CN102269911A - Optical demodulation method based on OTDR (Optical Time Domain Reflectometry) technology and optical demodulation device thereof - Google Patents
Optical demodulation method based on OTDR (Optical Time Domain Reflectometry) technology and optical demodulation device thereof Download PDFInfo
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- CN102269911A CN102269911A CN2011102731116A CN201110273111A CN102269911A CN 102269911 A CN102269911 A CN 102269911A CN 2011102731116 A CN2011102731116 A CN 2011102731116A CN 201110273111 A CN201110273111 A CN 201110273111A CN 102269911 A CN102269911 A CN 102269911A
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Abstract
The invention relates to the demodulation technology of a fiber grating system and specifically relates to an optical demodulation method based on OTDR (Optical Time Domain Reflectometry) technology and an optical demodulation device. The optical demodulation method is characterized by comprising the steps: firstly, a turnable light source is set with a wavelength, then a short pulse is output to fibers to be tested, which are connected with multiple fiber gratings in series, through a coupler or a circulator, optical signals which are reflected back by the fiber gratings are input into an OTDR receiver through the coupler or the circulator, and output signals of the OTDR receiver are transmitted into a data processing unit; then the turnable light source is set with other wavelengths to repeat the tests, and data are transmitted into the data processing unit; the data processing unit is used for integrating reflecting strength signals of different wavelengths of the fiber gratings in the same position to obtain a reflection spectrum of the fiber gratings; and the fiber gratings on the different positions are processed by repeating the process so that the reflection spectrums of all the fiber gratings which are serially connected with the fibers and/or the distribution positions of the fiber gratings on the fibers to be tested are obtained. The method and the device provided by the invention can break the number limit on sensor heads on the fibers to be tested.
Description
Technical field
The present invention relates to the demodulation techniques of fiber grating system, can be used for petroleum and petrochemical industry, highway, bridge, industries such as electric power are carried out temperature survey, fire alarm, ess-strain monitoring etc.Being specifically related to is a kind of optical modulator method and optical modulator instrument based on the OTDR technology, with the identical or close grating of OTDR technology identification, thus the probe quantity of increase grating demodulation instrument.
Background technology
Fiber grating sensing technology is widely used in petroleum and petrochemical industry, highway, and bridge, industries such as electric power can be used for temperature detection, fire alarm, ess-strain monitoring etc.Because of the sensing head of its use based on optical fiber, have good insulating, sensing head is not charged, detectable distance, advantages such as good reliability replace traditional sensor just gradually in some field.
The wavelength of fiber Bragg grating (FBG) demodulator measuring optical fiber grating sensing head again according to wavelength variations, calculates temperature, parameters such as strain.Common demodulation principle has wide light source+spectrometer to separate mediation tunable laser+detector two classes.
First kind is to use wide spectrum light source to incide optical fiber, only light beam identical that returns from fiber grating like this with the fiber grating reflectance spectrum, turn back to (FBG) demodulator through former optical fiber, separate with circulator or coupling mechanism, enter into spectrometer, measure the information that optical wavelength just can obtain temperature and strain.Can be with 1 to 30 sensing head on the same optical fiber, differ 2 to 3nm between the reflection wavelength of each sensing head, just can distinguish sensing head.In order to increase counting of measurement, use photoswitch to switch optical fiber, generally can be with 1 to 32 the tunnel, the sensing head sum is brought up to more than 90.Because of the time of photoswitch conversion long, it is very long that Measuring Time can become, and is not suitable for real-time detection.
Second kind is to use tunable laser to incide optical fiber, and the light belt that fiber grating returns has the reflectivity information of this wavelength, returns (FBG) demodulator through former optical fiber, separate with circulator or coupling mechanism, enter into photo-detector, detector measurement goes out light intensity signal, is equivalent to measure reflectivity.After length scanning one time, the reflectivity on all wavelengths is all measured to come out, and can restore the reflectance spectrum of fiber grating, calculates wavelength information in view of the above, changes out the information of temperature and strain.The same, can be with 1 to 30 sensing head on the same optical fiber.For increasing probe quantity, can be separated into 1 to 32 optical fiber to the light of tunable laser with optical branching device earlier, corresponding photo-detector on the every optical fiber.Can bring up to sensing head quantity more than 90.Because of every optical fiber has corresponding detector, do not need photoswitch to switch, can obtain real-time substantially measurement.
But be subjected to light source power, the restriction of spectral width and Measuring Time, more than two kinds of schemes at most the sensing head numbers of band be difficult to reach more.
Summary of the invention
Goal of the invention of the present invention is: at above-mentioned the deficiencies in the prior art, the invention provides a kind of the optical modulator method and optical modulator instrument based on the OTDR technology that can improve the sensing head quantity that is connected in series on the optical fiber.
For solving above technical matters, technical scheme of the present invention is: a kind of optical modulator method based on the OTDR technology, its difference is: at first tunable optical source is set a wavelength, export short pulse by coupling mechanism or circulator to the tested optical fiber that is in series with a plurality of fiber gratings then, entered the OTDR receiver by the light signal of fiber grating reflected back by coupling mechanism or circulator, the output signal of OTDR receiver is sent into data processing unit; Tunable optical source is set other wavelength more then, repeats above test, and data are sent into data processing unit.Data processing unit is integrated the reflection strength signal of same position fiber grating different wave length, obtains the reflectance spectrum of this fiber grating; Fiber grating to diverse location repeats above process, thus the reflectance spectrum of all fiber gratings that obtain being connected in series on the optical fiber and/or the fiber grating distributing position on tested optical fiber.
By above scheme, described tunable optical source is a tunable laser, tunable laser directly obtains the light short pulse by current-modulation, becomes the light short pulse by light modulator modulates again after perhaps directly exporting the light signal of firm power, and the width of light short pulse is that 10ns is between the 1us.
By above scheme, described fiber grating is the ordinary optic fibre grating, cut toe fiber grating, long period fiber grating or low light level grid.
A kind of optical modulator instrument based on the OTDR technology, its difference is: it comprises tunable optical source, OTDR receiver and photo-coupler or circulator, described photo-coupler or circulator are used for the light and from the light of tested optical fiber reflected back separately that incides in the tested optical fiber, the light pulse that tunable optical source produces is sent in the tested optical fiber that is in series with a plurality of fiber gratings by photo-coupler or circulator, the light signal of the fiber grating reflected back on the tested optical fiber enters the OTDR receiver by photo-coupler or circulator, and the output electric signal of OTDR receiver is sent into data processing unit.
By above scheme, described tunable optical source is that tunable laser or wide spectrum light source are exported through the light of tunable optic filter.
By above scheme, described tunable optical source also comprises an EDFA Erbium-Doped Fiber Amplifier (EDFA), to amplify the light signal of tunable laser output, obtains 0.1mW to the pulsed light power between the 500mW.
By above scheme, described OTDR receiver comprises the PIN detector or the APD detector that are used for light signal is transformed into electric signal.
By above scheme, described OTDR receiver comprises that is used to differentiate the high-speed data acquisition card that different time returns the light intensity signal that comes.
By above scheme, described data processing unit is selected a kind of in single-chip microcomputer, FPGA, ARM, embedded system, the computing machine for use.
The contrast prior art, principle of the present invention and beneficial effect are as follows:
Scheme in the original background technology can't identify the grating sensing head of same reflection wavelength, and the quantity of sensing head is subjected to the restriction of (FBG) demodulator light source coverage, can only increase sensing head quantity by widening the light source coverage.The present invention can tell a plurality of grating sensing heads of same reflection wavelength by the position, the restriction of the sensing head quantity of breaking by the mode of OTDR.
Description of drawings
Fig. 1 transfers the hardware architecture synoptic diagram of instrument for light;
Fig. 2 is the demodulation principle synoptic diagram;
Fig. 3 is the 1550nm long wavelength fiber grating demodulation instrument synoptic diagram of the embodiment of the invention.
Embodiment
Set forth enforcement thinking of the present invention at first generally: be connected on the tested optical fiber with 2m at interval to 50m a plurality of transonic fiber gratings, each fiber grating reflectivity is between 0.2% to 20%, form optical fiber optical grating array, fiber grating is the ordinary optic fibre grating, cut toe fiber grating, long period fiber grating or low light level grid.Use tunable optical source then, set a wavelength output, the modulator that modulated laser or use add produces the light pulse of a 10ns to 100ns.Return detector when light pulse runs into the fiber grating back reflection, the asynchronism(-nization) that the fiber grating of diverse location returns obtains one group of reflectivity and position data.Then, change the output of wavelength, can on same position, be reflected, but the reflectivity difference, can obtain the data of other one group of reflectivity and position.The reflectivity of same position fiber grating different wave length is combined, can obtain the optical grating reflection spectrum of that position fiber grating, calculate the grating wavelength of this position fiber grating, obtain the information of this fiber grating position by spectrometer.All positions are handled equally, just can obtain the wavelength information of fiber gratings all on the tested optical fiber, extrapolate the temperature or the strain information of all fiber gratings.
The enforcement of the technology of the present invention can improve the sensing head quantity that is connected in series on the tested optical fiber greatly.
Further specify the specific embodiment of the invention below in conjunction with accompanying drawing.
As Fig. 1-shown in Figure 2, a kind of optical modulator method based on the OTDR technology, at first tunable optical source 1 is set a wavelength, export short pulses by coupling mechanism 2 or circulator to the tested optical fiber 5 that is in series with a plurality of fiber gratings 6 then, entered OTDR receiver 3 by the light signal of fiber grating 6 reflected backs by coupling mechanism 2 or circulator, the output signal of OTDR receiver 3 is sent into data processing unit 4; Tunable optical source 1 is set other wavelength more then, repeats above test, and data are sent into data processing unit 4.Data processing unit 4 is integrated the reflection strength signal of same position fiber grating 6 different wave lengths, obtains the reflectance spectrum of this fiber grating 6; Fiber grating 6 to diverse location repeats above process, thereby obtains the reflectance spectrum and/or the distributing position of fiber grating 6 on tested optical fiber 5 of all fiber gratings 6 of serial connection on the tested optical fiber 5.
Concrete, described tunable optical source 1 is a tunable laser, tunable laser directly obtains the light short pulse by current-modulation, becomes the light short pulse by light modulator modulates again after perhaps directly exporting the light signal of firm power, and the width of light short pulse is that 10ns is between the 1us.
Concrete, fiber grating 6 optional ordinary optic fibre gratings, cut a kind of in toe fiber grating, long period fiber grating or the low light level grid.
A kind of optical modulator instrument based on the OTDR technology, it comprises tunable optical source 1, OTDR receiver 3 and photo-coupler 2 or circulator, described photo-coupler 2 or circulator are used for the light and from the light of tested optical fiber 5 reflected backs separately that incides in the tested optical fiber 5, the light pulse that tunable optical source 1 produces is sent in the tested optical fiber 5 that is in series with a plurality of fiber gratings 6 by photo-coupler 2 or circulator, the light signal of fiber grating 6 reflected backs on the tested optical fiber 5 enters OTDR receiver 3 by photo-coupler 2 or circulator, and the output electric signal of OTDR receiver 3 is sent into data processing unit 4.
As shown in Figure 3, concrete, described tunable optical source 1 comprises tunable laser 1-1.
Further, described tunable optical source 1 also comprises EDFA Erbium-Doped Fiber Amplifier (EDFA) 1-2, to amplify the light signal of tunable laser 1-1 output, obtains 0.1mW to the pulsed light power between the 500mW.
Concrete, described OTDR receiver 3 comprises the PIN detector or the APD detector that are used for light signal is transformed into electric signal.
Concrete, described OTDR receiver 3 comprises that is used to differentiate the high-speed data acquisition card that different time returns the light intensity signal that comes.
Concrete, described data processing unit 4 is selected a kind of in single-chip microcomputer, FPGA, ARM, embedded system, the computing machine for use.
As shown in Figure 3, modulation tunable laser 1-1 makes it out the light pulse that wavelength is λ n, amplifies the light pulse that becomes about 100mW by EDFA Erbium-Doped Fiber Amplifier (EDFA) 1-2 then; This light pulse is by after the coupling mechanism 2, and the light of half enters into the tested optical fiber 5 that has a plurality of fiber gratings 6.The reflectance spectrum difference of the fiber grating 6 of diverse location, so the light intensity that reflects is also different, the time is also different, returns the light that comes and passes through coupling mechanism 2, and half enters into OTDR receiver 3, and the PIN pipe or the APD pipe that are received in the machine are converted into electric signal; OTDR receiver 3 has the high-speed data acquisition function, can write down the reflected light signal that different time returns and the intensity of this light signal; This intensity-time is admitted to data processing unit together with wavelength signals; The signal that data processing unit 4 can return same time reflex divides into groups by wavelength, obtains the wavelength signals of fiber grating 6, and fiber grating 6 is positioned and wavelength measurement; The signal that the different time is returned is done same treatment, just can obtain the wavelength of diverse location fiber grating 6 on the tested optical fiber 5.
When the fiber grating serial connection, and wavelength is close the time, and the reflectivity of front fiber grating can have influence on the light intensity that incides the back fiber grating, so the reflectivity of fiber grating can not be too high, if 100 fiber gratings of tested optical fiber band, reflectivity should be approximately 0.1dB.If weak mirror based fiber optica then is more weak reflection, to obtain longer measuring distance.
Above content be in conjunction with concrete embodiment to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some simple deduction or replace, all should be considered as belonging to protection scope of the present invention.
Claims (9)
1. optical modulator method based on the OTDR technology, it is characterized in that: at first tunable optical source is set a wavelength, export short pulse by coupling mechanism or circulator to the tested optical fiber that is in series with a plurality of fiber gratings then, entered the OTDR receiver by the light signal of fiber grating reflected back by coupling mechanism or circulator, the output signal of OTDR receiver is sent into data processing unit; Tunable optical source is set other wavelength more then, repeats above test, and data are sent into data processing unit.Data processing unit is integrated the reflection strength signal of same position fiber grating different wave length, obtains the reflectance spectrum of this fiber grating; Fiber grating to diverse location repeats above process, thus the reflectance spectrum of all fiber gratings that obtain being connected in series on the optical fiber and/or the fiber grating distributing position on tested optical fiber.
2. the optical modulator method based on the OTDR technology as claimed in claim 1, it is characterized in that: described tunable optical source is a tunable laser, tunable laser directly obtains the light short pulse by current-modulation, become the light short pulse by light modulator modulates again after perhaps directly exporting the light signal of firm power, the width of light short pulse is that 10ns is between the 1us.
3. the optical modulator method based on the OTDR technology as claimed in claim 1 is characterized in that: described fiber grating is the ordinary optic fibre grating, cut toe fiber grating, long period fiber grating or low light level grid.
4. optical modulator instrument based on the OTDR technology, it is characterized in that: it comprises tunable optical source, OTDR receiver and photo-coupler or circulator, described photo-coupler or circulator are used for the light and from the light of tested optical fiber reflected back separately that incides in the tested optical fiber, the light pulse that tunable optical source produces is sent in the tested optical fiber that is in series with a plurality of fiber gratings by photo-coupler or circulator, the light signal of the fiber grating reflected back on the tested optical fiber enters the OTDR receiver by photo-coupler or circulator, and the output electric signal of OTDR receiver is sent into data processing unit.
5. the optical modulator instrument based on the OTDR technology as claimed in claim 4 is characterized in that: described tunable optical source is that tunable laser or wide spectrum light source are exported through the light of tunable optic filter.
6. the optical modulator instrument based on the OTDR technology as claimed in claim 5, it is characterized in that: described tunable optical source also comprises an EDFA Erbium-Doped Fiber Amplifier (EDFA), to amplify the light signal of tunable laser output, obtain 0.1mW to the pulsed light power between the 500mW.
7. the optical modulator instrument based on the OTDR technology as claimed in claim 4 is characterized in that: described OTDR receiver comprises the PIN detector or the APD detector that are used for light signal is transformed into electric signal.
8. as claim 4 or 7 described optical modulator instrument based on the OTDR technology, it is characterized in that: described OTDR receiver comprises that is used to differentiate the high-speed data acquisition card that different time returns the light intensity signal that comes.
9. the optical modulator instrument based on the OTDR technology as claimed in claim 4 is characterized in that: described data processing unit is selected a kind of in single-chip microcomputer, FPGA, ARM, embedded system, the computing machine for use.
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| CN103033205A (en) * | 2012-12-14 | 2013-04-10 | 张丽 | Fiber bragg grating interrogator based on digitization tunable light sources and method thereof |
| CN103171594A (en) * | 2011-12-23 | 2013-06-26 | 同方威视技术股份有限公司 | Railway foreign body line invading monitoring |
| 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 |
| CN104198160A (en) * | 2014-09-01 | 2014-12-10 | 江苏宇特光电科技股份有限公司 | Optical time domain reflectometer with narrow linewidth and tunable wavelength and control method thereof |
| CN104748772A (en) * | 2015-04-17 | 2015-07-01 | 安徽师范大学 | Positioning fiber grating sensor |
| CN106165315A (en) * | 2013-12-02 | 2016-11-23 | 株式会社秀利得 | Utilize the optical time domain reflectometer of polymer Wavelength tunable laser |
| CN108169150A (en) * | 2017-12-06 | 2018-06-15 | 中国电子科技集团公司第八研究所 | A kind of lossless on-Line Monitor Device of solid rocket propellant volatilization gas optical fiber |
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Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103171594A (en) * | 2011-12-23 | 2013-06-26 | 同方威视技术股份有限公司 | Railway foreign body line invading monitoring |
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| CN106165315B (en) * | 2013-12-02 | 2018-10-16 | 株式会社秀利得 | Utilize the optical time domain reflectometer of polymer Wavelength tunable laser |
| CN106165315A (en) * | 2013-12-02 | 2016-11-23 | 株式会社秀利得 | Utilize the optical time domain reflectometer of polymer Wavelength tunable laser |
| US20160363507A1 (en) * | 2013-12-02 | 2016-12-15 | Solid. Inc. | Optical time domain reflectometer using polymer wavelength tunable laser |
| US10139310B2 (en) * | 2013-12-02 | 2018-11-27 | Solid. Inc. | Optical time domain reflectometer using polymer wavelength tunable laser |
| US20190056290A1 (en) * | 2013-12-02 | 2019-02-21 | Solid, Inc. | Optical time domain reflectometer using polymer wavelength tunable laser |
| US10690567B2 (en) * | 2013-12-02 | 2020-06-23 | Solid, Inc. | Optical time domain reflectometer using polymer wavelength tunable laser |
| CN104198160B (en) * | 2014-09-01 | 2016-06-29 | 江苏宇特光电科技股份有限公司 | A kind of narrow line-width wavelengths tunable optical domain reflectometer and control method thereof |
| CN104198160A (en) * | 2014-09-01 | 2014-12-10 | 江苏宇特光电科技股份有限公司 | Optical time domain reflectometer with narrow linewidth and tunable wavelength and control method thereof |
| CN104748772A (en) * | 2015-04-17 | 2015-07-01 | 安徽师范大学 | Positioning fiber grating sensor |
| CN104748772B (en) * | 2015-04-17 | 2017-06-27 | 安徽师范大学 | Positioning optical fiber grating sensing device |
| CN108169150A (en) * | 2017-12-06 | 2018-06-15 | 中国电子科技集团公司第八研究所 | A kind of lossless on-Line Monitor Device of solid rocket propellant volatilization gas optical fiber |
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Application publication date: 20111207 |