CN201322623Y - Embedded multi-channel high-speed fiber grating sensor demodulation system - Google Patents

Abstract

An embedded multi-channel high-speed fiber grating sensor demodulation system comprises a broadband fluorescence source, a three-terminal circulator, a 1 x N optical switch, N fiber Bragg grating sensing probes, a 2 x 1 coupler, a high-precision FP interferometer, a photoelectric detection module, a temperature control module, a sawtooth wave generator, a signal acquisition and processing module and a computer, wherein N is a positive integer larger than or equal to 2. The utility model has the advantages of the wavelength resolution precision is high, control detects convenience, multichannel collection and demodulation are fast.

Description

Embedded type multichannel high speed optical fiber grating sensor demodulation system

Technical field

The utility model relates to optical fiber communication and Fibre Optical Sensor, and particularly a kind of embedded type multichannel high speed optical fiber grating sensor demodulation system is a kind of high-speed multiple channel optic fiber grating wavelength signal demodulating apparatus that optic fiber grating wavelength is measured and engineering is used that is used for.

Background technology

Optical fiber grating sensing is based on the effect of external physical environment change to fiber grating, cause its grating region refractive index and grating space to change, thereby the change that causes reflection wavelength is as sensing principle, the essence of its demodulation is exactly by detecting the displacement situation of grating wavelength, obtaining the changing condition of external physical quantity to be measured.

Fiber-optic grating sensor is little with its sensing probe, anti-electromagnetic interference capability is strong, precision is high, be easy to set up sensing network carries out distributed measurement, has been applied in the safety monitoring such as strain deformation, temperature early warning of building structure such as bridge, tunnel.

Existing general demodulation method is 1, the boundary filter method, 2, the coupling raster method, 3, non-equilibrium M-Z interferometric method, 4, the tunable optic filter method.Wherein tunable F-P wave filter method has higher wavelength resolution and bigger working range, can be used for the demodulation to the high speed Dynamic Signal, and is easy to carry out data processing, adopts the method on the engineering mostly.

At present, demodulating system that has occurred and method, the aspects such as safety monitoring that on using, are limited to large scale civil engineering structure more, i.e. monitoring to Dynamic Signal is limited to the low speed Dynamic Signal, be demodulation speed not high (generally being lower than 200Hz), secondly ratio of precision lower (generally about 3pm), stability and poor repeatability, volume also bigger, carry inconvenience, can not satisfy the demand in a plurality of monitorings field.Because the multi-channel fiber Bragg grating demodulation can detect the physical environment of more monitoring points, in application, obtain bigger demand.Domestic most demodulation scheme all is to adopt tunable F-P wave filter method now, but they have adopted a passage correspondence the demodulation mode of FP interferometer mostly, a plurality of FP interferometers are all used in the hyperchannel demodulation in practice, simultaneously because the functional limitation of signal Processing, promptly use MCU microprogram control units such as single-chip microcomputer basically, all adopt a plurality of signals collecting and processing module mostly, carry out time-division processing.And high speed FBG sensor import cost is very high, is about about 50,000 U.S. dollars.

Summary of the invention

The purpose of this utility model is to provide a kind of embedded type multichannel high speed optical fiber grating sensor demodulation system, and this system has higher demodulation speed, hyperchannel demodulation, demodulation wide ranges, characteristics that resolution is high.

Technical solution of the present utility model is as follows:

A kind of embedded type multichannel high speed optical fiber grating sensor demodulation system, be characterized in: it is by broadband fluorescence source, three end circulators, 1*N photoswitch, Fiber Bragg Grating FBG (fibber bragg gratting, being designated hereinafter simply as FBG) sensing probe, sloping optical fiber head, 2*1 coupling mechanism, high precision FP interferometer, Photoelectric Detection module, temperature control modules, saw-toothed wave generator, signals collecting form with processing module and computing machine, wherein N is 〉=2 positive integer, and the annexation of above-mentioned each component is as follows:

The output terminal of described broadband fluorescence source connects described 2*1 coupling mechanism first input end by optical fiber, and the output terminal of this 2*1 coupling mechanism connects described high precision FP interferometer; The output terminal of described broadband fluorescence source connects first port of described three end circulators through optical fiber, second port of this three ends circulator is connected with N described FBG optical fiber grating sensing head through described 1*N photoswitch, each FBG sensing head of this N FBG sensing head all has the sloping optical fiber head, and the 3rd port of described three end circulators is connected with described another input end of 2*1 coupling mechanism again; Described temperature control modules links to each other with described high precision FP interferometer, accurately controls the working temperature of described high precision FP interferometer; The output terminal of described saw-toothed wave generator connects described high precision FP interferometer, for it provides the driving high pressure, makes described high precision FP interferometer stablize the light signal that output wavelength changes; The light signal that the output of described high precision FP interferometer has a wavelength information detects to be transformed into through described Photoelectric Detection module and is transferred to described signals collecting behind the electric signal and processing module is carried out data processing, this signals collecting is set up communication with processing module with described computing machine and saw-toothed wave generator and is connected, this signals collecting links to each other with described 1*N photoswitch with processing module, and described 1*N photoswitch is controlled.

Described signals collecting is combined by field programmable gate array and digital signal processor with processing module and constitutes, described field programmable gate array, becomes numerical data and stores in the random access memory from the optical wavelength information data that described Photoelectric Detection module detects by the analog to digital converter collection; Described digital signal processor reads numerical data from described random access memory, make Fourier transform, by the RS-232 serial communication interface data after handling are sent to computing machine, for it provides the numerical information of wavelength, described field programmable gate array also links to each other with described saw-toothed wave generator by high-speed A/D converter, and described field programmable gate array also directly links to each other with described 1*N photoswitch.

Described computing machine has the software of VC++6.0 fiber grating demodulation, and described signals collecting and processing module are carried out Gauss curve fitting through the data of RS-232 serial communication port transmission, utilizes the interface of hommization conveniently to demonstrate demodulation.

Described broadband fluorescence source is the er-doped fluorescence source of high flat degree frequency spectrum.

Described hyperchannel demodulation is through described three end circulators, 1*N photoswitch and signals collecting and processing modules implement.

Described saw-toothed wave generator (10) is made of chip NE555.

All modules are integrated in the cabinet of an industrial computer.

Described wideband light source is by described three end circulators, propagate into described FBG optical fiber grating sensing probe, behind the physical action of described FBG optical fiber grating sensing probe through measured (FBG optical fiber grating sensing pop one's head in residing ambient temperature change or suffered adaptability to changes), the reflecting light long hair is given birth to skew, launching light through described three end circulators and broadband fluorescence source again enters described 2*1 coupling mechanism and is coupled, by described tunable high precision FP interferometer output, after described photodetection module detection, through described signals collecting and processing module handle back output the wavelength shift amount of surveying and its corresponding tested value in computing machine, after the further processing of the demodulation software of writing specially, show.

The beneficial effects of the utility model are:

By adopting field programmable gate array (Field-Programmable Gate Array, abbreviate FPGA as) and digital signal processor (Digital Signal Processor, abbreviate DSP as) dual micro processor, photoswitch, saw-toothed wave generator are regulated control, so the utility model can be realized high speed, hyperchannel, high-precision optic fiber grating wavelength demodulation.

Description of drawings

Fig. 1 is the syndeton schematic diagram of the utility model embedded type multichannel high speed optical fiber grating demodulating system:

Among the figure: 1-broadband fluorescence source 2-three end circulator 3-1*N photoswitch 4-FBG optical fiber grating sensings probe 5-sloping optical fiber head 6-2*1 coupling mechanism 7-high precision FP interferometer 8-Photoelectric Detection module 9-temperature control modules 10-saw-toothed wave generator 11-signals collecting and processing module 12-computing machine.

Fig. 2 is the structured flowchart of interior described signals collecting of the utility model embedded type multichannel high speed optical fiber grating demodulating system and processing module;

Among the figure: the 2-1-high-speed DAC, the 2-2-high-speed ADC, 2-3-FPGA, 2-4-is memory RAM immediately, 2-5-DSP, 2-6-RS-232 serial communication interface.

Embodiment

For further specifying above-mentioned purpose of the present utility model, design feature and effect, below with reference to accompanying drawing the utility model is described in detail, but should limit protection domain of the present utility model with this.

With reference to Fig. 1, the utility model embedded type multichannel high speed optical fiber grating sensor demodulation system, be made up of with processing module 11 and computing machine 12 broadband fluorescence source 1, three end circulators 2,1*N photoswitch 3, optical fiber Bragg grating sensing probe 4, sloping optical fiber head 5,2*1 coupling mechanism 6, high precision FP interferometer 7, Photoelectric Detection module 8, temperature control modules 9, saw-toothed wave generator 10, signals collecting, the annexation of above-mentioned each component is as follows:

The output terminal of described broadband fluorescence source 1 connects described 2*1 coupling mechanism 6 first input ends by optical fiber, and the output terminal of this 2*1 coupling mechanism 6 connects described high precision FP interferometer 7; The output terminal of described broadband fluorescence source 1 connects first port of described three end circulators 2 through optical fiber, second port of this three ends circulator 2 is connected with N described FBG optical fiber grating sensing head 4 through described 1*N photoswitch 3, each FBG sensing head 4 of this N FBG sensing head 4 all has sloping optical fiber head 5, and the 3rd port of described three end circulators 2 is connected with described 2*1 coupling mechanism 6 another input ends again; Described temperature control modules 9 links to each other with described high precision FP interferometer 7, accurately controls the working temperature of described high precision FP interferometer 7; The output terminal of described saw-toothed wave generator 10 connects described high precision FP interferometer 7, for it provides the driving high pressure, makes described high precision FP interferometer 7 stablize the light signal that output wavelength changes; The light signal that 7 outputs of described high precision FP interferometer have a wavelength information detects to be transformed into through described Photoelectric Detection module 8 and is transferred to described signals collecting behind the electric signal and processing module 11 is carried out data processing, this signals collecting is set up communication with described computing machine 12 with saw-toothed wave generator 10 with processing module 11 and is connected, this signals collecting links to each other with described 1*N photoswitch 3 with processing module 11, and described 1*N photoswitch 3 is controlled.

Described signals collecting and processing module 11, referring to Fig. 2, combine by field programmable gate array 2-3 and digital signal processor 2-5 and to constitute, described field programmable gate array 2-3 is by analog to digital converter 2-2 (Analog-to-Digital Converter, abbreviate ADC as), sampling rate 40M (sample rate) gathers the optical wavelength information data that detects from described Photoelectric Detection module 8, becomes numerical data and stores in the random access memory (2-4) (Random-Access Memory); Described digital signal processor (2-5) reads numerical data from described random access memory 2-4, make Fourier transform, by RS-232 serial communication interface 2-6 the data after handling are sent to computing machine 12, for it provides the numerical information of wavelength, described field programmable gate array 2-3 is also by high-speed A/D converter 2-1 (Digital-to-Analog Converter, abbreviating DAC as) inversion frequency (update rate 10M) links to each other with described saw-toothed wave generator 10, and described field programmable gate array 2-3 also directly links to each other with described 1*N photoswitch 3.

Described computing machine 12 has the software of VC++6.0 fiber grating demodulation, and described signals collecting and processing module 11 are carried out Gauss curve fitting through the data of RS-232 serial communication port transmission, utilizes the interface of hommization conveniently to demonstrate demodulation result.

Described broadband fluorescence source 1 is the er-doped fluorescence source of high flat degree frequency spectrum.

Described hyperchannel demodulation realizes through described three end circulators 2,1*N photoswitch 3 and signals collecting and processing module 11.

Described saw-toothed wave generator 10 is made of chip NE555.

All modules of the utility model embedded type multichannel high speed optical fiber grating sensor demodulation system are integrated in the cabinet of an industrial computer.

The course of work of the present utility model:

The broadband fluorescence of broadband fluorescence source 1 output is imported three end circulators, 2 first interfaces through coupled fiber, second interface of this three ends circulator 2 outputs to FBG optical fiber grating sensing probe 4 through 1*N photoswitch 3, through measured physical action, its reflecting light long hair is given birth to and is changed, and enters described high precision FP interferometer 7 after being coupled in described 2*1 coupling mechanism 6 by the emission light of the reflected light of the 3rd interface and broadband fluorescence source 1 through described three end circulators 2.High precision FP interferometer 7 satisfies:

1, the conducting frequency band is narrow, and passband is between 16pm～32pm;

2, sweep stabilization degree height, the multiple scanning error is less than 8pm;

3, wavelength resolution height, fineness reaches 4000;

4, sweep limit is big, is in the C-band and greater than 40nm;

5, tuned frequency height is 1KHz.

The voltage-sawtooth that described saw-toothed wave generator 10 is produced changes in 40V～120V scope, and by the characteristic of high precision FP interferometer 7 as can be known, the optical wavelength correspondence of high precision FP interferometer 7 outputs changes between 1527nm～1567nm.When reflected light enters described high precision FP interferometer 7, when the optical wavelength of broadband fluorescence source 1 emission equated with the centre wavelength of wherein a certain FBG optical fiber grating sensing head 4 reflections, reflected light will enter into Photoelectric Detection module 8 by high precision FP interferometer 7.Saw-toothed wave generator 10 adopts the NE555 timer to constitute high precision, low distortion saw-tooth wave generating circuit, and is adjustable in frequency 1KHz～10KHz scope.For making output light wavelength accurate, temperature control modules 8 inside are made up of the driver that the high precision integrated operational amplifier constitutes hardware PID circuit and semiconductor chilling plate, and the mode that combines by semiconductor chilling plate and thermistor is stablized the working temperature of high precision FP interferometer 7.Thermistor is given temperature control modules 8 with the Temperature Feedback of high precision FP interferometer 7, temperature control modules 8 is through inner PID computing, the result is fed back to the driver of inner semiconductor chilling plate, driver output corresponding driving amount by semiconductor chilling plate makes its refrigeration or heating to semiconductor chilling plate again, with the working temperature of stable control high precision FP interferometer 7.Semiconductor chilling plate and thermistor all need to be close to high precision FP interferometer 7, thereby reduce the temperature control error.Thermistor adopts the negative tempperature coefficient thermistor of @25 ℃ of 10K Ω, and it is 0.1 ℃ that whole temperature control modules finally reaches accuracy of temperature control.

Photoelectric Detection module 8 mainly is made of photodiode PIN, it is converted to electric signal from the optical wavelength side-play amount that FP interferometer 7 demodulates, and is converted to digital signal through the 40M high-speed ADC again after utilizing prime amplifier to amplify to be input to signals collecting and processing module 11.

In signals collecting and processing module 11, FPGA gathers the numerical information that obtains the optical wavelength displacement, carries out the primary treatment of data, gets rid of irrational data, the optical wavelength information that the Photoelectric Detection module 8 that reception obtains from analog to digital converter ADC2-2 detects.40M high-speed ADC 2-2 obtains the analog electrical signal of Photoelectric Detection module 8, converts thereof into digital signal then and is transferred to FPGA2-3 incessantly, after FPGA2-3 is errorless after testing, is input among the RAM2-4.RAM2-4 becomes FIFO (first in first out First-in First-out) formation with data-storing.FPGA sends notice DSP after the 16K byte data to RAM and reads data among the RAM.DSP2-5 utilizes its inner module that data are carried out Fourier transform then, removes the burr in the optical wavelength information, obtains the data point set of comparatively level and smooth similar Gaussian curve.The back DSP that disposes sends to computing machine 12 like the data point set of Gaussian curve by the RS232 serial communication interface with this category, for it provides the numerical information that detects wavelength.DSP is in waiting status then, waits for that FPGA sends the notice of reading of data.

Fiber grating reflection peak power spectral density plot can be with the Gaussian function approximate expression

$I\left(\mathrm{\λ}\right)=I_0\exp [-4\ln 2{\left(\frac{\mathrm{\λ}-{\mathrm{\λ}}_R}{\mathrm{\Δ}{\mathrm{\λ}}_R}\right)}^2]$

In the formula, I ₀Be reflection peak intensity peak, λ _RBe corresponding wavelength value this moment, Δ λ _RBe reflectance spectrum three dB bandwidth.In the software of the VC++6.0 fiber grating demodulation of computing machine 12 inside,, promptly data point set is carried out the approximating method of approximation of function, try to achieve the reflection peak central wavelength lambda with Gaussian function by Gauss curve fitting _RThereby, obtain heat transfer agent.We are according to the principle matched curve of the quadratic sum minimum that makes error.The quadratic sum of error is: $I\left({\mathrm{\λ}}_R\right)=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}[I_i-I({\mathrm{\λ}}_i;{\mathrm{\λ}}_R)].$ At first provide parameter lambda _RAn initial value, iteration progressively then ${{\mathrm{\λ}}_R}^{(k+1)}={{\mathrm{\λ}}_R}^{\left(k\right)}-\frac{\▿I\left({{\mathrm{\λ}}_R}^{\left(k\right)}\right)}{{\▿}^{2}I\left({{\mathrm{\λ}}_R}^{\left(k\right)}\right)}.$ I wherein _iBe the numerical value of each point in this group data point set, λ _iFor each puts pairing wavelength.Fit procedure is to finish in the software of VC++6.0 fiber grating demodulation, is shown by computing machine 12 then.

The high-speed DAC 2-1 that signals collecting and processing module 11 also reach 10M by a speed feeds back saw-toothed wave generator 10 and controls.Under the normal condition, can be by saw-toothed wave generator 10 sawtooth wave that to produce a peak-to-peak value voluntarily be 40V～120V, the optical wavelength correspondence of corresponding high precision FP interferometer 7 outputs changes between 1527nm～1567nm.When needing, can directly produce specific aanalogvoltage by the high-speed DAC 2-1 in signals collecting and the processing module 11 and enter described saw-toothed wave generator 10, corresponding FP interferometer 7 carries out the conducting frequency scan of specific wavelength.Signals collecting and processing module 11 inside have been moved FPGA and two microprocessors of DSP simultaneously, between them with a shared dual port random access memory RAM 2-4, can be when FPGA to store data, the content of being stored before DSP reads realizes the high speed demodulation of heat transfer agent.

In addition, signals collecting also directly links to each other with 1*N photoswitch 3 with processing module 11, and under default situations, 1*N photoswitch 3 is implemented the scanning successively of passage one by one automatically, can directly control the open channel of described 1*N photoswitch 3 in needs.The switching time of described 1*N photoswitch is less than 10ms, just can ALT-CH alternate channel in 1s 100 times.

Our experiments show that the embedded type multichannel high speed optical fiber grating demodulating system performance of final realization of the present utility model is: the single channel demodulation speed reaches 1KHz, demodulation accuracy is 1pm (10 ^-12M); Hyperchannel (=8 o'clock) demodulation speed simultaneously reaches 200Hz, and demodulation accuracy is 1pm (10 ^-12M).

Claims (6)

1, a kind of embedded type multichannel high speed optical fiber grating sensor demodulation system, it is characterized in that: it is made up of with processing module (11) and computing machine (12) broadband fluorescence source (1), three end circulators (2), 1*N photoswitch (3), N optical fiber Bragg grating sensing probe (4), 2*1 coupling mechanism (6), high precision FP interferometer (7), Photoelectric Detection module (8), temperature control modules (9), saw-toothed wave generator (10), signals collecting, wherein N is 〉=2 positive integer, and the annexation of above-mentioned each component is as follows:

The output terminal of described broadband fluorescence source (1) connects described 2*1 coupling mechanism (6) first input end by optical fiber, and the output terminal of this 2*1 coupling mechanism (6) connects described high precision FP interferometer (7); The output terminal of described broadband fluorescence source (1) connects first port of described three end circulators (2) through optical fiber, second port of this three ends circulator (2) is connected with N described FBG optical fiber grating sensing head (4) through described 1*N photoswitch (3), each FBG sensing head (4) of this N FBG sensing head (4) all has sloping optical fiber head (5), and the 3rd port of described three end circulators (2) is connected with another input end of described 2*1 coupling mechanism (6) again; Described temperature control modules (9) links to each other with described high precision FP interferometer (7), accurately controls the working temperature of described high precision FP interferometer (7); The output terminal of described saw-toothed wave generator (10) connects described high precision FP interferometer (7), for it provides the driving high pressure, makes described high precision FP interferometer (7) stablize the light signal that output wavelength changes; The light signal that described high precision FP interferometer (7) output has a wavelength information detects to be transformed into through described Photoelectric Detection module (8) and is transferred to described signals collecting behind the electric signal and processing module (11) is carried out data processing, this signals collecting is set up communication with described computing machine (12) with saw-toothed wave generator (10) with processing module (11) and is connected, this signals collecting links to each other with described 1*N photoswitch (3) with processing module (11), and described 1*N photoswitch (3) is controlled.

2, embedded type multichannel high speed optical fiber grating sensor demodulation system according to claim 1, it is characterized in that described signals collecting and processing module (11) are by field programmable gate array (2-3) and digital signal processor (2-5) formation that combines, described field programmable gate array (2-3) is gathered the optical wavelength information data that detects from described Photoelectric Detection module (8) by analog to digital converter (2-2), becomes numerical data and stores in the random access memory (2-4); Described digital signal processor (2-5) reads numerical data from described random access memory (2-4), make Fourier transform, by RS-232 serial communication interface (2-6) data after handling are sent to computing machine (12), for it provides the numerical information of wavelength, described field programmable gate array (2-3) also links to each other with described saw-toothed wave generator (10) by high-speed A/D converter (2-1), and described field programmable gate array (2-3) also directly links to each other with described 1*N photoswitch (3).

3, embedded type multichannel high speed optical fiber grating sensor demodulation system according to claim 1 is characterized in that described broadband fluorescence source (1) is the er-doped fluorescence source of high flat degree frequency spectrum.

4, embedded type multichannel high speed optical fiber grating sensor demodulation system according to claim 1 is characterized in that the hyperchannel demodulation that is realized realizes through described three end circulators (2), 1*N photoswitch (3) and signals collecting and processing module (11).

5, embedded type multichannel high speed optical fiber grating sensor demodulation system according to claim 1 is characterized in that described saw-toothed wave generator (10) is made of chip NE555.

6,, it is characterized in that all modules are integrated in the cabinet of an industrial computer according to each described embedded type multichannel high speed optical fiber grating sensor demodulation system of claim 1 to 5.

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