KR20160150457A - optical sensor system - Google Patents

optical sensor system Download PDF

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KR20160150457A
KR20160150457A KR1020150088479A KR20150088479A KR20160150457A KR 20160150457 A KR20160150457 A KR 20160150457A KR 1020150088479 A KR1020150088479 A KR 1020150088479A KR 20150088479 A KR20150088479 A KR 20150088479A KR 20160150457 A KR20160150457 A KR 20160150457A
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signal
optical
frequency band
optical fiber
light
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KR1020150088479A
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Korean (ko)
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KR101703960B1 (en
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김영호
김명진
노병섭
정은주
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한국광기술원
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/30—Testing of optical devices, constituted by fibre optics or optical waveguides
    • G01M11/31—Testing of optical devices, constituted by fibre optics or optical waveguides with a light emitter and a light receiver being disposed at the same side of a fibre or waveguide end-face, e.g. reflectometers
    • G01M11/3172—Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells
    • G01D5/353—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre
    • G01D5/35338—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells influencing the transmission properties of an optical fibre using other arrangements than interferometer arrangements
    • G01D5/35354—Sensor working in reflection
    • G01D5/35358—Sensor working in reflection using backscattering to detect the measured quantity
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
    • G01K11/32—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in transmittance, scattering or luminescence in optical fibres
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B26/00—Optical devices or arrangements for the control of light using movable or deformable optical elements
    • G02B26/001—Optical devices or arrangements for the control of light using movable or deformable optical elements based on interference in an adjustable optical cavity
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
    • G02B6/29358—Multiple beam interferometer external to a light guide, e.g. Fabry-Pérot, etalon, VIPA plate, OTDL plate, continuous interferometer, parallel plate resonator

Abstract

The present invention relates to a frequency variable based distribution type optical fiber sensor system, which comprises: a light source emitting broadband light; a tunable filter outputting a first light signal of a first frequency band with respect to the light emitted from the light source and a second light signal of a second frequency band left from the first frequency band, and varying frequencies of the first light signal and the second light signal in accordance with a control signal; a main optical divider dividing the signals outputted from the tunable filter into a first division signal and a second division signal; an optical circulator outputting the first division signal inputted through an input end to a sensing optical fiber, and outputting light reflected in the sensing optical fiber through a first output end; an optical coupler coupling and outputting the second division signal transmitted by passing through a reference optical fiber from the main optical divider and a signal outputted through the first output end; an optical detection unit detecting the signal outputted from the optical coupler; and a measurement processing unit calculating physical quantity to be measured with respect to the sensing optical fiber from the signal outputted from the optical detection unit while controlling the tunable filter for a wavelength of the first light signal and the second light signal outputted from the tunable filter to be varied. According to the frequency variable based distribution type optical fiber sensor system, by using light signals individually having different bands at the same time, all of a temperature and a strain can be accurately measured.

Description

주파수 가변 기반 분포형 광섬유 센서 시스템{optical sensor system}Frequency variable based optical fiber sensor system [

본 발명은 주파수 가변 기반 분포형 광섬유 센서 시스템에 관한 것으로서, 상세하게는 온도와 스트레인을 정밀하게 측정할 수 있는 주파수 가변 기반 분포형 광섬유 센서 시스템에 관한 것이다.The present invention relates to a frequency variable based optical fiber sensor system, and more particularly, to a frequency variable based optical fiber sensor system capable of accurately measuring temperature and strain.

광주파수영역 반사측정(OFDR) 시스템은 빛의 반사광을 이용하여 광섬유의 길이, 절단위치(fault position), 색분산(chromatic dispersion), 편광모드분산(polarization mode dispersion), 손실(loss) 등을 측정하는 시스템이다. Optical Frequency Domain Reflectometry (OFDR) systems use optical reflection of light to measure the length of a fiber, its fault position, chromatic dispersion, polarization mode dispersion, and loss .

OFDR시스템은 광시간영역반사측정(OTDR : optical time domain reflectometry) 시스템보다 분해능이 좋고 동적범위(dynamic range)가 넓어서 광통신과 광센서 분야에 응용되고 있다.The OFDR system has better resolution and dynamic range than optical time domain reflectometry (OTDR) system and is applied to optical communication and optical sensor fields.

이러한 OFDR시스템은 국내 공개특허 제10-2006-0102801호 등 다양하게 게시되어 있다.Such an OFDR system is variously disclosed in Korean Patent Laid-Open No. 10-2006-0102801.

한편, 종래의 OFDR시스템과 같이 시간에 따라 하나의 파장을 가변하는 방식의 경우 온도와 스트레인 모두가 센싱 광섬유에서 가변되는 경우 어느 물리량의 변화에 의한 것인지를 측정하기 어려운 단점이 있다.On the other hand, in the case of the conventional OFDR system in which a single wavelength is varied with time, it is difficult to measure which physical quantity changes when both the temperature and the strain are varied in the sensing optical fiber.

본 발명은 상기와 같은 문제점을 해결하기 위하여 창안된 것으로서, 상호 다른 주파수 대역의 광을 동시에 적용하여 측정대상 물리량에 대한 측정 정밀도를 높일 수 있는 주파수 가변 기반 분포형 광섬유 센서 시스템을 제공하는데 그 목적이 있다.Disclosure of Invention Technical Problem [8] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and it is an object of the present invention to provide a frequency variable based optical fiber sensor system capable of increasing measurement accuracy with respect to a measurement target physical quantity by simultaneously applying light of mutually different frequency bands. have.

상기의 목적을 달성하기 위하여 본 발명에 따른 주파수 가변 기반 분포형 광섬유 센서 시스템은 광대역 광을 출사하는 광원과; 상기 광원에서 출사되는 광에 대해 제1주파수 대역의 제1광신호와 상기 제1주파수 대역을 벗어난 제2주파수 대역의 제2광신호를 출력하되 제어신호에 따라 상기 제1광신호와 상기 제2광신호의 주파수를 가변할 수 있도록 된 튜너블 필터와; 상기 튜너블 필터에서 출력되는 신호를 제1분할신호와 제2분할신호로 분할하는 메인 광분할기와; 입력단을 통해 입력된 상기 제1분할신호를 센싱 광섬유에 출력하고, 상기 센싱 광섬유에서 반사된 광을 제1출력단을 통해 출력하는 광써큘레이터와; 상기 메인 광분할기로부터 기준광섬유를 경유하여 전송된 상기 제2분할신호와 상기 제1출력단을 통해 출력되는 신호를 커플링하여 출력하는 광커플러와; 상기 광커플러에서 출력되는 신호를 검출하는 광검출부와; 상기 튜너블 필터에서 출력되는 상기 제1광신호와 상기 제2광신호의 파장이 가변되게 상기 튜너블 필터를 제어하면서, 상기 광검출부에서 출력되는 신호로부터 상기 센싱광섬유에 대해 측정하고자 하는 물리량을 산출하는 측정처리부;를 구비한다.According to an aspect of the present invention, there is provided a frequency-variable-based optical fiber sensor system including: a light source for emitting broadband light; A first optical signal of a first frequency band and a second optical signal of a second frequency band deviating from the first frequency band with respect to light emitted from the light source, A tunable filter capable of varying the frequency of the optical signal; A main beam splitter for dividing a signal output from the tunable filter into a first divided signal and a second divided signal; An optical circulator outputting the first divided signal inputted through an input terminal to a sensing optical fiber and outputting the light reflected from the sensing optical fiber through a first output terminal; An optical coupler coupling and outputting the second split signal transmitted from the main optical splitter via the reference optical fiber and the signal output through the first output terminal; A photodetector for detecting a signal output from the optical coupler; Wherein the control unit controls the tunable filter so that the wavelengths of the first optical signal and the second optical signal output from the tunable filter are varied and calculates a physical quantity to be measured with respect to the sensing optical fiber from a signal output from the optical detection unit And a measurement processing unit.

본 발명의 일 측면에 따르면, 상기 광검출부는 상기 광커플러에서 출력되는 신호에 대해 제1주파수 대역신호와 상기 제2주파수 대역신호를 분리하여 출력하는 파장분할기와; 상기 파장분할기에 출력되는 상기 제1주파수 대역신호를 검출하는 제1광검출기와; 상기 파장분할기에 출력되는 상기 제2주파수 대역신호를 검출하는 제2광검출기;를 구비한다.According to an aspect of the present invention, the optical detector includes: a wavelength divider for separating a first frequency band signal and a second frequency band signal from a signal output from the optical coupler; A first photodetector for detecting the first frequency band signal output to the wavelength divider; And a second photodetector for detecting the second frequency band signal output to the wavelength divider.

또한, 상기 측정처리부는 제1주파수 대역의 제1광신호와 상기 제2주파수 대역의 제2광신호 각각에 대응하여 상기 광검출부에서 출력되는 신호를 이용하여 상기 센싱광섬유에 대한 온도와 스트레인에 대한 검출정보를 산출하도록 구축될 수 있다.Also, the measurement processing unit may use the signal output from the optical detecting unit corresponding to each of the first optical signal of the first frequency band and the second optical signal of the second frequency band, And can be constructed to calculate detection information.

본 발명에 따른 주파수 가변 기반 분포형 광섬유 센서 시스템에 의하면, 상호 다른 대역의 광신호를 동시에 이용함으로서 온도와 스트레인을 모두 정밀하게 측정할 수 있는 장점을 제공한다.The frequency-variable-based optical fiber sensor system according to the present invention provides advantages in that both temperature and strain can be accurately measured by simultaneously using optical signals of different bands.

도 1은 본 발명에 따른 주파수 가변 기반 분포형 광섬유 센서 시스템을 나타내 보인 도면이고,
도 2는 도 1의 튜너블 필터에서 출력되는 광신호를 나타내보인 그래프이다.1 is a view showing a frequency variable based optical fiber sensor system according to the present invention,
FIG. 2 is a graph showing optical signals output from the tunable filter of FIG. 1. FIG.

이하, 첨부된 도면을 참조하면서 본 발명의 바람직한 실시예에 따른 주파수 가변 기반 분포형 광섬유 센서 시스템을 더욱 상세하게 설명한다.Hereinafter, a frequency-variable-based distributed optical fiber sensor system according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

도 1은 본 발명에 따른 주파수 가변 기반 분포형 광섬유 센서 시스템을 나타내 보인 도면이다.1 is a view showing a frequency variable based optical fiber sensor system according to the present invention.

도 1을 참조하면, 광섬유 센서 시스템(100)은 광원(110), 튜너블 필터(120), 서브광분할기(131), 메인 광분할기(133), 광써큘레이터(137), 센싱광섬유(FUT)(140), 광커플러(150), 파장분할기(160), 제1 내지 제3광검출기(171 내지 173), 주파수 모니터링부(180), 측정처리부(190)를 구비한다.1, the optical fiber sensor system 100 includes a light source 110, a tunable filter 120, a sub optical splitter 131, a main optical splitter 133, an optical circulator 137, a sensing optical fiber (FUT A first coupler 150, a wavelength divider 160, first to third photodetectors 171 to 173, a frequency monitoring unit 180, and a measurement processing unit 190.

광원(110)은 광대역 광을 출사하는 광원이 적용된다.The light source 110 is a light source that emits broadband light.

튜너블 필터(120)는 광원(110)에서 출사되는 광대역 광에 대해 제1주파수 대역의 제1광신호와 제1주파수 대역을 벗어난 제2주파수 대역의 제2광신호를 동시에 출력한다.The tunable filter 120 simultaneously outputs a first optical signal of a first frequency band and a second optical signal of a second frequency band that are out of a first frequency band with respect to the broadband light emitted from the light source 110.

또한 튜너블 필터(120)는 측정처리부(190)의 제어신호에 따라 제1광신호와 제2광신호의 주파수가 각각 가변되게 출력한다.The tunable filter 120 outputs the first optical signal and the second optical signal so that the frequencies of the first optical signal and the second optical signal are varied, respectively, according to the control signal of the measurement processing unit 190.

즉, 튜너블 필터(120)는 도 2에 도시된 바와 같이 측정처리부(190)의 제1제어신호에 의해 실선으로 표기된 제1광신호(a)와 제2광신호(b)를 출력한 이후, 측정처리부(190)의 제2제어신호에 의해 점선으로 표기된 제1광신호(a')와 제2광신호(b')를 출력할 수 있도록 되어 있다.That is, as shown in FIG. 2, the tunable filter 120 outputs the first optical signal a and the second optical signal b indicated by solid lines by the first control signal of the measurement processing unit 190 , And can output the first optical signal a 'and the second optical signal b' represented by dotted lines by the second control signal of the measurement processing unit 190.

이러한 튜너블 필터(120)는 페브리-페로 가변필터가 적용될 수 있다.Such a tunable filter 120 may be a Fabry-Perot variable filter.

페브리-페로 가변필터 방식의 튜너블 필터(120) 구조는 국내 등록특허 제10-0286426호 등 다양하게 알려져 있어 상세한 설명은 생략한다.The structure of the tunable filter 120 of the Fabry-Perot variable filter type is variously known from Korean Patent No. 10-0286426 and will not be described in detail.

서브 광분할기(131)는 튜너블 필터(120)에서 출력되는 신호를 측정용과 모니터링용으로 분할하여 출력한다.The sub-beam splitter 131 divides the signal output from the tunable filter 120 for measurement and monitoring, and outputs the signal.

메인 광분할기(133)는 튜너블 필터(120)에서 서브 광분할기를 거쳐 측정용으로 출력되는 신호를 제1분할신호와 제2분할신호로 분할하여 출력한다.The main beam splitter 133 divides a signal output from the tunable filter 120 through a sub-beam splitter into a first divided signal and a second divided signal, and outputs the divided signal.

광서큘레이터(137)는 메인 광분할기(133)로부터 분할된 후 중계광섬유를 거쳐 입력단(137a)을 통해 입력된 제1분할신호를 센싱단(137b)를 통해 센싱 광섬유(140)에 출력하고, 센싱 광섬유(140)에서 반사되어 역으로 센싱단(137b)을 통해 입사된 광을 제1출력단(137c)을 통해 출력한다.The optical circulator 137 outputs the first divided signal inputted through the input terminal 137a through the relay optical fiber after being split from the main optical splitter 133 to the sensing optical fiber 140 through the sensing terminal 137b, And outputs the light reflected from the sensing optical fiber 140 and incident through the sensing end 137b through the first output end 137c.

편광제어기(PC)는 인지도(visibility) 향상을 위해 기준광섬유(135)와 센싱광섬유(140)에 적용되어 있다.The polarization controller PC is applied to the reference optical fiber 135 and the sensing optical fiber 140 in order to improve the visibility.

광커플러(150)는 메인 광분할기(133)로부터 기준광섬유(135)를 경유하여 전송된 제2분할신호와 광서큘레이터(137)의 제1출력단(137c)을 통해 출력되는 신호를 커플링하여 출력한다.The optical coupler 150 couples the second divided signal transmitted from the main optical splitter 133 via the reference optical fiber 135 and the signal output through the first output terminal 137c of the optical circulator 137 Output.

광검출부는 광커플러(150)에서 출력되는 신호를 검출하고, 검출된 광에 대응되는 전기적 신호를 출력한다.The optical detecting unit detects a signal output from the optical coupler 150 and outputs an electrical signal corresponding to the detected light.

광검출부는 파장분할기(WDM; wavelength division multiflex), 제1 및 제2광검출기(PD1)(PD2)(171)(172)를 구비한다.The optical detector includes a wavelength division multiplexer (WDM), first and second photodetectors (PD1) and (PD2) 171 and 172,

파장분할기(160)는 광커플러(150)에서 출력되는 신호에 대해 제1주파수 대역신호와 제2주파수 대역신호를 분리하여 출력한다.The wavelength divider 160 separates the first frequency band signal and the second frequency band signal from the signal output from the optical coupler 150.

제1광검출기(171)는 파장분할기(160)에 출력되는 제1주파수 대역신호를 검출하고, 검출된 신호를 측정 처리부(190)에 출력한다.The first photodetector 171 detects the first frequency band signal output to the wavelength divider 160 and outputs the detected signal to the measurement processing unit 190.

제2광검출기(172)는 파장분할기(160)에 출력되는 제2주파수 대역신호를 검출하고, 검출된 신호를 측정 처리부(190)에 출력한다.The second photodetector 172 detects a second frequency band signal output to the wavelength divider 160 and outputs the detected signal to the measurement processing unit 190.

주파수 모니터링부(180)는 튜너블 필터(120)에서 출력되는 광의 주파수를 모티터링하기 위해 적용된 것으로 서브광분할기(131)에서 분기된 모니터링용 광을 제1광분할기(181)를 통해 분할하여 제1경로(182)와 제1경로보다 경로가 길게 형성된 제2경로(184)를 통해 진행된 광을 다시 서브 광커플러(185)를 통해 합파하여 제3광검출기(173)로 출력하도록 되어 있다.The frequency monitoring unit 180 is used for monitoring the frequency of the light output from the tunable filter 120. The frequency monitoring unit 180 divides the monitoring light branched from the sub light splitter 131 through the first optical splitter 181, The light traveling through the first path 182 and the second path 184 having a path longer than the first path is again multiplexed through the sub optical coupler 185 and output to the third optical detector 173.

제3광검출기(173)는 검출된 광에 대응되는 신호를 측정처리부(190)에 출력한다.The third photodetector 173 outputs a signal corresponding to the detected light to the measurement processing unit 190.

주파수 모니터링부(180)를 통해 제3광검출기(173)에서 출력되는 신호는 측정처리부(190)의 주파수 선형화 동기 신호로 이용된다.The signal output from the third photodetector 173 through the frequency monitoring unit 180 is used as a frequency linearization synchronization signal of the measurement processing unit 190.

측정처리부(190)는 튜너블 필터(120)에서 출력되는 제1광신호와 제2광신호의 파장이 가변되게 튜너블 필터(120)를 제어하면서, 광검출부에서 출력되는 신호로부터 센싱광섬유(140)에 대해 측정하고자 하는 물리량을 산출한다. The measurement processing unit 190 controls the tunable filter 120 so that the wavelengths of the first and second optical signals output from the tunable filter 120 are varied so that the sensing optical fiber 140 ) Is calculated.

측정처리부(190)는 제1주파수 대역의 제1광신호와 제2주파수 대역의 제2광신호 각각에 대응하여 광검출부에서 출력되는 신호를 이용하여 센싱광섬유(140)에 대한 위치별 온도 또는 스트레인에 대한 검출정보를 산출한다.The measurement processing unit 190 measures the temperature or strain of the sensing optical fiber 140 with respect to the sensing optical fiber 140 by using signals output from the optical detecting unit corresponding to the first optical signal of the first frequency band and the second optical signal of the second frequency band, As shown in FIG.

먼저, 제1주파수 대역의 제1광신호와 제2주파수 대역의 제2광신호 각각에 대응하여 광검출부에서 출력되어 측정처리부(190)에 입력되는 신호(I(t))는 아래의 수학식 1로 표현할 수 있다.First, a signal I (t), which is output from the optical detection unit and input to the measurement processing unit 190 corresponding to each of the first optical signal of the first frequency band and the second optical signal of the second frequency band, 1 < / RTI >

Figure pat00001
Figure pat00001

여기서, β는 아래의 수학식2로 표현되는 주파수 스윕율(frequency sweep rate)이고, 아래첨자1과 2는 제1주파수대역과 제2주파수대역 각각을 지칭한다. 또한, τ는 기준광섬유(135)와 센싱광섬유(140)의 반사위치 사이의 거리를 시간으로 환산한 것으로 아래의 수학식3으로 표현할 수 있다.Here,? Is a frequency sweep rate expressed by the following equation (2), and subscripts 1 and 2 refer to the first frequency band and the second frequency band, respectively. Also, τ is a distance between the reference optical fiber 135 and the reflection position of the sensing optical fiber 140, which is expressed in terms of time, and can be expressed by the following equation (3).

Figure pat00002
Figure pat00002

Figure pat00003
Figure pat00003

위 수학식 2에서 F는 제1광신호 또는 제2광신호의 주파수이고, 위 수학식 3에서 n은 광섬유의 굴절율이고, C는 빛의 속도이며, l은 기준광섬유(135)와 센싱광섬유(140)의 반사위치 사이의 거리이다.In Equation (2), F is the frequency of the first optical signal or the second optical signal, n is the refractive index of the optical fiber, C is the speed of light, l is the distance between the reference optical fiber 135 and the sensing optical fiber 140).

한편, β1과 β2는 튜너블 필터(120)에서 서로 다른 값을 갖기 때문에 측정처리부(190)에서 광검출부에서 입력된 신호로부터 주파수 선형화와, 푸리에변환과정을 거쳐 획득된 정보로부터 센싱 광섬유(140)의 위치별 온도 또는 스트레인 변화값을 룩업테이블에 기록된 정보와 비교하여 산출한다.Since the values of 1 and 2 are different from each other in the tunable filter 120, the measurement processing unit 190 extracts the sensing optical fiber 140 from the information obtained through the frequency linearization and Fourier transform process, And compares it with the information recorded in the look-up table.

여기서, 측정처리부(190)의 룩업테이블에는 제1광신호에 의한 온도 또는 스트레인에 대응되는 측정값과 제2광신호에 의한 온도 또는 스트레인에 대응되는 측정값이 기록되어 있다.Here, in the look-up table of the measurement processing unit 190, measured values corresponding to temperature or strain due to the first optical signal and measured values corresponding to temperature or strain due to the second optical signal are recorded.

따라서, 측정처리부(190)는 센싱 광섬유(140)로부터 반사되어 검출된 신호에 대해 온도에 의한 변동신호인지 스트레인에 의한 변동신호인지를 판별할 수 있다.Therefore, the measurement processing unit 190 can determine whether the signal is reflected by the sensing optical fiber 140 and is a fluctuation signal due to temperature or a strain due to temperature.

이러한 주파수 가변 기반 분포형 광섬유 센서 시스템에 의하면, 상호 다른 대역의 광신호를 동시에 이용함으로서 온도 또는 스트레인을 모두 정밀하게 측정할 수 있는 장점을 제공한다.According to such a frequency variable based optical fiber sensor system, it is possible to precisely measure temperature or strain by simultaneously using optical signals of different bands.

110: 광원 110: 튜너블 필터
133: 메인 광분할기 137: 광써큘레이터
140: 센싱광섬유 150: 광커플러
160: 파장분할기 190: 측정처리부110: light source 110: tunable filter
133: main beam splitter 137: optical circulator
140: sensing optical fiber 150: optocoupler
160: Wavelength divider 190: Measurement processing section

Claims (4)

광대역 광을 출사하는 광원과;
상기 광원에서 출사되는 광에 대해 제1주파수 대역의 제1광신호와 상기 제1주파수 대역을 벗어난 제2주파수 대역의 제2광신호를 출력하되 제어신호에 따라 상기 제1광신호와 상기 제2광신호의 주파수를 가변할 수 있도록 된 튜너블 필터와;
상기 튜너블 필터에서 출력되는 신호를 제1분할신호와 제2분할신호로 분할하는 메인 광분할기와;
입력단을 통해 입력된 상기 제1분할신호를 센싱 광섬유에 출력하고, 상기 센싱 광섬유에서 반사된 광을 제1출력단을 통해 출력하는 광써큘레이터와;
상기 메인 광분할기로부터 기준광섬유를 경유하여 전송된 상기 제2분할신호와 상기 제1출력단을 통해 출력되는 신호를 커플링하여 출력하는 광커플러와;
상기 광커플러에서 출력되는 신호를 검출하는 광검출부와;
상기 튜너블 필터에서 출력되는 상기 제1광신호와 상기 제2광신호의 파장이 가변되게 상기 튜너블 필터를 제어하면서, 상기 광검출부에서 출력되는 신호로부터 상기 센싱광섬유에 대해 측정하고자 하는 물리량을 산출하는 측정처리부;를 구비하는 것을 특징으로 하는 주파수 가변 기반 분포형 광섬유 센서 시스템.A light source for emitting broadband light;
A first optical signal of a first frequency band and a second optical signal of a second frequency band deviating from the first frequency band with respect to light emitted from the light source, A tunable filter capable of varying the frequency of the optical signal;
A main beam splitter for dividing a signal output from the tunable filter into a first divided signal and a second divided signal;
An optical circulator outputting the first divided signal inputted through an input terminal to a sensing optical fiber and outputting the light reflected from the sensing optical fiber through a first output terminal;
An optical coupler coupling and outputting the second split signal transmitted from the main optical splitter via the reference optical fiber and the signal output through the first output terminal;
A photodetector for detecting a signal output from the optical coupler;
Wherein the control unit controls the tunable filter so that the wavelengths of the first optical signal and the second optical signal output from the tunable filter are varied and calculates a physical quantity to be measured with respect to the sensing optical fiber from a signal output from the optical detection unit And a measurement processing unit for measuring a wavelength of the optical fiber. 제1항에 있어서, 상기 광검출부는
상기 광커플러에서 출력되는 신호에 대해 제1주파수 대역신호와 상기 제2주파수 대역신호를 분리하여 출력하는 파장분할기와;
상기 파장분할기에 출력되는 상기 제1주파수 대역신호를 검출하는 제1광검출기와;
상기 파장분할기에 출력되는 상기 제2주파수 대역신호를 검출하는 제2광검출기;를 구비하는 것을 특징으로 하는 주파수 가변 기반 분포형 광섬유 센서 시스템.2. The optical pickup apparatus according to claim 1,
A wavelength divider for separating and outputting a first frequency band signal and a second frequency band signal to a signal output from the optical coupler;
A first photodetector for detecting the first frequency band signal output to the wavelength divider;
And a second photodetector for detecting the second frequency band signal output to the wavelength divider. 제1항에 있어서, 상기 측정처리부는 제1주파수 대역의 제1광신호와 상기 제2주파수 대역의 제2광신호 각각에 대응하여 상기 광검출부에서 출력되는 신호를 이용하여 상기 센싱광섬유에 대한 온도와 스트레인에 대한 검출정보를 산출하도록 된 것을 특징으로 하는 주파수 가변 기반 분포형 광섬유 센서 시스템.2. The apparatus of claim 1, wherein the measurement processing unit uses a signal outputted from the optical detecting unit corresponding to each of the first optical signal of the first frequency band and the second optical signal of the second frequency band, And the detection information for the strain is calculated. 제1항에 있어서, 상기 튜너블 필터는 페브리-페로 가변필터가 적용된 것을 특징으로 하는 주파수 가변 기반 분포형 광섬유 센서 시스템.
The frequency-variable-based optical fiber sensor system according to claim 1, wherein the tunable filter is a Fabry-Perot variable filter.
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