CN203587125U - Positioning system of fiber grating - Google Patents

Positioning system of fiber grating Download PDF

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Publication number
CN203587125U
CN203587125U CN201320749214.XU CN201320749214U CN203587125U CN 203587125 U CN203587125 U CN 203587125U CN 201320749214 U CN201320749214 U CN 201320749214U CN 203587125 U CN203587125 U CN 203587125U
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wavelength
fiber grating
grating
fiber
optical source
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张丽
刘清辉
刘翠青
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Wuhan Optogts Technology Co Ltd
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Wuhan Optogts Technology Co Ltd
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Abstract

The utility model discloses a positioning system of a fiber grating. The basic principle is based on a fiber grating wavelength demodulation device of a tunable light source, due to the fact that the tunable light source has a wavelength constant-speed linear scanning characteristic, the wavelength scanning order of the tunable light source is set, namely reciprocating scanning is carried out once respectively with a short wave as a start point and with a long wave as a start point, the practical central wavelength of the fiber grating and the difference between a calculation wavelength obtained through wavelength scanning and the practical wavelength can be calculated, and accordingly the distance between the fiber grating to be detected and the wavelength demodulation device can be obtained. The fiber grating is laid on a device with the temperature or a stress point to be detected, due to the positioning system, wavelength demodulation is carried out, meanwhile, positioning information, accurate wavelength information, corresponding temperature information and strain information and other parameters can be obtained, the structure of a fiber grating demodulation system is greatly simplified, and system cost is reduced due to the fact that an OTDR technique is needless.

Description

A kind of fiber grating positioning system
Technical field
The utility model belongs to Fibre Optical Sensor, field of optical measuring technologies, is specifically related to a kind of localization method and system of fiber grating.
Background technology
FBG (Fiber Bragg Grating, Fiber Bragg Grating FBG) there is reflection wavelength with temperature, the extraneous factors such as stress are the characteristic of linear change, therefore monitor the skew of FBG reflection wavelength and can measure the variation that obtains external parameter, and its detectivity is not fluctuateed by light source power, the impact of the factors such as bending loss of optical fiber and detector are aging, so be applicable to very much long-term safety monitoring, especially its Wavelength-encoding characteristic and can realize the advantage of quasi-distributed measurement on simple optical fiber other sensor is incomparable especially, have broad application prospects.
In some thermometric warning occasions, such as the long thermometric apart from power cable connector is reported to the police, user not only needs to learn temperature information, and need to learn the temperature alarming concrete which cable splice sends, so that maintainer investigates problem within the shortest time.Therefore, adopt FBG quasi-distributed optical fiber sensor-based system, the fiber grating of different centre wavelengths is laid on cable under test joint, utilizes optic fiber grating wavelength demodulation techniques and sensor localization addressing technique just to draw temperature information and the positional information of node to be measured.
At present, the addressing of optic fiber grating wavelength solution mediation sensor localization is the technological difficulties based on FBG optical fiber sensing network always.Domestic patent (CN102102998A) has been reported a kind of " based on the distributed sensing system of weak Bragg reflection structured optical fiber ", it is characterized in that merging the optical wavelength Time Domain Reflectometry OWTDR type location of wavelength-modulated sensing technology and OTDR location technology.According to investigation, domestic application is realized positioning function and is generally all adopted OTDR technology in distributed optical fiber sensing system, Wavelength demodulation technology and OTDR technology is combined, thereby realize temperature, stress, vibration and the positional information of tested point.
The realization of OTDR technology, needs the control circuit of the compositions such as complicated and expensive electrooptic modulator, function generator to support, expensive, is applicable to the occasion that positioning precision is very high (such as positioning precision <1 rice); But in most of distributed sensing systems field, positioning accuracy request is not very high, increase OTDR function, whole system cost is very high, has greatly limited the universal and application of distributed sensing system.
Separately in engineering construction, because the distance between optical fiber grating sensing head and demodulating equipment is very long, short several meters, long tens kilometers, even hundreds of, several thousand kilometers, the length of optical fiber directly causes understanding while adjusting optic fiber grating wavelength, will certainly be inconsistent with the optic fiber grating wavelength of the calibration of dispatching from the factory, therefore,, when engineering construction, in a lot of situations, need to carry out situ calibration to engineering site.
Therefore, how to realize one and can resolve optic fiber grating wavelength, thereby parse the information such as corresponding temperature, stress, can realize again location simple and effectively, solving the problems such as engineering construction and engineering maintenance, is the problem that the art developer need to face solution.
Summary of the invention
For the defect existing in prior art, it is a kind of easy that the purpose of this utility model is to provide, do not increase under the prerequisite of any hardware cost, just can realize the method for above-mentioned functions,, in Wavelength demodulation, utilize this method, just can draw the parameters such as locating information, temperature information and strain information simultaneously, this method has been simplified the structure of optical fiber grating regulating system greatly, owing to not needing OTDR technology, thereby has reduced system cost.Adopt the fiber grating demodulation equipment of this method to possess parsing grating simultaneously and realized the function of sensing head location.
For achieving the above object, the utility model provides following technical scheme:
A kind of fiber grating positioning system, its difference is, it comprises that at least one stylobate is carved with the optical fiber of fiber-optic grating sensor in the optical fiber grating wavelength demodulating equipment of tunable optical source and at least one road; The light path output port of optical fiber grating wavelength demodulating equipment is connected with the optical fiber that is carved with fiber-optic grating sensor, the data of returning through grating sensor obtain locating information and/or temperature information and/or strain information after the demodulation of Wavelength demodulation device, the light source of optical fiber grating wavelength demodulating equipment is the tunable optical source that can carry out at the uniform velocity linear sweep, its wavelength resolution can reach 1pm, and length scanning speed is greater than 10pm/2us.
By above scheme, the optical fiber grating wavelength demodulating equipment based on tunable optical source comprises a tunable optical source module, photo-coupler or circulator, a photoelectric conversion module, a data acquisition unit, a calculation control unit; The output termination photo-coupler of tunable optical source or the input end of circulator, one output terminal of photo-coupler or circulator reserves with the form of fiber port, external at least one bragg grating to be measured, another output terminal is access data collecting unit after photoelectric conversion module, finally enters calculation control unit.
By above scheme, optical fiber grating wavelength demodulating equipment based on tunable optical source is multi-channel fiber Bragg grating Wavelength demodulation device, the light of tunable optical source is divided into N road with shunt or the photoswitch of at least one 1xN and N >=1, then demodulation is carried out in each road, optical fiber grating wavelength demodulating equipment based on tunable optical source specifically comprises a tunable optical source, shunt or the photoswitch of at least 1 1xN and N >=1, at least one photo-coupler or circulator, single channel or hyperchannel photoelectricity modular converter, a data acquisition unit, a calculation control unit, tunable optical source is divided into the light of tunable optical source N road and outputs to the input end of photo-coupler or circulator through shunt or photoswitch, one output terminal of photo-coupler or circulator reserves with the form of fiber port, external at least one bragg grating to be measured, another output terminal is access data collecting unit after single channel or hyperchannel photoelectricity modular converter, finally enter calculation control unit.
By above scheme, described hyperchannel photoelectricity modular converter consists of N detector PIN, opto-electronic conversion, filtering, amplification, shaping circuit, N >=1.
Locating information and temperature information and strain information can independently show, also can send to other terminal or server by the communication port of this device (comprising network interface, RS485, RS232, USB etc.).
Computing Principle is as follows in detail: if raster center wavelength is λ, the distance of grating and demodulated equipment is L, from demodulated equipment, issue a signal to the return signal that receives grating, need elapsed-time standards △ t=2*L/(c/n) (c is the light velocity in vacuum, n fiber core refractive index).Because the length scanning speed of grating demodulation equipment is V=d λ/d t, through the time changed wavelength of dt, be dt*V again.So, the scanning wavelength of tunable laser is set sequentially, suppose when scanning from shortwave to long wave, elapsed-time standards △ t, obtains grating wavelength λ 1, than grating practical center wavelength, toward long wave direction, be offset △ t*V.Otherwise while scanning from long wave to shortwave, same elapsed-time standards △ t, obtains grating wavelength λ 2, than grating practical center wavelength, toward shortwave, be offset △ t*V.Therefore can draw the central wavelength lambda=(λ of grating reality 1+ λ 2)/2, the wavelength offset △ λ=(λ of twice sweep 1– λ)=(λ – λ 2)=dt*V.Because λ 1and λ 2can test and obtain, thereby can draw △ λ, as shown in Figure 1.Grating demodulation equipment length scanning speed is that V=d λ/d t is known again, so can calculate time △ t=△ λ/V that deviation △ λ experiences, thereby can obtain the position L=(c/n of fiber grating apart from demodulated equipment) * △ t/2=(c/n) * △ λ/2V(c is the light velocity in vacuum, n fiber core refractive index, V is the length scanning speed of tunable optical source), the location of realizing fiber grating.
The utility model also provides a kind of fiber grating positioning system, comprise at least one stylobate in the optical fiber grating wavelength demodulating equipment of tunable optical source and at least one road the optical fiber with fiber-optic grating sensor.Concrete annexation is: from the light path output port of Wavelength demodulation device, be connected with the optical fiber that is carved with fiber-optic grating sensor, the data of returning through grating sensor are after the demodulation of Wavelength demodulation device, locating information and temperature information and strain information can independently show, also can send to other terminal or server by the communication port of this device (comprising network interface, RS485, RS232, USB etc.).The light source of optical fiber grating wavelength demodulating equipment is tunable optical source, at the uniform velocity linear sweep, and its wavelength resolution can reach 1pm, and length scanning speed is greater than 10pm/2us.
Contrast prior art, principle of the present utility model and beneficial effect are as follows: utilize the utility model, do not increasing under the prerequisite of any hardware cost, just can realize the positioning function of fiber grating, in Wavelength demodulation, utilize this method, just can draw the parameters such as locating information, temperature information and strain information simultaneously; And utilize this method, the reflection kernel wavelength of actual grating can be calculated, thereby the different measurement wavelength that cause of length and the inconsistent problem of calibration wavelength because of dispatch from the factory optical fiber and working-yard optical fiber in engineering construction can be solved; Owing to providing locating information, therefore can greatly facilitate engineering construction personnel and maintainer to investigate problem, greatly shorten the time of dealing with problems.
This method has been simplified the structure of optical fiber grating regulating system greatly, thereby has reduced system cost.Adopt the fiber grating demodulation equipment of this method not adopt OTDR technology just can possess the function of resolving grating wavelength and location simultaneously.
Accompanying drawing explanation
Fig. 1 is the method schematic diagram of the utility model embodiment;
Fig. 2 is the system chart schematic diagram of the utility model embodiment;
Fig. 3 is that the multi-channel fiber Bragg grating Wavelength demodulation device in the utility model embodiment utilizes shunt implementation schematic diagram;
Fig. 4 is that the multi-channel fiber Bragg grating Wavelength demodulation device in the utility model embodiment utilizes photoswitch implementation schematic diagram.
Embodiment
Main thought of the present utility model is to propose a kind of simple and effective, fiber grating positioning system that cost performance is high, the utility model is not increasing under the prerequisite of any hardware cost, just can realize the positioning function of fiber grating, in Wavelength demodulation, utilize this method, just can draw the parameters such as locating information, temperature information and strain information simultaneously.And utilize this method, the reflection kernel wavelength of actual grating can be calculated, thereby the different measurement wavelength that cause of length and the inconsistent problem of calibration wavelength because of dispatch from the factory optical fiber and working-yard optical fiber in engineering construction can be solved; Owing to providing locating information, therefore can greatly facilitate engineering construction personnel and maintainer to investigate problem, greatly shorten the time of dealing with problems.
This method has been simplified the structure of optical fiber grating regulating system greatly, thereby has reduced system cost.Adopt the fiber grating demodulation equipment of this method not adopt OTDR technology just can possess the function of resolving grating wavelength and location simultaneously.
Now by reference to the accompanying drawings the utility model is described further: referring to Fig. 1-Fig. 4, a kind of fiber grating positioning system of the utility model, configure a stylobate in the optical fiber grating wavelength demodulating equipment of tunable optical source, its tunable optical source has at the uniform velocity linear sweep characteristic of wavelength, by the length scanning order of tunable optical source is set, from shortwave, be starting point and take long wave as starting point respectively, come and go run-down, just can calculate the centre wavelength of grating reality and calculating wavelength that length scanning brings and the deviation of actual wavelength, then can obtain the position of grating to be measured apart from Wavelength demodulation device.
Consult accompanying drawing 1 and accompanying drawing 2, suppose that fiber bragg grating center wavelength is λ, the distance of grating and demodulated equipment is L, from demodulated equipment, issues a signal to the return signal that receives grating, need elapsed-time standards △ t=2*L/(c/n) (c is the light velocity in vacuum, n fiber core refractive index).Because the length scanning speed of grating demodulation equipment is V=d λ/d t, through the time changed wavelength of dt, be dt*V again.So, the scanning wavelength of tunable laser is set sequentially, suppose when scanning from shortwave to long wave, elapsed-time standards △ t, obtains grating wavelength λ 1, than grating practical center wavelength, toward long wave direction, be offset △ t*V.Otherwise while scanning from long wave to shortwave, same elapsed-time standards △ t, obtains grating wavelength λ 2, than grating practical center wavelength, toward shortwave, be offset △ t*V.Therefore can draw the central wavelength lambda=(λ of grating reality 1+ λ 2)/2, within the twice sweep time, when other environmental parameter does not also have enough time to change, just can draw the wavelength offset △ λ=(λ causing due to the distance L between grating and demodulated equipment 1– λ)=(λ – λ 2)=dt*V.Because λ 1and λ 2can test and obtain, thereby can draw △ λ, again because grating demodulation equipment length scanning speed is that V=d λ/d t is known, so can calculate time △ t=△ λ/V that deviation △ λ experiences, thereby can obtain the position L=(c/n of fiber grating apart from demodulated equipment) * △ t/2=(c/n) * △ λ/2V(c is the light velocity in vacuum, n fiber core refractive index, the length scanning speed that V is tunable optical source), the location of realizing fiber grating.
Illustrate, the length scanning speed of supposing grating demodulation equipment is 10pm/2us, and scanning wavelength scope 1520nm~1570nm, scans 50nm bandwidth altogether, and run-down needs the 10ms time, and coming and going the twice sweep time is only 20ms; And fiber grating demodulation equipment is applied in temperature monitoring and static stress monitoring occasion at present, the corresponding speed of temperature alarming and stress monitoring is all in second (s) more than magnitude, therefore, within the time of temperature or stress monitoring, utilize the utility model, can test out quickly and easily the locating information of grating.According to the wavelength resolution of demodulated equipment in the utility model, being that 1pm calculates, utilizing formula: L=(c/n) * △ λ/2V(c is the light velocity in vacuum, n fiber core refractive index, V is the length scanning speed of tunable optical source),, get n=1.5 herein, △ λ=1pm, c=3 × 10 8m/s, V=10pm/2us, can calculate positioning precision is 20 meters.If the length scanning speed of grating demodulation equipment is risen to 10pm/0.2us, positioning precision can reach 2 meters.
Accompanying drawing 2 is a kind of fiber grating positioning systems of the present utility model, comprise at least one stylobate in the optical fiber grating wavelength demodulating equipment of tunable optical source and at least one road the optical fiber with fiber-optic grating sensor.Concrete annexation is: from the light path output port of Wavelength demodulation device, be connected with the optical fiber that is carved with fiber-optic grating sensor, the data of returning through grating sensor are after the demodulation of Wavelength demodulation device, locating information and temperature information and strain information can independently show, also can send to other terminal or server by the communication port of this device (comprising network interface, RS485, RS232, USB etc.).
Consult accompanying drawing 3, for multi-channel fiber Bragg grating Wavelength demodulation device of the present utility model utilizes shunt implementation schematic diagram.Specifically comprise the shunt of a tunable optical source module, 1 1xN (N >=1), at least one photo-coupler or circulator, a hyperchannel photoelectricity modular converter, a data acquisition unit, a calculation control unit.Light path realizes principle, first light is exported by tunable optical source module, shunt via at least one 1xN (N >=1) is divided into N(N >=1 by the light of tunable optical source simultaneously) road, then often lead up to incoming fiber optic after the photo-coupler of a 1x2 or circulator, and by optical fiber with N(N >=1) the fiber grating reflection of string different wave length, carry the light of information measured oppositely by after coupling mechanism or circulator, incide on hyperchannel photoelectricity modular converter, through data acquisition unit and calculation control unit, can calculate the wavelength information of fiber grating reflection.In this programme, adopt optical branching device to carry out light splitting, the light of each passage accesses in the testing fiber grating of different passages simultaneously, parallel processing.
Consult accompanying drawing 4, for multi-channel fiber Bragg grating Wavelength demodulation device of the present utility model utilizes photoswitch implementation schematic diagram.Specifically comprise a tunable optical source module, the photo-coupler of 1 1x2 or circulator, the photoswitch of a 1xN (N >=1), a single channel photoelectric conversion module, a data acquisition unit, a calculation control unit.Light path realizes principle, first light is exported by tunable optical source module, after photo-coupler or circulator via a 1x2, through the photoswitch timesharing of 1 1xN (N >=1), be switched to the testing fiber of different passages, on optical fiber with N(N >=1) the fiber grating reflection of string different wave length, carry the light backward channel photoswitch of information measured, through the other end of 1x2 coupling mechanism or circulator, export to single channel photoelectric conversion module, through data acquisition unit and calculation control unit, can calculate the wavelength information of fiber grating reflection.In this programme, adopt photoswitch to carry out light splitting, the light timesharing of each passage accesses in the testing fiber grating of different passages, and data processing is carried out in timesharing.
Those skilled in the art are known, and the utility model calculation control unit and other module all can adopt conventional on the market module or unit.
Above embodiment is only for illustration of the utility model; but not to restriction of the present utility model; person skilled in the relevant technique; in the situation that not departing from spirit and scope of the present utility model; can also make various conversion or modification; therefore all technical schemes that are equal to, all fall into protection domain of the present utility model.

Claims (4)

1. a fiber grating positioning system, is characterized in that, it comprises that at least one stylobate is carved with the optical fiber of fiber-optic grating sensor in the optical fiber grating wavelength demodulating equipment of tunable optical source and at least one road; The light path output port of optical fiber grating wavelength demodulating equipment is connected with the optical fiber that is carved with fiber-optic grating sensor, the data of returning through grating sensor obtain locating information and/or temperature information and/or strain information after the demodulation of Wavelength demodulation device, the light source of optical fiber grating wavelength demodulating equipment is the tunable optical source that can carry out at the uniform velocity linear sweep, its wavelength resolution can reach 1pm, and length scanning speed is greater than 10pm/2us.
2. a kind of fiber grating positioning system as claimed in claim 1: it is characterized in that, the optical fiber grating wavelength demodulating equipment based on tunable optical source comprises a tunable optical source module, photo-coupler or circulator, a photoelectric conversion module, a data acquisition unit, a calculation control unit; The output termination photo-coupler of tunable optical source or the input end of circulator, one output terminal of photo-coupler or circulator reserves with the form of fiber port, external at least one bragg grating to be measured, another output terminal is access data collecting unit after photoelectric conversion module, finally enters calculation control unit.
3. a kind of fiber grating positioning system as claimed in claim 1: it is characterized in that, optical fiber grating wavelength demodulating equipment based on tunable optical source is multi-channel fiber Bragg grating Wavelength demodulation device, the light of tunable optical source is divided into N road with shunt or the photoswitch of at least one 1xN and N >=1, then demodulation is carried out in each road, optical fiber grating wavelength demodulating equipment based on tunable optical source specifically comprises a tunable optical source, shunt or the photoswitch of at least 1 1xN and N >=1, at least one photo-coupler or circulator, single channel or hyperchannel photoelectricity modular converter, a data acquisition unit, a calculation control unit, tunable optical source is divided into the light of tunable optical source N road and outputs to the input end of photo-coupler or circulator through shunt or photoswitch, one output terminal of photo-coupler or circulator reserves with the form of fiber port, external at least one bragg grating to be measured, another output terminal is access data collecting unit after single channel or hyperchannel photoelectricity modular converter, finally enter calculation control unit.
4. a kind of fiber grating positioning system as described in claim 1 or 2 or 3: it is characterized in that: as described in hyperchannel photoelectricity modular converter by N detector PIN, opto-electronic conversion, filtering, amplification, shaping circuit, formed, N >=1.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103591971A (en) * 2013-11-22 2014-02-19 武汉朗睿科技有限公司 Positioning method and system of fiber grating

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103591971A (en) * 2013-11-22 2014-02-19 武汉朗睿科技有限公司 Positioning method and system of fiber grating
CN103591971B (en) * 2013-11-22 2016-04-20 武汉朗睿科技有限公司 A kind of localization method of fiber grating

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