CN210089716U - Multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing - Google Patents
Multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing Download PDFInfo
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- CN210089716U CN210089716U CN201921343263.7U CN201921343263U CN210089716U CN 210089716 U CN210089716 U CN 210089716U CN 201921343263 U CN201921343263 U CN 201921343263U CN 210089716 U CN210089716 U CN 210089716U
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Abstract
The utility model relates to an optical fiber sensing technical field, concretely relates to synchronous sensing acquisition instrument of many parameters based on multicore optical fiber sensing, include: the system comprises a grating demodulator, a Raman thermometer, a polarization analyzer, a synchronous trigger circuit and a multi-core fiber coupler; the grating demodulator, the Raman temperature measuring instrument and the polarization analyzer are respectively connected with the multi-core fiber coupler, and the multi-core fiber coupler is connected with the multi-core fiber so as to synchronously measure different fiber cores of the multi-core fiber through the grating demodulator, the Raman temperature measuring instrument and the polarization analyzer; the synchronous trigger circuit is respectively connected with the grating demodulator, the Raman temperature measuring instrument and the polarization analyzer and is used for triggering the three detection devices to synchronously transmit light pulses and acquire data. The utility model discloses it is integrated with grating demodulation appearance, raman thermoscope and polarization analysis appearance, the parallel optical link of multichannel of cooperation multicore optic fibre carries out synchronous measurement to the different fibre cores in the multicore optic fibre, realizes meeting an emergency, the sensing when temperature and the vibration to optic fibre.
Description
[ technical field ] A method for producing a semiconductor device
The utility model relates to an optical fiber sensing technical field, concretely relates to synchronous sensing acquisition instrument of many parameters based on multicore optical fiber sensing.
[ background of the invention ]
The multi-core fiber is an optical fiber with a single cladding and a plurality of fiber cores, and by utilizing the space division multiplexing technology based on the multi-core fiber, higher-density data transmission can be realized in the aspect of optical communication, and a new use method can be expanded in the aspect of optical sensing. As is well known, the fiber sensing technology can generally realize continuous measurement at each point on the fiber link due to the use of fiber as a sensor, and the sensing distance can reach tens of kilometers. In addition to the common advantages with other fiber optic sensing technologies, fiber optic sensors have several specific advantages: spatial structure advantages, parametric compensation advantages and channel integration advantages. For example, the multiple cores of the multi-core optical fiber have the advantage of a spatial structure, so that the curvature and torsion rate information of the optical fiber can be inverted through the bending strain and the torsion strain of the spatial geometry structure by virtue of the difference of the relative geometric positions and structures of the multiple cores in one optical fiber, and the three-dimensional shape sensing of spatial bending and torsion can be realized through reconstruction; for another example, since the cores of the multi-core fiber are integrated in a cladding of several hundred micrometers, the ambient temperature at each point can be considered to be approximately the same, and thus the change of the optical path formed by the cores is also approximately the same, and the temperature compensation of multiple optical paths is automatically realized.
At present, in the aspect of mechanical parameters, the multi-core optical fiber can be used for measuring bending, strain, acceleration and the like, wherein the multi-core optical fiber is most widely used for bending sensing; the multi-core optical fiber also has very important application in the temperature sensing aspect, and a temperature sensing scheme based on the multi-core optical fiber with double cores, seven cores, nineteen cores and the like is proposed at present; in addition to this, there has been a study on refractive index sensing.
The traditional optical fiber sensing technology mainly comprises an optical fiber grating technology, an optical fiber Brillouin sensing technology, a Raman optical time domain reflection technology, a polarized light time domain reflection technology, a phase sensitive optical time domain reflection technology, an optical frequency domain reflection technology and the like, and different physical quantities such as temperature, strain, vibration and the like can be measured by using optical fibers according to different measurement principles through corresponding optical fiber sensing instruments. However, the existing optical fiber sensing instruments are generally based on a single measurement principle, the measured physical quantity is single, and simultaneous measurement of multiple physical quantities cannot be realized, so that the application scenarios are limited. In addition, some measurement technologies, such as the fiber grating technology or the fiber brillouin sensing technology, have response to both temperature and strain, and are difficult to distinguish in practical application, so that the use is limited.
For example, for most of the devices with cables laid, it is necessary to prevent external forces from damaging the cables on the one hand and to monitor the working conditions of the cables on the other hand, so that it is necessary to be able to measure and distinguish between external disturbances and temperature simultaneously. For another example, in the field of bridge monitoring and building monitoring, on one hand, vibration events (such as earthquakes) need to be sensed, and on the other hand, fire and the like need to be warned, so that vibration and temperature need to be measured simultaneously. In the application scenarios, it is difficult to meet the use requirement by using the conventional optical fiber sensing technology.
In view of the above, it is an urgent problem in the art to overcome the above-mentioned drawbacks of the prior art.
[ Utility model ] content
The utility model discloses the technical problem that needs to solve is:
the traditional optical fiber sensing instrument is generally realized based on a single measurement principle, the measured physical quantity is single, the synchronous sensing measurement of multiple parameters cannot be realized, and the application scene is limited; in practical application, it is difficult to distinguish and quantitatively analyze different parameters for a sensing instrument with a measurement result responding to a plurality of parameters.
The utility model discloses a following technical scheme reaches above-mentioned purpose:
the utility model provides a multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing, which comprises a grating demodulator 1, a Raman temperature measuring instrument 2, a polarization analyzer 3, a synchronous trigger circuit 4 and a multi-core optical fiber coupler 6;
the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3 are respectively connected with the multicore fiber coupler 6, and the multicore fiber coupler 6 is connected with the multicore fiber 7, so that different fiber cores of the multicore fiber 7 can be synchronously measured through the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3, and simultaneous sensing of temperature, strain and vibration is realized;
the synchronous trigger circuit 4 is respectively connected with the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3, and is used for triggering the raman thermometer 2 and the polarization analyzer 3 to synchronously transmit light pulses on one hand, and is used for triggering the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3 to synchronously acquire data on the other hand, and simultaneously, the synchronization of pulse triggering and acquisition is kept.
Preferably, the multi-parameter optical fiber sensing instrument further comprises a first optical fiber interface, a second optical fiber interface, a third optical fiber interface and a fourth optical fiber interface;
the grating demodulator 1 is connected with the front end of a first fiber core in the multi-core fiber 7 through the first fiber interface and the multi-core fiber coupler 6;
the Raman temperature measuring instrument 2 is connected with the front end of a second fiber core in the multi-core fiber 7 through the second fiber interface and the multi-core fiber coupler 6;
the polarization analyzer 3 is connected with the front end of a third fiber core in the multi-core fiber 7 through the third fiber interface and the multi-core fiber coupler 6; the connection with the front end of a fourth fiber core in the multi-core fiber 7 is realized through the fourth fiber interface and the multi-core fiber coupler 6; wherein the end of the third core is connected to the end of the fourth core.
Preferably, the grating demodulator 1 comprises a first broadband light source 101, an optical circulator 102 and a spectrometer 103 which are connected in sequence;
the optical circulator 102 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, and the spectrometer 103 is connected with the synchronous trigger circuit 4;
after the continuous broadband light sent by the first broadband light source 101 is transmitted to the fiber bragg grating FBG, the reflected light enters the spectrometer 103 through the optical circulator 102, and the spectrometer 103 measures the wavelength shift.
Preferably, the grating demodulator 1 includes a second broadband light source 104, a first coupler 105, a first optical splitter 106, a first photodetector 107, an edge filter 108, a second photodetector 109, and a first data acquisition card 110, which are connected in sequence;
the first coupler 105 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, the first data acquisition card 110 is connected with the synchronous trigger circuit 4, and the second broadband light source 104 is used for emitting continuous broadband light;
the first photodetector 107 is connected to the first optical splitter 106 and the first data acquisition card 110, the second photodetector 109 is connected to the edge filter 108 and the first data acquisition card 110, and the edge filter 108 is connected to the first optical splitter 106.
Preferably, the grating demodulator 1 comprises a third broadband light source 111, a second coupler 112, an F-P tunable filter 113, a third photodetector 114 and a second data acquisition card 115, which are connected in sequence;
the second coupler 112 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, the second data acquisition card 115 is connected with the synchronous trigger circuit 4, and the third broadband light source 111 is used for emitting continuous broadband light.
Preferably, the grating demodulator 1 further comprises an amplifier 116, a control system 117 and a signal generator 118;
the amplifier 116 is connected to the third photodetector 114 and the control system 117, respectively, the control system 117 is connected to the signal generator 118, and the signal generator 118 is connected to the F-P tunable filter 113, so as to apply a scan voltage to the F-P tunable filter 113.
Preferably, the grating demodulator 1 includes a tunable narrowband light source 119, a third coupler 120, and a digital oscilloscope 121, which are sequentially connected, and the digital oscilloscope 121 is further connected to the tunable narrowband light source 119; the tunable narrow-band light source 119 is fixed on the PZT122, and the PZT122 is driven by a sawtooth wave or a sinusoidal voltage;
the third coupler 120 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, the digital oscilloscope 121 is connected with the synchronous trigger circuit 4, and the tunable narrowband light source 119 is used for emitting continuous narrowband light.
Preferably, the raman thermometer 2 comprises a pulse light source 201, a WDM coupler 202, a second optical splitter 203, a photoelectric detection module and a third data acquisition card 204, which are connected in sequence;
the WDM coupler 202 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, and the pulse light source 201 and the third data acquisition card 204 are respectively connected with the synchronous trigger circuit 4;
the photo-detection module includes a fourth photo-detector 205 and a fifth photo-detector 206 for detecting the stokes raman scattering light and the anti-stokes raman scattering light reflected back from the optical fiber, respectively.
Preferably, the polarization analyzer 3 includes a light source 301, a polarizer 302, an analyzer 303, a light detector 304 and a fourth data acquisition card 305, which are connected in sequence;
the polarizer 302 and the analyzer 303 are respectively externally connected with the multi-core fiber 7 through corresponding fiber interfaces, and the light source 301 and the fourth data acquisition card 305 are respectively connected with the synchronous trigger circuit 4.
The utility model has the advantages that:
the utility model provides a many parameter fiber sensing instrument, it is integrated with grating demodulation appearance, raman thermodetector and polarization analysis appearance, usable fiber grating technique, raman optical time domain reflectometer technique and polarized light technique, the parallel optical link of multichannel of cooperation multicore optic fibre carries out synchronous measurement to the different fibre cores in the multicore optic fibre, realizes meeting an emergency, the sensing when temperature and the vibration of optic fibre. The grating demodulation instrument and the Raman temperature measuring instrument are combined to respectively quantitatively analyze the temperature and the strain, and the state of the whole optical fiber can be effectively acquired through the combination of the grating demodulation instrument and the polarization analyzer.
[ description of the drawings ]
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly described below. It is obvious that the drawings described below are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be obtained from these drawings without inventive effort.
Fig. 1 is a structural composition diagram of a multi-parameter synchronous sensing acquisition instrument based on multi-core fiber sensing provided by an embodiment of the present invention;
fig. 2 is a schematic view of a connection relationship between a multi-parameter synchronous sensing acquisition instrument based on multi-core fiber sensing and a multi-core fiber provided by an embodiment of the present invention;
fig. 3 is a schematic diagram illustrating a demodulation principle of a fiber grating technology according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a grating demodulator based on a spectrometer demodulation method according to an embodiment of the present invention;
fig. 5 is a schematic structural diagram of a grating demodulator based on an edge filtering demodulation method according to an embodiment of the present invention;
fig. 6 is a schematic structural diagram of a grating demodulator based on a tunable F-P filter demodulation method according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a grating demodulator based on a tunable narrowband light source demodulation method according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a raman thermometer according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of a polarization analyzer according to an embodiment of the present invention;
fig. 10 is a schematic structural diagram of another multi-parameter synchronous sensing acquisition instrument based on multi-core fiber sensing according to an embodiment of the present invention;
fig. 11 is a flowchart of a multi-parameter synchronous sensing method according to an embodiment of the present invention.
[ detailed description ] embodiments
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
In the description of the present invention, the terms "inside", "outside", "longitudinal", "lateral", "up", "down", "top", "bottom", "left", "right", "front", "back", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description of the present invention and do not require that the present invention must be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention. Furthermore, the technical features mentioned in the embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
As described in the background art, the conventional distributed optical fiber sensing technology mainly includes an optical fiber grating technology, an optical fiber brillouin sensing technology, a raman optical time domain reflection technology, a polarized light time domain reflection technology, and the like. The utility model discloses in, the optical fiber sensing technique of mainly utilizing is fiber grating technique, raman optical time domain reflection technique and polarized light technique, and the introduction of each optical fiber sensing technique is as follows:
the sensing principle of the Raman optical time domain reflection technology is as follows: when a laser pulse is transmitted in an optical fiber, Stokes Raman scattered light and anti-Stokes Raman scattered light are generated, the intensity of the two kinds of scattered light is influenced by temperature (and is insensitive to other parameters), but the modulation coefficients are different; by analyzing the modulation coefficients of the scattered light at two different frequencies and the measured change in luminous flux, the change in temperature can be judged. This technique is capable of sensing temperature and performing quantitative analysis, but has a disadvantage in that only temperature parameters can be measured.
The sensing principle of the fiber grating technology is as follows: a plurality of Fiber Bragg Gratings (FBGs) are written in the optical Fiber in a point-type or quasi-distributed manner, when external factors capable of responding change, parameters such as the effective refractive index and the Grating period of the optical Fiber change, and further the resonant wavelength of the FBGs changes; the sensing of the ambient environment parameters can be realized by measuring the change of the resonance wavelength. However, for the multi-parameter sensing task, since the resonance wavelength of the sensing fiber can be changed by both temperature and strain, when only the fiber grating technology is used (i.e. only the grating demodulator is used), only the temperature or strain event can be judged to occur, the temperature and strain cannot be distinguished, and the quantitative analysis of the temperature and strain is more difficult to be carried out respectively. Meanwhile, the fiber grating technology can only realize point and quasi-distributed sensing, namely, whether vibration, strain or temperature change exists at the position where the FBG is located can only be detected, and the vibration, strain or temperature change at other positions cannot be detected, so that the state of the whole optical fiber cannot be obtained only by utilizing the fiber grating technology, and only the state of a specific position can be obtained.
According to the above-mentioned characteristics of fiber grating technique and raman optical time domain reflection technique (fiber grating technique can be simultaneously sensing temperature and meet an emergency, but is difficult to distinguish and quantitative analysis respectively, and raman optical time domain reflection technique only can be to temperature quantitative analysis), the utility model discloses consider to combine together two kinds of techniques, expect to realize sensing when temperature and meeting an emergency, can distinguish and carry out the quantitative analysis of temperature and meeting an emergency respectively.
The sensing principle of the polarized light technology is as follows: when light propagates in the optical fiber, the polarization state changes continuously; when the state of the fiber is stable, the change of the polarization state is relatively stable and slowly changed; when vibration or stress occurs, the polarization state changes suddenly, and the change is visually expressed as the change of light intensity after passing through the analyzer. The technology can realize the non-existent qualitative analysis on the disturbance, and if the vibration occurs, the vibration frequency can be demodulated according to the frequency of the detected pulse intensity change; the disadvantage is that when any point in the optical fiber has vibration or stress, the intensity of the optical pulse at the receiving end changes, so that the place of the event can not be determined.
Aiming at the defects of the polarized light technology, the polarized light time domain reflection technology can be directly used, and after the detection pulse is sent out, the time of arrival of the received signal is in proportional relation with the corresponding optical fiber position, so that the place of the occurrence of the event can be judged; however, the time domain reflection technique of polarized light utilizes scattered light in an optical fiber, the signal is weak, multiple averaging may be required to improve the signal-to-noise ratio, and the dynamic response capability is relatively low. Therefore, the utility model discloses consider to combine polarized light technique and fiber grating technique: as mentioned above, the polarized light technology can sense the stress and vibration events at all points of the optical fiber, but cannot distinguish the position; and the fiber grating technology can monitor the state of the grating position. Combining the two techniques can create some degree of complementarity.
The present invention will be described in detail with reference to the accompanying drawings and examples.
Example 1:
the embodiment of the utility model provides a synchronous sensing acquisition instrument of many parameters based on multicore fiber sensing, as shown in figure 1, many parameters fiber sensing instrument includes grating demodulation appearance 1, raman thermometer 2, polarization analysis appearance 3, synchronous trigger circuit 4, treater 5 and multicore fiber coupler 6, grating demodulation appearance 1 raman thermometer 2 with be parallelly connected state between the 3 three check out test set of polarization analysis appearance.
The grating demodulator 1, the raman thermometer 2, and the polarization analyzer 3 are respectively externally connected to different fiber cores of a multicore fiber 7 through corresponding fiber interfaces, as shown in fig. 1: the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3 are respectively connected with the multicore fiber coupler 6, the multicore fiber coupler 6 is connected with the multicore fiber 7, and then different fiber cores of the multicore fiber 7 can be synchronously measured through the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3, so that simultaneous sensing of temperature, strain and vibration is realized.
The synchronous trigger circuit 4 is respectively connected with the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3 through electric signal lines, and is used for triggering three devices to synchronously transmit light pulses and acquire data, specifically as follows: on one hand, the Raman temperature measuring instrument 2 and the polarization analyzer 3 are triggered to synchronously transmit light pulses, on the other hand, the grating demodulator 1, the Raman temperature measuring instrument 2 and the polarization analyzer 3 are triggered to synchronously acquire data, and the synchronization of light pulse transmission and data acquisition is kept. For the raman thermometer 2 and the polarization analyzer 3, the internal pulse light source and data acquisition need to be pulse synchronized. When the three detection devices are used in combination, except that the continuous light source used by the grating demodulator 1 does not need to be synchronized, the rest light sources and the light detection part not only need to be pulse-synchronized in each device, but also need to be synchronously triggered for light pulse and data acquisition among the three devices, so that a common synchronous trigger circuit 4 is introduced, and a sensing signal completely aligned in time can be obtained during signal processing, so that accurate compensation of cross sensitive signals is facilitated, and synchronous acquisition of the three devices is realized. The most common use of the synchronous trigger circuit 4 is to use a 555 timer, but in practical use, any circuit capable of stably outputting a periodic pulse electrical signal may be used, and the present invention is not limited thereto.
The processor 5 is respectively connected with the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3 through electric signal lines, and is used for comprehensively analyzing and processing data acquired by the three devices. The current temperature value and the strain value of the multi-core optical fiber 7 can be obtained by complementary analysis of data collected by the grating demodulator 1 and the Raman thermometer 2; by complementary analysis of the data collected by the grating demodulator 1 and the polarization analyzer 3, whether the whole optical fiber link has disturbance can be judged, and the current vibration frequency value of the multi-core optical fiber 7 can be obtained. The processor 5 may be a computer or other device with an analysis processing function, and is not limited to a specific one, and the three detection devices may share one processor to perform data analysis, as shown in fig. 1.
The utility model provides a many parameter fiber sensing instrument, with grating demodulation appearance, raman thermodetector and polarization analysis appearance integration, usable fiber grating technique, raman optical time domain reflectometer technique and polarized light technique, the multichannel parallel optical link of cooperation multicore optic fibre carries out synchronous measurement to different fibre cores in the multicore optic fibre, realizes sensing when meeting an emergency, temperature and the vibration to optic fibre; and, through setting up the synchronous trigger circuit of public, can effectively realize the synchronous collection of three check out test set.
The embodiment of the utility model provides an in, the connection between each check out test set and the optic fibre is external, is connected with optic fibre through external fiber interface promptly. The grating demodulator 1 and the Raman thermometer 2 are both reflective, and only any fiber core in the multi-core optical fiber 7 needs to be connected for sensing measurement, so that only one external optical fiber interface needs to be provided; the polarization analyzer 3 is not reflective, and usually needs to connect any two cores in the multi-core fiber 7 for sensing measurement, so two external fiber interfaces are needed to obtain output at a single end. According to the analysis, the following structure design is specifically adopted:
referring to fig. 2, the optical fiber interfaces include a first optical fiber interface b1, a second optical fiber interface b2, a third optical fiber interface b3 and a fourth optical fiber interface b4, and the multicore optical fiber coupler 6 is located between each optical fiber interface and the multicore optical fiber 7; the multi-core optical fiber coupler can realize optical coupling of a plurality of single-core optical fibers or optical coupling of each fiber core in the multi-core optical fiber, and achieves the functions of splitting light or combining beams. In the embodiment of the present invention, the multicore fiber coupler 6 is mainly used to connect different cores in the multicore fiber 7 to corresponding detection devices, so that light emitted by a light source in each detection device can enter a specific core. Specifically, the grating demodulator 1 is connected to the front end of the first fiber core a1 in the multicore fiber 7 through the first fiber interface b1 and the multicore fiber coupler 6. The raman thermometer 2 is connected to the front end of the second fiber core a2 in the multicore fiber 7 through the second fiber interface b2 and the multicore fiber coupler 6. The polarization analyzer 3 is connected with the front end of a third fiber core a3 in the multi-core optical fiber 7 through the third optical fiber interface b3 and the multi-core optical fiber coupler 6; the connection is realized with the front end of a fourth fiber core a4 in the multi-core optical fiber 7 through the fourth optical fiber interface b4 and the multi-core optical fiber coupler 6; wherein the ends of the third cores a3 and the fourth cores a4 are connected.
The multi-core fiber 7 includes n cores, n is equal to or greater than 4, and may be a seven-core fiber, for example. The first core a1, the second core a2, the third core a3 and the fourth core a4 are 4 cores selected from n cores, and are not limited in particular. Referring to fig. 2, the front end of the core is the left end in the figure, and the end of the core is the right end in the figure.
For three detection devices, the grating demodulator 1 mainly senses temperature and strain by measuring the wavelength change of the FBGs, the raman thermometer 2 mainly senses temperature by measuring the light intensity change, and the polarization analyzer 3 mainly performs qualitative analysis on strain and vibration by measuring the polarization state change. The detection principle and the structural design of the three detection devices will be specifically described below.
First, regarding the fiber grating technology and the grating demodulator 1:
the strain sensing network of the fiber Bragg grating generally adopts a wavelength division multiplexing technology, and the principle of the strain sensing network is shown in fig. 3: the light from a light source (typically a broadband light source) is transmitted through a coupler to an optical fiber on which a plurality of FBG sensors are distributed, each sensor having a different Bragg wavelength. After the broadband light passes through the FBGs, the transmitted light has a plurality of wave troughs on the spectrum, and the wave troughs correspond to the Bragg wavelengths of the FBGs respectively; the reflected light contains a plurality of peaks in the spectrum, also corresponding to the Bragg wavelengths of the respective FBGs. The spectrum of the reflected light passing through the coupler is detected by a wavelength signal demodulation device, so that the Bragg wavelength of the FBG can be obtained, and further the sensing signal of the FBG can be obtained. Wherein, FBG is inscribed in the multi-core optical fiber; it should be noted here that only the core (i.e. the first core a1) connected to the device of the grating demodulator 1 inscribes the grating FBG; after the grating demodulator 1 is externally connected with the multi-core fiber, the reflected light of the FBG can be used for sensing. The wavelength division multiplexing technique has an advantage in that a plurality of FBG sensors, which can measure a plurality of wavelengths at a time, can be compared with the time division multiplexing technique.
Based on the above demodulation principle, the grating demodulator 1 may have a plurality of implementation structures, specifically as follows:
(1) by adopting a spectrometer demodulation method, as shown in fig. 4, the grating demodulator 1 includes a first broadband light source 101, an optical circulator 102 and a spectrometer 103, which are connected in sequence, the optical circulator 102 is externally connected to the multi-core fiber 7 through a corresponding fiber interface, and the spectrometer 103 is connected to a common processor 5. The demodulation principle specifically comprises the following steps: after the continuous broadband light emitted by the first broadband light source 101 is transmitted to the fiber bragg grating FBG through the optical circulator 102, the reflected light passes through the optical circulator 102 and enters the spectrometer 103, and the offset of the wavelength is measured by the spectrometer 103, so that the processor 5 calculates the value of the physical quantity (temperature or strain) to be measured according to the wavelength change.
In order to ensure synchronous triggering of data acquisition, the spectrometer 103 is connected with the synchronous trigger circuit 4, and the synchronous trigger circuit 4 generates a pulse with a certain repetition frequency and sends a synchronous pulse to the spectrometer 103 to start data acquisition.
The spectrometer demodulation is the simplest and most direct demodulation method, and has the advantages of accurate detection, high sensitivity, convenient operation, high cost and large equipment volume. Therefore, the spectrometer demodulation method is not generally used in engineering environment, and is generally used as research in a laboratory.
(2) By using the edge filtering demodulation method, as shown in fig. 5, the grating demodulator 1 includes a second broadband light source 104, a first coupler 105, a first optical splitter 106, a first photodetector 107, an edge filter 108, a second photodetector 109, and a first data acquisition card 110, which are connected in sequence. The first coupler 105 is externally connected with the multi-core fiber 7 through a corresponding fiber interface, the first photodetector 107 is respectively connected with the first optical splitter 106 and the first data acquisition card 110, the second photodetector 109 is respectively connected with the edge filter 108 and the first data acquisition card 110, and the edge filter 108 is connected with the first optical splitter 106. The first data acquisition card 110 is embodied as a dual-channel data acquisition card and is connected to a common processor 5.
The demodulation principle specifically comprises the following steps: after the continuous broadband light emitted by the second broadband light source 104 is transmitted to the FBG through the first coupler 105, the reflected light passes through the first coupler 105 and enters the first optical splitter 106, and a part of the light is not attenuated, and is directly detected by the first photodetector 107 and then is subjected to data acquisition by the first data acquisition card 110; the other part of the light is attenuated after being filtered by the edge filter 108, and then is detected by the second photodetector 109 and then is subjected to data acquisition by the first data acquisition card 110. Therefore, the light intensity before and after the attenuation of the reflected light can be detected, the attenuation amount of the light intensity is determined, the offset of the wavelength is further obtained, and the processor 5 calculates the value of the physical quantity to be measured according to the wavelength change.
In order to ensure the synchronous triggering of data acquisition, the first data acquisition card 110 is connected to the synchronous trigger circuit 4, and the synchronous trigger circuit 4 generates a pulse with a certain repetition frequency, and sends a synchronous pulse to the first data acquisition card 110 to start data acquisition.
The edge filter demodulation method has the advantages that the signal processing is convenient and the price is low, but has the defect that the working area needs to be controlled, because the linear working area of the edge filter has a certain range, the Bragg condition needs to be specially set when the demodulation system is designed, and the central wavelength of the reflected light is in the linear working area of the edge filter.
(3) By adopting a tunable F-P filter demodulation method, as shown in fig. 6, the grating demodulator 1 includes a third broadband light source 111, a second coupler 112, an F-P tunable filter 113, a third photodetector 114, a second data acquisition card 115, an amplifier 116, a control system 117, and a signal generator 118, which are connected in sequence. The second coupler 112 is externally connected to the multi-core optical fiber 7 through a corresponding optical fiber interface, the amplifier 116 is respectively connected to the third photodetector 114 and the control system 117, the control system 117 is connected to the signal generator 118, and the signal generator 118 is connected to the F-P tunable filter 113, so as to load a scan voltage to the F-P tunable filter 113. The second data acquisition card 115 is connected to a common processor 5.
The demodulation principle specifically comprises the following steps: after the continuous broadband light emitted from the third broadband light source 111 is transmitted to the FBG through the second coupler 112, the reflected light passes through the second coupler 112 and enters the F-P tunable filter 113, and the F-P tunable filter 113 is loaded with a saw tooth scan voltage and scans back the center wavelength of the transmitted light of the F-P tunable filter 113 in the vicinity of the reflected wavelength. If the F-P tunable filter 113 just scans the reflection wavelength of the FBG at this time, since the reflection wavelengths of the F-P tunable filter 113 and the FBG are overlapped, the third photodetector 114 can detect the maximum intensity of the light intensity, and further obtain the offset of the wavelength, and the processor 5 calculates the value of the physical quantity to be measured according to the wavelength change.
In order to ensure the synchronous triggering of data acquisition, the second data acquisition card 115 is connected to the synchronous trigger circuit 4, and the synchronous trigger circuit 4 generates a pulse with a certain repetition frequency, and sends a synchronous pulse to the second data acquisition card 115 to start data acquisition.
The tunable F-P filter demodulation method has the advantages of wide demodulation wavelength range, high demodulation efficiency, small instrument and convenience in integration in a monitoring system, and is particularly suitable for a plurality of FBG detection systems (namely distributed fiber bragg grating sensing systems). The tunable F-P filter has the advantages that piezoelectric ceramics are adopted in the tunable F-P filter to control the cavity length of the F-P cavity and further control the transmission wavelength, so that the detection sensitivity is influenced by the characteristics of the piezoelectric ceramics, such as temperature drift, zero drift and the like, and the influence can be reduced by a certain external compensation measure, and the sensitivity of a detection system is improved.
(4) By adopting a tunable narrowband light source demodulation method, as shown in fig. 7, the grating demodulator 1 includes a tunable narrowband light source 119, a third coupler 120, and a digital oscilloscope 121, which are connected in sequence, where the tunable narrowband light source 119 is used to emit continuous narrowband light. The tunable narrow-band light source 119 is fixed on a lead zirconate titanate (PZT) piezoelectric ceramic (PZT) 122, and the PZT122 is driven by a sawtooth wave or a sinusoidal voltage; the digital oscilloscope 121 is connected with the tunable narrow-band light source 119 and is also connected with a common processor 5; the third coupler 120 is externally connected to the multi-core fiber 7 through a corresponding fiber interface. Wherein an isolator 123 may also be disposed between the tunable narrowband optical source 119 and the third coupler 120.
The demodulation principle specifically comprises the following steps: the reflection spectrum of the photosensitive grating FBG is periodically scanned by said digital oscilloscope 121 with a narrow band spectrum of wavelengths. When the PZT122 is driven by a sawtooth wave or a sinusoidal voltage, the spectrum of the tunable narrowband light source 119 changes within a certain range, and when the output wavelength of the tunable narrowband light source 119 is the same as the reflected wavelength of the sensing grating FBG, the signal intensity received by the digital oscilloscope 121 is the maximum; and then, the offset of the FBG wavelength can be obtained through the tuning relation between the voltage and the wavelength of the PZT122, and the processor 5 calculates the value of the physical quantity to be measured according to the wavelength change.
In order to ensure synchronous triggering of data acquisition, the digital oscilloscope 121 is connected to the synchronous trigger circuit 4, and the synchronous trigger circuit 4 generates a pulse with a certain repetition frequency and sends a synchronous pulse to the digital oscilloscope 121, so that the digital oscilloscope 121 starts data acquisition.
(5) And a matched grating filtering demodulation method is adopted. The matched grating filtering demodulation method is to use the wavelength of a known receiving grating to measure the wavelength of a sensing grating by a certain method, and the matched grating filtering demodulation method generally comprises two methods: the first mode is a reflection mode, namely, a sensing signal enters a matched grating through a sensing grating to detect the intensity of reflected light, and when a detector receives the maximum light intensity, the sensing grating is completely matched with the central wavelength of the matched grating; and the second mode is a transmission mode, which is similar to a reflection method for detecting the intensity of transmitted light, and when the detector receives the minimum light intensity, the central emission wavelength of the sensing grating can be obtained.
Second, regarding the raman optical time domain reflectometry technique and the raman thermometer 2:
referring to fig. 8, the raman thermometer 2 may generally include a pulse light source 201, a WDM coupler 202, a second optical splitter 203, a photo-detection module and a third data acquisition card 204, which are connected in sequence, wherein the photo-detection module includes a fourth photo-detector 205 and a fifth photo-detector 206 for detecting Stokes raman scattered light (Stokes light) and Anti-Stokes raman scattered light (Anti-Stokes light) reflected back from the optical fiber, respectively; the WDM coupler 202 is externally connected to the multicore fiber 7 through a corresponding fiber interface. The third data acquisition card 204 is a dual-channel data acquisition card and is connected to the common processor 5.
The demodulation principle specifically comprises the following steps: the optical pulse emitted from the pulse light source 201 is coupled into the sensing fiber (i.e. the multi-core fiber in the embodiment of the present invention) through the WDM coupler 202 (bidirectional coupler), and continuously generates the back-raman scattered light (the intensity of the scattered light is modulated by the temperature field along the fiber) by the interaction with the molecules in the fiber medium during the propagation process, the reflected back-raman scattered light is sent into the WDM coupler 202 for filtering, and then the separated Stokes scattered light and Anti-Stokes scattered light are respectively input into the fourth photodetector 205 and the fifth photodetector 206 through the second optical splitter 203 for photoelectric conversion, and the level signal is amplified to the effective collection range of the third data collection card 204. The third data acquisition card 204 acquires the scattering signals along the sensing optical fiber at a certain sampling frequency, the acquired data are sequentially stored in a designated memory or the processor 5, and the processor 5 calculates the temperature value to be measured according to the light intensity.
In order to ensure synchronous triggering of optical pulse and data acquisition, the pulse light source 201 and the third data acquisition card 204 are respectively connected with the synchronous trigger circuit 4, the synchronous trigger circuit 4 generates pulses with a certain repetition frequency, on one hand, the pulse light source 201 is modulated to generate narrow detection light pulses, and on the other hand, the synchronous pulses are sent to the third data acquisition card 204 to synchronously start data acquisition. After the process of acquiring temperature information is completed, the synchronous trigger circuit 4 controls the pulse light source 201 to emit the next detection pulse light. The system repeats the above process, and according to the system setting, the data in the memory or the processor 5 is subjected to accumulation average processing and the like, and finally the temperature measurement curve along the sensing optical fiber is obtained through temperature demodulation and graphic display.
Third, regarding the polarized light technique and the polarization analyzer 3:
referring to fig. 9, the polarization analyzer 3 includes a light source 301, a polarizer 302, an analyzer 303, a light detector 304 and a fourth data acquisition card 305, which are connected in sequence. The polarizer 302 and the analyzer 303 are respectively externally connected to the multicore fiber 7 through corresponding fiber interfaces, specifically, the polarizer 302 may be externally connected to the front end of a third fiber core a3 in the multicore fiber 7 through a third fiber interface b3, the analyzer 303 may be externally connected to the front end of a fourth fiber core a4 in the multicore fiber 7 through a fourth fiber interface b4, and the tail end of the third fiber core a3 is connected to the tail end of the fourth fiber core a 4.
The demodulation principle specifically comprises the following steps: the light source 301 emits a periodic light pulse signal, the light pulse signal is polarized by the polarizer 302 and then converted into linearly polarized light, the linearly polarized light enters the sensing fiber (i.e., the multi-core fiber 7 in the figure) and then enters the analyzer 303, the polarization information is converted into light intensity information, the signal is converted into an electrical signal through the optical detector 304, the electrical signal is collected and stored by the fourth data acquisition card 305, and the processor 5 performs further data processing.
In order to ensure the synchronous triggering of the optical pulse and the data acquisition, the light source 301 and the fourth data acquisition card 305 are respectively connected to the synchronous trigger circuit 4, the synchronous trigger circuit 4 generates a pulse with a certain repetition frequency, on one hand, the light source 301 is modulated to generate a detection optical pulse, and on the other hand, a synchronous pulse is sent to the fourth data acquisition card 305, so that the data acquisition is started synchronously.
The above-mentioned structures are designed for the grating demodulator 1, the raman thermometer 2 and the polarization analyzer 3, and other structures may be set as required during actual use, which is not repeated herein.
In the above embodiment, when three detection devices are used to perform synchronous sensing measurement, 4 detection fiber cores in the multi-core fiber are used. In a preferred embodiment, the number of detection cores can be reduced to two by using time division multiplexing and wavelength division multiplexing, thereby further simplifying the apparatus and the connection relationship. With reference to fig. 10, assuming that two used fiber cores are respectively denoted as a fifth fiber core a5 and a sixth fiber core a6, the grating demodulator 1, the raman thermometer 2, and the polarization analyzer 3 are all externally connected to the front end of the fifth fiber core a5 in the multicore fiber 7 through a fifth fiber interface b5, the polarization analyzer is also externally connected to the front end of the sixth fiber core a6 in the multicore fiber through a sixth fiber interface b6, and the tail end of the fifth fiber core a5 is connected to the tail end of the sixth fiber core a6, so that the two fiber cores in the multicore fiber 7 can be synchronously measured through a fiber grating technology, a raman optical time domain reflection technology, and a polarization technology, and simultaneous sensing of temperature, strain, and vibration is achieved. At this time, the multicore fiber 7 includes n cores, n is greater than or equal to 2, the fifth core a5 and the sixth core a6 are two cores selected from the n cores, and are not specifically limited herein, and the remaining cores are used for normal optical signal transmission.
Among three devices, namely a grating demodulator 1, a raman thermometer 2 and a polarization analyzer 3, wavelength division multiplexing is performed between the raman thermometer 2 and the polarization analyzer 3, and time division multiplexing is performed between the grating demodulator 1 and the other two devices. With the above structure, the control process of time division multiplexing and wavelength division multiplexing is specifically as follows:
the time division multiplexing may specifically be controlled by the switching time of the corresponding light sources: turning on the light sources of the Raman thermometer 2 and the polarization analyzer 3 at the time of T1, and turning off the light source of the grating demodulator 1; and at the time of T2, turning on the light source of the grating demodulator 1, and turning off the light sources of the Raman thermometer 2 and the polarization analyzer 3, thereby realizing the time division multiplexing of the fiber grating technology and the other two technologies.
When the light sources of the raman thermometer 2 and the polarization analyzer 3 are turned on, on the one hand, the raman thermometer 2 can sense the temperature, and on the other hand, the polarization analyzer 3 can perform qualitative sensing analysis of strain and vibration. In the process, wavelength division multiplexing is performed between raman detection and polarization detection, specifically: the forward light is detected by the polarized light technology, and the detection wavelength is consistent with the emission wavelength and is 1550nm waveband; the Stokes light and the anti-Stokes light correspond to Raman temperature measurement technologies, and the detected wavelengths are respectively at a 1660nm waveband and a 1450nm waveband, so that detection in different wavelength ranges can be performed. When a light source of the grating demodulator 1 is turned on, the grating demodulator 1 can realize sensing of temperature and strain; in terms of the fiber grating technology, the fiber grating technology is wavelength division multiplexing, and the original resonant frequencies corresponding to a plurality of written FBG gratings in the optical fiber are different and are distributed between 1525nm and 1565 nm.
In the preferred embodiment, the specific detection principle and the structural design of the three detection devices may refer to the related description in the foregoing embodiment, which is not described herein again.
Example 2:
in order to facilitate understanding of the usage of the optical fiber sensing instrument in embodiment 1, the embodiment of the present invention provides a multi-parameter synchronous sensing method, which is implemented by the multi-parameter synchronous sensing acquisition instrument described in embodiment 1. Before introducing the embodiment of the utility model of the multi-parameter synchronous sensing method, at first introduce each sensing technology's computational formula and derivation:
raman optical time domain reflection technology
For the Raman optical time domain reflection technology, the temperature parameter is mainly responded. The anti-stokes scattered light is sensitive to temperature, and the intensity of the anti-stokes scattered light is modulated by temperature; the intensity of stokes scattered light also has a certain relation with temperature, but is slightly influenced by the temperature. Therefore, in the measurement, it is necessary to collect the intensities of the stokes scattered light and the anti-stokes scattered light, demodulate the anti-stokes light as the signal light and the stokes light as the reference light. At any temperature T, the relationship between the signal light and the reference light is:
by T0As reference temperature, then at reference temperature T0The lower signal light and the reference light have the following relationship:
dividing the formula (1) and the formula (2) to obtain the temperature T of the optical fiber at any point, which satisfies the following relation:
wherein psisIs the luminous flux, ψ, corresponding to the Stokes scattered light (i.e. reference light) in the optical fiber at temperatureasThe luminous flux of anti-stokes scattered light (namely signal light) in the optical fiber at the corresponding temperature can be obtained by actual measurement through a Raman optical time domain reflection technology. k is Boltzmann constant, h is Planckian constant, and Δ v is phonon frequency in the optical fiber. v. ofasAnd vsα for anti-Stokes Raman scattered photon frequency and Stokes Raman scattered photon frequency, respectivelyasAnd αsβ optical fiber transmission losses of anti-Stokes Raman scattered light and Stokes Raman scattered light, respectivelyasAnd βsThe coefficients are related to anti-stokes Raman scattering and stokes Raman scattering cross sections respectively, and L is the position of the point to be measured in the optical fiber, specifically the distance from the point to be measured to the front end of the optical fiber. The raman formula is obtained from equation (3) as follows:
wherein, muTIs a Raman temperature coefficient, and
in the case of temperature demodulation using Raman equation,. mu.TThe details may be determined by pre-fitting.
Second, optical fiber grating technology
For fiber grating technology, the response to temperature and strain parameters is dominant. The wavelength matching condition of the optical fiber Bragg grating is lambdaB＝2neffLambda, which is a basic formula of the fiber grating and is the basis for carrying out sensing characteristic research; wherein λ isBIs the center wavelength, n, of the Bragg gratingeffAnd lambda is the effective refractive index of the fiber core, and lambda is the grating period. From this equation, the physical quantities that enable the effective refractive index or period of the grating to change affect its center wavelength, and stress and temperature are the most significant physical quantities that change the wavelength of the fiber Bragg grating. Before the calculation formula is given, it should be noted that research shows that the thermal effect generated by temperature and the force effect generated by strain can be considered to be relatively independent. From the above basic formula, the induced wavelength change is as follows:
ΔλB＝2Λ·Δneff+2neff·ΔΛ (5)
assuming that the temperature is unchanged, the grating is only under the action of strain, and the central wavelength change Delta lambda of the fiber Bragg grating caused by strain is considered under the action of uniform axial stressBAnd the strain epsilon satisfy the following relation:
modified from the above equation (6):
ΔλB＝λB(1-Pe)ε＝αεε (7)
wherein, PeIs an effective elasto-optical coefficient, and
v is the cedar ratio of the core material; p11And P12The elastic-optical coefficient is any two values, related to the core material, and refers to a matrix containing many values, and P11And P12Is a fraction of the elasto-optic coefficient αεIs a grating strain coefficient, and αε＝λB(1-Pe)。
From the above equation, it can be seen that when the grating material is determined, the strain ε and the change in the center wavelength Δ λBThe linear relation is formed, when the technology is actually used for strain measurement, only the Delta lambda needs to be determined through pre-fittingBRelating to e, i.e. determining the grating strain coefficient αε. It should be noted that the above linear relationship applies when the strain is small, since taylor expansion is performed and high-order terms are omitted in the formula derivation process. In the embodiment of the present invention, it is preferable that the corresponding linear relationship interval is obtained by calculation according to the measurement result, and the linear relationship interval may confirm the interval range by fitting a straight line, which is not described herein again. Therefore, in a specific application scene, the linear fitting interval and the fitting relation provided by the invention can directly feed back the stress value according to the linear relation when a specific detection value falls into the corresponding linear relation interval, so that the calculation and response efficiency of the whole system is improved. If the linear relation is exceeded, calculation is performed according to a common formula, which is the meaning of the linear relation interval provided by the embodiment of the invention. The "common formula" specifically refers to a formula before non-taylor expansion, and the calculation formula in the embodiment of the present invention is a formula for performing post-taylor expansion optimization.
Assuming that the strain is constant, the grating is only affected by temperature, the effective refractive index and the grating period are respectively affected by the temperature through the thermo-optic effect and the thermal expansion effect, and the central wavelength change Delta lambda of the fiber Bragg grating caused by the temperatureBAnd the temperature change amount delta T satisfy the following relation:
modified from the above equation (8):
ΔλB＝λB(α+ξ)ΔT＝αTΔT (9)
wherein α is the thermal expansion coefficient of the fiber grating, and
ξ is the thermo-optic coefficient of the fiber grating, and
αTis the temperature coefficient of the grating, and αT＝λB(α+ξ)。
As can be seen from the above formula, the temperature variation Δ T and the central wavelength variation Δ λBIn a linear relationship and similar to strain, when the technique is actually used for temperature measurement, only the delta lambda needs to be determined through pre-fittingBRelating to Δ T, i.e. determining the grating temperature coefficient αT。
The above description has been made assuming temperature invariance and analyzing temperature assuming strain invariance, respectively, and temperature and strain can be regarded as independent and linearly superposed. Therefore, combining equation (7) and equation (9), the central wavelength changes Δ λ when analyzing temperature and strain simultaneouslyBThe strain epsilon and the temperature change quantity delta T satisfy the following relations:
ΔλB＝αεε+αTΔT (10)
the above formula (10) is a grating formula to be used subsequently.
As shown in fig. 11, the multi-parameter synchronous sensing method provided by the embodiment of the present invention mainly includes the following steps:
and step 10, respectively utilizing a fiber grating technology, a Raman optical time domain reflection technology and a polarized light technology to perform synchronous sensing measurement on different fiber cores in the multi-core fiber.
With reference to embodiment 1, the fiber grating technology mainly implements sensing of temperature and strain through the grating demodulator 1, the raman optical time domain reflection technology mainly implements quantitative sensing analysis of temperature through the raman thermometer 2, and the polarized light technology mainly implements qualitative sensing analysis of strain and vibration through the polarization analyzer 3. The synchronous measurement of different fiber cores is realized by triggering through the synchronous trigger circuit 4, which specifically comprises the following steps: the synchronous trigger circuit 4 is respectively connected with the grating demodulator 1, the Raman temperature measuring instrument 2 and the polarization analyzer 3, and the grating demodulator 1, the Raman temperature measuring instrument 2 and the polarization analyzer 3 are triggered to synchronously transmit light pulses and acquire data through the synchronous trigger circuit 4.
According to the connection relationship between each detection device and different fiber cores described in embodiment 1, the specific measurement conditions are as follows: the first fiber core a1 in the multi-core fiber 7 is subjected to sensing measurement by using the fiber grating technology, and the wavelength variation delta lambda of the fiber Bragg grating FBG in the fiber is obtainedB(ii) a The Raman optical time domain reflection technology is used for sensing and measuring the second fiber core a2 in the multi-core optical fiber 7 to obtain the luminous flux psi of Stokes scattering light in the optical fibers(T) and anti-Stokes scattered light luminous flux ψas(T); and (3) carrying out sensing measurement on the third fiber core a3 and the fourth fiber core a4 in the multi-core optical fiber 7 by utilizing a polarized light technology to obtain the change condition of the light intensity in the optical fiber, and extracting the vibration frequency.
And 20, comprehensively processing data acquired by the fiber grating technology and the Raman optical time domain reflection technology to obtain the current temperature value and strain value of the multi-core fiber.
Firstly, realizing quantitative analysis of temperature by a Raman time domain reflection technology, specifically comprising the following steps: psi detected from Raman optical time domain reflectometrys(T) and psiasAnd (T), demodulating the current temperature value T of the multi-core optical fiber by using a Raman formula. Combined with Raman formulaPresetting a reference temperature T0Corresponding psias(T0) And psis(T0) Are all known, the Raman temperature coefficient μTCalibrating in advance; psi at temperature Tas(T) and psis(T) has been measured by the raman thermometer 2, so the unique unknown T can be solved using the raman formula.
Then, temperature compensation is carried out on the fiber grating technology through a Raman time domain reflection technology, and quantitative analysis of strain is realized, which specifically comprises the following steps: temperature value T demodulated based on Raman formula and delta lambda detected by fiber grating technologyBAnd demodulating the current strain value epsilon of the multi-core fiber by using a grating formula. Wherein the temperature variation Δ T can be determined based on the temperature value T, in combination with a grating formula Δ λB＝αεε+αTΔ T, Grating Strain coefficient αεAnd grating temperature coefficient αTAre all calibrated in advance, Δ λBMeasured by the grating demodulator 1, so that the unique unknown epsilon can be solved by the grating formula.
The process of pre-calibrating the coefficients in the raman formula and the grating formula specifically comprises the following steps:
heating the multi-core fiber to different temperatures for multiple times, and respectively measuring the corresponding psisAnd psiasDetermining the Raman temperature coefficient mu after multiple fitting according to the Raman formula (4)T；
Heating the multi-core fiber to different temperatures for multiple times (strain needs to be kept unchanged), and respectively measuring the corresponding wavelength variation delta lambdaBDetermining α grating temperature coefficients in the grating formula after multiple fits according to formula (9)TAnd the temperature range to which the grating formula is applicable;
applying different strains to the multi-core fiber for multiple times (temperature needs to be kept unchanged), and respectively measuring corresponding wavelength variation delta lambdaBDetermining α the grating strain coefficient in the grating formula after multiple fitting according to formula (7)εAnd the strain range for which the grating formula is applicable.
And step 30, comprehensively processing the data acquired by the fiber grating technology and the polarized light technology, determining whether the whole optical fiber link has vibration or strain, and obtaining the current vibration frequency value of the multi-core optical fiber.
For the magnitude of the strain or the vibration intensity, the polarized light technology can only realize qualitative analysis, so that the result of the qualitative analysis of the vibration by the polarized light technology is used as a supplement of the point type vibration measurement by the fiber grating technology, and whether the whole optical fiber link has the events such as vibration or strain can be further determined.
In addition, the polarized light technology can also realize the extraction of the vibration frequency, and in short, the vibration frequency of the whole optical fiber can be measured. And when the vibration continuously occurs and the vibration has a periodic relationship, the frequency extraction is not considered, and when the vibration continuously occurs and the vibration has a periodic relationship, the current vibration frequency value of the multi-core optical fiber can be calculated by using the pulse change times in a certain time interval detected by the polarized light technology. When the vibration is a single frequency, the pulse change is measured n times in the time interval t, and the vibration frequency f is equal to n/t. The multi-frequency condition is essentially the superposition of a plurality of single-frequency signals, and the signal frequency can be obtained only through Fourier transform.
In the above-mentioned multi-parameter sensing method provided by the utility model, the fiber grating technology, the raman optical time domain reflectometer technology and the polarized light technology are utilized, and the multi-path parallel optical link of the multi-core fiber is matched to perform synchronous measurement on different fiber cores in the multi-core fiber, so as to realize simultaneous sensing of strain, temperature and vibration of the fiber; the optical fiber grating technology and the Raman optical time domain reflectometer technology are combined, so that the temperature and the strain can be synchronously measured and effectively distinguished, quantitative analysis is carried out, the state of the whole optical fiber can be effectively obtained through the combination of the optical fiber grating technology and the polarized light technology, and the vibration frequency is extracted.
The above description is only exemplary of the present invention and should not be taken as limiting the scope of the present invention, as any modifications, equivalents, improvements and the like made within the spirit and principles of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing is characterized by comprising a grating demodulator (1), a Raman temperature measuring instrument (2), a polarization analyzer (3), a synchronous trigger circuit (4) and a multi-core optical fiber coupler (6);
the grating demodulator (1), the Raman temperature measuring instrument (2) and the polarization analyzer (3) are respectively connected with the multi-core fiber coupler (6), the multi-core fiber coupler (6) is connected with a multi-core fiber (7), so that different fiber cores of the multi-core fiber (7) can be synchronously measured through the grating demodulator (1), the Raman temperature measuring instrument (2) and the polarization analyzer (3), and simultaneous sensing of temperature, strain and vibration is realized;
the synchronous trigger circuit (4) is respectively connected with the grating demodulator (1), the Raman temperature measuring instrument (2) and the polarization analyzer (3) and is used for triggering the grating demodulator (1), the Raman temperature measuring instrument (2) and the polarization analyzer (3) to synchronously transmit light pulses and acquire data.
2. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the multi-parameter optical fiber sensing instrument further comprises a first optical fiber interface, a second optical fiber interface, a third optical fiber interface and a fourth optical fiber interface;
the grating demodulator (1) is connected with the front end of a first fiber core in the multi-core fiber (7) through the first fiber interface and the multi-core fiber coupler (6);
the Raman temperature measuring instrument (2) is connected with the front end of a second fiber core in the multi-core fiber (7) through the second fiber interface and the multi-core fiber coupler (6);
the polarization analyzer (3) is connected with the front end of a third fiber core in the multi-core fiber (7) through the third fiber interface and the multi-core fiber coupler (6); the connection with the front end of a fourth fiber core in the multi-core fiber (7) is realized through the fourth fiber interface and the multi-core fiber coupler (6); wherein the end of the third core is connected to the end of the fourth core.
3. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the grating demodulator (1) comprises a first broadband light source (101), an optical circulator (102) and a spectrometer (103) which are connected in sequence;
the optical circulator (102) is externally connected with the multi-core optical fiber (7) through a corresponding optical fiber interface, and the spectrometer (103) is connected with the synchronous trigger circuit (4);
after the continuous broadband light sent by the first broadband light source (101) is transmitted to a Fiber Bragg Grating (FBG), reflected light enters the spectrometer (103) through the optical circulator (102), and wavelength shift is measured by the spectrometer (103).
4. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the grating demodulator (1) comprises a second broadband light source (104), a first coupler (105), a first optical splitter (106), a first photodetector (107), an edge filter (108), a second photodetector (109) and a first data acquisition card (110) which are connected in sequence;
the first coupler (105) is externally connected with the multi-core optical fiber (7) through a corresponding optical fiber interface, the first data acquisition card (110) is connected with the synchronous trigger circuit (4), and the second broadband light source (104) is used for emitting continuous broadband light;
the first photoelectric detector (107) is respectively connected with the first optical splitter (106) and the first data acquisition card (110), the second photoelectric detector (109) is respectively connected with the edge filter (108) and the first data acquisition card (110), and the edge filter (108) is connected with the first optical splitter (106).
5. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the grating demodulator (1) comprises a third broadband light source (111), a second coupler (112), an F-P tunable filter (113), a third photodetector (114) and a second data acquisition card (115) which are connected in sequence;
the second coupler (112) is externally connected with the multi-core optical fiber (7) through a corresponding optical fiber interface, the second data acquisition card (115) is connected with the synchronous trigger circuit (4), and the third broadband light source (111) is used for emitting continuous broadband light.
6. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 5, wherein the grating demodulator (1) further comprises an amplifier (116), a control system (117) and a signal generator (118);
the amplifier (116) is connected to the third photodetector (114) and the control system (117), respectively, the control system (117) is connected to the signal generator (118), and the signal generator (118) is connected to the F-P tunable filter (113) to apply a scanning voltage to the F-P tunable filter (113).
7. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the grating demodulator (1) comprises a tunable narrow-band light source (119), a third coupler (120) and a digital oscilloscope (121) which are connected in sequence, and the digital oscilloscope (121) is further connected with the tunable narrow-band light source (119); the tunable narrow-band light source (119) is fixed on the PZT (122), and the PZT (122) is driven by a sawtooth wave or a sinusoidal voltage;
the third coupler (120) is externally connected with the multi-core optical fiber (7) through a corresponding optical fiber interface, the digital oscilloscope (121) is connected with the synchronous trigger circuit (4), and the tunable narrow-band light source (119) is used for emitting continuous narrow-band light.
8. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the Raman temperature measuring instrument (2) comprises a pulse light source (201), a WDM coupler (202), a second optical splitter (203), a photoelectric detection module and a third data acquisition card (204) which are connected in sequence;
the WDM coupler (202) is externally connected with the multi-core optical fiber (7) through a corresponding optical fiber interface, and the pulse light source (201) and the third data acquisition card (204) are respectively connected with the synchronous trigger circuit (4);
the photoelectric detection module comprises a fourth photoelectric detector (205) and a fifth photoelectric detector (206) which are respectively used for detecting Stokes Raman scattered light and anti-Stokes Raman scattered light reflected back in the optical fiber.
9. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing of claim 1, wherein the polarization analyzer (3) comprises a light source (301), a polarizer (302), an analyzer (303), a photodetector (304) and a fourth data acquisition card (305) which are connected in sequence;
the polarizer (302) and the analyzer (303) are respectively externally connected with the multi-core fiber (7) through corresponding fiber interfaces, and the light source (301) and the fourth data acquisition card (305) are respectively connected with the synchronous trigger circuit (4).
10. The multi-parameter synchronous sensing acquisition instrument based on multi-core optical fiber sensing according to any one of claims 1 to 9, wherein the synchronous trigger circuit (4) is realized by adopting a 555 timer.
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| CN111982166A (en) * | 2020-08-14 | 2020-11-24 | 桂林电子科技大学 | Photoelectric detector array and system for multi-core optical fiber spectral coupling |
| CN113310564A (en) * | 2021-05-08 | 2021-08-27 | 武汉理工大学 | System and method for measuring vibration parameter and temperature parameter of oil well casing |
| CN113310564B (en) * | 2021-05-08 | 2024-01-09 | 武汉理工大学 | System and method for measuring vibration parameters and temperature parameters of oil well casing |
| CN113446962A (en) * | 2021-07-13 | 2021-09-28 | 西南交通大学 | Temperature-insensitive curvature sensor based on strong-coupling multi-core fiber, curvature measuring device and method |
| CN113446962B (en) * | 2021-07-13 | 2022-12-06 | 西南交通大学 | Temperature-insensitive curvature sensor based on strong-coupling multi-core fiber, curvature measuring device and method |
| CN113532539A (en) * | 2021-07-27 | 2021-10-22 | 安徽理工大学 | Optical fiber sensing system, method and device for simultaneously measuring temperature, strain and pressure |
| CN113532539B (en) * | 2021-07-27 | 2024-01-26 | 安徽理工大学 | Optical fiber sensing system, method and device for simultaneously measuring temperature, strain and pressure |
| CN116295916A (en) * | 2023-05-22 | 2023-06-23 | 常州博瑞电力自动化设备有限公司 | Online monitoring device and monitoring method for temperature of voltage divider |
| CN116295916B (en) * | 2023-05-22 | 2023-10-24 | 常州博瑞电力自动化设备有限公司 | Online monitoring device and monitoring method for temperature of voltage divider |
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