A distributed optical fiber monitoring and early warning system for measuring damage to buried pipelines

Abstract

The application discloses a kind of distributed optical fiber monitoring and early warning systems for measuring buried pipeline damage, and relates to pipeline detection technical field.The distributed optical fiber detection module and monitoring and early warning module are included, the distributed optical fiber detection module includes, laser, first polarization maintaining coupler, first photoelectric modulator, erbium-doped fiber amplifier, polarization scrambler, first coupler, circulator, second polarization maintaining coupler, second photoelectric modulator, acoustooptic modulator, second coupler and sensing optical fiber;Detection and early warning module includes, photoelectric detector, first filter, second filter, central processing unit and display early warning terminal.The application obtains two different scattering signals by using first filter and second filter, detects the damage condition of buried pipeline by two detection methods, improves the detection accuracy of distributed optical fiber detection module, and can display the detection state by display early warning terminal and timely warning.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pipeline detection, and more particularly to a distributed optical fiber monitoring and early warning system for measuring damage of buried pipeline. BACKGROUND

[0002] Pipeline leakage accidents caused by construction, human damage and other reasons around the pipeline occur frequently, which not only causes economic losses to enterprises, but also causes great harm to personal safety and the natural environment.

[0003] At present, the technology and method applied to pipeline engineering monitoring at home and abroad is mainly the traditional electric measuring sensor, and the length of the pipeline is generally several kilometers or more. Thus, thousands of sensors from the point of laying to data acquisition are not only complex but also high in cost. In addition, due to the limitation of the number of points, the structure and function of the pipeline cannot be fully reflected. In recent years, optical fiber sensors have the characteristics of anti-electromagnetic interference, waterproof, corrosion resistance and long durability, and in particular, distributed sensing optical fiber has a good application prospect in pipeline engineering monitoring due to its unique advantages.

[0004] However, due to the changeable environment of pipeline laying, on the one hand, the existing distributed optical fiber sensor has the problem of single monitoring means when detecting the buried pipeline, and cannot accurately monitor the damage state of the buried pipeline, and on the other hand, the existing detection system cannot provide timely and effective early warning function after detecting the damage state.

[0005] Therefore, how to improve the detection accuracy of the distributed optical fiber sensor and provide timely early warning for the monitored damage state of the buried pipeline is a problem to be solved by those skilled in the art. SUMMARY

[0006] Therefore, the present application provides a distributed optical fiber monitoring and early warning system for measuring damage of buried pipeline, which solves the problems of low detection accuracy of the existing distributed optical fiber sensor and lack of timely and effective early warning means after detecting the damage state.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] A distributed optical fiber monitoring and early warning system for measuring damage of buried pipeline, comprising:

[0009] a distributed optical fiber detection module and a monitoring and early warning module;

[0010] The distributed optical fiber detection module comprises a laser, a first polarization maintaining coupler, a first optoelectronic modulator, an erbium-doped fiber amplifier, a polarization scrambler, a first coupler, a circulator, a second polarization maintaining coupler, a second optoelectronic modulator, an acousto-optic modulator, a second coupler and a sensing optical fiber.

[0011] The light source output by the laser is divided into two paths by a first polarization maintaining coupler, one path of the light source sequentially passes through a first optoelectronic modulator, an erbium-doped fiber amplifier and a depolarizer,

[0012] The other path of the light source is again divided into two continuous light paths by a second polarization maintaining coupler, one path of the continuous light passes through a second optoelectronic modulator and is connected to the input end of the first coupler together with the output light signal of the depolarizer, the output end of the first coupler is connected to a circulator, and the circulator is simultaneously connected to the sensing optical fiber and the second coupler;

[0013] The other path of the continuous light is connected to the second coupler after being modulated by an acousto-optic modulator;

[0014] The detection and early warning module comprises an optoelectronic detector, a first filter, a second filter, a central processing unit and a display terminal.

[0015] The input end of the optoelectronic detector is connected to the second coupler of the distributed optical fiber detection module, the output end of the optoelectronic detector is connected to the input end of the first filter and the second filter respectively, the output end of the first filter and the second filter is connected to the input end of the central processing unit, and the central processing unit is connected to the display terminal.

[0016] Preferably, the system further comprises a pulse generator connected to the first optoelectronic modulator, and the pulse generator is used to provide a pulse signal for the first optoelectronic modulator.

[0017] Preferably, the system further comprises a microwave generator connected to the second optoelectronic modulator, and the microwave generator is used to provide a microwave frequency signal for the second optoelectronic modulator.

[0018] Preferably, the splitting ratio of the first polarization maintaining coupler is set to 50:50.

[0019] Preferably, the sensing optical fiber is spirally wound and laid on the surface of the buried pipeline.

[0020] Preferably, in the detection and early warning module, the optoelectronic detector is used to perform heterodyne coherent detection to generate an optical heterodyne electrical signal, the first filter is used to receive the optical heterodyne electrical signal and perform filtering processing to obtain a Rayleigh scattering signal, and the second filter is used to receive the optical heterodyne electrical signal and perform filtering processing to obtain a Brillouin scattering signal.

[0021] Preferably, in the detection and early warning module, the central processing unit processes the input Rayleigh scattering signal and / or Brillouin scattering signal by the following steps:

[0022] The short-time average energy and the short-time zero-crossing rate of the input signal within a certain sampling period are calculated, and the input signal includes the Rayleigh scattering signal and / or the Brillouin scattering signal.

[0023] If the short-time average energy and the short-time zero-crossing rate are both greater than the respective set threshold values, an early warning signal is output.

[0024] Preferably, the display early warning terminal is connected to the central processor through a wireless transmission module.

[0025] Preferably, the early warning terminal comprises a smart phone and / or a tablet computer.

[0026] Compared with the prior art, the distributed optical fiber monitoring early warning system for measuring damage of a buried pipeline provided by the present application has the following beneficial effects:

[0027] The present application can obtain two different scattering signals by using the first filter and the second filter, thereby enabling detection of damage of the buried pipeline by using the two different scattering signals, solving the problem of inaccurate monitoring precision when a single scattering signal is used to detect the buried pipeline, and enabling display of the detection state by the display early warning terminal and timely early warning.

[0028] The present application simultaneously calculates the short-time average energy and the short-time zero-crossing rate of the input scattering signal when detecting and early warning the input scattering signal, and only outputs an early warning signal if the short-time average energy and the short-time zero-crossing rate are both greater than the respective set threshold values, thereby reducing false positives of early warning.

[0029] In the technical solution of the present application, the display early warning terminal is connected to the central processor through a wireless transmission module, thereby enabling detection of the damage condition of the buried pipeline at any time and place and timely acquisition of early warning information. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0031] Figure 1 The accompanying drawings are schematic diagrams of the overall structure of the system provided by the embodiments of the present application.

[0032] Figure 2 The accompanying drawings are schematic diagrams of the sensing optical fiber laying manner provided by the embodiments of the present application. DETAILED DESCRIPTION

[0033] With reference to the drawings of the embodiments of the present application, the technical solutions in the embodiments of the present application will be described clearly and completely. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0034] The embodiments of the present application disclose a distributed optical fiber monitoring and early warning system for measuring damage of buried pipeline, as shown in Figure 1 The distributed optical fiber detection module 1 and the monitoring and early warning module 2 are shown.

[0035] The distributed optical fiber detection module 1 comprises a laser, a first polarization maintaining coupler, a first photoelectric modulator, an erbium-doped fiber amplifier, a polarization scrambler, a first coupler, a circulator, a second polarization maintaining coupler, a second photoelectric modulator, an acousto-optic modulator, a second coupler and a sensing optical fiber.

[0036] The light source output by the laser is divided into two paths through the first polarization maintaining coupler, one path of the light source sequentially passes through the first photoelectric modulator, the erbium-doped fiber amplifier and the polarization scrambler,

[0037] The other path of the light source is again divided into two continuous light paths through the second polarization maintaining coupler, one continuous light path is connected to the input end of the first coupler together with the output light signal of the polarization scrambler after passing through the second photoelectric modulator, the output end of the first coupler is connected with the circulator, and the circulator is connected with the sensing optical fiber and the second coupler at the same time.

[0038] The other continuous light path is connected to the second coupler after being modulated by the acousto-optic modulator.

[0039] The monitoring and early warning module 2 comprises a photoelectric detector, a first filter, a second filter, a central processing unit and a display early warning terminal.

[0040] The input end of the photoelectric detector is connected with the second coupler of the distributed optical fiber detection module, the output end of the photoelectric detector is connected with the input end of the first filter and the second filter respectively, the output end of the first filter and the second filter is connected with the input end of the central processing unit, and the output end of the central processing unit is connected with the display early warning terminal.

[0041] In the embodiment, the laser in the distributed optical fiber detection module can use a narrow linewidth laser with a linewidth of 100 kHz and an output power of 16 dBm. The narrow linewidth laser is used as the light source of the distributed optical fiber detection module. First, the light source is split through a first polarization maintaining coupler with a splitting ratio of 50:50. The split upper light source is modulated into pulsed light signals by a first optoelectronic modulator, and then the pulsed light signals are power amplified by an erbium-doped fiber amplifier. The power amplified pulsed light signals are subjected to polarization state disturbance processing by a depolarizer. The subsequent pulsed light signals pass through the first coupler and the circulator and are injected into the sensing optical fiber.

[0042] The lower light source split by the first polarization maintaining coupler is split into two continuous lights by the second polarization maintaining coupler. One of the continuous lights is modulated and frequency shifted by an acousto-optic modulator to serve as the local oscillator light for coherent detection. The other continuous light is modulated by a second optoelectronic modulator to detect the sidebands (including Stokes and anti-Stokes sidebands). The detection sidebands and the pulsed light signals subjected to the depolarizer are injected into the sensing optical fiber through the first coupler and the circulator. The detection sidebands are reflected in the sensing optical fiber and interact with the pulsed light signals in the range of the Brillouin gain spectrum to produce stimulated Brillouin effect.

[0043] The detection sidebands mixed with the pulsed light signals pass through the circulator and are injected into the second coupler to mix with the local oscillator light for coherent detection. The mixed light enters the photodetector in the detection and warning module 2 for heterodyne coherent detection to obtain the optical heterodyne electrical signal.

[0044] In the embodiment, the first optoelectronic modulator is connected to a pulse generator, which provides the pulsed signal for the first optoelectronic modulator. The second optoelectronic modulator is connected to a microwave generator, which provides the microwave frequency signal for the second optoelectronic modulator. The microwave frequency signal modulation frequency f is set near the fiber Brillouin frequency shift.

[0045] In the detection and warning module 2, the first filter receives the optical heterodyne electrical signal and performs filtering to obtain the Rayleigh scattering signal. The second filter receives the optical heterodyne electrical signal and performs filtering to obtain the Brillouin scattering signal. The central processing unit receives the Rayleigh scattering signal input by the first filter and demodulates it to obtain the attenuation and vibration information of the sensing optical fiber along the line. The central processing unit receives the Brillouin scattering signal input by the second filter and demodulates it to obtain the temperature and strain information of the sensing optical fiber. The detected sensing optical fiber detection information is transmitted to the display and warning terminal for display. When the detection information exceeds the set threshold, corresponding warning information is generated to realize the detection of the damage condition of the buried pipeline.

[0046] As a preferred embodiment, as shown in Figure 2 the sensing optical fiber 3 is wound in a spiral manner on the surface of the buried pipeline 4.

[0047] In order to prevent false alarm caused by instantaneous vibration, in a preferred embodiment, the central processor calculates and processes the input Rayleigh scattering signal and / or Brillouin scattering signal by using short-time average energy and short-time zero-crossing rate, and only if both the short-time average energy and the short-time zero-crossing rate are greater than the respective set threshold, an early warning signal is output, thereby reducing the false alarm rate of the system.

[0048] The input Rayleigh scattering signal and / or Brillouin scattering signal is processed by the following steps:

[0049] The short-time average energy and the short-time zero-crossing rate of the input signal in a certain sampling period are calculated, the input signal including the Rayleigh scattering signal and / or the Brillouin scattering signal;

[0050] If both the short-time average energy and the short-time zero-crossing rate are greater than the respective set threshold, an early warning signal is output.

[0051] The calculation process of the short-time average energy and the short-time zero-crossing rate is described below.

[0052] The short-time energy Em refers to the total energy of the sampled signal in a short-time signal frame, and the calculation formula is:

[0053]

[0054] In the formula, m is the mth frame number after the signal x(n) is framed, n is the nth sampling point of the signal x(n) and takes a positive integer, L is the frame length after the signal x(n) is framed, and w(n) is a window function, the window length and the frame length being the same, both being L.

[0055] According to the above formula, the variation law of the energy or amplitude of the signal with time can be reflected by the short-time energy, and the selection of the window function directly determines the quality of the short-time energy. If the window length is too long and the smoothing effect is obvious, the short-time energy curve changes slowly with time and cannot reflect the variation characteristics of the signal; on the contrary, if the window length is too short, the short-time energy changes sharply with time and a smooth energy function cannot be obtained, which will introduce a large amount of disturbance. In order to characterize the signal characteristics, a suitable window length is selected, and the short-time average energy is used:

[0056]

[0057] In the formula, M is the total frame number, which is determined by the signal detection time length of the pipeline optical fiber

[0058] The short-time zero-crossing rate refers to the number of times that the sampled signal value changes from negative to positive or from positive to negative, i.e. the number of times of crossing the horizontal axis, in a short-time frame. The short-time zero-crossing rate simply reflects the average frequency of the time-varying signal in a short time, and the calculation formula is:

[0059] Zn = | sgn [x(n)] - sgn [x(n-1)] | w(n)

[0060] wherein:

[0061]

[0062] wherein: sgn [x(n)] is the sign function of signal x(n); Z n is the zero-crossing rate.

[0063] As a preferred embodiment, the display and warning terminal is connected with the central processor through a wireless transmission module, so as to realize remote display and warning function, and enable the maintenance personnel to check the pipeline information detected by the distributed optical fiber detection module at any time and randomly, and to timely warn the pipeline damage information.

[0064] Specifically, the wireless transmission module can adopt a 4G / 5G communication module, and the display and warning terminal can be an intelligent mobile phone or a tablet computer, which is convenient for the maintenance personnel to use.

[0065] The embodiments in the specification are described in a progressive manner, and each embodiment focuses on the difference from other embodiments. The same or similar parts of each embodiment can be referred to each other. For the device disclosed by the embodiments, since it corresponds to the method disclosed by the embodiments, the description is relatively simple, and the related parts can be referred to the method part.

[0066] The above description of the disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to the embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A distributed optical fiber monitoring and warning system for measuring damage to a buried pipeline, characterized in that, The application relates to a distributed optical fiber detection module and a monitoring and early warning module. The distributed optical fiber detection module comprises a laser, a first polarization maintaining coupler, a first photoelectric modulator, an erbium-doped fiber amplifier, a polarization scrambler, a first coupler, a circulator, a second polarization maintaining coupler, a second photoelectric modulator, an acousto-optic modulator, a second coupler and a sensing optical fiber. The light source output by the laser is divided into two paths through the first polarization maintaining coupler, one path of the light source sequentially passes through the first photoelectric modulator, the erbium-doped fiber amplifier and the polarization scrambler, the other path of the light source is again divided into two continuous light paths through the second polarization maintaining coupler, one continuous light path is connected to the input end of the first coupler together with the output light signal of the polarization scrambler after passing through the second photoelectric modulator, the output end of the first coupler is connected with the circulator, and the circulator is simultaneously connected with the sensing optical fiber and the second coupler; the other continuous light path is connected to the second coupler after being modulated by the acousto-optic modulator; The monitoring and early warning module comprises a photoelectric detector, a first filter, a second filter, a central processing unit and a display early warning terminal. The input end of the photoelectric detector is connected with the second coupler of the distributed optical fiber detection module, the output end of the photoelectric detector is connected with the input end of the first filter and the second filter respectively, the output end of the first filter and the second filter is connected with the input end of the central processing unit, and the central processing unit is connected with the display early warning terminal. The sensing optical fiber is spirally wound and laid on the surface of the buried pipeline. The photoelectric detector is used for heterodyne coherent detection to generate an optical heterodyne electric signal, the first filter is used for receiving the optical heterodyne electric signal and performing filtering processing to obtain a Rayleigh scattering signal, and the second filter is used for receiving the optical heterodyne electric signal and performing filtering processing to obtain a Brillouin scattering signal. The central processing unit processes the input Rayleigh scattering signal and / or Brillouin scattering signal through the following steps: calculating the short-time average energy and the short-time zero-crossing rate of the input signal in a certain sampling period, wherein the input signal comprises the Rayleigh scattering signal and / or the Brillouin scattering signal; if the short-time average energy and the short-time zero-crossing rate are both greater than the set threshold values, an early warning signal is output. Further comprising a pulse generator connected with the first photoelectric modulator, wherein the pulse generator is used for providing a pulse signal for the first photoelectric modulator.

2. The distributed fiber optic monitoring warning system for measuring damage to a buried pipeline according to claim 1, wherein, Further comprising a microwave generator connected with the second photoelectric modulator, wherein the microwave generator is used for providing a microwave frequency signal for the second photoelectric modulator.

3. The distributed fiber optic monitoring warning system for measuring damage to a buried pipeline according to claim 2, wherein, The light splitting ratio of the first polarization maintaining coupler is set as 50:

50.

4. The distributed fiber optic monitoring warning system for measuring damage to buried pipelines of claim 1, wherein, The display early warning terminal is connected with the central processing unit through a wireless transmission module.

5. The distributed fiber optic monitoring warning system for measuring damage to buried pipelines of claim 1, wherein, The display early warning terminal comprises a smart phone and / or a tablet computer.

6. The distributed fiber optic monitoring warning system for measuring damage to a buried pipeline according to claim 5, wherein, ​

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