CN100494909C - High speed optic fiber grating wavelength demodulating system - Google Patents
High speed optic fiber grating wavelength demodulating system Download PDFInfo
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- CN100494909C CN100494909C CNB2006101249553A CN200610124955A CN100494909C CN 100494909 C CN100494909 C CN 100494909C CN B2006101249553 A CNB2006101249553 A CN B2006101249553A CN 200610124955 A CN200610124955 A CN 200610124955A CN 100494909 C CN100494909 C CN 100494909C
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Abstract
The system is composed of lithium niobate electro-optical switch, coupler, triangle filter of optical fiber grating, optical detector, and processor. Being switched by passing through electro-optical switch, wavelength signals to be modulated enter into each triangle filter of optical fiber grating in turn. Sensed signals inside range of reflectance spectrum of triangle filter of optical fiber grating are reflected and converted to change of wavelength. After passing through corresponding coupler, the reflected wavelength signals are received by each optical detector, and entered to processor finally. Based on change of light intensity, the processor predicts the magnitude of change of wavelength. By using combination between electro-optical switches in high speed and triangle filter of optical fiber grating implement modulation of wavelength in high speed. Increasing number of triangle filter of optical fiber grating can realize modulating wavelength in larger range.
Description
Technical field
The invention belongs to sensory field of optic fibre, be used for fiber-optic grating sensor is carried out Wavelength demodulation.Be particularly suitable for high speed and broadband demodulator, dynamically combine measurement with static parameter.
Background technology
Fiber-optic grating sensor has reliability height, anti-electromagnetic interference (EMI), characteristics such as anticorrosive, its Wavelength-encoding characteristic and can on simple optical fiber, realize the advantage of quasi-distributed measurement other sensor is incomparable especially in addition, have broad application prospects, but one of main obstacle of present limit fibre grating sensor large-scale practical application is the demodulation to the fiber grating sensor wavelength signal.
In fiber grating sensing system, external physical quantity is that the reflection wavelength with fiber grating is that carrier transmits, therefore, the Wavelength demodulation technology is the research focus in this field always, develops that tuning range is big, precision is high, good stability, demodulating system is the key of fiber-optic grating sensor practicability cheaply.Domestic and international research mechanism and associated companies are very many to the fiber grating demodulation Study on Technology, up to the present, have developed and ten multi-wavelength's rectification technology.People such as S.M.Melle proposed the edge filter method in 1992, utilized the linear segment of wave filter to the wavelength response function, and wavelength information is converted into strength information.The same year, people such as A.D.Kersey proposed non-equilibrium Mach-Zehnder interferometric method, utilized non-equilibrium Mach-Zehnder interferometer that the catoptrical wavelength variations of fiber-optic grating sensor is converted to phase change, changed obtaining wavelength variation information by detected phase; This method has very high wavelength resolution, but interferometer is affected by environment bigger, and this method only is fit to detect dynamic strain, and, can only detect the wave length shift of a plurality of Bragg gratings by time-division multiplex technology, be not suitable for adopting the compartment system of wavelength-division multiplex.After this, people such as A.D.Kersey has successively proposed the adjustable Fabry-Perot filter method again, has added the non-equilibrium Mach-Zehnder interferometric method of modulation.People such as P.K.C.Chan have reported a kind of subcarrier demodulation method in 1999, flashlight is loaded on the another one frequency range, and receiving end is downloaded useful signal and carry out demodulation from carrier wave; Even being that several roads array Bragg grating reflection wavelength is identical, this method biggest advantage also can respectively its demodulation be come out.2000 the end of the year people such as Bai Ou fiber laser length scanning method has been proposed, adopt the narrow-band light source raster grating reflection spectrum of wavelength period variation, the output wavelength of narrow-band light source can be learnt corresponding optical grating reflection wavelength when the strongest according to each scanning reflection light; This method has higher signal to noise ratio (S/N ratio) and resolution, but the laser spectrum narrow range, and be interfered easily, influence precision.People such as Jauregui in 2004 have proposed the method for utilizing the inclination chirp grating to carry out demodulation, and the demodulator structure of making of this method is simple, volume is little, but precision and signal to noise ratio (S/N ratio) are not high.
Because the optic fiber grating wavelength demodulation method is a lot, but because these technology limitation separately, the product of input practical application is also few, does not also have a kind of demodulation scheme can satisfy frequency height, bandwidth simultaneously and greatly, dynamically combines measurement and the not high requirement of cost with static parameter.
Summary of the invention
The purpose of this invention is to provide a kind of high speed optic fiber grating wavelength demodulating system, this system has big demodulation scope simultaneously and dynamically combines measurement with static parameter, and reusable detects.
For achieving the above object, the technical solution used in the present invention is by the combination of adopting lithium niobate electrooptical switching and fiber grating triangle filter to reflect, thereby to have realized the high speed optic fiber grating wavelength demodulation.The concrete solution of the present invention is as follows: fiber grating sensing system mainly comprises wideband light source 3, fiber-optic grating sensor 2, Wavelength demodulation device 1 and annular device 8.Wideband light source 3 provides light source for fiber-optic grating sensor 2, the variation that fiber-optic grating sensor 2 perception are to be measured, and be converted into wavelength change and reflect; Wavelength demodulation device 1 receives reflected light signal, and it is reduced to variation to be measured.In order to make signal demodulating equipment tell each fiber-optic grating sensor, the centre wavelength (λ of each fiber-optic grating sensor
1, λ
2λ
n) different, and it differs by more than 2nm, to guarantee the investigative range of sensor.The optic fiber grating wavelength demodulating equipment by 4, lithium niobate electrooptical switching 5, coupling mechanism 6, fiber grating triangle filter 7, photo-detector 8, circulator, 9, processor form.
As wavelength signals (λ to be demodulated
1, λ
2λ
nN is a positive integer, the number of expression fiber-optic grating sensor): after entering demodulating equipment, switching through lithium niobate electrooptical switching 4, enter each fiber grating triangle filter 6 successively, sense light signal in fiber grating triangle filter reflectance spectrum scope is reflected, and the wavelength signals after being reflected is received by each photo-detector 7 behind corresponding coupling mechanism 5.Extrapolate the size of changed wavelength according to intensity variations processor 9.Said process switches by the circulation of photoswitch 4, constantly detects the wavelength variations of each sensor fibre grating.Because photoswitch 4 adopts the lithium niobate electrooptical switching, its switching frequency can reach 10
6Hz is so the frequency, demodulation frequency of system can reach 10
6/ n Hz.
Advantage of the present invention is: the combination by high-speed optical switch and fiber grating triangle filter, realized the high speed Wavelength demodulation, and by increasing the quantity of fiber grating triangle filter, can realize large-scale Wavelength demodulation simultaneously.
Description of drawings
Fig. 1 fiber grating sensing system synoptic diagram;
The spectral response synoptic diagram of Fig. 2 fiber grating triangle filter;
Fig. 3 high speed optic fiber grating wavelength demodulating system structural representation;
1. Wavelength demodulation device 2, fiber-optic grating sensor 3, wideband light source 4, photoswitch 5, coupling mechanism 6, fiber grating triangle filter 7, photo-detector 8, circulator 9, processor
Embodiment
Introduce detailed content of the present invention in detail according to Fig. 1, Fig. 2, Fig. 3
As shown in Figure 1, fiber grating sensing system mainly comprises wideband light source 3, fiber-optic grating sensor 2 and Wavelength demodulation device 1 and annular device 8.Wideband light source 3 provides light source for fiber-optic grating sensor 2, the variation that fiber-optic grating sensor 2 perception are to be measured, and be converted into wavelength change and reflect; Wavelength demodulation device 1 receives reflected light signal, and it is reduced to variation to be measured.In order to make signal demodulating equipment tell each fiber-optic grating sensor, the centre wavelength (λ of each fiber-optic grating sensor
1, λ
2λ
n) different, and it differs by more than 2nm, to guarantee the investigative range of sensor.
Among the spectral response figure of fiber grating triangle filter shown in Figure 2, the spectral shape of this wave filter is a triangle, adopts the chirped fiber grating phase mask plate to obtain by the method for non-homogeneous exposure.
High speed optic fiber grating wavelength demodulating equipment shown in Figure 3 is made up of lithium niobate electrooptical switching 4, coupling mechanism 5, fiber grating triangle filter 6, photo-detector 7, circulator 8, processor 9.As wavelength signals (λ to be demodulated
1, λ
2λ
nN is a positive integer, the number of expression fiber-optic grating sensor): after entering demodulating equipment, switching through lithium niobate electrooptical switching 4, enter each fiber grating triangle filter 6 successively, sense light signal in fiber grating triangle filter reflectance spectrum scope is reflected, for example wavelength signals λ
1By the 1st fiber grating triangle filter reflection, wavelength signals λ
2By the reflection of the 2nd fiber grating triangle filter ..., wavelength signals λ
nBy n fiber grating triangle filter reflection, can see that from the spectral response figure of fiber grating triangle filter 6 spectral shape of this wave filter is a triangle, adopt the chirped fiber grating phase mask plate to obtain by the method for non-homogeneous exposure.The reflectivity of this wave filter is relevant with wavelength, if to wavelength X
iReflectivity be R
i, then to wavelength X
i+ Δ λ
iReflectivity be:
R(λ
i+Δλ
i)＝R
i+k×Δλ
i (1)
Wherein k is the slope of spectrogram intermediate cam shape.
Wavelength signals after being reflected is received by each photo-detector 7 behind corresponding coupling mechanism 5.If the wavelength X of certain signal
i(1≤i≤n) small drift has taken place, then Dui Ying fiber grating triangle filter also changes to its reflectivity, thereby the light intensity of accepting of corresponding photo-detector is changed, and extrapolates the size of changed wavelength according to the intensity variations processor.Said process switches by the circulation of photoswitch 4, constantly detects the wavelength variations of each sensor fibre grating.Because photoswitch 4 adopts the lithium niobate electrooptical switching, its switching frequency can reach 10
6Hz is so the frequency, demodulation frequency of system can reach 10
6/ n Hz.
Claims (2)
1, a kind of high speed optic fiber grating wavelength demodulating system is characterized in that comprising lithium niobate electrooptical switching (4), coupling mechanism (5), fiber grating triangle filter (6), photo-detector (7), processor (9); After wavelength signals to be demodulated enters demodulating equipment, switching through lithium niobate electrooptical switching (4), enter each fiber grating triangle filter (6) successively, sense light signal in fiber grating triangle filter reflectance spectrum scope is reflected, wavelength signals after being reflected is received by each photo-detector (7) behind corresponding coupling mechanism (5), extrapolates the size of changed wavelength according to intensity variations processor (9).
2, a kind of high speed optic fiber grating wavelength demodulating system according to claim 1 is characterized in that: the quantity of fiber grating triangle filter (6) increases or reduces according to the quantity of sensor fibre grating; Can increase the Wavelength demodulation scope by the quantity that increases the fiber grating triangle filter.
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| CNB2006101249553A CN100494909C (en) | 2006-11-07 | 2006-11-07 | High speed optic fiber grating wavelength demodulating system |
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|---|---|---|---|
| CNB2006101249553A CN100494909C (en) | 2006-11-07 | 2006-11-07 | High speed optic fiber grating wavelength demodulating system |
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| CN100494909C true CN100494909C (en) | 2009-06-03 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100541138C (en) * | 2007-09-07 | 2009-09-16 | 李东升 | Optical fibre grating digital demodulation method and system thereof based on autocorrelation principle |
| CN102353394A (en) * | 2011-06-17 | 2012-02-15 | 武汉理工大学 | Time division multiplexing (TDM)-based low-reflectivity triangle spectrum-shaped fiber grating sensing system |
| CN113340421B (en) * | 2021-07-05 | 2023-02-28 | 西安交通大学 | All-fiber micro spectrometer based on fiber end face Fizeau interference |
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Effective date of registration: 20170628 Address after: 430079 Hubei science and Technology Park, East Lake Development Zone, Wuhan, China Patentee after: Wuhan Feng Li Photoelectric Technology Co Ltd Address before: Wuhan University of Technology No. 122 fiber center 430070 Hubei province Wuhan city Hongshan District Luoshi Road Patentee before: Wuhan University of Technology |
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