CN103837179A - Distributed optic fiber sensor based on multi-domain mixed and multiplex mode and modulation and demodulation method thereof - Google Patents
Distributed optic fiber sensor based on multi-domain mixed and multiplex mode and modulation and demodulation method thereof Download PDFInfo
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Abstract
The invention relates to a distributed optic fiber sensor based on a multi-domain mixed and multiplex mode and a modulation and demodulation method of the distributed optic fiber sensor. The optic fiber sensor comprises a data processing and controlling device (1), a light source module, an optical fiber sensing unit (13), a filter (4), a filter controlling module, a data collecting module and a light circulator (9). The data processing and controlling device (1) is respectively connected with the light source module, the filter controlling module and the data collecting module, the light circulator (9) is respectively connected with the light source module, the optical fiber sensing unit (13) and the filter (4), the filter controlling module is connected between the data processing and controlling device (1) and the filter (4), and the output end of the filter (4) is further connected with the input end of the data processing and controlling device (1) through the data collecting module. The distributed optic fiber sensor based on the multi-domain mixed and multiplex mode has the advantages of being large in capacity, low in cost, high in modulation and demodulation speed, compact in structure and the like and is suitable for large-scale and distributed sensing multiplexing.
Description
Technical field
The present invention relates to technical field of optical fiber sensing, realize high-capacity optical fiber sensing by the multiple domain characteristic of expanding fiber middle light signal, and for the embedded demodulating system of this method for sensing specialized designs.
Background technology
Fibre Optical Sensor is widely used in the monitoring of the field such as geologic hazard, ocean, large scale structure, and its anti-electromagnetic property, cramped construction, sensing accuracy is high, extensibility is high etc., and characteristic makes it receive increasing concern.Fibre Optical Sensor is because its demodulating system is more expensive, therefore improves the multiplexing quantity of single fiber and can obviously reduce the demodulation cost of single sensing node, expands its application.
The people such as United States Naval Research Laboratory T.A.Berkoff are at paper " HYBRID TIME AND WAVELENGTH DIVISION MULTIPLEXED FIBER BRAGG GRATING SENSOR ARRAY " Proc.SPIE2444; Smart Structures and Materials1995:Smart Sensing; Processing; and Instrumentation; 288 (April20,1995); Doi:10.1117/12.207684 " in time-division, wavelength-division multiplex concept are proposed, but its time division signal demodulation cannot reach real-time, and too low causing of demodulation accuracy cannot be carried out frequency division multiplexing.
Application number is 201110420315.8, the patented claim that name is called " based on the quasi-distributed sensor of micro-structure fiber optic Fabry-Perot cavity " has proposed wavelength-division, frequency division multiplexing, it uses spectroanalysis instrument, expensive, can only realize two dimension multiplexing, because the demodulation cycle of spectroanalysis instrument is long, and spectroanalysis instrument can not provide external control interface, cannot carry out TDM(time division multiplex) multiplexing.
Summary of the invention
Technical matters to be solved by this invention is: a kind of distributed fiberoptic sensor and modulation-demo-demodulation method thereof based on multiple domain hybrid multiplex is provided, this invention has the features such as large capacity, low cost, demodulation speed are fast, compact conformation, is applicable to large-scale distributed sensing multiplexing.
It is as follows that the present invention solves the problems of the technologies described above adopted scheme: based on the distributed fiberoptic sensor of multiple domain hybrid multiplex, comprise data processing and control device, light source module, Fibre Optical Sensor unit, wave filter, FILTER TO CONTROL module, data acquisition module and optical circulator, data processing and control device and light source module, FILTER TO CONTROL module is all connected with data acquisition module, optical circulator and light source module, Fibre Optical Sensor unit, wave filter is all connected, between data processing and control device and wave filter, be connected to FILTER TO CONTROL module, the output terminal of wave filter is also connected with the input end of data processing and control device by data acquisition module.
Further, data processing and control device adopt the SOC (system on a chip) that comprises arm processor and field programmable gate array.
Further, light source module comprises connected wideband light source and Erbium-Doped Fiber Amplifier, and data processing and control device are connected with wideband light source, and Erbium-Doped Fiber Amplifier is connected with optical circulator.
Further, wave filter adopts fabry-perot filter.
Further, FILTER TO CONTROL module comprises connected D/A switch module and operational amplifier module, and D/A switch module is connected with data processing and control device, and operational amplifier module is connected with wave filter.
Further, data acquisition module comprises connected photodetector and mould/number conversion module, and photodetector is connected with wave filter, and mould/number conversion module is connected with data processing and control device.
Further, data processing and control device are also connected to power module, display platform and SD storage card.
Further, Fibre Optical Sensor unit comprises K*M*N Fabry-Perot cavity pair, and wherein K is that time-domain multiplexed number, M are that the multiplexing number of wave zone, N are frequency domain multiplexing number.
The modulation-demo-demodulation method of the distributed fiberoptic sensor based on multiple domain hybrid multiplex, its modulator approach comprises: data processing and control device transmitted electric signal, pulse electrical signal is that dutycycle is the square wave of 1/K, pulse electrical signal number is 1/(FT), wherein K is time-domain multiplexed number, F is the frequency of wave filter, T is pulse electrical signal time domain width, pulse electrical signal drives wideband light source to export the pulsed optical signals of certain sequential relationship, the output of wideband light source connects Erbium-Doped Fiber Amplifier, light signal after amplifying is connected to the first input end mouth of optical circulator, output to Fibre Optical Sensor unit by the second output port, described Fibre Optical Sensor unit carries out time domain differentiation by K group sensor fibre by optical fiber, every group of sensor fibre the inside has the sensor array of M group different wave length to carry out wave zone differentiation, there is the Fabry-Perot cavity of N group different cavity length each sensor array the inside to carrying out frequency domain differentiation.
Further, demodulation method comprises:
Light signal after described amplification enters behind Fibre Optical Sensor unit, and K group reflection light pulse, by the 3rd output port output of optical circulator, comprises different Fabry-Perot cavities to corresponding wavelength and frequency information in every group of reflection light pulse;
Described reflection light pulse enters after wave filter, effective demodulation region by data processing and control device and FILTER TO CONTROL module at wave filter, according to the linear piezoelectric ceramics voltage that increases of the minimum step voltage Δ V of wave filter, thereby drive the linear narrow light pulse (three dB bandwidth is pm level) increasing of wave filter output center wavelength; Wave filter (4) scans after the reflection light pulse of certain time domain by the narrow band light pulse of certain wave band, and the reflection light pulse of next time domain continues to be scanned by the narrow band light pulse of this wave band; Then the wave band that changes the narrow band light pulse of wave filter (4) output scans the reflection light pulse of next Time Domain Piecewise again, until point 1/(FT) section scanned the full wavelength coverage of wideband light source (7), thereby obtained all reflection light pulse spectral informations;
The reflection light pulse light signal of the different wave length of wave filter output is converted to electric signal through photodetector, by the digital sample of mould/number conversion module, enter data processing and control device, data processing and control device by the digital sample result cache in the whole sensing cycle of receiving in the memory storage on it, different time domain signal enters the single level address of memory storage, and different wave zone signals enter the two-level address of memory storage; The scope of described single level address is to configure according to the maximum number number of samples of all time domain scopes, and the scope of described two-level address is to configure according to the maximum number number of samples of all wave zone scopes in a certain time domain;
Data processing and control device complete a time domain, all after dates of wave zone demodulation, carrying out data parallel according to one-level, two-level address reads, different time domain, wave zone signal parallel enter the Fast Fourier Transform (FFT) array of data processing and control device, export the right spectrum information of all Fabry-Perot cavities, and contrast with the original signal spectrum information of the ROM (read-only memory) storage of data processing and control device, thereby complete demodulating process.
The present invention compared with prior art mainly contains following advantage:
1. adopt three-dimensional multiplex technique of time-division, wavelength-division, frequency division, multiplexing with existing two dimension compared with, can significantly improve multiplexing capacity, meet the large capacity sensing of single fiber demand.
2. complete major control and data processing by SOC (system on a chip) SOC, single-chip completes demodulation, data collecting card that need not be special or computer processor, and low-power consumption, low cost, compact conformation, processing speed are fast, are conducive to large-scale application and promote.
3. extensibility is strong, improves FP filter accuracies or light source bandwidth, can significantly improve sensing capacity.
4.ns the clock technology of level, by accurately positioning optical waveguides sensing unit position of parameter configuration, thereby realizes the distributed sensing of sensing unit.
5. pair FP wave filter carries out segmentation control, solves (ms level) at a slow speed contradiction of time domain real-time (us level) requirement and wave zone demodulation.
Accompanying drawing explanation
Fig. 1 is multiple domain Fibre Optical Sensor and demodulating system block diagram.
Fig. 2 is SOC (system on a chip) SOC built-in function block diagram.
Fig. 3 is Optical Fiber Sensing Array.
Fig. 4 is the effective demodulation of time division multiplex region.
Fig. 5 is FP wave filter segmentation demodulation method.
In figure: 1. SOC (system on a chip) SOC; 2.DA module; 3. amplifier module; 4.FP wave filter; 5. photodetector; 6.AD module; 7. wideband light source; 8. image intensifer; 9. optical circulator; 10. power module; 11. display platforms; 12.SD storage card; 13. Fibre Optical Sensor unit.
Embodiment
The present invention is directed to the capacity limit of existing two-dimentional multiplex technique, time domain, wave zone, frequency domain three-dimensional are proposed multiplexing, and for time domain demodulation real-time and the long conflict of wave zone frequency-domain demodulation cycle, multiple domain Fibre Optical Sensor and demodulating system software and hardware thereof, Fibre Optical Sensor unit and algorithm are designed, can greatly improve multiplexing capacity, realize the extensive sensing of single fiber multiplexing.
The distributing optical fiber sensing of multiple domain hybrid multiplex and a demodulating equipment thereof, be made up of SOC (system on a chip) (SOC), light source module, Fibre Optical Sensor unit, FILTER TO CONTROL module, data acquisition module, data memory module and data transmission blocks.
Described SOC (system on a chip) SOC is arm processor and FPGA(field programmable gate array) merge chip, comprise clock control cell, data processing unit, result and report unit, the output access result of data processing unit reports the input of unit, and two unit of clock control cell and all the other are all connected.This SOC can carry out the functions such as synchro control, sawtooth wave generation, light pulse driving, signal processing.
Described synchronization control function, is mainly information time phase of controlling between the sending and receiving of light source module pulsed light, determines the time domain waveform of sawtooth wave by Fibre Optical Sensor position distribution simultaneously.
Described light source module, by wideband light source, EDFA(Erbium-Doped Fiber Amplifier) image intensifer, optical circulator form, SOC (system on a chip) SOC transmitted electric signal, drive wideband light source to export the pulsed optical signals of certain sequential relationship, the output of wideband light source connects EDFA image intensifer, light signal after amplifying is connected to the input port 1 of optical circulator, outputs to Fibre Optical Sensor unit by port 2.
Described Fibre Optical Sensor unit carries out time domain differentiation by n group sensor fibre by optical fiber, and there is the sensor array of m group different wave length every group of sensor fibre the inside, and there is the long grating pair of k group different cavity each sensor array the inside.
Described light signal enters after sensor fibre, and n group reflection light pulse, by optical circulator 3 port outputs, comprises wavelength and frequency information that different sensing units are corresponding in every group of reflection light pulse.
The pulse length of described reflected light signal depends on optical fibre time division distance L, therefore pulse length is us level, enter FP(Fabry-Perot) after wave filter, the PZT(piezoelectric ceramics of SOC (system on a chip) SOC and FILTER TO CONTROL module controls FP wave filter) voltage, after the pulse signal of certain wavelength coverage interscan us level, wait for this time domain light signal next time, change wavelength coverage and again scan, until scanned the full wavelength coverage of wide spectrum light source.
Described FILTER TO CONTROL module is by SOC (system on a chip) SOC, DA(D/A) module and amplifier module composition, by setting SOC (system on a chip) SOC inner parameter, control the Voltage-output of amplifier module, thereby drive FP wave filter to produce the linear narrow light pulse increasing of centre wavelength, light signal is carried out to filtering.
Described data acquisition module is by photodetector and AD(mould/number) module composition, the light signal of the different wave length of FP wave filter output is through PD(photodiode) be converted to electric signal, by the digital sample of AD module, enter SOC (system on a chip) SOC, SOC by the whole sensing cycle result cache of receiving to Block RAM(piece random access memory on sheet) or SD storage card 12 in, and according to system design parameters, storage data are extracted, splicing, finally distinguish time domain, wave zone information is also carried out FFT(fast fourier transform) conversion, the chamber of the corresponding grating pair of normalized frequency after FFT conversion is long, the long skew in chamber demodulating changes inductive sensing parameter.
Described data memory module is by a SD(safe digital card) card formation, because sensing and demodulating is to complete at embedded chip, a demodulating system reported result information, each node 2 bytes, the in the situation that of one second refresh rate, 1000 nodes, the storage chip of 8G can be stored the data of 46 days.
Described data reporting module, can be reported to data center or server by sensing object information by netting twine, Wifi, 2G/3G/4G module.
Be described in further detail the present invention below in conjunction with concrete enforcement.
A kind of high-capacity optical fiber microstructure sensor-based system based on time-division, wavelength-division, frequency division three-dimensional hybrid multiplex technique, by the distributed architecture of design Fibre Optical Sensor unit, and design time domain, wave zone, the frequency domain that demodulating system realizes light signal and distinguish, thereby greatly improve Fibre Optical Sensor capacity, this sensor-based system comprises: SOC (system on a chip) (SOC) 1, DA module 2, amplifier module 3, FP wave filter 4, photodetector 5, AD module 6, wideband light source 7, image intensifer 8, optical circulator 9, power module 10, display platform 11, SD storage card 12, Fibre Optical Sensor unit 13.
Described SOC (system on a chip) SOC1 and wideband light source 7, image intensifer 8, optical circulator 9 form light transmitting element.SOC (system on a chip) SOC1 and DA module 2, amplifier module 3, FP wave filter 4 form length scanning unit.SOC (system on a chip) SOC1 and optical circulator 9, photodetector 5, AD module 6 form light receiving unit.SOC (system on a chip) SOC1 realizes inside clock control cell, data processing unit, result and reports unit.
Described SOC (system on a chip) SOC1 inside drives wideband light source 7 with the pulse signal generator of accurate clock control, drive FP wave filter 4 with the saw-toothed wave generator of clock control cell control, finally the reflected light signal collecting is carried out to digital signal processing by photodetector 5 and AD module 6, data result is reported to display platform 11 and is stored into SD card by data line or wireless network the most at last.
SOC system on described sheet, switch speed control output electric pulse with ns level drives wideband light source 7, output pulsed optical signals through image intensifer 8 laggard enter the port one of optical circulator 9, and inciding Fibre Optical Sensor unit 13 from the port 2 of optical circulator, each sensing unit is reflected back low light level signal.
Described Fibre Optical Sensor unit 13, its reflected light signal has different time domains, wavelength, frequency characteristic, time domain interval T is us level, through optical circulator 9, incide FP wave filter 4 and carry out filtering sampling, the frequency of FP wave filter is F, and a demodulation cycle is that 1/F is ms level, therefore need FP wave filter to carry out repetitive wave long scan to multiple light pulse time sharing segments, completing a Free Spectral Range (FSR) length scanning, to need segmentation multiplicity be 1/ (FT).
Described FP wave filter 4 time sharing segments carry out length scanning, send self-defined sawtooth wave by SOC (system on a chip) SOC1, digital signal outputs to DA module 2 and produces the analog voltage signal of 0～Vpp, amplifier module 3 amplified A doubly to 0～(A*Vpp) control FP wave filter, the output signal of FP wave filter 4, be connected to photodetector 5 by optical fiber and carry out opto-electronic conversion, electric signal enters SOC1 and carries out signal demodulation, divided data when ADSui road clock is distinguished as demodulation major clock after AD conversion.
Described pulse signal generator, saw-toothed wave generator and signal demodulation major clock, between SOC1 chip internal pulse signal generator, saw-toothed wave generator and signal demodulation major clock, carry out strict ns level synchronous, guarantee the degree of accuracy of time domain, wave zone, frequency-domain demodulation, improve the scanning accuracy of master clock frequency and FP wave filter, can significantly improve the multiplexing quantity of sensing unit.
SOC (system on a chip) SOC1 chip need to transmit the digital signal receiving into inner Block RAM or plug-in DDR and carry out buffer memory with high-speed-differential line, different time domain signal enters single level address scope, different wave zone signals enter two-level address scope, complete a time domain, the all after dates of wave zone demodulation, different time domain, wave zone signal parallel enters Fast Fourier Transform (FFT) (FFT) array, FFT conversion needs C clock period, can us step velocity export the spectrum information of all sensing units, and contrast with the original signal spectrum information of the inner ROM storage of SOC (system on a chip) SOC, report the object information of few byte to data center, thereby complete the fast demodulation of large capacity information at low cost SOC (system on a chip) SOC, low cost and compact structure are conducive to distributed sensing application.
Below in conjunction with accompanying drawing, the invention will be further described.
Native system is made up of light path, mimic channel and digital circuit, as shown in Figure 1, mainly comprise SOC (system on a chip) SOC1, DA module 2, amplifier module 3, FP wave filter 4, photodetector 5, AD module 6, wideband light source 7, image intensifer 8, optical circulator 9, power module 10, display platform 11, SD storage card 12, Fibre Optical Sensor unit 13.SOC (system on a chip) SOC1 and wideband light source 7, image intensifer 8, optical circulator 9 form light transmitting element.SOC (system on a chip) SOC1 and DA module 2, amplifier module 3, FP wave filter 4 form length scanning unit.SOC (system on a chip) SOC1 and optical circulator 9, photodetector 5, AD module 6 form light receiving unit.SOC (system on a chip) SOC1 inside reports cell formation by clock control cell, data processing unit, result, as shown in Figure 2.
Described wavelength sensor array is long by different cavity, the grating pair of different centre wavelengths forms, according to time domain, wave zone, frequency domain characteristic is inscribed, with one group of time domain (K), wave zone (M), the case study on implementation that is multiplexed with of upper K*M*N the sensing unit of frequency domain (N) is analyzed principle of work of the present invention, as shown in Figure 3, a Fibre Optical Sensor unit is by a pair of weak reflectivity optical grating constitution, raster center consistent wavelength, this weak reflectivity method Fabry-Perot-type of a pair of optical grating constitution (FP) chamber, distance between grating pair is the Free Spectral Range (FSR) that d determines FP chamber.If the distance between each grating pair is H, H>>d.The long d in described chamber is according to stepping Δ d (size is d+H) multiplexing N group, i.e. D in figure
1, D
2... D
n, n=N.In M group wavelength-division multiplex situation, the centre wavelength of every N group grating pair is respectively λ
1, λ
2... λ
m, m=M.A sensor array length is about M*N*H.Each time-division distance is L, and the time-division between every two sensor arrays is apart from being followed successively by L
1, L
2... L
k-2, L
k-1, L
k, k=K.
In the situation of K when group subregion, i.e. the T of Fig. 4
1, T
2... T
k-2, T
k-1, T
kthe TDM of corresponding diagram 5
1, TDM
2... TDM
k, pulsed optical signals enters after sensor fibre, can be reflected back K group light signal, and every group of optical signals K wavelength is formed by stacking.2n in Fig. 4
1l
k-1/ c, 2n
1l
kthe 2n of/c, Fig. 5
1l/c is that the time domain that optical fiber brings postpones, the 2n in Fig. 4
1d/c is the time delay of adjacent wave zone sensors reflected light signal time domain.If light impulse length τ is >2n
1l
k-1/ c, second group of time domain light signal meeting and first group of time domain light signal aliasing, only have the <2n as light impulse length τ
1l
k/ c, could obtain effective demodulation region.Wherein n
1for optical fiber effective refractive index, c is the light velocity.
In described effective demodulation region, carry out Wavelength demodulation, the FP filters demodulate frequency of commercialization is at present F, a Wavelength demodulation cycle is 1/F, if the light impulse length of corresponding 1/F, in the situation that current commercialization FP filters demodulate frequency F is thousands of Hz, need the optical fibre time division distance of several thousand km, in actual applications, first the optical fiber of so long distance bring great loss, secondly with high costs, cannot drop into application at all, therefore need the light pulse of the 1/F segmentation of cutting into slices, as shown in Figure 5, one section of wavelength information of each light pulse section demodulation, next section of wavelength information of demodulation when next light pulse arrives.
Described Wavelength demodulation system as shown in Figure 1, wideband light source bandwidth S, SOC (system on a chip) SOC sends recurrent pulse information, pulse width is T1, repetition frequency is f, accordingly, can hold f/F group time division multiplex sensing unit, optical fibre time division distance C T1/2n can meet time domain and distinguish, and wherein C is the clock period that FFT conversion needs.It is P that adjustment light amplifier gain makes the Output optical power of image intensifer, and light signal enters sensing unit through optical circulator, and weak reflection sense unit reflectivity is designed to R, and reflected signal luminous power is about PR.
Described reflected signal is connected with FP wave filter, the wavelength of FP wave filter selects to be subject to the pressure reduction control of PZT two ends, SOC (system on a chip) SOC is by the pressure reduction (maximum Vpp) of DA module and amplifier module controls PZT, thereby realize FP wave filter in the scope of bandwidth S, scan (Scan Period) take the scanning accuracy of FP as stepping.V in Fig. 5 represents the modulation voltage value of PZT, T represents the time that modulation voltage is corresponding, λ pp is the peak wavelength of FP wave filter output, Δ V is that the modulation voltage of PZT changes stepping, Δ λ is the output wavelength stepping of FP wave filter, modulation voltage value or output wavelength that V/ λ is PZT, and (V+ Δ V)/(λ+Δ λ) is modulation voltage value or the output wavelength of the next point of sawtooth wave output, Vpp/ λ pp is peak value modulation voltage value or peak wavelength, V
1, V
2... V
i-1, V
i(being Vpp) represents to be respectively divided into every section of corresponding maximum modulation magnitude of voltage after i section, P
1, P
2... P
1/ (FT)represent respectively, in each segmentation, corresponding k group time-domain signal is carried out to repetition demodulation, wherein k=i=1/ (FT).
Output optical signal is converted to electric signal by photodetector and enters AD module, after analog to digital conversion, SOC (system on a chip) SOC1 chip need to transmit with high-speed-differential line the digital signal receiving into inner Block RAM or plug-in DDR(Double Data Rate synchronous DRAM) carry out buffer memory, different time domain signal enters single level address scope, different wave zone signals enter two-level address scope, complete a time domain, wave zone, the all after dates of frequency-domain demodulation, different time domain, wave zone signal parallel enters Fast Fourier Transform (FFT) (FFT) array, FFT conversion needs C clock period, can us step velocity export the spectrum information of all sensing units, and with the inner ROM(read-only memory of SOC (system on a chip) SOC) the original signal spectrum information of storage contrasts, final by knowing the chamber long message of grating pair, the initialization information of storing in change of cavity length and SOC (system on a chip) SOC is contrasted, variation that can perception monitoring parameter, monitoring parameter comprises temperature, pressure, vibration etc., but be not limited only to these parameters.Report the object information of few byte to data center, thereby complete the fast demodulation of large capacity information at low cost SOC (system on a chip) SOC, described parameter result of variations can be stored in SD card, is reported to data center to monitor by network simultaneously.
According to time-domain multiplexed K group, the multiplexing M group of wave zone, frequency domain multiplexing N group, can realize the multiplexing and demodulation of the single fiber of K*M*N sensing unit, can reach the multiplexing scale of several thousand sensing units, by adjusting sensing unit parameter and improving FP wave filter and photodetector precision, the multiplexing quantity in each territory can also promote simultaneously, thus the multiplexing capacity of Hoisting System significantly.
Example explanation:
Wideband light source and FP filter bandwidht are all 1510nm-1590nm, the sweep frequency of FP wave filter is 800Hz, SOC (system on a chip) SOC sends recurrent pulse information, pulse width is 1us, frequency is 50kHz, accordingly, can hold 20 groups of time division multiplex sensing units, optical fibre time division can meet time domain apart from 1km left and right and distinguish.Adjust light amplifier gain and make the Output optical power of image intensifer be-10dBm, light signal enters sensing unit through optical circulator, and sensing unit reflectivity is designed to 1%, be about-30dBm of reflected signal luminous power.
A described demodulation cycle 1/800=1.25ms, the sampling time 1.25*10 of each 10pm sampled point
6ns/8000=156.25ns, it is minimum 64MHz that the triangular wave of FPGA is driven to control accuracy, triangular wave is divided into 8000 points, each Cycle(cycle) be 15.625ns.TDM FFP optical pulse time depends on optical fibre time division distance, supposes 12.5us, 1.25 kilometers of optical fibre time division distances, 1.25ms/12.5us=100,8*10
3/ 100=80, each triangular wave is divided into 100 parts to be processed, and every part of 80 points, if shorten optical fibre time division distance, need to increase umber, reduce each cycle sampling number.Suppose 16V triangular wave, 8k point, each some 2mV, is first paragraph data during since 0,160mV, FPGA triangular wave counting stops, and gathers the data of 80 points; Second light pulse gathers lower 80 somes while arrival, interval total demodulation time of time domain 1 is 12.5us*10
5(TDM organizes number)=1.25*10
3ms.
In 80nm wavelength coverage, each centre wavelength takies 4nm width, M=80/4=20 group; On frequency domain, the scope of the long d in chamber is 0-2cm, and stepping is 1mm, and the FP filters demodulate precision of 10pm can realize frequency-domain demodulation, therefore multiplexing group of number N=2cm/1mm=20 group, and final single fiber sensor-based system reusable quantity reaches 20*20*20=8000 group sensing unit.
Claims (10)
1. the distributed fiberoptic sensor based on multiple domain hybrid multiplex, it is characterized in that: comprise data processing and control device (1), light source module, Fibre Optical Sensor unit (13), wave filter (4), FILTER TO CONTROL module, data acquisition module and optical circulator (9), data processing and control device (1) and light source module, FILTER TO CONTROL module is all connected with data acquisition module, optical circulator (9) and light source module, Fibre Optical Sensor unit (13), wave filter (4) is all connected, between data processing and control device (1) and wave filter (4), be connected to FILTER TO CONTROL module, the output terminal of wave filter (4) is also connected with the input end of data processing and control device (1) by data acquisition module.
2. sensor according to claim 1, is characterized in that: data processing and control device (1) adopt the SOC (system on a chip) that comprises arm processor and field programmable gate array.
3. sensor according to claim 1, it is characterized in that: light source module comprises connected wideband light source (7) and Erbium-Doped Fiber Amplifier (8), data processing and control device (1) are connected with wideband light source (7), and Erbium-Doped Fiber Amplifier (8) is connected with optical circulator (9).
4. sensor according to claim 1, is characterized in that: wave filter (4) adopts fabry-perot filter.
5. sensor according to claim 1, it is characterized in that: FILTER TO CONTROL module comprises connected D/A switch module (2) and operational amplifier module (3), D/A switch module (2) is connected with data processing and control device (1), and operational amplifier module (3) is connected with wave filter (4).
6. sensor according to claim 1, it is characterized in that: data acquisition module comprises connected photodetector (5) and mould/number conversion module (6), photodetector (5) is connected with wave filter (4), and mould/number conversion module (6) is connected with data processing and control device (1).
7. sensor according to claim 1, is characterized in that: data processing and control device (1) are also connected to power module (10), display platform (11) and SD storage card (12).
8. sensor according to claim 1, is characterized in that: Fibre Optical Sensor unit (13) comprise K*M*N Fabry-Perot cavity pair, and wherein K is that time-domain multiplexed number, M are that the multiplexing number of wave zone, N are frequency domain multiplexing number.
9. the modulation-demo-demodulation method of the distributed fiberoptic sensor based on multiple domain hybrid multiplex, it is characterized in that modulator approach comprises: data processing and control device (1) transmitted electric signal, pulse electrical signal is that dutycycle is the square wave of 1/K, pulse electrical signal number is 1/(FT), wherein K is time-domain multiplexed number, F is the frequency of wave filter (4), T is pulse electrical signal time domain width, pulse electrical signal drives wideband light source (7) to export the pulsed optical signals of certain sequential relationship, the output of wideband light source (7) connects Erbium-Doped Fiber Amplifier (8), light signal after amplifying is connected to the first input end mouth of optical circulator (9), output to Fibre Optical Sensor unit (13) by the second output port, described Fibre Optical Sensor unit (13) carries out time domain differentiation by K group sensor fibre by optical fiber, every group of sensor fibre the inside has the sensor array of M group different wave length to carry out wave zone differentiation, there is the Fabry-Perot cavity of N group different cavity length each sensor array the inside to carrying out frequency domain differentiation.
10. method according to claim 9, is characterized in that demodulation method comprises:
Light signal after described amplification enters behind Fibre Optical Sensor unit (13), and K group reflection light pulse, by the 3rd output port output of optical circulator (9), comprises different Fabry-Perot cavities to corresponding wavelength and frequency information in every group of reflection light pulse;
Described reflection light pulse enters after wave filter (4), effective demodulation region by data processing and control device (1) and FILTER TO CONTROL module at wave filter (4), according to the linear piezoelectric ceramics voltage that increases of the minimum step voltage Δ V of wave filter (4), thereby drive the linear narrow band light pulse increasing of wave filter (4) output center wavelength; Wave filter (4) scans after the reflection light pulse of certain time domain by the narrow band light pulse of certain wave band, and the reflection light pulse of next time domain continues to be scanned by the narrow band light pulse of this wave band; Then the wave band that changes the narrow band light pulse of wave filter (4) output scans the reflection light pulse of next Time Domain Piecewise again, until point 1/(FT) section scanned the full wavelength coverage of wideband light source (7), thereby obtained all reflection light pulse spectral informations;
The reflection light pulse light signal of the different wave length of wave filter (4) output is converted to electric signal through photodetector (5), by the digital sample of mould/number conversion module (6), enter data processing and control device (1), data processing and control device (1) by the digital sample result cache in the whole sensing cycle of receiving in the memory storage on it, different time domain signal enters the single level address of memory storage, and different wave zone signals enter the two-level address of memory storage; The scope of described single level address is to configure according to the maximum number number of samples of all time domain scopes, and the scope of described two-level address is to configure according to the maximum number number of samples of all wave zone scopes in a certain time domain;
Data processing and control device (1) complete a time domain, all after dates of wave zone demodulation, carrying out data parallel according to one-level, two-level address reads, different time domain, wave zone signal parallel enter the Fast Fourier Transform (FFT) array of data processing and control device (1), export the right spectrum information of all Fabry-Perot cavities, and contrast with the original signal spectrum information of the ROM (read-only memory) storage of data processing and control device (1), thereby complete demodulating process.
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