CN218271048U

CN218271048U - Vibration sensing and acoustic emission monitoring system of distributed optical fiber

Info

Publication number: CN218271048U
Application number: CN202220396788.2U
Authority: CN
Inventors: 邱德武; 范鑫烨; 邱德全; 邱德才
Original assignee: China Enterprise Kexin Technology Co ltd
Current assignee: China Enterprise Kexin Technology Co ltd
Priority date: 2022-02-26
Filing date: 2022-02-26
Publication date: 2023-01-10
Anticipated expiration: 2032-02-26

Abstract

The utility model discloses a vibration sensing and acoustic emission monitoring system of distributed optical fiber, distributed optical fiber vibration sensing system includes the light source module that comprises laser instrument and drive unit, the sensing module that comprises sensing optical fiber, signal processing module and display module and connects gradually, optical fiber acoustic emission monitoring system includes laser light source, circulator, photoelectric detector, preamplifier, data acquisition display system, the circulator is connected with photoelectric detector, photoelectric detector is connected with preamplifier, preamplifier is connected with data acquisition display system; by utilizing the characteristic that light waves are transmitted in the optical fiber, the vibration information sensed by the optical fiber can be continuously sensed and measured (temperature, pressure, stress, strain and the like) along the length direction of the optical fiber, then the signal processing is carried out on the vibration information, and an early warning signal is sent out, so that the early warning purpose is achieved.

Description

Vibration sensing and acoustic emission monitoring system of distributed optical fiber

Technical Field

The utility model belongs to the technical field of the semiconductor, particularly, relate to a vibration sensing and acoustic emission monitoring system of distributed optical fiber.

Background

In the existing domestic vibration sensing technology, some point-type fiber bragg grating sensors are adopted, but the existing vibration sensing technology is only suitable for measuring static physical quantity and is not suitable for monitoring dynamic signals, the false alarm and missing report rate is high, the installation, debugging, maintenance and the like are complex, the cost is high, the existing vibration sensing technology is only suitable for perimeter security protection, and the user experience is general; some adopt distributed optical fiber, but still have the false alarm rate height, do not have the problem such as reaction to single event, lead to user's experience sense very poor.

SUMMERY OF THE UTILITY MODEL

To above defect, the utility model provides a distributed optical fiber's vibration sensing and acoustic emission monitoring system, distributed optical fiber vibration sensing system includes the light source module that comprises laser instrument and drive unit, the sensing module, the signal processing module and the display module that constitute by sensing optical fiber and connects gradually, acoustic emission monitoring system includes laser source, circulator, photoelectric detector, preamplifier, data acquisition display system, the circulator is connected with photoelectric detector, photoelectric detector is connected with preamplifier, preamplifier and data acquisition display system are connected.

Furthermore, the signal processing module is an optical fiber sentinel, and the display module comprises a photoelectric conversion unit, a signal processing unit and a display unit.

Furthermore, the sensing optical fiber is distributed optical fiber vibration sensing.

Further, the photoelectric conversion unit is used as a photosensor that can convert an optical signal into an electrical signal.

Furthermore, the sensing optical fiber and the guiding optical fiber in the distributed optical fiber vibration sensing system both use non-zero dispersion single-mode optical fiber.

Further, the output center wavelength of the laser light source used in the acoustic emission monitoring system is 1310nm, and the maximum power output is 2mw.

Furthermore, the acoustic emission monitoring system is composed of a laser light source, a circulator, a photoelectric detector, a preamplifier and a data acquisition and display system.

Furthermore, the interference light intensity signal output by the distributed optical fiber vibration sensing system should be converted into an electrical signal first, and the electrical signal needs to be filtered and amplified.

Compared with the prior art, the utility model following beneficial effect has:

a vibration sensing and acoustic emission monitoring system of distributing type optic fibre, distributed optical fiber vibration sensor can sense in succession at big spatial dimension in this application, simultaneously, the sensing is same root optic fibre with biography light, sensing part simple structure, convenient to use, as long as lay this sensing optic fibre to measurand department and can use. Compared with a point-type sensor, the distributed optical fiber vibration sensor has the advantages that the cost for acquiring information in unit length is greatly reduced, the traditional acoustic emission technology mostly adopts a resonance piezoelectric acoustic emission technology, the defects are obvious, the volume is large, the frequency band is wide, the optical fiber vibration sensor must be in contact with an object and cannot be used in severe environments such as high temperature, strong electromagnetic interference and corrosion, the optical fiber acoustic emission technology used in the application has the advantages of small volume, wide frequency band, high sensitivity and high damage threshold value, does not need to be in contact with the object to be measured, is suitable for severe environments and the like, and generally utilizes the characteristic that light waves are transmitted in optical fibers, can continuously sense the measured value (temperature, pressure, stress, strain and the like) along the length direction of the optical fibers and then processes signals of vibration information sensed by the optical fibers and sends early warning signals to achieve the early warning purpose.

To sum up, the utility model discloses special structure, it has above-mentioned a great deal of advantage and practical value to do not see in like product that similar method is published or is used and really belongs to the innovation, produced well-used and practical effect, had the multinomial efficiency of promoting than current technique, thereby comparatively be suitable for the practicality, and have extensive industrial value.

Drawings

Fig. 1 is a schematic flow chart of the present invention.

Fig. 2 is a schematic view of the optical fiber acoustic emission according to the present invention.

Fig. 3 is a schematic diagram of the beat frequency demodulation of the present invention.

Fig. 4 shows the beat frequency signal demodulation circuit of the present invention.

Detailed Description

In order to facilitate understanding of the present invention, the present invention will be described more fully hereinafter with reference to the accompanying drawings. Embodiments of the device are given in the figures. However, the apparatus may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Examples

As shown in fig. 1-4, the present embodiment provides a distributed optical fiber vibration sensing and acoustic emission monitoring system, which includes (as shown in fig. 1):

(1) A light source module composed of a laser and a driving unit thereof;

(2) The sensing module is composed of sensing optical fibers (the sensing optical fibers are distributed optical fiber vibration sensing), and the sensing optical fibers and the guide optical fibers in the optical fiber sensing system all use non-zero dispersion single-mode optical fibers, so that the optical fiber product is widely applied to networks such as long-distance communication, trunk lines, cable televisions, loop feeder lines and the like, and has the advantages of low internal loss, large broadband, easy upgrading and capacity expansion and low cost;

(3) The signal processing module (fiber-optic sentinel) and the display module (the display module comprises a photoelectric conversion unit, a signal processing unit and a display unit):

the photoelectric conversion unit is a photosensor that can convert an optical signal into an electrical signal. Compared with the traditional electromagnetic mutual inductor, the frequency range measured by the photoelectric mutual inductor is mainly determined by an electronic circuit part, and the problem of iron core saturation is avoided, so that the transient state process can be accurately reflected once, and the transient response range is wide. Meanwhile, a digital interface is adopted, the communication capacity is high, the photoelectric sensor downloads optical digital signals, the optical digital signals are easily interfaced with a communication network, and no measurement error exists in the transmission process. Meanwhile, with the wide adoption of microcomputer protection control equipment, the photoelectric transformer can directly provide digital quantity for secondary equipment, so that a converter and an A/D sampling part in the original protection device can be omitted, the secondary equipment is greatly simplified, and it needs to be explained that interference light intensity signals output by the distributed optical fiber vibration sensing system must be converted into electric signals firstly, and because the amplitude of the directly converted electric signals is small and the noise is more, the electric signals must be filtered and amplified before the signals are collected.

The signal processing is directly related to a series of important performance indexes such as detection sensitivity, precision, response time, stability and reliability of the optical fiber sensing system, relates to whether objective and accurate reflection and evaluation can be carried out on the measured object, and is a core part of the optical fiber sensing system. The signal processing part demodulates the optical signal modulated by the external measured parameter, so as to obtain the measured parameter.

The fiber sentinel has the functions of processing signals and sending out early warning signals, wherein the fiber sentinel adopts the technology of beat frequency demodulation and full spectrum analysis. The beat frequency demodulation refers to that from the image, the local shape of the wave is still the wave vibrating at the original frequency, but the outer edge of each peak forms a waveform with longer wavelength (i.e. the amplitude varies in space). For sound waves, the intensity of sound we hear depends on the amplitude of the sound wave, so when such a wave is transmitted into the human ear, the amplitude of the wave at the human ear (fixed point in space) changes with time, and "the sound volume is perceived as periodically strong and weak in hearing". "a strong or weak beat" is called a beat, and the number of beats heard in a unit time is the beat frequency. The algorithm can be optimized by the full-spectrum analysis, so that the detection result is more accurate, and the false alarm rate is reduced. The beat demodulation technique is to monitor the frequency drift of the beat signal by using a frequency meter or a spectrometer. Because the frequency of the beat frequency signal is detected by the technology instead of the intensity, and the frequency is not interfered in the transmission process, the technology reduces the noise influence of extra light source disturbance, loss of an optical connector and the like in the demodulation process, and the stability of the signal is greatly improved by the all-electronic demodulation scheme.

The acoustic emission monitoring system comprises a detection system and a demodulation system (as shown in fig. 2), wherein any change of the optical path difference between two coherent light beams can be used for very sensitively causing the change of the interference fringes, and the optical path change of one coherent light beam is caused by the change of the geometric path passed by the coherent light beam or the refractive index of a medium, so that the change of the movement of the interference fringes can be used for measuring the small variable of the geometric length or the refractive index, and other physical quantities related to the change of the optical path difference can be measured. The demodulation system is composed of photoelectric detection and signal processing, a single-mode optical fiber is used as a wavelength modulation type sensor, the detected information causes the shift of laser wavelength, and the detected information is converted into the shift of characteristic wavelength. In order to obtain the original measurand, it is necessary to detect the drift of the optical wave from the measured optical signal. The signal demodulation mainly has the functions of timely and accurately extracting the amplitude of the signal and detecting the change process of the signal along with time on line.

The acoustic emission monitoring system consists of a laser light source, a circulator, a photoelectric detector, a preamplifier and a data acquisition and display system, wherein the circulator is connected with the photoelectric detector, the photoelectric detector is connected with the preamplifier, and the preamplifier is connected with the data acquisition and display system

The monitoring part is optical fiber acoustic emission monitoring. Acoustic emission monitoring is a dynamic nondestructive monitoring method and plays an important role in nondestructive testing technology. On the other hand, the internal structure of the material is changed due to the action of the factors, such as crystal structure change, sliding deformation and crack propagation, and the sound is generated in the process of changing the internal structure of the material. Only when the internal structure changes, the energy can be released, and the sound can be produced, so the acoustic emission detection is a dynamic nondestructive detection method, namely, the internal structure, the defect or the potential defect of the component or the material is subjected to nondestructive detection in the process of motion change. Therefore, defects such as cracks actively participate in the detection process during detection. If the defects such as cracks and the like are in a static state and do not change or expand, no acoustic emission occurs, and acoustic emission detection cannot be realized. This feature of acoustic emission detection distinguishes it from other non-destructive detection methods such as ultrasound, X-ray, eddy currents, and the like. The optical fiber acoustic emission detection technology is that light emitted by a laser passes through an optical isolator and an optical attenuator, one end of the light enters PD, data processing is carried out through an acquisition board, and the other end of the light enters an interferometer. The optical fiber vibration early warning host provides a light source for the whole system, and light is transmitted to the segmentation package through the transmission optical cable and then sequentially transmitted to the polarization optical cable and the next prevention area segmentation package. The vibration optical cable converts external vibration signals into optical signals, then the optical signals are sent back to the host computer to be subjected to photoelectric conversion, and the early warning system collects and processes the signals. According to the set parameters, the invasion prevention area is displayed on a screen, after light output by the laser light source is coupled into the optical fiber, if isolation is not added, a certain amount of light can be reflected back to the laser to form a new resonant frequency, so that unstable periodic change of interference output is caused, and therefore, an optical fiber isolator is required to be selected to prevent the influence of reflected light in the optical fiber on the light source.

The distributed optical fiber vibration sensor can continuously sense in a large space range, and meanwhile, sensing and light transmitting are the same optical fiber, so that the sensing part is simple in structure and convenient to use, and the sensing optical fiber can be used as long as being laid at a measured position. Compared with a point type sensor, the distributed optical fiber vibration sensor has the advantage that the cost for acquiring information in unit length is greatly reduced.

It should be noted that, besides communication and information transmission, the optical fiber itself is also a sensing device, and any point on the optical fiber can sense the surrounding environment, so the optical fiber can be used as a distributed sensor. In this case, the optical fiber is both a sensing medium and a transmission medium to be measured. Therefore, the distributed optical fiber vibration sensor can continuously sense in a large space range, meanwhile, sensing and light transmitting are the same optical fiber, the sensing part is simple in structure and convenient to use, and the sensing optical fiber can be used as long as being laid at a measured position. The distributed optical fiber vibration sensor utilizes optical fibers laid along a pipeline as a sensing element, any point on the sensing optical fibers has sensing capacity, and the optical fibers are maintenance-free and can meet the requirements of early warning and positioning of the whole damage behavior of a pipeline over dozens of kilometers. Therefore, the research of the distributed optical fiber sensing technology with the functions of early warning and positioning of pipeline damage behaviors has huge social and economic benefits.

Compared with a point type sensor, the distributed optical fiber vibration sensor has the advantage that the cost for acquiring information in unit length is greatly reduced. The whole adopts the optical fiber coherent technology. A light beam emitted from a laser source is divided into two beams of coherent light by a coupler, and one beam of coherent light is directly called as reference light without participating in modulation through a reference arm; the other beam is transmitted in the sensing arm, and the optical signal is modulated into signal light by external parameters during transmission. When vibration acts on the sensing arm, the length and the refractive index of the optical fiber of the sensing arm are changed, and the phase of the light wave is correspondingly changed. The reference arm optical fiber is not interfered by external vibration, and the phase of the reference arm optical fiber is not changed, so that the phases of two light waves propagating along the sensing arm and the reference arm are different, the two light waves interfere when passing through the coupler, and a generated signal is detected by a detector (PD).

The insertion loss of each device is small in the whole optical fiber link. The birefringence of the fiber has a large effect on the final alignment result, and to reduce this effect, the wavelength of the light source must be selected to ensure that the polarization mode dispersion is minimized when the light is transmitted through the fiber. The 1310nm laser source is selected according to the characteristic that the dispersion value of the single mode fiber at 1310nm is minimum. The method is characterized in that factors such as light source wavelength, output power, coupling efficiency and spectral width are finally considered, the output center wavelength is 1310nm, the maximum power output is 2mw, the test system adopts single-mode optical fibers as sensing and guiding optical fibers, so the test result is inevitably influenced by optical fiber birefringence, and according to the previous test result, a polarization controller is selected by a system polarization control scheme to eliminate the depolarization effect of the optical fiber birefringence on polarized light.

It should be noted that the structure of the present invention can be realized in many different forms, and is not limited to the embodiments, and any equivalent transformation, which is directly or indirectly applied to other related technical fields, such as loading and unloading of other articles, by using the contents of the present invention and the attached drawings, by a person skilled in the art are all included in the protection scope of the present invention.

Claims

1. The utility model provides a vibration sensing and acoustic emission monitoring system of distributing type optic fibre which characterized in that: the distributed optical fiber vibration sensing system comprises a light source module consisting of a laser and a driving unit thereof, a sensing module consisting of sensing optical fibers, a signal processing module and a display module which are sequentially connected, the acoustic emission monitoring system comprises a laser source, a circulator, a photoelectric detector, a preamplifier and a data acquisition and display system, the circulator is connected with the photoelectric detector, the photoelectric detector is connected with the preamplifier, and the preamplifier is connected with the data acquisition and display system.

2. A distributed fibre optic vibration sensing and acoustic emission monitoring system according to claim 1 wherein: the signal processing module is an optical fiber sentinel, the display module comprises a photoelectric conversion unit, a signal processing unit and a display unit, and the sensing module is an optical fiber sensor.

3. The distributed fiber optic vibration sensing and acoustic emission monitoring system of claim 1, wherein: the sensing optical fiber is distributed optical fiber vibration sensing.

4. A distributed fibre optic vibration sensing and acoustic emission monitoring system according to claim 2 wherein: the photoelectric conversion unit is used as a photosensor that can convert an optical signal into an electrical signal.

5. The distributed fiber optic vibration sensing and acoustic emission monitoring system of claim 1, wherein: the sensing optical fiber and the guide optical fiber in the distributed optical fiber vibration sensing system both use non-zero dispersion single-mode optical fiber.

6. A distributed fibre optic vibration sensing and acoustic emission monitoring system according to claim 1 wherein: the central wavelength of the output of the laser light source used in the acoustic emission monitoring system is 1310nm, and the maximum power output is 2mw.

7. The distributed fiber optic vibration sensing and acoustic emission monitoring system of claim 1, wherein: the acoustic emission monitoring system consists of a laser light source, a circulator, a photoelectric detector, a preamplifier and a data acquisition and display system.

8. A distributed fibre optic vibration sensing and acoustic emission monitoring system according to claim 1 wherein: the interference light intensity signal output by the distributed optical fiber vibration sensing system is converted into an electric signal firstly, and the electric signal is required to be filtered and amplified.