阅读说明：本技术 一种基于分布式光纤传感的多路光电复合缆区分方法 (Distributed optical fiber sensing-based multi-path photoelectric composite cable distinguishing method ) 是由 张益昕 宋金玉 熊菲 张旭苹 佟帅 张驰 王峰 于 2020-12-18 设计创作，主要内容包括：本发明公开了一种基于分布式光纤传感的多路光电复合缆区分方法,实现该方法的系统包括：特殊设计的光纤传感装置、简易振动器等。本发明使用特殊设计的光纤传感装置探测简易振动器所施加在线缆上的特定频率的振动信号,利用线缆本身内部具有的光纤作为传感载体,并使用通过处理探测信号得到的频谱分布图作为判断依据,最终达到快速区分不同线缆的目的。解决了长距离和复杂铺设环境下的多路光电复合缆铺设的辅助区分问题,从而帮助线缆铺设工人高效地完成施工作业。(The invention discloses a distributed optical fiber sensing-based multi-path photoelectric composite cable distinguishing method, and a system for realizing the method comprises the following steps: specially designed optical fiber sensing device, simple vibrator, etc. The invention uses a specially designed optical fiber sensing device to detect the vibration signal with specific frequency applied on the cable by the simple vibrator, uses the optical fiber in the cable as a sensing carrier, and uses the frequency spectrum distribution graph obtained by processing the detection signal as a judgment basis, thereby finally achieving the purpose of quickly distinguishing different cables. The problem of supplementary differentiation that multichannel photoelectricity composite cable laid under long distance and the complicated environment of laying is solved to help cable laying workman accomplish the construction operation high-efficiently.)

1. A multi-path photoelectric composite cable distinguishing method based on distributed optical fiber sensing is characterized by comprising the following steps:

step 1, fixing a vibrator on one end of a selected cable to be distinguished;

2, leading out an internal optical fiber at the other end of the cable, and connecting the internal optical fiber to a circulator;

step 3, setting a vibrator and a circulator to synchronously start vibration and receive signals, and injecting laser signals into the cable at the front end of the circulator; the generated Rayleigh backscattering signals are received and detected by the photoelectric detector through the circulator, collected by the data acquisition card and then sent to the PC end;

step 4, demodulating the phase of the received backward Rayleigh scattering signal at the PC end, then obtaining a spectrogram through short-time Fourier transform, and judging whether the frequency point of a resonance peak on the spectrogram is the same as the applied vibration frequency;

step 5, if the two cables are different, fixing a vibrator on the other cable, applying vibration, and repeating the steps 3-4 until the frequency point of a resonance peak on a spectrogram measured by the current measured cable is the same as the applied vibration frequency, namely distinguishing one cable from the cable cluster to be distinguished;

and 6, connecting the circulator to a new cable to be distinguished, fixing the vibrator at one end of the other cables except the distinguished cable, and distinguishing all the cables according to the steps in sequence.

2. The method for distinguishing the multi-path photoelectric composite cable based on the distributed optical fiber sensing as claimed in claim 1, wherein the vibration frequency of the vibrator is different from the natural vibration frequency of the cable.

3. The method for distinguishing the multichannel photoelectric composite cable based on the distributed optical fiber sensing according to claim 1 or 2, wherein the vibration signal of the vibrator vibrates NUM times at intervals within a period of time, and a resonance peak at a frequency point corresponding to the vibration frequency on a spectrogram at least correspondingly appears NUM/2 times, so that the cable where the vibrator and the circulator are located is considered to be the same cable.

4. A multi-path photoelectric composite cable distinguishing method based on distributed optical fiber sensing is characterized by comprising the following steps:

(1) marking the N cables to be distinguished from 1 to N;

(2) grouping the N cables, wherein M cables in each group are bundled into a bundle;

(3) fixing a vibrator on one end of one grouped cable bundle, leading out the other end of one of the N cables to be distinguished to be an internal optical fiber and connecting the other end of the one of the N cables to be distinguished to a circulator;

(4) applying corresponding vibration to the whole cable bundle by using a vibrator, setting the vibrator and the optical fiber sensing device to start vibration and detection synchronously, and injecting a laser signal into the cable at the front end of the circulator; the generated Rayleigh backscattering signal is received and detected by a photoelectric detector through a circulator, the Rayleigh backscattering signal is collected through a data acquisition card and then is sent to a PC end, after the phase of the received backscattering signal is demodulated at the PC end, a frequency spectrogram is obtained through short-time Fourier transform, whether the frequency point of a resonance peak on the frequency spectrogram is the same as the applied vibration frequency is judged, if not, a vibrator is fixed on the next grouped cable bundle, the next grouped cable bundle is continuously detected, and the step (4) is repeated; if the cables are the same, grouping the M cables, fixing the vibrator on one grouped cable bundle, and repeating the step (4) until the same cable is detected;

(5) and (3) connecting the circulator to a new cable to be distinguished, fixing the vibrator on one end of one grouped cable bundle, and repeating the steps for the rest N-1 cables to be distinguished until all the cables are distinguished.

Technical Field

The invention relates to the field of distributed optical fiber sensing, and provides a method for distinguishing a multi-path photoelectric composite cable based on distributed optical fiber sensing.

Background

Laying cables is a basic engineering project for constructing power and communication networks in modern society, and the laying cables not only comprise cables for transmitting power, but also comprise optical-electrical composite cables such as OPGW (optical fiber composite overhead ground wire), OPLC (optical fiber composite low-voltage cable) and the like, or ADDS (all-dielectric self-supporting optical cable), wherein optical units are used for tasks of power grid internal communication and data acquisition.

In actual cable laying construction, whether the laying modes are direct-buried, overhead, pipeline, underwater and the like, the distinguishing problem of the multi-path photoelectric composite cable is often encountered. When a plurality of cables are mixed together, especially the external visual expressions such as the thickness, the color and the package of the cables are relatively close, and the distance between two ends of each cable is long, the cables are difficult to distinguish through simple visual observation. The inability to accurately distinguish these hybrid cables can be a nuisance to the connection and laying of the lines, a practical problem often encountered by field laying workers. The existing solutions mostly depend on the field treatment experience of construction workers. For example, the arrangement of the cables is drawn in advance by a table or a figure to prevent the cables from crossing and being disordered; or the stretching degree of the cable is observed by applying mechanical external force to different cables during laying, so that different cables are distinguished. However, when the cable laying length is too long, the number of cables is too large, or the line is too complex, the manual processing mode becomes inefficient or even infeasible, and if a reasonable distinguishing method is not provided, the construction progress is greatly influenced.

Sound is a very important information carrier, which is essentially a vibration wave, with two important features: intensity and frequency. When a vibration event occurs, the vibration wave emitted by the vibration event is transmitted through a sound field and influences the properties of the sensing optical fiber. The distributed optical fiber sensing technology senses the intensity and frequency of a sound field through the change of the optical fiber property, and then monitors the vibration event. The optical fiber is used as a transmission medium and a sensing medium simultaneously, vibration information along the whole optical fiber can be obtained by one-time measurement, and continuous monitoring of thousands of meters or even dozens of kilometers in a long distance can be realized. The cable laying device has the advantages of electromagnetic interference resistance, corrosion resistance, light weight, small size and the like, and is suitable for auxiliary distinguishing of cable laying in ultra-long distance and complex laying terrain.

Disclosure of Invention

The purpose of the invention is as follows: aiming at the problems, the invention discloses a multichannel photoelectric composite cable distinguishing technology based on distributed optical fiber sensing. The internal optical fiber of utilizing cable itself to have is as the sensing carrier, through the vibration signal that surveys and apply, distinguishes different cables fast, and then helps cable laying workman to accomplish the construction operation high-efficiently.

In order to achieve the purpose, the invention provides the following technical scheme:

the simple low-power-consumption vibrator is fixed at one end of the cable, a vibration signal with a certain frequency can be applied to the cable, and meanwhile, an internal optical fiber interface is led out from the other end of the cable and connected with an optical fiber sensing device to detect the vibration signal. The specially designed optical fiber sensing device has an internal structure as shown in fig. 1, a narrow line width laser (NLL) directly injects continuous light into a cable to be detected, and a generated Rayleigh Backscattering Signal (RBS) is received and detected by a Photodetector (PD) through a circulator and received by a master control system (PC) through a data acquisition card (DAQ). The RBS signal is phase demodulated and then a spectral profile is obtained using a Short Time Fourier Transform (STFT). The simple vibrator and the optical fiber sensing device are matched for use, and the simple vibrator and the optical fiber sensing device work simultaneously. If the vibration signal with a specific frequency applied by the simple vibrator can be observed in the frequency spectrum distribution diagram obtained by the final processing, the two vibration signals are connected to the same cable, and the purpose of distinguishing different cables can be finally achieved by sequentially detecting the vibration signals. Compared with the traditional distributed optical fiber sensing device, the device does not need to use an acousto-optic modulator (AOM) to convert continuous light into pulse light and does not need to use an optical amplifier (such as an EDFA). The device can obtain a vibration sensing signal with enough strength without using an optical amplifier by detecting an interference superposition signal of Rayleigh backscattering of the whole cable length. The method comprises the following specific steps:

step 1, selecting a proper position, and fixing a simple vibrator on one end of a selected cable to be distinguished;

2, leading out an internal optical fiber at the other end of the cable, and connecting the internal optical fiber to an optical fiber sensing device;

step 3, setting a vibrator and an optical fiber sensing device to synchronously start vibration and detection;

and 4, demodulating the phase of the received backward Rayleigh scattering (RBS) signal at the PC end, then obtaining a spectrogram through short-time Fourier transform (STFT), and judging whether the frequency point of a resonance peak on the spectrogram is the same as the applied vibration frequency.

If the spectral characteristics are not obvious or obvious interference exists, the vibration frequency of the vibrator can be changed, and then the measured spectrogram is contrasted and observed. By selecting proper vibration frequency, a spectrogram with obvious and clear characteristics can be obtained, so that the judgment of whether the optical fiber sensing device and the simple oscillator are connected to the same cable or not is facilitated, and the judgment difficulty and the misjudgment rate are reduced.

And 5, if a resonance peak corresponding to the applied vibration cannot be observed in the spectrogram measured by the optical fiber sensing device, fixing the vibrator to the other cable, applying the vibration, and repeating the steps 3-4 until the spectrogram measured by the current cable is matched with the applied vibration frequency, namely distinguishing one cable from the cable cluster to be distinguished.

And 6, connecting the optical fiber sensing device to a new cable to be distinguished, and distinguishing all the cables according to the steps in sequence.

The invention relates to a further optimization scheme of a multi-path photoelectric composite cable distinguishing technology based on an optical fiber sensing device, which comprises the following steps: before the vibrator applies vibration on the cable, the natural frequency and the environmental noise of the cable are measured by using the optical fiber sensing device, and then when the vibration frequency of the vibrator is adjusted, the natural frequency and the environmental interference frequency band of the cable are actively adjusted to avoid influencing the judgment of the vibration signal to be detected.

The invention relates to a further optimization scheme of a multi-path photoelectric composite cable distinguishing technology based on an optical fiber sensing device, which comprises the following steps: the fibre sensing system collects the RBS signal for at least more than 10s to ensure that sufficient data points are obtained. And judging whether the frequency point of the resonance peak on the spectrogram is the same as the applied vibration frequency or not on the spectrogram obtained through STFT, wherein the amplitude of the vibration signal is adjustable. For example, if the amplitude of the vibration signal is turned on for 1s and turned off for 1s, in an observation period of 10s, if 1s is taken as a window, the upper limit of the switching at the corresponding frequency point is 10 times. If more than 5 switches are captured, the cable is considered to correspond.

Because the operation of leading out optical fibers from the inside of most types of cables is complex, the optical fiber interface is not easy to frequently replace in the field construction environment. Therefore, the more practical operation is to fix the interface of the optical fiber and the optical fiber sensing device inside the cable, change the vibrator at the other end, apply the vibrator on different cables, and finally judge and distinguish different cables according to different obtained spectrum distribution diagrams. Because the cables actually selected for measurement have randomness, according to the retrieval principle, if all the cables are to be distinguished, if there are N cables to be distinguished, the maximum measurement frequency for distinguishing the first cable is N-1, the maximum measurement frequency for distinguishing the second cable is N-2, and so on, until the last two remaining cables need to be measured for 1 time, therefore, the theoretically maximum measurement frequency is:

when the number of wires to be discriminated is excessive, discriminating all the wires may require measuring a considerable number of times, and it is troublesome to fix and remove the vibrator to and from the wires. In order to simplify the operation flow, all cables can be distinguished by using the least possible measuring times and procedures, and a plurality of cables can be bundled together to apply vibration or a plurality of oscillators can be used in the actual operation, so that the retrieval range can be quickly reduced in the initial measurement, and the distinguishing efficiency is improved. The grouping bundling method specifically comprises the following steps:

1. all cables, for example N cables to be distinguished, are numbered before the measurement, and the cables can be numbered from 1 to N.

2. The N cables are evenly divided into a plurality of groups, and the M cables in each group are bundled into a bundle which can be simply fixed by using a binding belt. The specific number of M is required to be adjusted according to the actual thickness of the cable, and the diameter of the whole bundle cannot exceed the maximum extension diameter of the inner wall of the vibrator.

3. And applying corresponding vibration to the whole bundle of cables by using a vibrator, and observing whether a resonance peak of corresponding vibration frequency appears in the obtained spectrogram. If the detection is not possible, the next cable is continuously detected, and if the detection is possible, the initial search range is changed from N to M, and then the M cables are distinguished. Thus, the maximum number of measurements to theoretically distinguish the first cable is:

4. if the value of M after one-time grouping is overlarge, the M cables can be continuously grouped according to the actual situation, the maximum measurement times are continuously reduced, but the value of M after grouping is at least 2, otherwise, the measurement method of grouping into bundles loses significance. In addition, a plurality of vibrators can be applied to different cables, the vibration frequency is adjusted to be the same, the same effect can be achieved by a grouping method, and the method is suitable for the case that the cables are particularly thick, but the required cost is increased correspondingly.

5. And repeating the steps for the remaining N-1 cables to be distinguished until all the cables are distinguished. In the process, the situation that the number of the remaining cables to be distinguished cannot be evenly divided, namely the number of the remaining cables is a prime number, is possible to occur, and the number of cables in each group does not need to be equal during actual processing, so that the method does not influence the reduction of the total measurement times. Using the packet bundling method, the theoretical maximum number of measurements is:

has the advantages that: compared with the prior art or the prior art, the technical scheme of the invention has the following beneficial effects:

(1) the internal optical fiber of the cable is utilized, an auxiliary detection circuit does not need to be additionally built, and convenience and rapidness are achieved. In addition, the specially designed optical fiber sensing device reduces the use of original expensive devices such as an acousto-optic modulator, an optical amplifier and the like, is economical and practical, and saves cost.

(2) The detection means of the invention can not damage the cable, and the device is portable and easy to use, and is suitable for the site operation of cable laying workers.

(3) The identification means of the invention is to distinguish the distribution characteristics of the resonance peak of the spectrogram, has high detection precision, sensitive response and strong anti-interference capability, and is suitable for complex cable laying environments.

Drawings

FIG. 1 is a schematic view of an optical fiber sensing device;

FIG. 2 is a schematic diagram of an oscillator;

fig. 3 is a schematic diagram of the frequency spectrum distribution, in which (a) is a schematic diagram of the frequency spectrum distribution before vibration is applied and (b) is a schematic diagram of the frequency spectrum distribution after vibration is applied.

Detailed Description

The technical scheme of the invention is further explained by combining the attached drawings and the embodiment.

The invention provides a distributed optical fiber sensing-based multi-path photoelectric composite cable distinguishing technology, which measures mechanical vibration applied to one end of a cable by a simple vibrator through a specially designed optical fiber sensing device, and achieves the purpose of quickly distinguishing different cables by using optical fibers in the cable as sensing carriers.

In order to be able to couple vibrations of a certain frequency to the optical fiber inside the cable through the vibrator, the inner hollow part of the simple oscillator is designed as a flexible structure that can be adjusted by means of the outer wall knob, as shown in fig. 2. Rotating the knob clockwise, tightening the inner wall of the oscillator and extruding the cable inwards; the counterclockwise rotation expands the inner wall, relieving inward compression. Only when the inside of the oscillator is sufficiently attached to the cable, the mechanical vibration generated by the oscillator can be transmitted to the optical fiber inside the cable well. Whether the oscillator is fully attached to the cable or not is simply and accurately judged for field workers conveniently, meanwhile, the rotary knob is protected from being damaged due to excessive screwing, and the outer wall knob is protected from excessive screwing. When the inner wall of the oscillator is subjected to outward stress generated by the extruded cable, the inner part of the outer wall adjusting knob is unhooked, and then the knob is rotated, so that the inner wall of the oscillator cannot be continuously extruded inwards, and the 'click' sound generated by unhooking the inner part of the knob can be heard. In addition, when the cable is too thick or the internal structure is special, the internal optical cable cannot be effectively transmitted by directly applying mechanical vibration to the outside of the cable, and in this case, structures which are easy to apply vibration to the internal optical fiber, such as an optical fiber ring or an optical fiber splice box, which may be left at the cable joint, can also be used.

In order to obtain a spectrum diagram with obvious characteristics, a proper vibration frequency of the vibrator should be selected in practical operation. This frequency should be distinguished from the natural resonant frequency of the cable and the potentially disturbing ambient noise. For this reason, the no-load resonance frequency profile of the cable can be measured first without using an oscillator and in a field construction environment. The field spectrum profile thus determined includes both the resonance spectrum and the ambient noise spectrum, and can be used as a reference spectrum profile for selecting the vibration frequency of the simple vibrator. As shown in FIG. 3, the spectral distribution before and after the vibration application was measured, wherein the abscissa represents the frequency (unit: Hz) and the ordinate represents the amplitude (relative quantity, dimensionless). According to practical experience, the horizontal axis can be divided into three main distribution bands: a low frequency region (typical range: 0 to 200Hz), a medium frequency region (typical range: 500 to 1kHz), and a high frequency region (typical range: 1.2 to 2.0 kHz). The natural resonant frequency of the cable is generally in a low-frequency range, and the low-frequency part is susceptible to environmental noise interference, such as a lot of environmental noise existing at 0-200 Hz in the schematic diagram a. Therefore, when selecting the vibration frequency of the simple vibrator, the frequency band in which the above-mentioned interference may exist should be avoided, and a vibration frequency value (typical value: 1 to 2kHz) in the middle and high frequency band is generally selected. For example, in the schematic diagram a, a vibration signal is applied near 1.2kHz, and a low frequency band with large interference is avoided, so that a clear resonance peak can be observed.

In order to quickly distinguish all cables, simplify the operation flow, and distinguish all cables only by using the least possible measuring times and procedures, a grouping and bundling method is adopted. For example, there are 20 cables to be distinguished, and the 20 cables can be divided into 5 groups, which are respectively identified as A, B, C, D, E groups. Each set of 4 cables is bundled into a bundle and vibration is applied as a whole. Now, the detection is performed from group a, that is, the vibrator simultaneously applies vibration to the 4 cables, and the spectrogram obtained by the processing at the PC end is observed. Assuming that no resonance peak corresponding to the applied vibration frequency is observed in the spectrogram obtained at this time, the detection of the group B is continued. And observing the obtained spectrogram, wherein if the spectrogram can be observed at the moment, the situation that one cable in the 4 cables in the group B is the same as the cable accessed by the sensing device is shown. The 4 cables are grouped, that is, every 2 cables form a group, so that the first cable can be distinguished by measuring at most twice. In the process, the first cable is distinguished by only using 4 times of measurement, and theoretically, the maximum measurement times of the first cable is distinguished by using the method to be 8 times, which is far less than the maximum measurement times of the method which is not used to be 19 times.