0100] The embodiment also provides a storage medium having a computer program stored thereon, and the program is executed by a processor to realize the method for improving the performance of the BOTDR system proposed in the above embodiment.

[0101] The storage medium proposed in the embodiment belongs to the same inventive concept as the method for improving the performance of the BOTDR system proposed in the above embodiment, and the technical details not described in the embodiment can be referred to the above embodiment, and the embodiment has the same beneficial effects as the above embodiment.

[0102] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and all modifications or replacements should be covered in the scope of the claims of the present application.

Claims

1. A method for improving performance of a BOTDR system, characterized by, include: The output light of a single narrow linewidth laser is split into three paths by an optical coupler, and each path is processed differently to generate different types of signals. After splitting, the Brillouin scattering signal returned from the fiber under test is split into two paths and then subjected to different beat frequency interference operations. By performing mixing, downconversion, spectrum transformation and curve fitting on the high-frequency beat frequency electrical signal, the Brillouin frequency shift obtained by beat frequency demodulation of the reference fiber signal is obtained; A secondary down-conversion RF receiver module is used to process the high-frequency beat frequency electrical signal to achieve linear sweep frequency coverage of the Brillouin frequency shift, and the Brillouin frequency shift obtained by direct beat frequency demodulation via local optical signal is obtained. Based on the Brillouin frequency shift obtained by beat frequency demodulation of the reference fiber signal and the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light, the results demodulated by different optical paths are judged and processed according to different temperature and stress changes.

2. The method of claim 1, wherein the BOTDR system performance is improved by, The process of judging and processing the demodulated results from different optical paths based on the Brillouin frequency shift obtained by beat frequency demodulation of the reference fiber signal and the Brillouin frequency shift obtained by direct beat frequency demodulation of local light, according to different temperature and stress changes, includes: Different dynamic thresholds are set to judge the temperature and strain values ​​demodulated from different optical paths; when the dynamic threshold determines that it is a conventional temperature or stress measurement, the cumulative average method is used to process the detection results of the two interference signals; when the temperature or stress is determined to be changing rapidly and significantly based on the dynamic threshold, only the beat frequency signal generated by the microwave heterodyne detection optical path is demodulated; when the temperature or stress is determined to be changing slightly based on the dynamic threshold, only the beat frequency signal generated by the reference fiber heterodyne detection optical path is demodulated.

3. The method of claim 2, wherein the BOTDR system performance is improved by, The process of using a double down-conversion RF receiving module to process the high-frequency beat frequency electrical signal to achieve linear frequency sweep coverage of the Brillouin frequency shift, and obtaining the Brillouin frequency shift obtained by direct beat frequency demodulation via local optical transmission, includes: The beat frequency signal and the first local oscillator signal are mixed for the first time in the first mixer to output the intermediate frequency signal. The intermediate frequency signal is then passed through a narrowband intermediate frequency filter and the signal amplitude is boosted by a low-noise intermediate frequency amplifier. The intermediate frequency signal is then mixed for the second local oscillator signal to output the low-frequency signal. The linear frequency sweep coverage of the Brillouin frequency shift is achieved by controlling the frequency synthesizer.

4. The method of claim 3, wherein the BOTDR system performance is improved by, The process of using a double down-conversion RF receiving module to process the high-frequency beat frequency electrical signal to achieve linear frequency sweep coverage of the Brillouin frequency shift, and obtaining the Brillouin frequency shift obtained by direct beat frequency demodulation via local optical transmission, further includes: The baseband signal is filtered by a low-pass filter to remove high-frequency spurious signals before entering the data acquisition card. The acquired time-domain signal is subjected to spectral transformation, and the Brillouin frequency shift is extracted by Lorentz curve fitting.

5. The method of claim 4, wherein the BOTDR system performance is improved by, The method of using a single narrow-linewidth laser to output light, splitting it into three paths via optical coupling, and processing each path differently to generate different types of signals includes: The first path is injected into the fiber under test via a pulse modulator to generate a backward spontaneous Brillouin scattering signal; the second path is injected into the reference fiber via a circulator to excite stable stimulated Brillouin scattering as a reference light for high signal-to-noise ratio beat frequency; the third path is directly used as the reference light and interferes with the backward Brillouin scattering light to generate beat frequency signal light.

6. The method of claim 5, wherein the BOTDR system performance is improved by, The Brillouin scattering signal returned in the optical fiber to be tested is split after the splitting processing, and is split into two paths after the splitting processing, and different beat frequency interference operations are performed on the two paths respectively, including: The Brillouin scattering signal is split into two paths by the optical splitter, one of which performs beat frequency interference with the local reference light on the photodetector to output a high-frequency beat frequency electrical signal; the other is used to obtain the Brillouin frequency shift difference between the reference optical fiber and the backscattered light.

7. The method of claim 6, wherein the BOTDR system performance is improved by, The high-frequency beat frequency electrical signal is mixed, down-converted, spectrum-transformed and curve-fitted to obtain the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal. The high-frequency beat frequency electrical signal is mixed with a low-frequency local oscillator source and then down-converted to baseband; the time-domain signal is subjected to fast Fourier transform to obtain a frequency spectrum, and the Brillouin frequency shift is extracted by Lorentz curve fitting.

8. A system for improving the performance of a BOTDR system, applying the method according to any one of claims 1 to 7, characterized in that, It comprises: A laser splitting module for splitting the output light of a single narrow linewidth laser into three paths by an optical coupler, and performing different processing on the three paths to generate different types of signals; A scattering splitting beat frequency module for splitting the Brillouin scattering signal returned in the optical fiber to be tested after the splitting processing, and performing different beat frequency interference operations on the two paths after the splitting processing; A reference frequency shift demodulation module for mixing, down-converting, spectrum-transforming and curve-fitting the high-frequency beat frequency electrical signal to obtain the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal; A local frequency shift demodulation module for processing the high-frequency beat frequency electrical signal by using a secondary down-conversion radio frequency receiving module to realize linear sweep coverage of the Brillouin frequency shift, and obtaining the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light; A result judgment processing module for judging and processing the results demodulated by different optical paths based on the Brillouin frequency shift obtained by beat frequency demodulation of the reference optical fiber signal and the Brillouin frequency shift obtained by direct beat frequency demodulation of the local light according to different temperature and stress changes.

9. An electronic device, comprising: It comprises: A memory and a processor; The memory is used to store computer executable instructions, and the processor is used to execute the computer executable instructions, which realize the steps of the method of any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that, It stores computer executable instructions, which realize the steps of the method of any one of claims 1 to 7 when executed by the processor.

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