A fiber-optic point / distributed cooperative-based sensing system and method

Abstract

The application discloses a kind of sensing system and method based on optical fiber point type / distributed coordination, it is related to optical fiber sensing technical field, including: fusion light source module, optical circulator, point / combination sensing optical fiber module, point / distributed optical fiber sensing signal separation module, signal detection and demodulation module, to be measured parameter calculation module and data fusion and analysis module.Fusion light source module contains distributed sensing light source and point type sensing light source, two kinds of light sources are coupled and are injected into point / combination sensing optical fiber by optical circulator;After scattering light and reflected light returned are separated by point / distributed optical fiber sensing signal separation module, are respectively demodulated by corresponding demodulation unit, are fused after demodulation mapping and analysis;The application realizes the organic fusion of the full domain continuous monitoring of distributed sensing and the high-precision measurement of key position of point type sensing on single optical fiber, realizes multidimensional multi-parameter high-performance sensing of full coverage, key highlight.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical fiber sensing technology, in particular to a sensing system and method based on optical fiber point / distributed coordination. BACKGROUND

[0002] In the field of modern industry and infrastructure, real-time, online, and full-life-cycle structural health monitoring of key facilities such as large equipment structures, wind turbine blades, long-distance pipelines, and bridges has become an inevitable requirement for ensuring operational safety, optimizing maintenance strategies, and reducing operating costs. Such a monitoring system needs to meet the dual requirements of wide coverage and high-precision detection of key parts, that is, it should not only be able to implement state patrol in a wide area, but also be able to perform pinpoint accurate measurement in stress concentration areas, connection nodes, and welds.

[0003] Traditional sensor technology is difficult to achieve wide-area networking and multi-parameter fusion sensing due to limitations such as discrete arrangement, single function, and insufficient measurement accuracy, and cannot meet the above comprehensive monitoring requirements. Optical fiber sensing technology provides a feasible path to solve this problem. The current mainstream optical fiber sensing schemes can be divided into point-type and distributed-type:

[0004] Point-type sensing is represented by Fiber Bragg Grating sensors (FBG) and Fabry-Perot sensors (F-P). The former detects the shift of the reflection center wavelength of the grating directly or indirectly to demodulate physical quantities such as strain and temperature, and the latter converts the change in cavity length into changes in intensity / phase information to achieve high-sensitivity detection of vibration and static quantities. Point-type sensors have the advantages of high sensitivity, good measurement accuracy, and strong anti-electromagnetic interference capability, and are easy to implement wavelength division multiplexing based on wavelength coding characteristics, supporting quasi-distributed measurement of multiple sensing points. However, its sensing information is limited to pre-set discrete points, and it cannot achieve full-coverage monitoring in continuous space, resulting in monitoring blind areas in areas where sensors are not arranged.

[0005] Distributed sensing takes phase-sensitive optical time domain reflectometry (Φ-OTDR) as an example, which analyzes the phase or intensity changes of backscattered Rayleigh light in the optical fiber to realize distributed sensing of vibration, strain, or temperature disturbance. This technology does not require pre-marked sensing units, and the entire optical fiber serves as a sensor, enabling continuous spatial measurement without monitoring blind areas. However, it is generally sensitive to dynamic strain response, and the measurement process for static strain is relatively complex, and the spatial resolution is generally only on the order of meters, making it difficult to perform high-precision quantitative monitoring of micro-strain in key areas.

[0006] At present, point and distributed sensing technology is usually independently deployed and functionally separated in practical application. The point sensor can only provide discrete vibration, strain / temperature information at the preset point; the distributed sensor can realize vibration monitoring of the whole optical fiber path, but the dynamic vibration measurement accuracy and static strain measurement accuracy and stability are generally lower than that of the point sensor, and it is difficult to independently complete the quantitative evaluation of the safety state of the key position. If the two types of sensors are combined by mechanical means, the system complexity will be high, the cost will be greatly increased, and the data sources will be scattered and difficult to analyze collaboratively.

[0007] Therefore, how to realize the deep integration of point and distributed sensing mechanisms on a single optical fiber, and build an integrated monitoring system with hardware sharing and data intercommunication, has become a technical bottleneck that needs to be broken through in the field. SUMMARY

[0008] The purpose of the present application is to provide a sensing system and method based on optical fiber point / distributed collaboration, to solve the problems of the prior art.

[0009] To achieve the above purpose, the present application provides a sensing system based on optical fiber point / distributed collaboration, comprising:

[0010] A distributed sensing light source and a point sensing light source, the distributed sensing light source is used to generate pulsed light, and the point sensing light source is used to generate scanning light / broad spectrum light, the pulsed light and the scanning light / broad spectrum light are coupled out as fused light signals through an optical fiber coupler;

[0011] An optical circulator is used to inject the fused light signal into a sensing optical fiber, and output the light signal returned from the sensing optical fiber to a point / distributed optical fiber sensing signal separation module;

[0012] A point / combined sensing optical fiber module, which is a single-mode optical fiber integrated with multiple optical fiber point sensors, the point / combined sensing optical fiber body is used as a distributed sensing medium to generate backscattering light, and the optical fiber point sensors are used to reflect light signals of specific wavelengths;

[0013] A point / distributed optical fiber sensing signal separation module is used to separate the backscattering light in the returned light signal from the reflected light of the optical fiber point sensors;

[0014] A signal detection and demodulation module includes a distributed signal demodulation unit and a point signal demodulation unit, the distributed signal demodulation unit is used to detect and demodulate the backscattering light to obtain vibration information, and the point signal demodulation unit is used to detect the optical fiber point sensors and demodulate to obtain reflected light parameter change information;

[0015] A to-be-measured parameter calculation module is used to map vibration parameters and static strain / temperature values according to the vibration information and the reflected light parameter change information;

[0016] A data fusion and analysis module is configured to perform spatial alignment and fusion analysis and early warning on the vibration parameters and static strain / temperature values.

[0017] Further, the optical fiber point sensor includes an optical fiber Bragg grating sensor and a Fabry-Perot sensor.

[0018] Further, the distributed sensing light source is a narrow linewidth laser, which is modulated into narrow pulse light / chirped pulse light by an acousto-optic modulator / electro-optic modulator, and the pulse light is output after being amplified by an optical fiber amplifier.

[0019] Further, the point sensing probe light source is a wavelength tunable scanning laser.

[0020] Further, the point / distributed optical fiber sensing fiber is a single-mode optical fiber on which a plurality of optical fiber point sensors are integrated by wavelength division multiplexing technology.

[0021] Further, the point / distributed optical fiber sensing signal separation module includes a second optical coupling module, a first optical filter and a second optical filter, and the backward Rayleigh scattering light and the optical fiber point sensor reflected light of different wavebands are separated and output to the signal detection and demodulation module by time domain or frequency domain filtering technology.

[0022] Further, the distributed signal demodulation unit adopts a coherent detection scheme, converts the backward Rayleigh scattering light into an electrical signal through a balanced detector, and demodulates the vibration information through a disturbance positioning algorithm.

[0023] Further, the reflected light parameter change information includes center wavelength drift information or cavity length change information, and specifically includes:

[0024] If the optical fiber point sensor is an optical fiber Bragg grating sensor, the point signal demodulation unit realizes vibration, temperature / strain sensing by measuring the center wavelength drift information.

[0025] If the optical fiber point sensor is a Fabry-Perot sensor, the point signal demodulation unit realizes vibration, temperature / strain sensing by measuring the cavity length change information.

[0026] Further, the fusion analysis and early warning specifically includes triggering the linkage early warning function of high-frequency acquisition of the corresponding area of the optical fiber point sensor when abnormal vibration is detected.

[0027] A sensing method based on optical fiber point / distributed coordination, based on any one of the above-mentioned sensing systems based on optical fiber point / distributed coordination, includes the following steps:

[0028] Step 1: The fusion light signal output by the fusion light source module is injected into the point / combined sensing optical fiber through the optical circulator injection point, and the pulsed light output by the distributed sensing light source generates backscattering Rayleigh light in the point / combined sensing optical fiber, and the light output by the point sensing light source generates fiber point sensor reflection light at the point sensing sensor position of each optical fiber;

[0029] Step 2: The backscattering Rayleigh light and the fiber point sensor reflection light returned from the point / combined sensing optical fiber are received through the optical circulator;

[0030] Step 3: The backscattering Rayleigh light and the fiber point sensor reflection light in the returned light signal are separated through the point / distributed optical fiber sensing signal separation module;

[0031] Step 4: The backscattering Rayleigh light is demodulated by the distributed signal demodulation unit to obtain vibration information, and the fiber point sensor reflection light is demodulated by the point signal demodulation unit to obtain reflection light parameter change information;

[0032] Step 5: The vibration information and the reflection light parameter change information are mapped to vibration parameters and static strain value / temperature value of each fiber point sensor position;

[0033] Step 6: The vibration parameters and the static strain value / temperature value are fused, analyzed and warned.

[0034] Therefore, the sensing system and method based on the fiber point / distributed collaborative sensing system have the following beneficial effects:

[0035] 1. Global coverage and key highlighting: the Φ-OTDR realizes continuous distributed monitoring of the whole optical fiber path, and there is no blind area; the point sensor array realizes high-precision measurement of the preset key points, and overcomes the limitations of a single technology.

[0036] 2. Multi-dimensional information sensing: vibration information, static / quasi-static strain and temperature information of the structure are obtained at the same time, which provides more comprehensive and reliable data support for structure health assessment.

[0037] 3. High system integration: two sensing mechanisms are integrated on a single optical fiber, and the transmission medium is shared, which simplifies the layout complexity and reduces the cost, and is particularly suitable for long-term monitoring of large infrastructure.

[0038] 4. High reliability: the fiber sensor itself is resistant to electromagnetic interference and corrosion, and the fusion system provides redundant monitoring capability, when one signal is abnormal, the other can provide auxiliary judgment, and the overall reliability of the system is improved.

[0039] The technical solutions of the present application will be further described in detail below through the drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 A structure diagram of a sensing system based on optical fiber point / distributed coordination of the present application;

[0041] Figure 2 A structure diagram of a fusion light source module A in a sensing system based on optical fiber point / distributed coordination of the present application;

[0042] Figure 3 A structure diagram of a point / distributed optical fiber sensing signal separation module D in a sensing system based on optical fiber point / distributed coordination of the present application. DETAILED DESCRIPTION

[0043] The following detailed description of embodiments of the application provided in the accompanying drawings is not intended to limit the scope of the application claimed, but merely represents selected embodiments of the application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0044] Please refer to Figure 1 A sensing system based on optical fiber point / distributed coordination, comprising a fusion light source module A, an optical circulator B, a point / distributed combined sensing optical fiber module C, a point / distributed optical fiber sensing signal separation module D, a signal detection and demodulation module E, a to-be-measured parameter calculation module F, and a data fusion and analysis module G connected in sequence.

[0045] As shown in Figure 2 The fusion light source module A is used to generate and couple two optical signals required to drive the entire system, including a distributed sensing light source and a point sensing light source, as follows:

[0046] Distributed sensing light source: a narrow linewidth laser with a wavelength of 1550 nm and a linewidth of kHz level is used, a pulse signal is loaded onto the narrow linewidth laser through a pulse modulation module (acousto-optic modulator / electro-optic modulator), and the pulse signal is amplified through an optical gain module (such as an erbium-doped fiber amplifier) to form a pulse optical signal for Φ-OTDR detection.

[0047] Point sensing light source: a wavelength tunable scanning laser with a wavelength tunable range of 1305-1315 nm is used for scanning detection of the reflection wavelength of each FBG sensor.

[0048] The output ends of the two light sources are respectively connected to the two input ports of a first optical coupling module (a 2×1 optical fiber coupler), and the output end of the first optical coupling module is connected to port 1 of the optical circulator B. The two light sources use different working wavebands to avoid mutual interference and ensure that the two sensing signals can be effectively separated and detected.

[0049] Optical circulator B is a three-port optical circulator. Its port 1 receives the fused optical signal output by the fused light source module A, its port 2 is connected to the point / split-combined sensing fiber module C, which is used to inject the fused light into the point / split-combined sensing fiber and receive the returned optical signal, and its port 3 is connected to the point / distributed fiber sensing signal separation module D, which is used to output the returned optical signal.

[0050] The point / splitter combined sensing fiber optic module C is a single-mode fiber optic cable that integrates multiple fiber optic point sensors.

[0051] The sensing fiber is selected from standard single-mode communication fiber and protected (e.g., coated, sheathed) to suit different environments and working conditions. The point / split combined sensing fiber body serves as the distributed sensing medium, used to generate backscattered Rayleigh light to achieve Φ-OTDR distributed sensing.

[0052] The fiber optic point sensor employs a fiber Bragg grating (FBG) sensor or a Fabry-Perot (FP) sensor. This embodiment uses a fiber Bragg grating sensor as an example, employing a phase mask method to inscribe the data at pre-selected key structural points. In embodiments of this invention, key points include, but are not limited to: the mid-span and near supports of bridges; the root of wind turbine blades; and welds and connections in large equipment and facilities.

[0053] To achieve wavelength division multiplexing (WDM), a different Bragg wavelength is assigned to each fiber optic cable (FBG), ranging from 1305 to 1315 nm. The wavelength spacing between adjacent FBGs is 0.2 to 0.4 nm to ensure that the reflection spectra of each FBG do not overlap. Multiple FBGs are integrated on the same optical fiber, and quasi-distributed measurements are achieved through WDM technology.

[0054] like Figure 3 As shown, the point / distributed optical fiber sensing signal separation module D is used to separate the backscattered Rayleigh light from the FBG reflected light in the returned optical signal, and includes a second optical coupling module, a first optical filter, and a second optical filter.

[0055] Since the reflected signal of FBG (1305-1315nm band) and the Rayleigh scattering signal of Φ-OTDR (1550nm band) are significantly different in the frequency domain, an optical filter is used to separate the signals in the frequency domain.

[0056] Specifically, the return optical signal output from port 3 of the optical circulator B is split into two paths by the second optical coupling module, and enters the first optical filter and the second optical filter respectively.

[0057] In the embodiment of the present application, the first optical filter has a center wavelength of 1550 nm and a passband bandwidth of 1 nm, and is used to filter out the scattered signal (back Rayleigh scattering light) of the distributed sensing; the second optical filter has a center wavelength of 1310 nm and a passband bandwidth of 20 nm, and is used to filter out the reflected signal (FBG reflected light) of the point sensor.

[0058] The signal detection and demodulation module E is used to receive and process the two optical signals output from the point / distributed optical fiber sensing signal separation module D, and includes a distributed signal demodulation unit E2 and a point signal demodulation unit E1.

[0059] The point signal demodulation unit E1 receives the FBG reflected light signal filtered by the second optical filter, and directly or indirectly measures the center wavelength drift of each FBG by using a spectrum analysis method, an edge filtering method, a wavelength scanning method or an interference demodulation method, to obtain the reflected light parameter change information.

[0060] It should be noted that if the fiber point sensor uses a Fabry-Perot sensor, the point signal demodulation unit E1 is used to realize high-precision demodulation by using intensity detection or phase demodulation to realize the demodulation of the cavity length change information, to obtain the reflected light parameter change information.

[0061] The distributed signal demodulation unit E2 receives the back Rayleigh scattering light filtered by the first optical filter, and converts the optical signal into an electrical signal through a balanced detector by using a coherent detection scheme, and then collects the electrical signal through a data acquisition card, and processes the collected signal through a disturbance positioning algorithm (such as a differential method, a cross-correlation method, etc.), to demodulate the vibration information, including the phase waveform amplitude, the phase waveform frequency and the demodulation signal time.

[0062] The to-be-measured parameter calculation module F is used to map the actual physical parameters in real time according to the vibration information and the obtained reflected light parameter change information, including high-precision dynamic vibration and static strain / temperature F1 and high-precision vibration measurement and positioning F2.

[0063] The high-precision dynamic vibration and static strain / temperature F1 maps the vibration parameters and static strain values / temperature values of each FBG position in real time according to the reflected light parameter change information obtained by demodulation through a preset linear or nonlinear calculation formula.

[0064] The high-precision vibration measurement and positioning F2 maps the vibration parameters of each position of the optical fiber in real time according to the vibration information obtained by demodulation of the Φ-OTDR through a preset linear or nonlinear calculation formula, including the vibration frequency, the amplitude and the position of the vibration event.

[0065] The data fusion and analysis module G is used to fuse and analyze the distributed sensing data and the point sensing data, and mainly includes the following functions:

[0066] Spatial alignment: Align the position of vibration events calculated by Φ-OTDR demodulation with the position of FBG in spatial coordinates.

[0067] Linkage early warning: When Φ-OTDR detects abnormal vibration in a certain area, trigger FBG near the area to collect data at a higher frequency, realizing the linkage mechanism of distributed monitoring trigger point type precise measurement.

[0068] Data calibration: Combine the static strain value measured by FBG to calibrate and quantify the dynamic strain measured by Φ-OTDR, providing more accurate strain amplitude information.

[0069] The specific implementation process of the sensing method based on the cooperation of optical fiber point / distributed is as follows:

[0070] Step 1: Fuse the distributed sensing pulse light (1550nm) and the point sensing scanning light (1305-1315nm) output by the light source module A, and after coupling through the coupler, input through port 1 and output through port 2 of the optical circulator B, and inject into the point / distributed combined sensing optical fiber module C.

[0071] Step 2: In the point / distributed combined sensing optical fiber, the pulse light generates backscattering light, and the scanning light generates FBG reflection light at each FBG position. The returned backscattering light and FBG reflection light are input through port 2 and output through port 3 of the optical circulator B, and enter the point / distributed optical fiber sensing signal separation module D.

[0072] Step 3: The point / distributed optical fiber sensing signal separation module D separates the 1550nm backscattering light and the 1305-1315nm FBG reflection light through the optical filter, and outputs them to the corresponding demodulation unit.

[0073] Step 4: The distributed signal demodulation unit E2 performs coherent detection and signal processing on the backscattering light to obtain vibration information, and the point signal demodulation unit E1 demodulates the FBG reflection light using the asymmetric MZI structure to obtain the center wavelength shift of each FBG.

[0074] Step 5: The parameter calculation module F maps the vibration parameters along the optical fiber and the dynamic vibration and static strain / temperature values of each FBG position according to the vibration information and the reflection light parameter change information in real time.

[0075] Step 6: The data fusion and analysis module G performs spatial alignment and fusion analysis on the two kinds of sensing data, realizes linkage early warning and comprehensive evaluation.

[0076] It should be pointed out finally that the above examples are only used to illustrate the technical solutions of the present application but not to limit it, and although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can still be modified or replaced equivalently, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A fiber optic point / distributed collaborative based sensing system, characterized in that, The system comprises: a distributed sensing light source for generating pulsed light and a point sensing light source for generating scanning light / broad spectrum light, the pulsed light and the scanning light / broad spectrum light being coupled to output a fused light signal through a fiber coupler; an optical circulator for injecting the fused light signal into a sensing optical fiber and outputting a light signal returned from the sensing optical fiber to a point / distributed fiber sensing signal separation module; a point / distributed combined sensing optical fiber module, the point / distributed combined sensing optical fiber being a single-mode optical fiber integrated with a plurality of optical fiber point sensors, the point / distributed combined sensing optical fiber serving as a distributed sensing medium for generating backscattered Rayleigh light, and the optical fiber point sensors being used for reflecting light signals of specific wavelengths; a point / distributed fiber sensing signal separation module for separating backscattered Rayleigh light from the returned light signal and light reflected by the optical fiber point sensors; a signal detection and demodulation module comprising a distributed signal demodulation unit and a point signal demodulation unit, the distributed signal demodulation unit being used for detecting and demodulating the backscattered Rayleigh light to obtain vibration information, and the point signal demodulation unit being used for detecting the optical fiber point sensors and demodulating to obtain reflected light parameter change information; a to-be-measured parameter calculation module for mapping vibration parameters and static strain values / temperature values according to the vibration information and the reflected light parameter change information; a data fusion and analysis module for spatial alignment and fusion analysis and early warning of the vibration parameters and the static strain values / temperature values.

2. A fiber optic point / distributed collaborative based sensing system according to claim 1, wherein, The optical fiber point sensors comprise fiber Bragg grating sensors and Fabry-Perot sensors.

3. A fiber optic point / distributed collaborative based sensing system according to claim 2, wherein, The distributed sensing light source is a narrow linewidth laser, continuous light is modulated into narrow pulsed light / chirped pulsed light through an acousto-optic modulator / electro-optic modulator, and the pulsed light is output after being amplified by a fiber amplifier.

4. A fiber optic point / distributed collaborative based sensing system according to claim 3, wherein, The point sensing detection light source is a wavelength tunable scanning laser.

5. A fiber optic point / distributed collaborative based sensing system according to claim 4, wherein, The point / distributed combined sensing optical fiber is a plurality of optical fiber point sensors integrated on a single-mode optical fiber through wavelength division multiplexing technology.

6. A fiber optic point / distributed collaborative based sensing system according to claim 5, wherein, The point / distributed fiber sensing signal separation module comprises a second optical coupling module, a first optical filter and a second optical filter, and backscattered Rayleigh light and light reflected by the optical fiber point sensors of different wavebands are separated and output to the signal detection and demodulation module through time domain or frequency domain filtering technology.

7. A fiber optic point / distributed collaborative based sensing system according to claim 6, wherein, The distributed signal demodulation unit adopts a coherent detection scheme, backscattered Rayleigh light is converted into an electrical signal through a balanced detector, and vibration information is demodulated through a disturbance positioning algorithm.

8. A fiber optic point / distributed collaborative based sensing system according to claim 7, wherein, The reflected light parameter change information comprises center wavelength drift information or cavity length change information, and specifically: If the optical fiber point sensor is a fiber Bragg grating sensor, the point signal demodulation unit realizes vibration, temperature / strain sensing by measuring the center wavelength drift information; If the optical fiber point sensor is a Fabry-Perot sensor, the point signal demodulation unit realizes vibration, temperature / strain sensing by measuring the cavity length change information.

9. A fiber optic point / distributed collaborative based sensing system according to claim 8, wherein, The fusion analysis and early warning specifically refers to triggering a linkage early warning function of high-frequency acquisition of the corresponding area of the optical fiber point sensor when an abnormal vibration is detected.

10. A sensing method based on fiber point / distributed cooperative, characterized in that, The system of claim 1-9, comprising the following steps: Step 1: The fusion light signal output by the fusion light source module is injected into the point / combined sensing optical fiber through the optical circulator injection point; the pulsed light output by the distributed sensing light source generates backscattering Rayleigh light in the point / combined sensing optical fiber; the light output by the point sensing light source generates optical fiber point sensor reflected light at the point sensing sensor position of each optical fiber; Step 2: The backscattering Rayleigh light and the optical fiber point sensor reflected light returned from the point / combined sensing optical fiber are received through the optical circulator; Step 3: The backscattering Rayleigh light and the optical fiber point sensor reflected light in the returned light signal are separated through the point / distributed optical fiber sensing signal separation module; Step 4: The backscattering Rayleigh light is demodulated by the distributed signal demodulation unit to obtain vibration information; the optical fiber point sensor reflected light is demodulated by the point signal demodulation unit to obtain reflected light parameter change information; Step 5: The vibration information and the reflected light parameter change information are mapped to vibration parameters and static strain value / temperature value at each optical fiber point sensor position; Step 6: The vibration parameters and the static strain value / temperature value are fused, analyzed and warned.

Images