CN104864911B - High-speed demodulating apparatus and method based on Fabry-perot optical fiber chamber and the double parameter combined measurements of fiber grating - Google Patents

Abstract

The invention is a high-speed demodulation device and method based on the double-parameter joint measurement of optical fiber P-cavity and optical fiber grating. The high-speed demodulation device includes a light source module, a 3dB coupler, a circulator, a sensing unit and a demodulation unit. The high-speed demodulation method includes: obtaining the relationship between the demodulation error of the fiber grating, the temperature change, and the pressure/strain change through calibration, and the calibration to obtain the cavity length change, temperature change, pressure/strain The relationship between the variation; demodulate the cavity length variation of the optical fiber FAP cavity and the drift of the reflection center wavelength of the fiber grating; obtain the temperature variation and pressure/strain variation. Compared with the prior art, the present invention can realize dual-parameter measurement through fast demodulation based on the sensing of the fiber-optic F-P cavity and the fiber-optic grating, and at the same time compensates for the interference caused by the fiber-optic F-P interference spectrum to the demodulated fiber grating. The impact on the temperature measurement caused by this method, and the cost of realizing this solution is low.

Description

High-speed demodulation device based on double-parameter joint measurement of fiber-optic P-cavity and fiber Bragg grating and method

technical field

The invention relates to the technical field of optical fiber sensing, in particular to a high-speed demodulation device and method based on dual-parameter joint measurement of an optical fiber peroxide cavity and an optical fiber grating.

Background technique

In recent years, dual-parameter (temperature, pressure/strain) simultaneous sensing technology based on optical fiber sensors is a very active research field. This type of sensing is mainly used in composite materials, large building structures, aerospace vehicles, military products, etc. Structural health self-diagnosis, environmental adaptation, damage self-healing, etc.

As a sensor, the optical fiber F-P cavity obtains the change of the external physical quantity by demodulating the length of the cavity. It has the advantages of simple structure, small size, convenient installation, high reliability, high sensitivity, fast response, and single optical fiber signal transmission. It has become an optical fiber sensor. One of the hot spots of technology and application research. Fiber Bragg grating can realize the detection to be measured by demodulating the drift of the center wavelength of fiber Bragg grating reflection. Its passive characteristics, anti-electromagnetic interference, corrosion resistance and temperature resistance make fiber Bragg grating suitable for health monitoring in some harsh environments. In recent years, combining the characteristics of fiber FAP cavity and fiber Bragg grating to realize dual-parameter measurement has attracted the attention of scholars.

In the prior art, in the technology of composite sensing and demodulation of fiber-optic Perot cavity and fiber Bragg grating [such as document 1: Rao Yunjiang, Zeng Xiangkai, Zhu Yong, etc., the strain temperature of fiber Bragg grating in extrinsic Fabry-Perot interferometer Sensors and their applications [J]. Acta Optics Sinica, 2002, 22(1): 85-88; Literature 2: Baochen Sun, Liping Yang, Yanliang Du, etal. Research on integrated fiber Bragg grating/extrinsic Fabry-Perot sensor [C ], Proceedings of the 6th World Congress on Intelligent Control and Automation, Dalian, China, 2006;], generally a spectrometer is used to scan the spectrum, and by observing the spectral information, the phase demodulation method is used to demodulate the cavity length of the optical fiber F-P cavity, directly Observe the movement of the center wavelength of the fiber grating in the spectrum to demodulate the center wavelength of the fiber grating reflection. The existing demodulation method has a slow demodulation speed and cannot meet the requirement of fast demodulation.

Contents of the invention

Aiming at the problem of slow demodulation speed in the prior art, the invention provides a high-speed demodulation device and method based on joint measurement of dual parameters of optical fiber FRP cavity and optical fiber grating. The high-speed demodulation device and method of dual-parameter joint measurement of the present invention are suitable for measurement based on optical fiber P-cavity and optical fiber Bragg grating sensing, and can realize rapid measurement of temperature, pressure/strain changes in the environment.

The present invention provides a high-speed demodulation device based on dual-parameter joint measurement of fiber optic F-P cavity and fiber Bragg grating, including: a light source module, a 3dB coupler, a circulator, a sensing unit and a demodulation unit.

The light source module includes three narrow-band light sources and a wide-spectrum light source, and the spectra of the three narrow-band light sources and the spectrum of the wide-spectrum light source do not overlap each other; the sensing unit includes a fiber optic peroxide cavity sensing structure and a fiber grating sensing structure; The demodulation unit includes a 1×3 dense wavelength division multiplexer (DWDM), a 1×2 coarse wavelength division multiplexer (CWDM), a photoelectric detector, a signal conditioning circuit, a data acquisition card and a computer.

Three beams of narrow-band lasers and one beam of broad-spectrum light emitted from the light source module are simultaneously transmitted to the 4×1 3dB coupler by four single-mode optical fibers, and the four beams are coupled into the circulator and then transmitted to the sensing unit .

The optical signal introduced into the sensing unit first enters the FBG sensing structure, and the light wave conforming to the reflection center wavelength of the FBG is reflected, and other light waves are transmitted into the FRP cavity sensing structure where multi-beam interference occurs, and the interfering light returns The fiber grating senses the structure and is directly transmitted by it, and the interfering light and the reflected light of the fiber grating form a superimposed spectrum.

The superimposed spectrum is respectively incident into 1×3DWDM and 1×2CWDM through 1×2 3dB coupler, and the optical signal is divided into five channels. 1×3DWDM is matched with three narrow-band light sources, and the three beams of light output by 1×3DWDM are used to demodulate the cavity length of the optical fiber FRP cavity; the two beams of light output by 1×2CWDM are used for demodulation of the reflection center wavelength of the fiber grating . The five optical signals are converted into electrical signals by photodetectors and enter the signal conditioning unit. The electrical signals are converted into digital signals by the signal conditioning unit and transmitted to the computer for storage by the data acquisition card. The electrical signal is demodulated in the computer to obtain the variation of the cavity length of the fiber Fab cavity and the drift of the reflection center wavelength of the fiber grating.

The sensing unit is a composite sensor composed of a fiber optic Fab cavity and a stress-free packaged fiber grating, or a series structure of a fiber optic Fab pressure/strain sensor and a fiber grating temperature sensor.

According to the requirement of light source for demodulation, the narrow-band light source is a DFB laser, and the broad-spectrum light source is an amplified spontaneous emission source (ASE) or a superfluorescent light source (SFS) based on a doped fiber.

Based on the above-mentioned high-speed demodulation device, the present invention also provides a high-speed demodulation method based on the dual-parameter joint measurement of the fiber-optic cavity and the fiber Bragg grating, including the following specific steps:

Step 1: Carry out a calibration experiment to obtain the relationship between the error drift Δλ ₁ caused by the demodulation of the FBG reflection center wavelength, the ambient temperature change ΔT, and the pressure/strain change ΔX, as shown below:

Δλ ₁ =K ₁ ΔT+K ₂ ΔX (1)

Obtain the relationship between the cavity length variation ΔL of the optical fiber F-P cavity, the ambient temperature variation ΔT, and the pressure/strain variation ΔX:

ΔL=K ₃ ΔT+K ₄ ΔX (2)

Step 2: demodulating the variation of the cavity length of the optical fiber FAP cavity and the drift of the reflection center wavelength of the fiber grating;

Through the three-wavelength digital phase demodulation method, the cavity length variation ΔL of the FRP cavity can be obtained, and the drift of the FBG reflection center wavelength Δλ can be obtained through the edge filtering method; where Δλ includes the FBG reflection center wavelength The demodulation error drift Δλ ₁ and the actual center wavelength drift Δλ ₂ of the FBG due to temperature changes, and the actual drift Δλ ₂ of the FBG reflection center wavelength can be expressed as:

Δλ ₂ =Δλ-Δλ ₁ (3)

Step 3: Solve the temperature change ΔT and pressure/strain change ΔX

Utilize formula (1), ( ₂ ), (3), and comprehensive temperature change Δ T and the relation between the actual drift Δ λ of FBG center wavelength, obtain temperature change Δ T can be expressed as:

The variation ΔX of pressure/strain is:

In formulas (4) and (5), A is the temperature sensitivity coefficient of the fiber grating. Using formulas (4) and (5) to finally obtain the variation of temperature and pressure/strain in the environment.

The present invention has the following beneficial effects: the present invention is based on the advantages of fast demodulation speed of intensity demodulation, and completes the design of a demodulation device and method for simultaneous rapid measurement of two parameters (temperature, pressure/strain), so that the two parameters can be quickly measured simultaneously On the other hand, through the calibration experiment, the influence of the interference spectrum returned by the fiber-optic P-cavity on the temperature measurement caused by the demodulation of the fiber-optic grating is compensated, making the measurement results more accurate; the demodulation scheme avoids the use of traditional fiber-based P-cavities The expensive spectrometer required for dual-parameter measurement with fiber gratings greatly reduces the cost of demodulation.

Description of drawings

Fig. 1 is the structural representation of the high-speed demodulation device based on the double-parameter joint measurement of the optical fiber Perth cavity and the fiber Bragg grating of the present invention;

Fig. 2 is the schematic diagram of the simulated superimposed spectrum returned by the wide-spectrum light in the present invention after passing through the fiber-optic cavity and the fiber grating;

Fig. 3 is the schematic diagram of the experimental device for the relationship between the demodulation error drift and the temperature variation of the calibration fiber grating reflection center wavelength provided by the present invention;

Fig. 4 is the simulated superimposed spectrogram of the superimposed spectrum returned by the broad-spectrum light after passing through the optical fiber peroxide cavity and the fiber grating before and after the ambient temperature changes when there is no pressure/strain effect;

Fig. 5 is the schematic diagram of the experimental device for the relationship between the demodulation error drift and the pressure/strain variation of the calibration fiber grating reflection center wavelength provided by the present invention;

Fig. 6 is the simulated superimposed spectrogram of the superimposed spectrum returned by the wide-spectrum light after passing through the optical fiber peroxide cavity and the fiber grating before and after the environmental pressure/strain change when there is no temperature change;

Fig. 7 is a detailed schematic diagram of the fiber grating part in the simulated superimposed spectrogram before and after the environmental pressure/strain change of the superimposed spectrum returned by the broadband light after passing through the fiber peroxide cavity and the fiber grating when there is no temperature change;

8 is a schematic diagram of an experimental device for calibrating the relationship between the cavity length variation, temperature variation, and pressure/strain variation of an optical fiber FAP cavity provided by the present invention;

Fig. 9 is a schematic diagram of an experimental device for calibrating the temperature sensitivity of an optical fiber grating in the present invention.

in:

1-light source module, 2-first DFB laser, 3-second DFB laser, 4-third DFB laser, 5-broad spectrum light source, 6-single-mode fiber, 7-4×1 3dB coupler, 8- Circulator, 9-1×2 3dB coupler, 10-fiber grating sensing structure, 11-fiber Perth cavity sensing structure, 12-sensing unit, 13-1×3DWDM, 14-1×2CWDM, 15 -Photodetector, 16-Signal Conditioning Circuit, 17-Data Acquisition Card, 18-Computer, 19-Demodulation Unit, 20-Fiber Bragg Grating Reflection Spectrum, 21-Fiber Perth Cavity Interference Spectrum, 22-Temperature Loading Device, 23 -Optical fiber connector, 24-flange, 25-spectrometer, 26-pressure/strain loading device, 27-temperature, pressure/strain loading device, 28-SM125 demodulator.

detailed description

Specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

The invention senses changes in external temperature and pressure/strain, and simultaneously demodulates the cavity length variation of the optical fiber FAP cavity and the reflection center wavelength drift of the fiber grating, thereby realizing the measurement of the temperature, pressure/strain variation. The present invention integrates the three-wavelength digital phase demodulation method based on intensity demodulation and the edge filtering method into a set of demodulation schemes, respectively demodulates the fiber-optic cavity and the fiber grating, instead of using the spectral scanning method, This greatly improves the speed of demodulation. On the other hand, a calibration experiment was carried out before the measurement, which compensated the influence on the temperature measurement caused by the return interference spectrum of the fiber Fab cavity to the demodulation of the fiber grating, so that the measurement results were more accurate.

As shown in FIG. 1 , the high-speed demodulation device based on the dual-parameter joint measurement of fiber optic F-P cavity and fiber Bragg grating includes a light source module 1 , a 3dB coupler, a circulator 8 , a sensing unit 12 and a demodulation unit 19 . A single-mode optical fiber is used for optical signal transmission between each component.

The light source module 1 includes three DFB lasers and a wide-spectrum light source 5 , and the three DFB lasers are a first DFB laser 2 , a second DFB laser 3 and a third DFB laser 4 . The spectra of the three narrow-band light sources do not overlap with the spectrum of the broadband light source. According to the requirement of light source for demodulation, the narrow-band light source is DFB (Distributed Feed Back) laser, and the wide-spectrum light source is Amplified Spontaneous Emission Source (ASE) or Super Fluorescence Source (SFS) based on doped fiber.

The sensing unit 12 includes a fiber Bragg grating sensing structure 10 and a fiber Fab cavity sensing structure 11 . The sensing unit 12 is a composite sensor composed of a fiber optic Fab cavity and a stress-free packaged fiber grating, or a series structure of a fiber optic Fab pressure/strain sensor and a fiber grating temperature sensor.

Demodulation unit 19 includes 1×3 dense wavelength division multiplexer (DWDM) 13, 1×2 coarse wavelength division multiplexer (CWDM) 14, photodetector 15, signal conditioning circuit 16, data acquisition card 17 and computer 18 .

The three beams of narrow-band lasers and one beam of broad-spectrum light emitted from the light source module 1 are coupled into four single-mode optical fibers 6 at the same time. into the sensing unit 12. The optical signal first enters the FBG sensing structure 10, and the light wave conforming to the reflection center wavelength of the FBG is reflected, and other light waves are transmitted into the FRP cavity sensing structure 11, where multi-beam interference occurs, and the interfering light returns to the FBG sensing structure. The structure 10 is directly transmitted by it, and the interference light and the reflected light of the fiber grating form a superimposed spectrum, and the superimposed spectrum is shown in FIG. 2 . Among them, the optical fiber Fab cavity sensing structure 11 is used for pressure/strain measurement, and the fiber grating sensing structure 10 is used for temperature measurement.

The superimposed spectrum shown in Figure 2 is respectively incident into 1×3DWDM13 and 1×2CWDM14 through 1×2 3dB coupler 9, thereby dividing the optical signal into five paths. The 1×3DWDM13 is matched with three narrow-band light sources, and the three beams of light passing through are used to demodulate the cavity length of the optical fiber FAP cavity; the light passing through the 1×2CWDM14 is used for demodulation of the center wavelength of the fiber grating reflection. Through the photodetector 15 , the five optical signals are converted into electrical signals and enter the signal conditioning unit 16 . The electrical signal is converted into a digital signal by the signal conditioning unit 16 and transmitted by the data acquisition card 17 to the computer 18 for storage. Through the signal processing program, the stored digital signal is analyzed, and the three-wavelength digital phase demodulation method and the edge filter method are used to quickly demodulate the cavity length variation of the optical fiber PWP cavity and the drift of the fiber Bragg grating reflection center wavelength, respectively. In this way, joint measurement of two parameters (temperature, pressure/strain) is realized.

Since the three narrow-band lasers are independent of the broad-spectrum light, the three laser beams used to demodulate the length information of the optical fiber FP cavity will not be affected by the broad-spectrum light. However, when using the broadband light returned from the fiber Bragg grating to demodulate the fiber Bragg grating, since the returned broadband light is affected by the interference spectrum of the fiber FRP cavity, the error drift will be generated when the fiber Bragg grating reflects the center wavelength, which needs to be passed calibration to compensate. On the other hand, since the variation of the cavity length of the optical fiber Fab cavity is due to the dual effects of temperature variation and pressure/strain variation, it also needs to be compensated.

Based on the above-mentioned high-speed demodulation device, the high-speed demodulation method based on the dual-parameter joint measurement of fiber-optic cavity and fiber Bragg grating provided by the present invention, the specific implementation steps are as follows:

Step 1: Carry out a calibration experiment.

① Calibration experiment 1: Obtain the relationship between the demodulation error drift Δλ ₁ of the FBG reflection center wavelength, the ambient temperature change ΔT, and the pressure/strain change ΔX, as shown below:

Δλ ₁ =K ₁ ΔT+K ₂ ΔX (1)

K1 acquisition method: _In the embodiment of the present invention, the calibration experiment device shown in FIG. 3 is used, and the temperature loading device 22 is used to load only temperature on the sensing unit 12, and the temperature change ΔT is given. The superimposed spectrum returned by the sensing unit 12 before and after the temperature change is shown in Fig. 4. The temperature change ΔT not only causes the reflection center wavelength of the fiber grating to drift by Δλ, but also causes the length of the FRP cavity of the fiber to change by ΔL _T. The light intensity change information obtained after the light passes through 1×2 CWDM is demodulated by the edge filter method to obtain the drift amount of the reflection center wavelength of the fiber grating including the error demodulation amount. The spectrometer 25 is used to obtain the actual shift amount of the reflection center wavelength of the fiber grating. Through the difference between the actual drift and the demodulation drift, the error demodulation drift of the reflection center wavelength of the fiber grating caused by the temperature change can be obtained, so as to obtain K ₁ through calibration.

As shown in Figure 3, the sensor unit 12 in the high-speed demodulation device of the present invention is placed in the temperature loading device 22, and an optical fiber connector 23 and a flange are arranged at the output end of the circulator 8 in the high-speed demodulation device of the present invention The disk 24 can be connected to the spectrometer 25 through the optical fiber connector 23 and the flange 24. The temperature loading device 22 carries out temperature loading on the sensing unit 12, and the optical signal in the sensing unit 12 after temperature modulation is detected by the demodulation unit 19, and finally demodulated by the linear filtering method in the computer to obtain the reflection center wavelength of the fiber grating. Drift Δλ. Δλ includes the demodulation error drift Δλ ₁ of the fiber Bragg grating reflection center wavelength and the actual center wavelength drift Δλ ₂ of the fiber Bragg grating due to temperature changes. The optical fiber connector 23 and the flange 24 are connected to the spectrometer 25, and the optical signal in the sensing unit 12 after temperature modulation is detected by the spectrometer 25 to obtain the actual drift Δλ ₂ of the reflection center wavelength of the fiber grating. Thus, the demodulation error drift Δλ ₁ of the reflection center wavelength of the fiber grating can be obtained. Through the difference between the demodulation drift and the actual drift, the demodulation error drift of the center wavelength reflected by the fiber grating due to the temperature change can be obtained, so as to obtain K ₁ through calibration.

K ₂ acquisition method: the schematic diagram of the calibration experiment device shown in Figure 5, under the condition that the ambient temperature does not change, the pressure/strain loading device 26 is used to load the pressure/strain on the sensing unit 12, and the pressure/strain causes the optical fiber Fab cavity Figure 6 shows the comparison of the superimposed spectrum before and after the change of ΔL, and the corresponding detailed view of the fiber grating part is shown in Figure 7. When the superimposed spectrum passes through 1×3CWDM, the change of light intensity will be detected, and the error drift of the reflection center wavelength of the fiber grating can be obtained through demodulation by the linear filtering method, so as to obtain K ₂ through calibration.

As shown in Figure 5, the sensing unit 12 in the high-speed demodulation device of the present invention is placed in a pressure/strain loading device 26, and the stress/strain loading device 26 carries out stress/strain loading on the sensing unit 12, and the sensing unit 12 After the optical signal in is modulated by stress/strain, it is detected by demodulation unit 19, and the linear filtering method is used to demodulate to obtain the error demodulation drift of the fiber grating reflection center wavelength caused by stress/strain, so as to calibrate and obtain K ₂ .

②Calibration experiment 2: The relationship between the cavity length variation ΔL of the optical fiber FRP cavity, the ambient temperature variation ΔT, and the pressure/strain variation ΔX:

ΔL=K ₃ ΔT+K ₄ ΔX (2)

K ₃ , K ₄ acquisition method: use the calibration device shown in Figure 8, use the temperature, pressure/strain loading device 27 to load the temperature and pressure/strain on the sensing unit 12, and use the SM125 demodulator 28 to calibrate the optical fiber P-cavity Long, so as to calibrate the values of K ₃ and K ₄ .

As shown in Figure 8, the sensor unit 12 of the present invention is put into temperature, pressure/strain loading device 27 separately, the output end of the sensor unit 12 is connected with the SM125 demodulator 28, and the SM125 demodulator 28 is connected to the computer 18. The light emitted by the built-in light source of the SM125 demodulator 28 enters the sensing unit 12, and the temperature, pressure/strain loading device 27 is used to load the sensing unit 12 with temperature and pressure/strain, and the optical signal modulated by the temperature and stress/strain returns to the SM125 The demodulator 28 opens the demodulation program of SM125 on the computer, and runs the demodulation program to obtain the calibrated cavity length value of the optical fiber F-P cavity. Use the SM125 demodulator 28 to calibrate the cavity length of the optical fiber F-P-cavity, so as to calibrate K ₃ and K ₄ .

The calibration experiment in step 1 is completed before the dual-parameter measurement. Equation (1) is used to compensate for the influence of the demodulated fiber grating on the temperature measurement caused by the interference spectrum returned by the fiber-optic F-P cavity.

Step 2: demodulating the variation of the cavity length of the optical fiber FAP cavity and the drift of the reflection center wavelength of the optical fiber grating.

Using the schematic diagram of the device shown in Figure 1, the sensing unit 12 senses the external temperature, pressure/strain, uses the three-wavelength digital phase demodulation algorithm to demodulate the cavity length variation ΔL of the fiber-optic P-cavity, and uses the edge filter method to demodulate the optical fiber The change amount Δλ of the grating reflection center wavelength. Among them, Δλ includes the demodulation error drift of the fiber Bragg grating reflection center wavelength Δλ ₁ and the actual drift of the reflection center wavelength of the fiber Bragg grating due to temperature changes Δλ ₂ , the actual drift of the fiber Bragg grating reflection center wavelength Δλ ₂ can be Expressed as:

Δλ ₂ =Δλ-Δλ ₁ (3)

Step 3: Solve the temperature variation ΔT and the pressure/strain variation ΔX.

_The relationship between the temperature change ΔT and the actual drift Δλ of the fiber grating reflection center wavelength is:

Δλ ₂ =AΔT (4)

Among them, A is a constant, which is called the temperature sensitivity coefficient of the fiber Bragg grating. For the bare fiber Bragg grating sensing structure, its value is A=λ _B (α+ξ), α is the thermal expansion coefficient of the fiber used in the fiber Bragg grating; ξ is the fiber Bragg grating used The thermo-optic coefficient of the fiber; λ _B is the reflection center wavelength of the fiber grating in the free state. It should be noted that, first, due to the difference in doping composition and doping concentration, the thermal expansion coefficient and thermo-optic coefficient of various optical fibers are quite different, resulting in the difference in A value; Different conditions will also lead to differences in A values. Therefore, in practical applications, it needs to be calibrated before it can be used for actual temperature measurement. As shown in the schematic diagram of the experimental device in Figure 9, the light emitted by the wide-spectrum light source 5 is transmitted to the sensing unit 12 by the 3dB coupler 9 of 1×2, and the sensing unit 12 is placed in the temperature loading device 22, and the temperature loading device 22 pairs The sensing unit 12 is subjected to temperature loading, and the temperature-modulated optical signal in the sensing unit 12 returns to the 1×2 3dB coupler 9 and is detected by the spectrometer 25 . The spectrometer 25 is used to detect the reflection center wavelength of the fiber grating sensing structure at the corresponding temperature, so as to obtain the A value through calibration.

Using formulas (1), (2), (3), and (4), the temperature change ΔT can be expressed as:

The variation ΔX of pressure/strain is:

Using formulas (5) and (6) to finally obtain the variation of temperature and pressure/strain in the environment.

Claims (5)

1. a kind of high-speed demodulating apparatus based on Fabry-perot optical fiber chamber and the double parameter combined measurements of fiber grating, it is characterised in that should Device includes：Light source module, three-dB coupler, circulator, sensing unit and demodulating unit；Single-mode fiber is used between each part Carry out optical signal transmission；

The light source module includes three narrow-band light sources and a wide spectrum light source, the spectrum of three narrow-band light sources and wide spectrum light source Spectrum non-overlapping copies；The sensing unit includes Fabry-perot optical fiber chamber sensing arrangement and optical fiber grating sensing structure；The demodulation is single Member includes 1 × 3 dense wave division multiplexer, 1 × 2 Coarse Wave Division Multiplexer, photodetector, signal conditioning circuit, data collecting card With computer；

The three beams laser of narrowband that is sent in light source module and a branch of wide spectrum optical by four single-mode fiber simultaneous transmissions to 4 × 1 3dB After coupler, four bundles light is coupled to be incided in circulator, then incoming sensing unit；

The optical signal of incoming sensing unit is first incident to enter optical fiber grating sensing structure, meets fiber grating reflection kernel wavelength Light wave is reflected, and other light-wave transmissions enter Fabry-perot optical fiber chamber sensing arrangement and multiple-beam interference occurs wherein, and interference light is returned Back into optical fibers grating sensing structure is simultaneously directly transmitted by it, and interference light is superimposed spectrum with the reflected light formation of fiber grating；

It is superimposed spectrum incident into 1 × 3 dense wave division multiplexer and 1 × 2 CWDM respectively by 1 × 2 three-dB coupler Device, is divided into five tunnels by optical signal；1 × 3 dense wave division multiplexer matches with three narrow-band light sources, by 1 × 3 dense wave division multipurpose The chamber that the three-beam of device output is used to demodulate Fabry-perot optical fiber chamber is long；The two-beam of 1 × 2 Coarse Wave Division Multiplexer output is used for optical fiber light The demodulation of grid reflection kernel wavelength；Five road optical signals are converted to electric signal through photodetector and enter signal condition unit, electricity Signal, which is changed into data signal by signal condition unit and is transferred to computer by data collecting card, to be stored, by telecommunications Number it is demodulated, obtains the change of cavity length amount of Fabry-perot optical fiber chamber and the drift value of fiber grating reflection kernel wavelength.

2. a kind of high speed based on Fabry-perot optical fiber chamber and the double parameter combined measurements of fiber grating according to claim 1 is demodulated Device, it is characterised in that the sensing unit is the composite sensing of the fiber grating composition of Fabry-perot optical fiber chamber and Non-stress packaging Device, or be Fabry-perot optical fiber pressure/strain transducer and the cascaded structure of fiber-optical grating temperature sensor.

3. a kind of high speed based on Fabry-perot optical fiber chamber and the double parameter combined measurements of fiber grating according to claim 1 is demodulated Device, it is characterised in that described narrow-band light source is distributed feedback laser, described wide spectrum light source uses Amplified Spontaneous spoke Penetrate light source or the super-fluorescence light source based on doped fiber.

4. the high speed demodulation method based on the high-speed demodulating apparatus described in claim 1, it is characterised in that the high speed demodulation method Realize that step is as follows：

Step one：Carry out calibration experiment；

Obtain error drift amount Δ λ caused by demodulating fiber bragg grating reflection kernel wavelength₁With variation of ambient temperature amount Δ T, pressure/ Relation between strain variation amount Δ X, it is as follows：

Δλ₁=K₁ΔT+K₂ΔX (1)

Between the change of cavity length amount Δ L and variation of ambient temperature amount Δ T, pressure/strain variation amount Δ X that obtain Fabry-perot optical fiber chamber Relation：

Δ L=K₃ΔT+K₄ΔX (2)

K₁、K₂、K₃And K₄For four coefficients, obtained by rating test；

Step 2：Demodulate the drift value of the change of cavity length amount of Fabry-perot optical fiber chamber and the reflection kernel wavelength of fiber grating；

Enter traveling optical signal measurement using high-speed demodulating apparatus, demodulated in a computer using the digital phase demodulating method of three wavelength To the change of cavity length amount Δ L of Fabry-perot optical fiber chamber, the drift for obtaining fiber grating reflection kernel wavelength is demodulated using edge filter method Measure Δ λ；The actual drift value Δ λ of fiber grating reflection kernel wavelength₂It is expressed as：

Δλ₂=Δ λ-Δ λ₁ (3)

Step 3：Solve temperature variation Δ T and pressure/strain variation amount Δ X；

Temperature variation Δ T is obtained according to formula (4)：

<mrow> <mi>&amp;Delta;</mi> <mi>T</mi> <mo>=</mo> <mfrac> <mrow> <msub> <mi>K</mi> <mn>4</mn> </msub> <mi>&amp;Delta;</mi> <mi>&amp;lambda;</mi> <mo>-</mo> <msub> <mi>K</mi> <mn>2</mn> </msub> <mi>&amp;Delta;</mi> <mi>L</mi> </mrow> <mrow> <msub> <mi>K</mi> <mn>4</mn> </msub> <mi>A</mi> <mo>+</mo> <msub> <mi>K</mi> <mn>1</mn> </msub> <msub> <mi>K</mi> <mn>4</mn> </msub> <mo>-</mo> <msub> <mi>K</mi> <mn>2</mn> </msub> <msub> <mi>K</mi> <mn>3</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>

The variation delta X of pressure/strain is obtained according to formula (5)：

<mrow> <mi>&amp;Delta;</mi> <mi>X</mi> <mo>=</mo> <mfrac> <mrow> <mo>-</mo> <msub> <mi>K</mi> <mn>3</mn> </msub> <mi>&amp;Delta;</mi> <mi>&amp;lambda;</mi> <mo>+</mo> <mrow> <mo>(</mo> <mi>A</mi> <mo>+</mo> <msub> <mi>K</mi> <mn>1</mn> </msub> <mo>)</mo> </mrow> <mi>&amp;Delta;</mi> <mi>L</mi> </mrow> <mrow> <msub> <mi>K</mi> <mn>4</mn> </msub> <mi>A</mi> <mo>+</mo> <msub> <mi>K</mi> <mn>1</mn> </msub> <msub> <mi>K</mi> <mn>4</mn> </msub> <mo>-</mo> <msub> <mi>K</mi> <mn>2</mn> </msub> <msub> <mi>K</mi> <mn>3</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow>

Wherein, A is the temperature sensitive coefficient of fiber grating；

Temperature and the variable quantity of pressure/strain in environment are finally obtained using formula (4), (5).

5. high speed demodulation method according to claim 4, it is characterised in that in described step one, passes through following demarcation Test to determine K₁, it is specifically：

Sensing unit in described high-speed demodulating apparatus is inserted in temperature loading device, temperature loading device is to sensing unit Enter the optical signal after temperature modulation in trip temperature loading, sensing unit, be demodulated unit detection, line is utilized in a computer Property filter method demodulation obtain fiber grating reflection kernel wavelength drift value Δ λ；Δ λ includes fiber grating reflection kernel wavelength Demodulating error drift value Δ λ₁With practical center wavelength shift of the fiber grating caused by temperature change；

Light letter in the output end connection spectrometer of the circulator of high-speed demodulating apparatus, sensing unit after temperature modulation Number, by spectrometer detection, obtain the actual drift value of fiber grating reflection kernel wavelength；Drifted about by demodulating drift value with actual Difference between amount, is obtained because temperature change causes the error of fiber grating reflection kernel wavelength to demodulate drift value Δ λ₁, from And demarcate and obtain K₁。