Pole tower positioning system and method based on differential pulse pair Brillouin optical time domain analyzer

Abstract

The present invention discloses a tower positioning system and method based on a differential pulse pair Brillouin optical time domain analyzer, relating to the field of optical technology. The system includes a data acquisition module and a data processing module. The data acquisition module is used to acquire the Brillouin time domain signal returned by the optical fiber under test, and the data acquisition module includes a pump light modulator submodule, a probe light modulator submodule, and a data acquisition card. The pump light modulator submodule is used to modulate the pulse width and amplitude of the pump light and couple the modulated light pulse into the optical fiber under test. The probe light modulator submodule is used to frequency modulate the probe light intensity and couple the frequency-modulated reference light from the other end into the optical fiber under test. The data acquisition card is used to acquire the Brillouin time domain signal. The data processing module is used to process the Brillouin time domain signal to obtain the linear tower position between two fusion points. The present invention has high precision and high sensitivity, and can improve the accuracy and reliability of tower positioning.

Description

Technical Field

[0001] The present invention relates to the field of optical technology, and in particular to a tower positioning system and method based on a differential pulse pair Brillouin optical time domain analyzer. Background Art

[0002] Optical fiber composite overhead groundwire (OPGW) cable, a medium that integrates optical communications and power transmission, plays a key role in modern communications networks. It is widely used in urban, rural, and even international communication networks. Overhead optical cables are highly favored over underground cables due to their ease of installation and maintenance, lower costs, and ease of expansion. In the current information age, with the rapid advancement of communications technology, the positioning of OPGW cables has become increasingly important. However, OPGW cables can cause failures due to environmental factors, human factors, material aging, and maintenance. Rapid fault location is crucial for repair. Traditional methods rely on original as-built materials and the use of an OTDR (Optical Detector) to locate optical cable faults. However, due to cable coiling, sag, and excess fiber length, the optical distance measured by the OTDR cannot accurately correspond to the physical markings on the cable, impacting the efficiency of fault recovery.

[0003] Brillouin Optical Time Domain Analysis (BOTDA) is a fiber optic sensing technology based on the principle of Brillouin scattering. When a pump light pulse passes through an optical fiber, Brillouin scattering occurs between photons, generating scattered photons. The frequency of these scattered photons is affected by strain and temperature changes within the fiber. By measuring the frequency changes of these scattered photons, the strain and temperature changes within the fiber can be calculated. BOTDA offers high-precision temperature and strain measurement capabilities, enabling real-time monitoring of minute temperature and strain changes within the fiber, providing accurate data for fault detection and location. It can cover long fiber distances, enabling remote monitoring of the status of optical cable systems without manual intervention, improving monitoring efficiency. It can monitor temperature and strain changes within the fiber in real time, generating timely alerts upon abnormal conditions, facilitating rapid response and resolution. It can also simultaneously monitor temperature and strain at multiple points, improving monitoring efficiency and providing a comprehensive understanding of the status of the optical cable system. BOTDR operates based on the scattering of optical signals and is a non-invasive detection technology that does not damage the optical cable system. The existing technology has clearly described the use of distributed Brillouin sensing technology to locate connecting towers. However, the positioning of a straight tower between two connecting towers only uses a calculation and estimation method, which cannot achieve high-precision identification and positioning. Summary of the Invention

[0004] To this end, the present invention proposes a tower positioning system and method based on a differential pulse pair Brillouin optical time domain analyzer, in an effort to solve or at least alleviate at least one of the above problems.

[0005] According to one aspect of the present invention, a tower positioning system based on a differential pulse pair Brillouin optical time domain analyzer is proposed. The system includes a data acquisition module and a data processing module; wherein,

[0006] The data acquisition module is used to collect the Brillouin time domain signal returned by the optical fiber to be tested, wherein the optical fiber to be tested is the core inside the optical fiber composite overhead ground wire cable, and the optical fiber composite overhead ground wire cable is installed on the tower;

[0007] The data acquisition module includes a pump light modulation submodule, a detection light modulation submodule, and a data acquisition card 13; the pump light modulation submodule is used to modulate the pulse width and amplitude of the pump light and couple the modulated light pulse into the optical fiber under test; the detection light modulation submodule is used to frequency modulate the detection light intensity and couple the frequency-modulated reference light from the other end into the optical fiber under test; the data acquisition card 13 is used to collect the Brillouin time domain signal returned by the optical fiber under test;

[0008] The data processing module is used to process the collected Brillouin time domain signal to obtain the position of the straight pole tower between the two fusion points; the collected Brillouin time domain signal includes the Brillouin time domain signals of the two time trajectories returned by the optical fiber to be tested; wherein, processing the collected Brillouin time domain signal includes: subtracting the Brillouin time domain signals of the two time trajectories to obtain a differential time domain signal, thereby obtaining differential time domain signals of multiple frequencies around the Brillouin frequency shift; constructing a differential distribution Brillouin spectrum based on the differential time domain signal; fitting to obtain a fitting spectrum of the differential distribution Brillouin spectrum at each position point, and obtaining the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum as the Brillouin center frequency shift of the position point, and the Brillouin center frequency shift of each position point constitutes the Brillouin center frequency shift curve of the entire optical fiber to be tested; finding the local minimum point of the Brillouin center frequency shift curve, and the local minimum point corresponds one-to-one to the position of the straight pole tower between the two fusion points.

[0009] Furthermore, the data acquisition module also includes a laser 1, a coupler 2, a pulse source 14, and a microwave source 15; wherein the output end of the laser 1 is connected to the input end of the coupler 2, and the output end of the coupler 2 is respectively connected to the input end of the pump light modulator module and the input end of the detection light modulator module; the output end of the pulse source 14 is respectively connected to the modulation end of the first electro-optical modulator 3 in the pump light modulator module and the trigger end of the data acquisition card 13; the output end of the microwave source 15 is connected to the modulation end of the second electro-optical modulator 7 in the detection light modulator module.

[0010] Furthermore, the pump light modulation submodule includes a first electro-optical modulator 3, a polarization controller 4, an erbium-doped fiber amplifier 5, and a first circulator 6; wherein, the output end of the coupler 2 is connected to the input end of the first electro-optical modulator 3, the output end of the first electro-optical modulator 3 is connected to the input end of the polarization controller 4, the output end of the polarization controller 4 is connected to the input end of the erbium-doped fiber amplifier 5, the output end of the erbium-doped fiber amplifier 5 is connected to port 1 of the first circulator 6, and port 2 of the first circulator 6 is connected to one end of the optical fiber to be tested.

[0011] Furthermore, the detection light modulation submodule includes a second electro-optical modulator 7, an adjustable attenuator 8, and an isolator 9; wherein the output end of the coupler 2 is connected to the input end of the second electro-optical modulator 7, the output end of the second electro-optical modulator 7 is connected to the input end of the adjustable attenuator 8, the output end of the adjustable attenuator 8 is connected to the input end of the isolator 9, and the output end of the isolator 9 is connected to the other end of the optical fiber to be tested.

[0012] Furthermore, the data acquisition module also includes a second circulator 10, a fiber Bragg grating filter 11, and a photodetector 12; wherein, port 3 of the first circulator 6 is connected to port 1 of the second circulator 10, port 2 of the second circulator 10 is connected to the fiber Bragg grating filter 11, port 3 of the second circulator 10 is connected to the input end of the photodetector 12, and the output end of the photodetector 12 is connected to the data acquisition card 13.

[0013] Furthermore, the laser 1 uses a narrow linewidth distributed feedback laser as a light source.

[0014] Furthermore, the splitting ratio of the coupler 2 is 50:50; and the extinction ratio of the first electro-optical modulator 3 is 40 dB.

[0015] According to another aspect of the present invention, a tower positioning method based on a differential pulse pair Brillouin optical time domain analyzer is proposed. The method is implemented by the tower positioning system based on the differential pulse pair Brillouin optical time domain analyzer, and the method comprises:

[0016] The pulse source 14 is configured to output two electrical pulses of different widths to the first electro-optical modulator 3, and the first electro-optical modulator 3 is used to modulate the two optical pulses of different widths. The Brillouin time domain signals of the two time traces are collected by the data acquisition module. The data processing module subtracts the Brillouin time domain signals of the two time traces to obtain a differential time domain signal.

[0017] Changing the microwave frequency of the microwave source 15 to obtain differential time domain signals of multiple frequencies around the Brillouin frequency shift, and constructing a differential Brillouin spectrum based on the differential time domain signals;

[0018] The fitting spectrum of the Brillouin spectrum of the differential distribution at each position point is obtained by fitting, and the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum is obtained as the Brillouin center frequency shift of the position point. The Brillouin center frequency shifts of each position point constitute the Brillouin center frequency shift curve of the entire optical fiber to be tested;

[0019] Find the local minimum point of the Brillouin center frequency shift curve, which corresponds one-to-one to the position of the straight tower between the two welding points.

[0020] Furthermore, the process of using the data acquisition module to collect the Brillouin time domain signal returned by the optical fiber under test includes:

[0021] Laser 1 emits continuous light, which is split into two branches, pump light and probe light, by coupler 2. A first electro-optical modulator 3 with a high extinction ratio modulates the intensity of the pump light in the upper branch into a differential pulse pair via a pulse source 14. A polarization controller 4 converts the single polarization state output by the first electro-optical modulator 3 into two orthogonal polarization states. The polarization controller 4 is synchronized with an electrical pulse signal triggered by a data acquisition card 13. An erbium-doped fiber amplifier 5 amplifies the peak power of the optical pulse output by the polarization controller 4. The amplified optical pulse is then coupled into the optical fiber under test via port 2 of the first circulator.

[0022] The probe light of the lower branch is frequency modulated by the second electro-optical modulator 7 driven by the microwave source 15, and the power is adjusted by the variable attenuator 8. It then enters the isolator 9 and is injected into the optical fiber to be tested, where it undergoes stimulated Brillouin scattering with the pump light.

[0023] The Brillouin scattering signal returned by the optical fiber to be tested is reflected by port No. 3 of the first circulator 6, enters the fiber Bragg grating filter 11 through port No. 2 of the second circulator 10, and the low-frequency sideband is filtered out; the high-frequency sideband enters the photodetector 12 from port 3 of the second circulator 10, and is converted into an electrical signal by the photodetector 12; the data acquisition card 13 collects the electrical signal.

[0024] The beneficial technical effects of the present invention are:

[0025] The present invention proposes a tower positioning system and method based on a differential pulse pair Brillouin optical time domain analyzer. The system includes a data acquisition module and a data processing module; wherein the data acquisition module is used to collect the Brillouin time domain signal returned by the optical fiber to be tested, wherein the optical fiber to be tested is the core inside the optical fiber composite overhead ground wires (OPGW) cable, and the OPGW cable is installed on the tower at the top of the overhead line; the data acquisition module includes a pump light modulator submodule, a detection light modulator submodule, and a data acquisition card; the pump light modulator submodule is used to modulate the pulse width and amplitude of the pump light and couple the modulated light pulse into the optical fiber to be tested; the detection light modulator submodule is used to frequency modulate the intensity of the detection light and couple the frequency-modulated reference light from the other end into the optical fiber to be tested; the data acquisition card is used to collect the Brillouin time domain signal returned by the optical fiber to be tested; the data processing module is used to process the collected Brillouin time domain signal to obtain the position of the straight tower between two fusion points. This invention utilizes a Differential Pulse Pair Brillouin Optical Time Domain Analyzer (DPP-BOTDA) to acquire Brillouin time-domain signals with high precision and sensitivity. It also accounts for temperature effects, specifically differential heat conduction, enabling accurate positioning of towers in environments with rapid temperature fluctuations. The DPP-BOTDA records and analyzes extensive data, helping users understand the operating status and performance trends of optical cables, providing data support for routine maintenance and management. This invention achieves a one-to-one correspondence between optical fiber length and tower position, improving the accuracy and reliability of tower positioning. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The above and other objects, features and advantages of the exemplary embodiments of the present invention will become readily apparent by reading the following detailed description with reference to the accompanying drawings, in which several embodiments of the present invention are shown by way of example and not limitation, in which:

[0027] Figure 1 This is a structural schematic diagram of a data acquisition module in a tower positioning system based on a differential pulse pair Brillouin optical time domain analyzer according to an embodiment of the present invention.

[0028] Figure 2 Schematic diagram of the installation between the OPGW optical cable and the tower in an embodiment of the present invention.

[0029] Figure 3 Schematic diagram of the working principle of the differential pulse pair in an embodiment of the present invention.

[0030] Figure 4 Graphs showing the results after processing by the data processing module in an embodiment of the present invention; graph (a) corresponds to the measured distance; graph (b) corresponds to the strain measurement accuracy.

[0031] Figure 5 This is a diagram of the tower positioning results in an embodiment of the present invention.

[0032] Figure 6 This is a detailed diagram of the tower positioning in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments. It should be understood that these embodiments are provided solely to enable those skilled in the art to better understand and implement the present invention, and are not intended to limit the scope of the present invention in any way. Rather, these embodiments are provided to make this disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0034] The embodiment of the present invention proposes a tower positioning system based on a differential pulse pair Brillouin optical time domain analyzer, which includes a data acquisition module and a data processing module; wherein,

[0035] The data acquisition module is used to collect the Brillouin time domain signal returned by the optical fiber under test. The optical fiber under test is the core inside the optical fiber composite overhead ground wire (OPGW) cable. The OPGW cable is installed on a pole tower at the top of the overhead line, with both ends fixed to the tension tower and the middle hung on the top of the straight tower using a suspension clamp. Usually, OPGW cable is reeled for several kilometers. Two adjacent sections of optical cable are fused on the tension tower, which is defined as a connected pole tower, and the middle support is a straight pole tower.

[0036] The data acquisition module includes a pump light modulation submodule, a detection light modulation submodule, and a data acquisition card 13; the pump light modulation submodule is used to modulate the amplitude and pulse width of the pump light and couple the modulated light pulses into the optical fiber under test; the detection light modulation submodule is used to frequency modulate the intensity of the detection light and couple the frequency-modulated reference light from the other end into the optical fiber under test; the data acquisition card 13 is used to collect the Brillouin time domain signal returned by the optical fiber under test;

[0037] The data processing module is used to process the collected Brillouin time domain signal to obtain the position of the straight pole tower between the two fusion points; the collected Brillouin time domain signal includes the Brillouin time domain signals of the two time trajectories returned by the optical fiber to be tested; wherein, processing the collected Brillouin time domain signal includes: subtracting the Brillouin time domain signals of the two time trajectories to obtain a differential time domain signal, thereby obtaining differential time domain signals of multiple frequencies around the Brillouin frequency shift; constructing a differential distribution Brillouin spectrum based on the differential time domain signal; fitting to obtain a fitting spectrum of the differential distribution Brillouin spectrum at each position point, and obtaining the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum as the Brillouin center frequency shift of the position point, and the Brillouin center frequency shift of each position point constitutes the Brillouin center frequency shift curve of the entire optical fiber to be tested; finding the local minimum point of the Brillouin center frequency shift curve, and the local minimum point corresponds one-to-one to the position of the straight pole tower between the two fusion points.

[0038] In this embodiment, optionally, the data acquisition module further includes a laser 1, a coupler 2, a pulse source 14, and a microwave source 15; wherein the output end of the laser 1 is connected to the input end of the coupler 2, and the output end of the coupler 2 is respectively connected to the input end of the pump light modulation submodule and the input end of the detection light modulation submodule; the output end of the pulse source 14 is respectively connected to the modulation end of the first electro-optical modulator 3 in the pump light modulation submodule and the trigger end of the data acquisition card 13; and the output end of the microwave source 15 is connected to the modulation end of the second electro-optical modulator 7 in the detection light modulation submodule.

[0039] In this embodiment, optionally, the pump light modulation submodule includes a first electro-optical modulator 3, a polarization controller 4, an erbium-doped fiber amplifier 5, and a first circulator 6; wherein, the output end of the coupler 2 is connected to the input end of the first electro-optical modulator 3, the output end of the first electro-optical modulator 3 is connected to the input end of the polarization controller 4, the output end of the polarization controller 4 is connected to the input end of the erbium-doped fiber amplifier 5, the output end of the erbium-doped fiber amplifier 5 is connected to port 1 of the first circulator 6, and port 2 of the first circulator 6 is connected to one end of the optical fiber to be tested.

[0040] In this embodiment, optionally, the detection light modulation submodule includes a second electro-optical modulator 7, an adjustable attenuator 8, and an isolator 9; wherein, the output end of the coupler 2 is connected to the input end of the second electro-optical modulator 7, the output end of the second electro-optical modulator 7 is connected to the input end of the adjustable attenuator 8, the output end of the adjustable attenuator 8 is connected to the input end of the isolator 9, and the output end of the isolator 9 is connected to the other end of the optical fiber to be tested.

[0041] In this embodiment, optionally, the data acquisition module further includes a second circulator 10, a fiber Bragg grating filter 11, and a photodetector 12; wherein, port No. 3 of the first circulator 6 is connected to port No. 1 of the second circulator 10, port No. 2 of the second circulator 10 is connected to the fiber Bragg grating filter 11, port No. 3 of the second circulator 10 is connected to the input end of the photodetector 12, and the output end of the photodetector 12 is connected to the data acquisition card 13.

[0042] Another embodiment of the present invention provides a tower positioning method based on a differential pulse pair Brillouin optical time domain analyzer. The method is implemented by the tower positioning system based on the differential pulse pair Brillouin optical time domain analyzer described above. The method includes:

[0043] The pulse source 14 is configured to output two electrical pulses of different widths to the first electro-optical modulator 3, and the first electro-optical modulator 3 is used to modulate the two optical pulses of different widths. The Brillouin time domain signals of the two time traces are collected by the data acquisition module. The data processing module subtracts the Brillouin time domain signals of the two time traces to obtain a differential time domain signal.

[0044] Changing the microwave frequency of the microwave source 15 to change the reference light frequency, thereby obtaining differential time domain signals of multiple frequencies around the Brillouin frequency shift, and constructing a differential Brillouin spectrum based on the differential time domain signals;

[0045] The fitting spectrum of the Brillouin spectrum of the differential distribution at each position point is obtained by fitting, and the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum is obtained as the Brillouin center frequency shift of the position point. The Brillouin center frequency shifts of each position point constitute the Brillouin center frequency shift curve of the entire optical fiber to be tested;

[0046] Find the local minimum point of the Brillouin center frequency shift curve, which corresponds one-to-one to the position of the straight tower between the two welding points.

[0047] In this embodiment, optionally, the process of collecting the Brillouin time domain signal using the data acquisition module includes:

[0048] Laser 1 emits continuous light, which is split into two branches, pump light and probe light, by coupler 2. A first electro-optical modulator 3 with a high extinction ratio modulates the intensity of the pump light in the upper branch into a differential pulse pair via a pulse source 14. A polarization controller 4 converts the single polarization state output by the first electro-optical modulator 3 into two orthogonal polarization states. The polarization controller 4 is synchronized with an electrical pulse signal triggered by a data acquisition card 13. An erbium-doped fiber amplifier 5 amplifies the peak power of the optical pulse output by the polarization controller 4. The amplified optical pulse is then coupled into the optical fiber under test via port 2 of the first circulator.

[0049] The detection light of the lower branch is frequency modulated by the second electro-optical modulator 7 driven by the microwave source 15, and the power is adjusted by the adjustable attenuator 8. It then enters the isolator 9 and is injected into the optical fiber to be tested, where it undergoes stimulated Brillouin scattering with the pump light. The Brillouin scattered signal returned by the optical fiber to be tested is reflected by port 3 of the first circulator 6, and enters the fiber Bragg grating filter 11 through port 2 of the second circulator 10, where the low-frequency sideband is filtered out. The high-frequency sideband enters the photodetector 12 from port 3 of the second circulator 10 and is converted into an electrical signal by the photodetector 12. The data acquisition card 13 collects the electrical signal.

[0050] Another embodiment of the present invention provides a tower positioning system based on a differential pulse pair Brillouin optical time domain analyzer, the system includes a data acquisition module and a data processing module, the data acquisition module uses a DPP-BOTDA device, such as Figure 1 As shown, the data acquisition module includes: a laser 1, a coupler 2, a first electro-optical modulator (EOM1) 3, a polarization controller (PS) 4, an erbium-doped fiber amplifier (EDFA) 5, a first circulator 6, a second electro-optical modulator (EDFA2) 7, a variable attenuator (VOA) 8, an isolator 9, a second circulator 10, a fiber grating filter (FBG) 11, a photodetector (PD) 12, a data acquisition card (DAQ) 13, a pulse source 14, and a microwave source 15; wherein,

[0051] The output end of the laser 1 is connected to the input end of the 50:50 coupler 2, and the output end of the 50:50 coupler 2 is connected to the input end of the first electro-optical modulator 3 and the input end of the second electro-optical modulator 7 respectively;

[0052] The output end of the first electro-optical modulator 3 is connected to the input end of the polarization controller 4, the output end of the polarization controller 4 is connected to the input end of the erbium-doped fiber amplifier 5, the output end of the erbium-doped fiber amplifier 5 is connected to port 1 of the first circulator 6, and port 2 of the first circulator 6 is connected to one end of the optical fiber to be tested;

[0053] The output end of the second electro-optical modulator 7 is connected to the input end of the adjustable attenuator 8, the output end of the adjustable attenuator 8 is connected to the input end of the isolator 9, and the output end of the isolator 9 is connected to the other end of the optical fiber to be tested;

[0054] Port 3 of the first circulator 6 is connected to port 1 of the second circulator 10, port 2 of the second circulator 10 is connected to the fiber grating filter 11, port 3 of the second circulator 10 is connected to the input end of the photodetector 12, and the output end of the photodetector 12 is connected to the data acquisition card 13;

[0055] The output end of the pulse source 14 is connected to the modulation end of the first electro-optical modulator 3 and the trigger end of the data acquisition card 13 respectively;

[0056] The output end of the microwave source 15 is connected to the modulation end of the second electro-optical modulator 7 .

[0057] The optical fiber to be tested is the core inside the optical fiber composite overhead ground wire (OPGW) cable. The OPGW cable is installed on the pole tower at the top of the overhead line. Both ends are fixed on the tension tower. The middle part is hung on the top of the straight tower using a suspension clamp. Usually, OPGW cable is a few kilometers in a coil. Two adjacent sections of cable are fused together at the tension tower, which is defined as a connected pole tower. The middle support is a straight pole tower. The installation diagram between the OPGW cable and the pole tower is shown in the figure below. Figure 2 shown.

[0058] In this embodiment, preferably, the laser 1 uses a 1550 nm narrow linewidth distributed feedback (DFB) laser as a light source, and the peak pulse power is about 12 mW.

[0059] In this embodiment, preferably, the splitting ratio of the coupler 2 is 50:50, and the extinction ratio of the first electro-optical modulator (EOM1) 3 is 40 dB.

[0060] The working principle of the data acquisition module is as follows:

[0061] Laser 1 emits continuous light, which is divided into two branches, pump light and probe light, by a 3dB coupler 2. A first electro-optical modulator 3 with a high extinction ratio is used to modulate the intensity of the upper branch pump light into a differential pulse pair through a pulse source 14. Since a single-mode optical fiber to be tested is used, polarization fading may occur. To solve this problem, a polarization controller 4 is used to convert the single polarization state output by the first electro-optical modulator 3 into two orthogonal polarization states. The polarization controller 4 is synchronized with the electrical pulse signal triggered by the data acquisition card 13. This synchronization ensures that the two sets of signals collected by the data acquisition card 14 are orthogonally polarized and have equal cumulative average values, effectively reducing power fluctuations caused by polarization fading. The peak power of the optical pulse output by the polarization controller 4 is relatively low. To solve this problem, an erbium-doped fiber amplifier 5 is used to increase the peak power of the optical pulse. Subsequently, the amplified optical pulse is coupled into the optical fiber to be tested through port 2 of the first circulator.

[0062] The lower branch detection light changes the frequency of the reference light through the second electro-optical modulator 7 under the drive of the microwave source 15, and tunes to an appropriate frequency around the Brillouin frequency shift. In order to obtain the entire Brillouin spectrum, it is necessary to change the frequency of the local oscillator light multiple times and repeatedly inject pulse light into the optical fiber to be tested for multiple measurements. The power of the frequency-modulated local oscillator light is appropriately adjusted using the adjustable attenuator 8. After entering the isolator 9, it is injected into the optical fiber to be tested to produce stimulated Brillouin scattering effect with the pump light.

[0063] The Brillouin scattered signal is reflected back through port 3 of the first circulator 6, and then enters the fiber grating filter 11 through port 2 of the second circulator, where the low-frequency sideband is filtered out; the high-frequency sideband is output from port 3 of the second circulator 10, and then converted into an electrical signal by the photodetector 12; the data acquisition card 13 collects the electrical signal.

[0064] The data processing module processes the collected signals, including: using two pulses of different widths to capture two time traces of the Brillouin signal, subtracting the Brillouin time-domain signals of the two time traces to obtain a differential time-domain signal, and constructing a differential Brillouin spectrum by repeatedly changing the local oscillator light frequency to obtain differential time-domain signals at multiple frequencies around the Brillouin frequency shift.

[0065] The fitting spectrum of the Brillouin spectrum of each point difference distribution is obtained by fitting, and the frequency shift corresponding to the maximum value of the Brillouin spectrum is obtained as the Brillouin center frequency shift of the point. The center frequency shifts of each position point constitute the Brillouin frequency shift curve of the entire optical fiber;

[0066] Find the local minimum point of the Brillouin frequency shift curve, which corresponds one-to-one with the tower position.

[0067] In this embodiment, preferably, the pulse source 14 uses a pulse pair, such as 20ns and 19.8ns, with a pulse width difference of 0.2ns, so that the spatial resolution of the data acquisition module reaches 20cm. Spatial resolution is the ability of the BOTDA to distinguish two adjacent events, which affects the positioning accuracy and time recognition accuracy. It is usually determined by the detection light pulse width. If the detection light pulse width difference is W, the theoretical spatial resolution SR of the BOTDA is Where c is the speed of light in vacuum, which is c=3×10 8 m / s, n is the core refractive index of single-mode optical fiber, and its value is n=1.46.

[0068] Figure 3 The working principle diagram of differential pulse pair (DPP) is given. Differential pulse pair technology generates two pulse signals with different pulse widths at a certain interval through the pulse source 14, such as Figure 3 As shown in (a) and (b), t1 and t3 are two pulse signals, and the equivalent pulse width is t3-t1. Figure 3 (c) The Brillouin spectrum generated by the t1 pulse is shown as Figure 3 As shown in (d), the Brillouin spectrum generated by the t3 pulse is as follows Figure 3 As shown in (e), the equivalent Brillouin spectrum is Figure 3 As shown in (f), a narrower Brillouin spectrum has a higher spatial resolution. However, if a narrow pulse is directly selected, such as Figure 3As shown in (g), due to the limitation of photon lifetime, the Brillouin spectrum produced is as follows: Figure 3 As shown in (h), the spectrum is severely broadened, affecting the measurement accuracy.

[0069] Figure 4 The maximum sensing distance of the system is 20km. Figure 4 As shown in (a), the strain measurement accuracy is ±20με, as Figure 4 (b) shown.

[0070] The data acquisition module boasts high spatial resolution, a characteristic determined by the difference in pulse width within the differential pulse pair. The DPP-BOTDA (Differential Pulse Pair Brillouin Optical Time Domain Analyzer) technology monitors and analyzes the Brillouin frequency shift in optical cables. The DPP-BOTDA system calculates the Brillouin frequency shift in the optical fiber by analyzing the received Brillouin scattering signal. The magnitude of the Brillouin frequency shift is related to physical quantities such as temperature and strain in the optical fiber. By analyzing and calculating the Brillouin frequency shift, information such as temperature and strain in the optical fiber can be obtained.

[0071] Heat conduction is the process of heat transfer inside a substance. It is the mechanism by which heat is automatically transferred from a high-temperature area to a low-temperature area. Thermal conductivity is a physical quantity that describes the ability of a substance to conduct heat. The rate of heat conduction is closely related to thermal conductivity. Different substances have different thermal conductivities, which leads to differences in the rate of heat conduction. In this embodiment, the main focus is on identifying the suspension points of a straight pole tower between two welding points. In an environment where the temperature changes rapidly, there is a temperature difference between the pole tower suspension point and the span (welding point), resulting in inconsistent changes in the Brillouin frequency shift. The optical cable at the non-suspension point is directly in contact with the air after being covered with ice, while the optical cable at the suspension point is in contact with the suspension clamp. The conduction mode is different. The conduction of the optical cable at the suspension point is slower than that of the suspension clamp, and the temperature is lower than that at the optical cable. There are differences in temperature changes, and the suspension point is determined based on the difference in this change. That is, the fusion point is first determined. The fusion point is determined by the difference in Brillouin frequency shifts of different sections of optical cable, and a step change occurs at the fusion point for identification. At the suspension point, the Brillouin frequency shift of the optical fiber usually has a local minimum. This is because the temperature at this location is lower than that on ordinary optical cables during ice accumulation. Based on these positions, the tower position corresponding to the optical cable suspension point is determined.

[0072] Figure 5 This is a diagram of the tower positioning results in an embodiment of the present invention. Figure 5 The red and black lines in the middle are the Brillouin frequency shift curves of the optical fiber at two different times. The blue dotted line represents the connected towers, 1#, 15#, 19#, 31#, and 41# are the towers where the splicing points are located, and the red dotted line represents the straight towers. 2# to 14#, 16# to 18#, 20# to 30#, and 32# to 40# are straight towers.

[0073] Figure 6 This is a detailed diagram of the tower positioning in the embodiment of the present invention. The purple and green lines are Figure 5 In the detailed picture of the 1#~15# towers, the red circle is the fusion point of the two sections of optical cable. Since the optical cable is fusion-connected at the 1# tower, part of the two sections of optical cable will be left as the down conductor for the optical cable. After fusion, it is coiled and hung on the tower.

[0074] In summary, the DPP-BOTDA system is connected to the optical cable under test to monitor the Brillouin frequency shift of the fiber core in real time. Based on the differences in the basic Brillouin frequency shift of different fiber segments, the splicing point is located and mapped one-to-one with the splicing tower. Rapid temperature fluctuations cause the Brillouin frequency shift in the cable to change accordingly, but the rate of change at the suspension point is different from that at the span. By analyzing the Brillouin frequency shift trend and finding the minimum point, the tower position corresponding to the suspension point can be determined. By establishing a one-to-one correspondence between each minimum point and the corresponding tower position, the fiber length and tower position are accurately matched, improving positioning accuracy and reliability.

[0075] It should be noted that although several units, modules, or submodules are mentioned in the detailed description above, such division is merely exemplary and not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules described above may be embodied in one module. Conversely, the features and functions of one module described above may be further divided and embodied by multiple modules.

[0076] Although the spirit and principles of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the specific embodiments disclosed, and the division into various aspects does not mean that the features of these aspects cannot be combined to benefit. Such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A tower positioning system based on a differential pulse pair Brillouin optical time domain analyzer, characterized in that: It includes data acquisition module and data processing module; among them, The data acquisition module is used to collect the Brillouin time domain signal returned by the optical fiber to be tested, wherein the optical fiber to be tested is the core inside the optical fiber composite overhead ground wire cable, and the optical fiber composite overhead ground wire cable is installed on the tower; The data acquisition module comprises a pump light modulation submodule, a detection light modulation submodule, and a data acquisition card (13); the pump light modulation submodule is used to modulate the pulse width and amplitude of the pump light, and couple the modulated light pulse into the optical fiber to be tested; the detection light modulation submodule is used to frequency modulate the intensity of the detection light, and couple the frequency-modulated reference light from the other end into the optical fiber to be tested; the data acquisition card (13) is used to collect the Brillouin time domain signal returned by the optical fiber to be tested; The data processing module is used to process the collected Brillouin time domain signal to obtain the position of the straight pole tower between the two fusion points; the collected Brillouin time domain signal includes the Brillouin time domain signals of the two time trajectories returned by the optical fiber to be tested; wherein, processing the collected Brillouin time domain signal includes: subtracting the Brillouin time domain signals of the two time trajectories to obtain a differential time domain signal, thereby obtaining differential time domain signals of multiple frequencies around the Brillouin frequency shift; constructing a differential distribution Brillouin spectrum based on the differential time domain signal; fitting to obtain a fitting spectrum of the differential distribution Brillouin spectrum at each position point, and obtaining the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum as the Brillouin center frequency shift of the position point, and the Brillouin center frequency shift of each position point constitutes the Brillouin center frequency shift curve of the entire optical fiber to be tested; finding the local minimum point of the Brillouin center frequency shift curve, and the local minimum point corresponds one-to-one to the position of the straight pole tower between the two fusion points.

2. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 1, characterized in that: The data acquisition module further comprises a laser (1), a coupler (2), a pulse source (14), and a microwave source (15); wherein the output end of the laser (1) is connected to the input end of the coupler (2), and the output end of the coupler (2) is respectively connected to the input end of the pump light modulation submodule and the input end of the detection light modulation submodule; the output end of the pulse source (14) is respectively connected to the modulation end of the first electro-optical modulator (3) in the pump light modulation submodule and the trigger end of the data acquisition card (13); and the output end of the microwave source (15) is connected to the modulation end of the second electro-optical modulator (7) in the detection light modulation submodule.

3. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 2, characterized in that: The pump light modulation submodule comprises a first electro-optical modulator (3), a polarization controller (4), an erbium-doped fiber amplifier (5), and a first circulator (6); wherein the output end of the coupler (2) is connected to the input end of the first electro-optical modulator (3), the output end of the first electro-optical modulator (3) is connected to the input end of the polarization controller (4), the output end of the polarization controller (4) is connected to the input end of the erbium-doped fiber amplifier (5), the output end of the erbium-doped fiber amplifier (5) is connected to port No. 1 of the first circulator (6), and port No. 2 of the first circulator (6) is connected to one end of the optical fiber to be tested.

4. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 3, characterized in that: The detection light modulation submodule comprises a second electro-optical modulator (7), an adjustable attenuator (8), and an isolator (9); wherein the output end of the coupler (2) is connected to the input end of the second electro-optical modulator (7), the output end of the second electro-optical modulator (7) is communicated with the input end of the adjustable attenuator (8), the output end of the adjustable attenuator (8) is communicated with the input end of the isolator (9), and the output end of the isolator (9) is connected to the other end of the optical fiber to be tested.

5. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 4, characterized in that: The data acquisition module further comprises a second circulator (10), a fiber Bragg grating filter (11), and a photodetector (12); wherein port No. 3 of the first circulator (6) is connected to port No. 1 of the second circulator (10), port No. 2 of the second circulator (10) is connected to the fiber Bragg grating filter (11), port No. 3 of the second circulator (10) is connected to the input end of the photodetector (12), and the output end of the photodetector (12) is connected to the data acquisition card (13).

6. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 2, characterized in that: The laser (1) uses a narrow linewidth distributed feedback laser as a light source.

7. The tower positioning system based on differential pulse pair Brillouin optical time domain analyzer according to claim 2, characterized in that: The splitting ratio of the coupler (2) is 50:50; the extinction ratio of the first electro-optical modulator (3) is 40 dB.

8. A tower positioning method based on a differential pulse pair Brillouin optical time domain analyzer, characterized in that: The method is implemented by the tower positioning system according to any one of claims 1 to 7; the method comprises: The pulse source (14) is caused to output two electric pulses of different widths to the first electro-optical modulator (3), and the first electro-optical modulator (3) is used to modulate and obtain two optical pulses of different widths. The Brillouin time domain signals of the two time trajectories are collected by a data acquisition module; the data processing module performs a difference operation on the Brillouin time domain signals of the two time trajectories to obtain a differential time domain signal. Changing the microwave frequency of the microwave source (15) to obtain differential time domain signals of multiple frequencies around the Brillouin frequency shift, and constructing a differential Brillouin spectrum based on the differential time domain signals; The fitting spectrum of the Brillouin spectrum of the differential distribution at each position point is obtained by fitting, and the frequency shift corresponding to the maximum value of the Brillouin fitting spectrum is obtained as the Brillouin center frequency shift of the position point. The Brillouin center frequency shifts of each position point constitute the Brillouin center frequency shift curve of the entire optical fiber to be tested; Find the local minimum point of the Brillouin center frequency shift curve, which corresponds one-to-one to the position of the straight tower between the two welding points.

9. The tower positioning method based on differential pulse pair Brillouin optical time domain analyzer according to claim 8, characterized in that: The process of using the data acquisition module to collect the Brillouin time domain signal returned by the optical fiber under test includes: A laser (1) emits continuous light, which is divided into two branches, namely, pump light and detection light, by a coupler (2); a first electro-optical modulator (3) with a high extinction ratio is used to modulate the pump light of the upper branch into a differential pulse pair via a pulse source (14); a polarization controller (4) is used to convert the single polarization state output by the first electro-optical modulator (3) into two orthogonal polarization states, wherein the polarization controller (4) is synchronized with an electrical pulse signal triggered by a data acquisition card (13); an erbium-doped fiber amplifier (5) is used to amplify the peak power of the optical pulse output by the polarization controller (4); and then, the amplified optical pulse is coupled to the optical fiber to be tested via port 2 of the first circulator; The detection light of the lower branch is frequency modulated by the second electro-optical modulator (7) driven by the microwave source (15), and the power is adjusted by the adjustable attenuator (8). Then, the detection light enters the isolator (9) and is injected into the optical fiber to be tested, where it undergoes stimulated Brillouin scattering effect with the pump light. The Brillouin scattering signal returned by the optical fiber to be tested is reflected by port No. 3 of the first circulator (6), enters the fiber grating filter (11) through port No. 2 of the second circulator (10), and the low-frequency sideband is filtered out; the high-frequency sideband enters the photodetector (12) from port No. 3 of the second circulator (10), and is converted into an electrical signal by the photodetector (12); and the data acquisition card (13) collects the electrical signal.

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