CN1448695A - Optical fibre transducer general purpose high speed waveguide wavelength scanning demodulation process and apparatus - Google Patents
Optical fibre transducer general purpose high speed waveguide wavelength scanning demodulation process and apparatus Download PDFInfo
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- CN1448695A CN1448695A CN 03117714 CN03117714A CN1448695A CN 1448695 A CN1448695 A CN 1448695A CN 03117714 CN03117714 CN 03117714 CN 03117714 A CN03117714 A CN 03117714A CN 1448695 A CN1448695 A CN 1448695A
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Abstract
The key of the general and high speed waveguide wavelength scan demodulating method is to apply periodical scanning voltage signal on a tunable waveguide filter to make the reflected wavelength vary periodically and to realize the scan of spectrum. The initial reflection wavelength, bandwidth, reflectivity and other parameters of the tunable waveguide filter are designed based on the required light source wavelength and demodulation precision of the demodulator; and the filter wavelength scanning range, scanning frequency and other parameters are controlled through altering the amplitude and frequency of the driving electric signal for the modulator. The equipment consists of light source, fiber optical path, tunable waveguide filter, which comprises single-mode light waveguide, Bragg grating and modulator, and detecting and signal processing device with intelligent distinguish function.
Description
Technical field
The invention belongs to the crossing domain in sensory field of optic fibre and civilian infrastructure status monitoring field, be specifically related to a kind of general, fast wave guide wavelength scan demodulating method and device of Fibre Optical Sensor.
Technical background
Compare with other sensors, Fibre Optical Sensor has that volume is little, in light weight, pliability is good, corrosion-resistant, waterproof, anti-electromagnetic interference (EMI), and is easy to and advantage such as communication network is interconnected, is a kind of advanced person's sensor.Be that the Fibre Optical Sensor of representative is applied in large-scale civilian states such as bridge, dam, power station, highway, tunnel (strain, temperature, vibration etc.) monitorings and promotes with optical fiber Fabry-Perot sensor, fiber-optic grating sensor in recent years.Particularly in the long-term on-line condition monitoring of infrastructure, Fibre Optical Sensor begins to play an important role gradually, and the trend that replaces traditional sensor is arranged greatly.Consider the precision and the stability thereof of demodulation, at present with " spectroscopic methodology " Fibre Optical Sensor is carried out demodulation usually, the core of this method is the spectrogram that obtains the output signal of Fibre Optical Sensor, and by extracting the feature of its Wavelength distribution, obtains the information of corresponding measurand.Wherein, mainly adopt spectrometer to obtain spectrogram and demodulation, then adopt based on piezoelectric scanning device tunable optical filter for fiber-optic grating sensor and come demodulation for optical fiber Fabry-Perot sensor.There are the following problems respectively for these methods:
1, adopt spectrometer to obtain parts as spectrum
The core of this method is a spectrometer, and it uses optical system (grating, prism etc.) that spectrum is separated usually, and utilizes detector array collections such as CCD or CMOS to read spectral signal; Because the restriction body of principle, the volume of spectrometer are big usually, price is expensive and reading speed slow (sample frequency is about tens Hz usually).At first price and volume problem limit its applying on engineering; In addition, slow-footed shortcoming makes it only be applicable to static or quasi-static measurement, not competent kinetic measurement.
2, adopt based on the piezoelectric scanning tunable optical filter
The core of this demodulation method is a tunable Fabry-perot optical fiber wave filter of Piezoelectric Ceramic.Add the voltage signal of periodic scan to piezoelectric ceramics after, piezoelectric ceramics produces periodic mechanical modification, and the wavelength that causes the Fabry-perot optical fiber wave filter to be considered produces periodic the variation, realizes the scanning to spectrum.Adopt this demodulation method, shortcoming be: 1) scanning be a kind of mechanical motion, its speed is subjected to the restriction of piezo ceramic element self response frequency, can only measure the signal of hundreds of hertz, not the signal of energy measurement higher frequency (more than the 1KHz); 2) sluggishness that has of piezoelectric element, drift, shortcoming such as linear bad have also influenced measuring accuracy, the linearity and the measuring repeatability of this demodulation method greatly; 3) in the work, tunable optic filter is actually a kind of mechanical motion under piezoelectric element drives, and the bonding easy fatigure failure between piezoelectric element and the wave filter influences serviceable life of instrument; 4) in order to obtain high resolution, the fiber end face of Fabry-perot optical fiber wave filter need plate high-reflecting film, and this technology difficulty is big, poor repeatability.
3, do not possess versatility
Spectrally resolved power, spectral range, sample frequency that two kinds of sensors of demodulating fiber bragg grating and Fabry-perot optical fiber need are all different.Be subjected to hardware constraints, above-mentioned two kinds of demodulation methods can't adapt to automatically according to the characteristics of sensor, thereby versatility is poor.For not only needing the high-precision optical fiber Fabry-Perot sensor but also need the measurement occasion of fiber-optic grating sensor at a high speed then to need to have increased the complicacy of system, improved the cost of measuring with two cover gauge systems.
Summary of the invention
Purpose of the present invention is formally for fear of the deficiency of above-mentioned prior art and general, the fast wave guide wavelength scan demodulating method of a kind of Fibre Optical Sensor that designs.
The objective of the invention is to adopt following proposal to realize:
The core general, fast wave guide wavelength scan demodulating method of Fibre Optical Sensor is a tunable waveguide filter.Its basic step is as follows: at first, light source luminescent incides on the sensor through optic fibre light path, and the reflected signal of sensor incides on the tunable waveguide filter through optic fibre light path once more; Add the voltage signal of periodic scan for then tunable waveguide filter, cause the cyclical variation of reflection wavelength, realize scanning spectrum; The reflected light of tunable waveguide filter enters through optic fibre light path again and surveys and signal processor, and light signal is converted into electric signal, reverts to spectrogram after handling; With digital signal processor spectrogram is analyzed at last, obtained the value of measurand, realize the Fibre Optical Sensor demodulation.
In the said method, parameters such as tunable waveguide filter initial reflection wavelength, bandwidth, reflectivity design according to optical source wavelength, the demodulation accuracy requirement of described demodulating equipment; The amplitude and the frequency of the driving electric signal of parameters such as tunable guide filter wavelength scanning range, sweep frequency by changing the modulator in the tunable waveguide filter are controlled.
Realize that said method is general, the fast wave guide wavelength scanning demodulating equipment that the present invention designs, it is made of light source, optic fibre light path, tunable waveguide filter and detection and signal processor four parts with Intelligent Recognition function, light source, tunable waveguide filter, detection and signal processor are connected with optic fibre light path by three ports of optic fibre light path respectively, another port of optic fibre light path links to each other with the ambient light fiber sensor as the light output/input port of instrument.
The tunable waveguide filter in the core of said apparatus is to constitute by being integrated in three elements such as monomode optical waveguide on a slice electro-optic crystal, Bragg grating, modulator.Wherein the effect of monomode optical waveguide is to be convenient to being of coupled connections of this wave filter and extraneous optic fibre light path; The selective reflecting wave filter that then is used as an arrowband of Bragg grating, the wavelength X of its reflection
BWith grating periods lambda, waveguide equivalent refractive index n
EffBetween satisfy following formula:
λ
B=2
NeffΛ therefore, if cycle or refractive index change, the wavelength of its reflection also can change; Similar to previously described wave filter based on piezoelectric scanning, utilize it can realize scanning to spectrum.For fear of changing the grating periods lambda with mechanical motion, the present invention has designed the modulator that is parallel to this grating on the both sides of Bragg grating; Utilize the characteristics of electro-optic crystal, add the suitable voltage signal, the equivalent refractive index n of above-mentioned Bragg grating at modulator two electrodes
EffTo change, and then cause the variation of reflection wavelength, realize scanning spectrum.
Adopt the advantage of above method as follows:
1, tunable waveguide filter is actually the characteristic of utilizing electro-optic crystal and carries out spectral scan, does not have the machinery motion in the work, the component wear that can avoid fatigue to cause, so reliability and life-span improve greatly.
2, demodulation speed (sample frequency) is by the operating rate decision of modulator.The operating rate of electrooptic modulator can arrive the above order of magnitude of GHz usually, if adopt the method for row ripple modulation, and operating rate even can reach higher; Therefore as long as cooperate corresponding high-speed digital signal processor, the sample frequency of this demodulation method can be than high many of previously described two kinds of existing methods.
3, under suitable working condition, the linearity and the repeatability to electric response of electro-optic crystal are all very good, and is linear and repeated than improving greatly based on the piezoelectric scanning optically filtering.
4, integrated optics technology is ripe relatively, and make above-mentioned tunable waveguide filter quality and guarantee easily, and the high conformity of the device that processes.
5, change amplitude and the frequency that is added in voltage signal on the modulator, can control the scope and the sample frequency of the scanning of tunable waveguide filter; System can require according to the demodulation of Fabry-perot optical fiber or fiber-optic grating sensor to adapt to automatically like this, so its general character improves greatly; Particularly in the measuring system of multiple Fibre Optical Sensor, use convenient.
6, avoided the employing spectrometer to obtain part owing in the system, so cost descend greatly as spectrum.
Therefore, the advantage of the comprehensive existing fiber sensor of the present invention demodulation method compensates its defect, and has advantages such as high speed, long-life, high reliability, high precision, high universalizable.
Description of drawings
The structural drawing of Fig. 1 one embodiment of this invention
Tunable waveguide filter in Fig. 2 the present embodiment
Embodiment
The present invention is further elaborated below in conjunction with accompanying drawing:
Referring to accompanying drawing 1, general, the fast wave guide wavelength scanning demodulating equipment of Fibre Optical Sensor are made of four parts such as broadband superradiation light-emitting (SLD) light source 1, optic fibre light path 2, tunable waveguide filter 3, detection and signal processors 4.Optic fibre light path 2 is made of two Y type single-mode fiber beam splitters; Its three ports are connected with SLD light source 1, tunable waveguide filter 3, detection and signal processor 4 respectively; Another port links to each other with ambient light fiber sensor 5 as the light output/input port of instrument.Referring to Fig. 2, tunable waveguide filter 3 constitutes by being integrated in three elements such as monomode optical waveguide 9 on a slice lithium columbate crystal, modulator 10, Bragg grating 11; Wherein monomode optical waveguide is connected with a port of optic fibre light path 2, and the cycle of Bragg grating and length design according to the requirement of real work wavelength, bandwidth and reflectivity.The acquisition of signal processor comprises high sensitivity photodiode 6, A/D change-over circuit 7 and high speed digital signal processor (DSP) 8.
During work, sensor 5 is received on the demodulating equipment; Light source 1 luminous process optic fibre light path 2 incides on the sensor 5; The reflected signal of sensor incides on the tunable waveguide filter 3 through optic fibre light path 2 once more, and the reflected light after tunable waveguide filter 3 filtering enters in detection and the signal processor 4 again through optic fibre light path 2.Particularly, the reflected light of sensor is to be coupled in the Bragg grating 11 by monomode optical waveguide 9, and grating reflection light incides on the photodiode 6 by waveguide 9, optic fibre light path 2 again.Add that at 10 liang of electrodes of modulator the cycle changes voltage signal, the equivalent refractive index n of Bragg grating 11
EffWith the generating period variation, and then cause that the cycle of reflection wavelength changes, realizes the scanning to spectrum.Photodiode 6 is converted to electric signal to light signal, through entering high speed digital signal processors (DSP) 8 after the A/D change-over circuit 7; DSP8 reverts to spectrogram to the electric signal of scanning, and utilize intelligent identification technology, judge that according to the characteristics of signal amplitude and waveform the sensor 5 that inserts is optical fiber Fabry-Perot sensor, fiber-optic grating sensor or fiber grating and Fabry-perot optical fiber mixed type sensor, and the amplitude and the frequency of change modulation signal, and then change tunable waveguide filter 3 sweep limit and frequency, adapt to sensor automatically; Call the corresponding signal process module simultaneously and calculate, obtain the information of measurand.
Adopt thinking of the present invention like this, can realize general, the high speed demodulation of multiple Fibre Optical Sensor.
Although the present invention is primarily aimed at Fabry-perot optical fiber and fiber-optic grating sensor demodulation design, yet application of the present invention is not limited to this two kinds of Fibre Optical Sensors, can be generalized to the other types Fibre Optical Sensor that other need utilize the spectroscopic methodology demodulation.In addition,, adopted independently optic fibre light path, adopted DSP to make signal processor although adopt lithium columbate crystal to make tunable optic filter in the embodiment of the present invention; Still can utilize other electro-optic crystal to make tunable optic filter, can utilize integrated optics technology that optic fibre light path (Y beam splitter) and tunable optic filter directly are integrated on the same block of electro-optic crystal, can utilize high-speed microprocessor or PC computing machine to make signal processor, thereby realize the present invention and do not deviate from defined essence of the present invention and scope in claims.
Claims (9)
1, general, the fast wave guide wavelength scan demodulating method of Fibre Optical Sensor, it is characterized in that it is the core that realizes the high speed spectral scan with tunable waveguide filter: at first, light source luminescent incides on the sensor through optic fibre light path, and the reflected signal of sensor incides on the tunable waveguide filter through optic fibre light path once more; Add the voltage signal of periodic scan for then tunable waveguide filter, cause the cyclical variation of reflection wavelength, realize scanning spectrum; The reflected light of tunable waveguide filter enters through optic fibre light path again and surveys and signal processor, and light signal is converted into electric signal, reverts to spectrogram after handling; With digital signal processor spectrogram is analyzed at last, obtained the value of measurand, realize the Fibre Optical Sensor demodulation.
2, method according to claim 1 is characterized in that parameters such as tunable waveguide filter initial reflection wavelength, bandwidth, reflectivity require to design according to optical source wavelength, the demodulation accuracy of described demodulating equipment.
3, method according to claim 1 is characterized in that the amplitude and the frequency of the driving electric signal of parameters such as tunable guide filter wavelength scanning range, sweep frequency by changing the modulator in the tunable waveguide filter controlled.
4, realize general, the fast wave guide wavelength scanning demodulating equipment of the Fibre Optical Sensor of claim 1,2 or 3 described methods, it is characterized in that it is made of light source, optic fibre light path, tunable waveguide filter and detection and signal processor four parts with Intelligent Recognition function, light source, tunable waveguide filter, detection and signal processor are connected with optic fibre light path by three ports of optic fibre light path respectively, another port of optic fibre light path links to each other with the ambient light fiber sensor as the light output/input port of instrument.
5, device according to claim 4, it is characterized in that tunable waveguide filter by be integrated in one block on the electro-optic crystal monomode optical waveguide, Bragg grating and the modulator that is parallel to this grating on ground, Bragg grating both sides constitute, wherein monomode optical waveguide is connected with a port of optic fibre light path, and the cycle of Bragg grating and length design according to the requirement of real work wavelength, bandwidth and reflectivity.
6, device according to claim 4 is characterized in that optic fibre light path is made of two Y type single-mode fiber beam splitters.
7, device according to claim 4 is characterized in that utilizing integrated optics technology that optic fibre light path and tunable optic filter directly are integrated on the same block of electro-optic crystal,
8, device according to claim 4 is characterized in that the acquisition of signal processor comprises high sensitivity photodiode 17, A/D change-over circuit 18 and signal processor.
9, device according to claim 8, it is characterized in that signal processor can be high speed digital signal processor DSP, high-speed microprocessor or PC computing machine, it can judge the sensor type that inserts according to the characteristics of signal amplitude and waveform, and the amplitude and the frequency of change modulation signal, make the duty of tunable waveguide filter adapt to sensor automatically.
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| Application Number | Priority Date | Filing Date | Title |
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| CN 03117714 CN1186592C (en) | 2003-04-18 | 2003-04-18 | Optical fibre transducer general purpose high speed waveguide wavelength scanning demodulation process and apparatus |
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| CN 03117714 CN1186592C (en) | 2003-04-18 | 2003-04-18 | Optical fibre transducer general purpose high speed waveguide wavelength scanning demodulation process and apparatus |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102684691A (en) * | 2011-03-14 | 2012-09-19 | 精工爱普生株式会社 | Optical module for atomic oscillator and atomic oscillator |
| CN104579459A (en) * | 2013-10-25 | 2015-04-29 | 华为技术有限公司 | Fiber link identification method, equipment and system |
| CN106767959A (en) * | 2016-12-26 | 2017-05-31 | 重庆大学 | A kind of Demodulation System for Fiber Optic Fabry-Perot Sensors |
-
2003
- 2003-04-18 CN CN 03117714 patent/CN1186592C/en not_active Expired - Fee Related
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102684691A (en) * | 2011-03-14 | 2012-09-19 | 精工爱普生株式会社 | Optical module for atomic oscillator and atomic oscillator |
| CN104579459A (en) * | 2013-10-25 | 2015-04-29 | 华为技术有限公司 | Fiber link identification method, equipment and system |
| US9774390B2 (en) | 2013-10-25 | 2017-09-26 | Huawei Technologies Co., Ltd. | Fiber link recognition method, device, and system |
| CN104579459B (en) * | 2013-10-25 | 2018-03-16 | 华为技术有限公司 | A kind of method, apparatus and system of fiber link identification |
| CN106767959A (en) * | 2016-12-26 | 2017-05-31 | 重庆大学 | A kind of Demodulation System for Fiber Optic Fabry-Perot Sensors |
| CN106767959B (en) * | 2016-12-26 | 2019-04-30 | 重庆大学 | A kind of Demodulation System for Fiber Optic Fabry-Perot Sensors |
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| CN1186592C (en) | 2005-01-26 |
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