WO2018016734A1 - Optical fiber acoustic sensor supporting temperature measurement - Google Patents

Optical fiber acoustic sensor supporting temperature measurement Download PDF

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Publication number
WO2018016734A1
WO2018016734A1 PCT/KR2017/005774 KR2017005774W WO2018016734A1 WO 2018016734 A1 WO2018016734 A1 WO 2018016734A1 KR 2017005774 W KR2017005774 W KR 2017005774W WO 2018016734 A1 WO2018016734 A1 WO 2018016734A1
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Prior art keywords
light
sensing
optical fiber
output
scattered
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PCT/KR2017/005774
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French (fr)
Korean (ko)
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김명진
노병섭
김영호
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한국광기술원
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Publication of WO2018016734A1 publication Critical patent/WO2018016734A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J5/20—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using resistors, thermistors or semiconductors sensitive to radiation, e.g. photoconductive devices
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/02—Details
    • G01J1/04—Optical or mechanical part supplementary adjustable parts
    • G01J1/0407—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings
    • G01J1/0425—Optical elements not provided otherwise, e.g. manifolds, windows, holograms, gratings using optical fibers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
    • G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
    • G01J5/28—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors using photoemissive or photovoltaic cells
    • 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
    • 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
    • G02B6/29331—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 evanescent wave coupling
    • G02B6/29335—Evanescent coupling to a resonator cavity, i.e. between a waveguide mode and a resonant mode of the cavity
    • G02B6/29338—Loop resonators
    • G02B6/2934—Fibre ring resonators, e.g. fibre coils

Definitions

  • the present invention relates to an optical fiber acoustic sensor supporting a temperature measurement, and more particularly, to an optical fiber acoustic sensor capable of measuring a vibration frequency distribution and a temperature distribution using an optical fiber.
  • Distribution type optical fiber sensor that operates by installing the optical fiber over a long distance of about 10 km has been posted in various ways, such as domestic Patent No. 10-1223105.
  • the distributed fiber optic sensor uses scattering in the optical fiber, and measures the intensity of backscattered light in the optical fiber that is reflected back according to the physical quantity acting on a specific position of the optical fiber cable. Can be built.
  • DAS Distributed Acoustic Sensor
  • the optical fiber acoustic sensor is a sensor for measuring the scattered light generated due to the nonuniform distribution of the density of the optical fiber from the light traveling inside the optical fiber, it is possible to obtain the back scattered light containing the phase component by the high coherence pulsed light.
  • the conventional distributed acoustic sensor has a change in backscattered light even with a temperature change, but it may be mistaken as a vibration or sound signal because it is difficult to quantitatively measure the temperature by a conventional method of measuring only Rayleigh scattered light. Therefore, it is necessary to simultaneously measure the temperature distribution in order to distinguish the temperature change along the optical fiber cable from the vibration or sound signal.
  • Raman scattering refers to a phenomenon in which a backscattering signal is generated by molecular vibration when light is transmitted in an optical fiber, and the molecular vibration at this time changes only by thermal change.
  • the Raman backscattered light is about 1 / 1,000 smaller than the Rayleigh backscattered light and is measured by a cumulative average value.
  • the present invention has been made to improve the above problems, and an object of the present invention is to provide an optical fiber acoustic sensor that can simultaneously measure the frequency and intensity of the sound source and the temperature distribution while sharing the optical fiber.
  • the optical fiber acoustic sensor comprises: a pulsed light generator for generating and outputting pulsed light according to a control signal; An optical circulator for outputting pulsed light output from the pulsed light generator and input to an input terminal through a first output terminal, and outputting light incident from the first output terminal through the detection terminal; A sensing optical fiber installed to transmit light output through the first output terminal of the optical circulator; A first sensing light detector for detecting Rayleigh backscattered light which is scattered in the sensing optical fiber and is reversed; A second sensing light detector for detecting Raman backscattered light which is scattered in the sensing optical fiber and proceeds backward; The Rayleigh backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is output to the first sensing light detector, and the Raman backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is separated and output to the second sensing light detector.
  • An installed wavelength filter Controlling the generation of the pulsed light of the pulsed light generator, measuring the vibration frequency and intensity from the signal detected by the first sensing light detector based on the output time point of the pulsed light, and from the signal detected by the second sensed light detector And a signal processor for measuring temperature.
  • the wavelength filter is connected between the sensing optical fiber and the optical circulator to transmit the light from the first output terminal to the sensing optical fiber, the rail which is scattered in the sensing optical fiber and proceeds in reverse Ray backscattered light propagates through the first filtering stage to the first output stage, and Raman backscattered light scattered from the sensing optical fiber and reversed through the second filtering stage is outputted to the second sensing light detector.
  • the first sensing light detector detects the light output from the detection stage
  • the second sensing light detector detects the light output from the second filtering stage.
  • the wavelength filter is connected to the detection end of the optical circulator is scattered from the sensing optical fiber and the reverse ray scattered light propagated in the reverse direction through the first filtering light detection unit
  • the Raman backscattered light is transmitted to the second sensing light detector by being separated by the second filtering stage.
  • the pulse light generator may include a pulse generator configured to generate a pulse according to a driving control signal output from the signal processor; And a light source for outputting pulsed light corresponding to the pulse output from the pulse generator, wherein the signal processor may be configured to determine an output time point of the pulsed light by receiving a pulse output from the pulse generator.
  • an optical splitter for distributing the pulsed light output from the pulsed light generator to the input terminal and the reference terminal of the optical circulator; And a reference signal photo detector for detecting the light output from the reference stage and providing the signal to the signal processor, wherein the signal processor determines the output point of the pulsed light by using the signal output from the reference signal photo detector. Can be rescued.
  • the pulsed light generating unit generates light having a central wavelength of 1550 nm and a bandwidth of 1 KHz to 44 MHz, and the wavelength filter separates 1450 nm and 1650 nm Raman scattered light and outputs the light to the second sensing light detector.
  • the apparatus may further include an erbium optical amplifier installed between the pulsed light generator and the optical splitter to amplify the light.
  • the apparatus may further include a low pass filter for removing an AC component from the signal detected by the second sensing light detector and outputting the alternating component to the signal processor.
  • the temperature distribution measurement as well as the frequency and intensity of the sound source or vibration for the entire length of the sensing optical fiber provides an advantage that can be simultaneously.
  • FIG. 1 is a view showing a temperature measurement-supported optical fiber acoustic sensor according to an embodiment of the present invention
  • FIG. 2 is a view showing a temperature measurement support optical fiber acoustic sensor according to another embodiment of the present invention
  • FIG. 3 is a diagram illustrating a temperature measuring assisted optical fiber acoustic sensor to which a pulsed light generator is applied according to another exemplary embodiment of the present invention.
  • FIG. 1 is a view showing a temperature measurement-supported optical fiber acoustic sensor according to an embodiment of the present invention.
  • the optical fiber acoustic sensor 100 includes a pulsed light generator 110, an erbium optical amplifier (EDFA) 130, an optical splitter 140, an optical circulator 150, and a wavelength filter. 160, the sensing optical fiber 170, the reference signal photodetector (PDR) 180, the first sensing photodetector (PD1) 181, the second sensing photodetector (PD2) 182, and the low pass filter 185. And a signal processing unit 190.
  • EDFA erbium optical amplifier
  • the pulsed light generator 110 generates and outputs pulsed light according to the control signal of the signal processor 190.
  • the pulsed light generator 110 may generate a pulse according to a driving control signal output from the signal processor 190, and a light source that outputs pulsed light corresponding to the pulse output from the pulsed generator 112. (114).
  • the pulsed light generator 110 applies light having a center wavelength of 1550 nm and a bandwidth of 1 KHz to 44 MHz.
  • the pulsed light generator 110 is controlled by the signal processor 190 with respect to the light source 116 and the light generated by the light source 116 as shown in FIG. 3 to generate pulsed light.
  • the signal processor 190 can be constructed with an electro-optic modulator 118.
  • the erbium optical amplifier (EDFA) 130 is installed between the pulsed light generator 110 and the optical splitter 140 described later to amplify the pulsed light output from the pulsed light generator 110 to split the optical splitter 140. )
  • the optical splitter 140 distributes the pulsed light output from the pulsed light generator 110 and amplified through the erbium optical amplifier 130 to the input terminal 151 and the reference terminal 142 of the optical circulator 150. Output
  • the optical splitter 140 preferably applies pulse light to the input terminal 151 and the reference terminal 142 of the optical circulator 150 at a ratio of 99: 1.
  • the reference signal photodetector (PDR) 180 detects the light distributed from the reference stage 142 and outputs the light to the signal processor 190.
  • the signal processor 190 may determine an output time point of the pulsed light using the signal output from the reference signal photodetector 180.
  • the signal processor 190 may be configured to receive the pulse output from the pulse generator 112 in a manner indicated by reference numeral 112a to determine an output time point of the pulsed light.
  • the reference signal photodetector PDR 180 and the optical splitter 140 may be omitted, and the amplified pulsed light may be configured to be input only to the input terminal 151 of the optical circulator 150.
  • the optical circulator 150 outputs the pulsed light output from the pulsed light generator 110 and input to the input terminal 151 through the first output terminal 152, and is incident to the first output terminal 152 in reverse. Is output through the detection stage 153.
  • the sensing optical fiber 170 may be provided over the measurement target area so that light output through the first output terminal 152 of the optical circulator 150 can be transmitted.
  • the wavelength filter 160 is scattered by the sensing optical fiber 170 and the reverse ray scattered light is output to the first sensing light detector (PD1) 181, and is scattered by the sensing optical fiber 170 to be reversed
  • the Raman backscattered light is separated and output to the second sensing light detector PD2 182.
  • the wavelength filter 160 is connected between the sensing optical fiber 170 and the first output terminal 152 of the optical circulator 150.
  • the wavelength filter 160 transmits light that passes from the first output terminal 152 of the optical circulator 150 to the sensing optical fiber 170, is scattered by the sensing optical fiber 170, and is reversed toward the optical circulator 150.
  • the Rayleigh backscattered light proceeds to the first output terminal 152 through the first filtering stage 161.
  • the wavelength filter 160 is scattered by the sensing optical fiber 170 and the Raman backscattered light traveling backward toward the optical circulator 150 is different from the first output terminal 152 of the optical circulator 150. Separating through the filtering stage 162 is provided to output to the second sensing light detector 182.
  • the wavelength filter 160 is constructed to output Raman scattered light of 1450 nm and 1650 nm through the second filtering stage 162.
  • the first sensing light detector PD1 181 detects the light output from the detection terminal 153 of the optical circulator 150, that is, the Rayleigh backscattered light and provides the signal to the signal processor 190.
  • the second sensing light detector PD2 182 detects Raman scattered light output from the second filtering end 162 of the wavelength filter 160.
  • the wavelength filter 160 may be connected to the detection end 153 of the optical circulator 150 as shown in FIG. 2.
  • the wavelength filter 160 is scattered by the sensing optical fiber 170 and proceeds in reverse to separate the Ray-ray backscattered light input through the detection terminal 153 of the optical circulator 150 to separate the first filtering stage 161. It is constructed to be transmitted to the first sensing light detector (PD1) (181) through.
  • the wavelength filter 160 is scattered by the sensing optical fiber 170 and proceeds in reverse to separate the Raman backscattered light input through the detection stage 153 of the optical circulator 150 to separate the second filtering stage 162. It may be configured to output to the second sensing light detector (PD2) 182 through.
  • PD2 second sensing light detector
  • the low pass filter 185 removes an AC component from the signal detected by the second sensing light detector 182 and outputs the AC component to the signal processor 190.
  • the data measured as a function of time through the second sensing photodetector 182 includes a self interference signal generated by the sensing optical fiber 170, the AC component is removed through the low pass filter 185. do.
  • the low pass filter 185 may be applied to remove the AC component in hardware or may be constructed to remove the AC component from the collected signal.
  • the signal processor 190 controls the generation of the pulsed light of the pulsed light generator 110 by on / off switching control and outputs a reference time point at which the pulsed light is output from the reference signal photodetector (PDR) 180. Determining by using a signal, by collecting the signal detected by the first sensing light detector 181 based on the determined reference time in time to measure the vibration frequency and intensity, the second sensing light detector 182 to detect in time Collect the signal to measure the temperature.
  • the signal processing unit 190 is rearward of the Ray Ray through the first sensing light detector 181 and the second sensing light detector 182 based on the pulsed light output reference time detected by the reference signal light detector 180. Scattered light and Raman backscattered light are collected and processed as a function of time.
  • the signal processor 190 measures the vibration frequency and the intensity distribution from the signal received through the first sensing light detector 181 as follows.
  • the position resolution, the sampling period N, and the measurement frequency range N / 2 are determined accordingly.
  • the position resolution determines the data interval with respect to the sensing optical fiber 170 longitudinal direction.
  • N traces are collected as optical time domain reflectometry (OTDR) data for Rayleigh backscattered light that is continuously generated and returned in the longitudinal direction of the sensing optical fiber 170.
  • OTDR optical time domain reflectometry
  • the signal to noise ratio can be increased.
  • the signals measured from the first and second sensing light detectors 181 and 182 are converted into a function of distance in consideration of the speed of light in the sensing optical fiber 170.
  • the intensity of the Rayleigh backscattered light transformed as a function of the distance is reconstructed into NxM arrays according to the position interval M for N pulsed lights, and Fourier transforms N data for each position to obtain the frequency and Analyze the size.
  • N should be about twice the frequency of the sound source to be measured as the light pulse generation period, it is necessary to drive pulsed light having a period of 2 kHz or more to detect a sound source of 1 kHz.
  • M is a value obtained by dividing the minimum position interval for dividing the position of the sound source by the total length of the sensing optical fiber 170.
  • M is set to 1,000.
  • the temperature distribution is measured from the signal received through the second sensing light detector 182 in the signal processor 190 as follows.
  • the position resolution and the sampling period N are determined accordingly.
  • the Raman backscattered light that is continuously generated and returned in the longitudinal direction of the sensing optical fiber 170 is summed to remove noise as much as possible, and then the AC component is removed through the low pass filter 185.
  • temperature information is obtained by continuously summing unlike vibration frequency and intensity measurement methods.
  • the intensity of the Raman backscattered light converted as a function of distance after the AC component is removed from the low pass filter 185 is accumulated for N pulsed lights, and the light intensity according to the position is analyzed.
  • the Raman backscattered light is continuously accumulated to the accumulated value for N pulsed light, and the temperature change is analyzed from the accumulated value of 60,000 times, and the cumulative frequency can be changed by adjusting the measurement time.
  • the above-described optical fiber acoustic sensor 100 separates the Ray-ray scattered light and the Raman scattered light generated in the sensing optical fiber 170 and simultaneously processes the signal to provide an advantage of measuring vibration frequency, intensity distribution, and temperature distribution together. do.

Abstract

The present invention relates to an optical fiber acoustic sensor supporting temperature measurement, comprising: an optical circulator for outputting, through a first output stage, a pulse light inputted from a pulse light generation unit and outputting, through a detection stage, light which is incident on the first output stage back from the first output stage; a sensing optical fiber provided so that the light outputted through the first output stage of the optical circulator can be transmitted; a first sensing photodetection unit for detecting a Rayleigh backscattered light which is scattered in the sensing optical fiber and is back-propagated; a second sensing photodetection unit for detecting a Raman backscattered light which is scattered in the sensing optical fiber and is back-propagated; a wavelength filter provided so that the Rayleigh backscattered light is outputted to the first sensing photodetector and the Raman backscattered light is outputted to the second sensing photodetection unit; and a signal processing unit for measuring a vibration frequency and an intensity from a signal detected by the first sensing photodetection unit on the basis of an output time point of the pulse light and measuring temperature from a signal detected by the second sensing photodetection unit.

Description

온도 측정 지원형 광섬유 음향센서Optical fiber acoustic sensor with temperature measurement
본 발명은 온도 측정 지원형 광섬유 음향센서에 관한 것으로서, 상세하게는 광섬유를 이용하여 진동주파수 분포 및 온도 분포를 측정할 수 있도록 된 광섬유 음향센서에 관한 것이다.The present invention relates to an optical fiber acoustic sensor supporting a temperature measurement, and more particularly, to an optical fiber acoustic sensor capable of measuring a vibration frequency distribution and a temperature distribution using an optical fiber.
광섬유를 10 km 내외의 장거리에 걸쳐 설치하여 운영하는 분포형 광섬유 센서는 국내 등록특허 제10-1223105호 등 다양하게 게시되어 있다.Distribution type optical fiber sensor that operates by installing the optical fiber over a long distance of about 10 km has been posted in various ways, such as domestic Patent No. 10-1223105.
이러한 분포형 광섬유 센서는 광섬유 내 산란현상을 이용하며, 이때 광섬유 케이블의 특정 위치에 작용하는 물리량에 따라 다르게 반사되어 돌아오는 광섬유 내 후방 산란광의 세기를 측정하는 것으로 온도 이외에도 변형 등 다양한 물리량을 검출하도록 구축될 수 있다.The distributed fiber optic sensor uses scattering in the optical fiber, and measures the intensity of backscattered light in the optical fiber that is reflected back according to the physical quantity acting on a specific position of the optical fiber cable. Can be built.
이러한 분포형 광섬유 센서 중 레일레이(Rayleigh) 산란을 이용하는 광섬유 음향센서(DAS: Distributed Acoustic Sensor)가 있다.Among such distributed optical fiber sensors, there is a Distributed Acoustic Sensor (DAS) using Rayleigh scattering.
광섬유 음향센서는 광섬유 내부를 진행하는 광으로부터 광섬유의 밀도의 불균일 분포에 기인하여 발생하는 산란광을 측정하는 센서로, 고간섭성 펄스광에 의한 위상성분이 포함된 후방 산란광을 얻을 수 있다. 이러한 종래의 분포형 음향센서는 온도 변화에도 후방 산란광의 변화가 있으나 레일레이 산란광만을 측정하는 종래의 방식으로는 온도를 정량적으로 측정하기 어렵기 때문에 진동 또는 음향 신호로 오인될 수 있다. 따라서, 광섬유 케이블을 따라 달라지는 온도변화를 진동 또는 음향신호와 구분하기 위해서는 온도분포를 동시에 측정할 필요가 있다.The optical fiber acoustic sensor is a sensor for measuring the scattered light generated due to the nonuniform distribution of the density of the optical fiber from the light traveling inside the optical fiber, it is possible to obtain the back scattered light containing the phase component by the high coherence pulsed light. The conventional distributed acoustic sensor has a change in backscattered light even with a temperature change, but it may be mistaken as a vibration or sound signal because it is difficult to quantitatively measure the temperature by a conventional method of measuring only Rayleigh scattered light. Therefore, it is necessary to simultaneously measure the temperature distribution in order to distinguish the temperature change along the optical fiber cable from the vibration or sound signal.
한편, 라만 산란은 광섬유 내에서 빛이 전달될 때 분자 진동에 의하여 후방 산란 신호가 발생하는 현상을 지칭하며, 이때의 분자 진동은 열적인 변화에 의해서만 변화한다. 이러한 라만 후방산란광은 레일레이 후방산란광에 비해 1/1,000 정도로 작으며 누적된 평균값으로 측정하기 때문에 고간섭성 펄스광을 사용하여도 외부 진동 또는 음향 신호에 의한 영향이 없다. Meanwhile, Raman scattering refers to a phenomenon in which a backscattering signal is generated by molecular vibration when light is transmitted in an optical fiber, and the molecular vibration at this time changes only by thermal change. The Raman backscattered light is about 1 / 1,000 smaller than the Rayleigh backscattered light and is measured by a cumulative average value. Thus, even when a high coherent pulsed light is used, there is no influence by external vibration or acoustic signals.
본 발명은 상기와 같은 문제점을 개선하기 위하여 창안된 것으로서, 광섬유를 공유하면서 음원의 주파수 및 세기 측정과 온도분포를 동시에 측정할 수 있는 광섬유 음향센서를 제공하는데 그 목적이 있다.The present invention has been made to improve the above problems, and an object of the present invention is to provide an optical fiber acoustic sensor that can simultaneously measure the frequency and intensity of the sound source and the temperature distribution while sharing the optical fiber.
상기의 목적을 달성하기 위하여 본 발명에 따른 광섬유음향센서는 제어신호에 따라 펄스광을 생성하여 출력하는 펄스광 생성부와; 상기 펄스광 생성부에서 출력되어 입력단으로 입력되는 펄스광을 제1출력단을 통해 출력하고, 상기 제1출력단에서 역으로 입사되는 광을 검출단을 통해 출력하는 광서큘레이터와; 상기 광서큘레이터의 제1출력단을 통해 출력되는 광이 전송될 수 있게 설치된 센싱 광섬유와; 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광을 검출하는 제1센싱광검출부와; 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광을 검출하는 제2센싱광검출부와; 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 상기 제1센싱광검출부에 출력하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 분리하여 상기 제2센싱광검출부로 출력하도록 설치된 파장필터와; 상기 펄스광 생성부의 펄스광의 생성을 제어하고, 상기 펄스광의 출력 시점을 기준으로 상기 제1센싱광검출부에서 검출되는 신호로부터 진동주파수 및 세기를 측정하고, 상기 제2센싱광검출부에서 검출되는 신호로부터 온도를 측정하는 신호 처리부;를 구비한다.In order to achieve the above object, the optical fiber acoustic sensor according to the present invention comprises: a pulsed light generator for generating and outputting pulsed light according to a control signal; An optical circulator for outputting pulsed light output from the pulsed light generator and input to an input terminal through a first output terminal, and outputting light incident from the first output terminal through the detection terminal; A sensing optical fiber installed to transmit light output through the first output terminal of the optical circulator; A first sensing light detector for detecting Rayleigh backscattered light which is scattered in the sensing optical fiber and is reversed; A second sensing light detector for detecting Raman backscattered light which is scattered in the sensing optical fiber and proceeds backward; The Rayleigh backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is output to the first sensing light detector, and the Raman backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is separated and output to the second sensing light detector. An installed wavelength filter; Controlling the generation of the pulsed light of the pulsed light generator, measuring the vibration frequency and intensity from the signal detected by the first sensing light detector based on the output time point of the pulsed light, and from the signal detected by the second sensed light detector And a signal processor for measuring temperature.
본 발명의 일 측면에 따르면, 상기 파장필터는 상기 센싱 광섬유와 상기 광서큘레이터 사이에 접속되어 상기 제1출력단에서 상기 센싱 광섬유로 향하는 광은 투과시키고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 제1필터링단을 통해 상기 제1출력단으로 진행되게 하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 제2필터링단을 통해 분리하여 상기 제2센싱광검출부에 출력하도록 설치되어 있고, 상기 제1센싱광검출부는 상기 검출단에서 출력되는 광을 검출하도록 설치되어 있고, 상기 제2센싱광검출부는 상기 제2필터링단에서 출력되는 광을 검출하도록 설치된다.According to an aspect of the present invention, the wavelength filter is connected between the sensing optical fiber and the optical circulator to transmit the light from the first output terminal to the sensing optical fiber, the rail which is scattered in the sensing optical fiber and proceeds in reverse Ray backscattered light propagates through the first filtering stage to the first output stage, and Raman backscattered light scattered from the sensing optical fiber and reversed through the second filtering stage is outputted to the second sensing light detector. And the first sensing light detector detects the light output from the detection stage, and the second sensing light detector detects the light output from the second filtering stage.
본 발명의 또 다른 측면에 따르면, 상기 파장필터는 상기 광서큘레이터의 검출단에 접속되어 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 제1필터링단을 통해 상기 제1센싱광검출부에 전송되게 하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 제2필터링단을 통해 분리하여 상기 제2센싱광검출부에 출력하도록 되어 있다.According to another aspect of the present invention, the wavelength filter is connected to the detection end of the optical circulator is scattered from the sensing optical fiber and the reverse ray scattered light propagated in the reverse direction through the first filtering light detection unit The Raman backscattered light is transmitted to the second sensing light detector by being separated by the second filtering stage.
또한, 상기 펄스광 생성부는 상기 신호처리부에서 출력되는 구동 제어신호에 따라 펄스를 생성하는 펄스 발생기와; 상기 펄스 발생기에서 출력되는 펄스에 대응되게 펄스광을 출력하는 광원;을 구비하고, 상기 신호처리부는 상기 펄스 발생기에서 출력되는 펄스를 인가받아 상기 펄스광의 출력 시점을 결정하도록 구축될 수 있다.The pulse light generator may include a pulse generator configured to generate a pulse according to a driving control signal output from the signal processor; And a light source for outputting pulsed light corresponding to the pulse output from the pulse generator, wherein the signal processor may be configured to determine an output time point of the pulsed light by receiving a pulse output from the pulse generator.
또 다르게는 상기 펄스광 생성부에서 출력되는 펄스광을 상기 광서큘레이터의 입력단과 기준단으로 분배하여 출력하는 광스플릿터와; 상기 기준단에서 출력되는 광을 검출하여 상기 신호처리부에 제공하는 기준신호 광검출부;를 더 구비하고, 상기 신호처리부는 상기 기준신호 광검출부에서 출력되는 신호를 이용하여 상기 펄스광의 출력 시점으로 결정하도록 구출될 수 있다.Alternatively, an optical splitter for distributing the pulsed light output from the pulsed light generator to the input terminal and the reference terminal of the optical circulator; And a reference signal photo detector for detecting the light output from the reference stage and providing the signal to the signal processor, wherein the signal processor determines the output point of the pulsed light by using the signal output from the reference signal photo detector. Can be rescued.
바람직하게는 상기 펄스광 생성부는 중심파장이 1550nm이고 대역폭이 1KHz 내지 44MHz 인 광을 생성하고, 상기 파장필터는 1450nm와 1650nm의 라만 산란광을 분리하여 상기 제2센싱광검출부로 출력하도록 되어 있다.Preferably, the pulsed light generating unit generates light having a central wavelength of 1550 nm and a bandwidth of 1 KHz to 44 MHz, and the wavelength filter separates 1450 nm and 1650 nm Raman scattered light and outputs the light to the second sensing light detector.
또한, 상기 펄스광 생성부와 상기 광스플릿터 사이에 설치되어 광을 증폭하는 어븀광증폭기;를 더 구비할 수 있다.The apparatus may further include an erbium optical amplifier installed between the pulsed light generator and the optical splitter to amplify the light.
또한, 상기 제2센싱광검출부에서 검출되는 신호에서 교류성분을 제거하여 상기 신호처리부로 출력하는 로우패스 필터;를 더 구비하는 것이 바람직하다.The apparatus may further include a low pass filter for removing an AC component from the signal detected by the second sensing light detector and outputting the alternating component to the signal processor.
본 발명에 따른 온도 측정 지원형 광섬유 음향센서에 의하면, 센싱 광섬유 전체 길이에 대해 음원 또는 진동의 주파수 및 세기뿐만 아니라 온도분포 측정이 동시에 가능한 장점을 제공한다.According to the temperature measurement-supported optical fiber acoustic sensor according to the present invention, the temperature distribution measurement as well as the frequency and intensity of the sound source or vibration for the entire length of the sensing optical fiber provides an advantage that can be simultaneously.
도 1은 본 발명의 일 실시 예에 따른 온도측정 지원형 광섬유 음향센서를 나타내 보인 도면이고,1 is a view showing a temperature measurement-supported optical fiber acoustic sensor according to an embodiment of the present invention,
도 2는 본 발명의 또 다른 실시 예에 따른 온도측정 지원형 광섬유 음향센서를 나타내 보인 도면이고,2 is a view showing a temperature measurement support optical fiber acoustic sensor according to another embodiment of the present invention,
도 3은 본 발명의 또 다른 실시예에 따른 펄스광생성부가 적용된 온도측정 지원형 광섬유 음향센서를 나타내 보인 도면이다.3 is a diagram illustrating a temperature measuring assisted optical fiber acoustic sensor to which a pulsed light generator is applied according to another exemplary embodiment of the present invention.
이하, 첨부된 도면을 참조하면서 본 발명의 바람직한 실시예에 따른 온도측정 지원형 광섬유 음향센서를 더욱 상세하게 설명한다.Hereinafter, with reference to the accompanying drawings will be described in more detail a temperature measurement-supported optical fiber acoustic sensor according to a preferred embodiment of the present invention.
도 1은 본 발명의 일 실시 예에 따른 온도측정 지원형 광섬유 음향센서를 나타내 보인 도면이다.1 is a view showing a temperature measurement-supported optical fiber acoustic sensor according to an embodiment of the present invention.
도 1을 참조하면, 본 발명에 따른 광섬유 음향센서(100)는 펄스광 생성부(110), 어븀광증폭기(EDFA)(130), 광스플리터(140), 광서큘레이터(150), 파장필터(160), 센싱광섬유(170), 기준신호 광검출부(PDR)(180), 제1센싱 광검출부(PD1)(181), 제2센싱 광검출부(PD2)(182), 로우패스필터(185), 신호처리부(190)를 구비한다.Referring to FIG. 1, the optical fiber acoustic sensor 100 according to the present invention includes a pulsed light generator 110, an erbium optical amplifier (EDFA) 130, an optical splitter 140, an optical circulator 150, and a wavelength filter. 160, the sensing optical fiber 170, the reference signal photodetector (PDR) 180, the first sensing photodetector (PD1) 181, the second sensing photodetector (PD2) 182, and the low pass filter 185. And a signal processing unit 190.
펄스광 생성부(110)는 신호처리부(190)의 제어신호에 따라 펄스광을 생성하여 출력한다.The pulsed light generator 110 generates and outputs pulsed light according to the control signal of the signal processor 190.
펄스광 생성부(110)는 신호처리부(190)에서 출력되는 구동 제어신호에 따라 펄스를 생성하는 펄스 발생기(112)와, 펄스 발생기(112)에서 출력되는 펄스에 대응되게 펄스광을 출력하는 광원(114)으로 되어 있다.The pulsed light generator 110 may generate a pulse according to a driving control signal output from the signal processor 190, and a light source that outputs pulsed light corresponding to the pulse output from the pulsed generator 112. (114).
바람직하게는 펄스광 생성부(110)는 중심파장이 1550nm이고 대역폭이 1KHz 내지 44MHz 인 광을 생성하는 것을 적용한다.Preferably, the pulsed light generator 110 applies light having a center wavelength of 1550 nm and a bandwidth of 1 KHz to 44 MHz.
펄스광 생성부(110)는 도시된 예와 다르게, 도 3에 도시된 바와 같이 광원(116)과, 광원(116)에서 생성된 광에 대해 신호처리부(190)에 제어되어 펄스광을 생성하는 전기광학 변조기(118)로 구축될 수 있음은 물론이다.Unlike the illustrated example, the pulsed light generator 110 is controlled by the signal processor 190 with respect to the light source 116 and the light generated by the light source 116 as shown in FIG. 3 to generate pulsed light. Of course, it can be constructed with an electro-optic modulator 118.
어븀광증폭기(EDFA)(130)는 펄스광 생성부(110)와 후술되는 광스플릿터(140) 사이에 설치되어 펄스광 생성부(110)에서 출력되는 펄스광을 증폭시켜 광스플릿터 (140)로 출력한다.The erbium optical amplifier (EDFA) 130 is installed between the pulsed light generator 110 and the optical splitter 140 described later to amplify the pulsed light output from the pulsed light generator 110 to split the optical splitter 140. )
광스플릿터(140)는 펄스광 생성부(110)에서 출력되어 어븀광증폭기(130)를 거쳐 증폭된 펄스광을 광서큘레이터(150)의 입력단(151)과 기준단(142)으로 분배하여 출력한다.The optical splitter 140 distributes the pulsed light output from the pulsed light generator 110 and amplified through the erbium optical amplifier 130 to the input terminal 151 and the reference terminal 142 of the optical circulator 150. Output
광스플릿터(140)는 펄스광을 99:1의 비율로 광서큘레이터(150)의 입력단(151)과 기준단(142)으로 각각 분배하도록 된 것을 적용하는 것이 바람직하다.The optical splitter 140 preferably applies pulse light to the input terminal 151 and the reference terminal 142 of the optical circulator 150 at a ratio of 99: 1.
기준신호 광검출부(PDR)(180)은 기준단(142)에서 분배되어 출력되는 광을 검출하여 신호처리부(190)에 제공한다.The reference signal photodetector (PDR) 180 detects the light distributed from the reference stage 142 and outputs the light to the signal processor 190.
이 경우 신호처리부(190)는 기준신호 광검출부(180)에서 출력되는 신호를 이용하여 펄스광의 출력 시점을 결정할 수 있다.In this case, the signal processor 190 may determine an output time point of the pulsed light using the signal output from the reference signal photodetector 180.
이와는 다르게, 신호처리부(190)는 펄스 발생기(112)에서 출력되는 펄스를 참조번호 112a로 표기된 방식으로 인가받아 펄스광의 출력 시점을 결정하도록 구축될 수 있고, 이 경우 기준신호 광검출부(PDR)(180) 및 광스플릿터(140)는 생략되고, 증폭된 펄스광은 광서큘레이터(150)의 입력단(151)으로만 입력되게 구축하면 된다.Alternatively, the signal processor 190 may be configured to receive the pulse output from the pulse generator 112 in a manner indicated by reference numeral 112a to determine an output time point of the pulsed light. In this case, the reference signal photodetector PDR ( 180 and the optical splitter 140 may be omitted, and the amplified pulsed light may be configured to be input only to the input terminal 151 of the optical circulator 150.
광서큘레이터(150)는 펄스광 생성부(110)에서 출력되어 입력단(151)으로 입력되는 펄스광을 제1출력단(152)을 통해 출력하고, 제1출력단(152)에서 역으로 입사되는 광을 검출단(153)을 통해 출력한다.The optical circulator 150 outputs the pulsed light output from the pulsed light generator 110 and input to the input terminal 151 through the first output terminal 152, and is incident to the first output terminal 152 in reverse. Is output through the detection stage 153.
센싱광섬유(170)는 광서큘레이터(150)의 제1출력단(152)을 통해 출력되는 광이 전송될 수 있게 측정대상 영역에 걸쳐 설치되면 된다.The sensing optical fiber 170 may be provided over the measurement target area so that light output through the first output terminal 152 of the optical circulator 150 can be transmitted.
파장필터(160)는 센싱 광섬유(170)에서 산란되어 역으로 진행되는 레일레이 후방산란광은 제1센싱광검출부(PD1)(181)에 출력하고, 센싱 광섬유(170)에서 산란되어 역으로 진행되는 라만 후방산란광은 분리하여 제2센싱광검출부(PD2)(182)로 출력하도록 설치되어 있다.The wavelength filter 160 is scattered by the sensing optical fiber 170 and the reverse ray scattered light is output to the first sensing light detector (PD1) 181, and is scattered by the sensing optical fiber 170 to be reversed The Raman backscattered light is separated and output to the second sensing light detector PD2 182.
도시된 예에서는 파장필터(160)는 센싱 광섬유(170)와 광서큘레이터(150)의 제1출력단(152) 사이에 접속되어 있다.In the illustrated example, the wavelength filter 160 is connected between the sensing optical fiber 170 and the first output terminal 152 of the optical circulator 150.
파장필터(160)는 광서큘레이터(150)의 제1출력단(152)에서 센싱 광섬유(170)로 진행하는 광은 투과시키고, 센싱 광섬유(170)에서 산란되어 광서큘레이터(150)를 향해 역으로 진행되는 레일레이 후방산란광은 제1필터링단(161)을 통해 제1출력단(152)으로 진행되게 한다.The wavelength filter 160 transmits light that passes from the first output terminal 152 of the optical circulator 150 to the sensing optical fiber 170, is scattered by the sensing optical fiber 170, and is reversed toward the optical circulator 150. The Rayleigh backscattered light proceeds to the first output terminal 152 through the first filtering stage 161.
또한, 파장필터(160)는 센싱 광섬유(170)에서 산란되어 광서큘레이터(150)를 향해 역으로 진행되는 라만 후방산란광은 광서큘레이터(150)의 제1출력단(152)과는 다른 제2필터링단(162)을 통해 분리하여 제2센싱광검출부(182)에 출력하도록 설치되어 있다.In addition, the wavelength filter 160 is scattered by the sensing optical fiber 170 and the Raman backscattered light traveling backward toward the optical circulator 150 is different from the first output terminal 152 of the optical circulator 150. Separating through the filtering stage 162 is provided to output to the second sensing light detector 182.
바람직하게는 파장필터(160)는 1450nm 및 1650nm의 라만 산란광을 제2필터링단(162)을 통해 출력하도록 구축된다.Preferably, the wavelength filter 160 is constructed to output Raman scattered light of 1450 nm and 1650 nm through the second filtering stage 162.
제1센싱광검출부(PD1)(181)는 광서큘레이터(150)의 검출단(153)에서 출력되는 광, 즉 레일레이 후방산란광을 검출하여 신호처리부(190)에 제공한다.The first sensing light detector PD1 181 detects the light output from the detection terminal 153 of the optical circulator 150, that is, the Rayleigh backscattered light and provides the signal to the signal processor 190.
제2센싱광검출부(PD2)(182)는 파장필터(160)의 제2필터링단(162)에서 출력되는 라만 산란광을 검출한다.The second sensing light detector PD2 182 detects Raman scattered light output from the second filtering end 162 of the wavelength filter 160.
한편, 파장필터(160)는 도 2에 도시된 바와 같이 광서큘레이터(150)의 검출단(153)에 접속될 수 있다.Meanwhile, the wavelength filter 160 may be connected to the detection end 153 of the optical circulator 150 as shown in FIG. 2.
이 경우 파장필터(160)는 센싱 광섬유(170)에서 산란되어 역으로 진행되어 광서큘레이터(150)의 검출단(153)을 통해 입력되는 레일레이 후방산란광은 분리하여 제1필터링단(161)을 통해 제1센싱광검출부(PD1)(181)에 전송되게 구축한다. In this case, the wavelength filter 160 is scattered by the sensing optical fiber 170 and proceeds in reverse to separate the Ray-ray backscattered light input through the detection terminal 153 of the optical circulator 150 to separate the first filtering stage 161. It is constructed to be transmitted to the first sensing light detector (PD1) (181) through.
또한, 파장필터(160)는 센싱 광섬유(170)에서 산란되어 역으로 진행되어 광서큘레이터(150)의 검출단(153)을 통해 입력되는 라만 후방산란광은 분리하여 제2필터링단(162)을 통해 제2센싱광검출부(PD2)(182)에 출력하도록 구축하면된다.In addition, the wavelength filter 160 is scattered by the sensing optical fiber 170 and proceeds in reverse to separate the Raman backscattered light input through the detection stage 153 of the optical circulator 150 to separate the second filtering stage 162. It may be configured to output to the second sensing light detector (PD2) 182 through.
로우패스필터(185)는 제2센싱광검출부(182)에서 검출되는 신호에서 교류성분을 제거하여 신호처리부(190)로 출력한다.The low pass filter 185 removes an AC component from the signal detected by the second sensing light detector 182 and outputs the AC component to the signal processor 190.
즉, 제2센싱 광검출부(182)를 통해 시간의 함수로 측정된 데이터에는 센싱광섬유(170)에서 발생한 자기간섭신호(self interference)를 포함하고 있으므로 로우패스필터(185)를 통해 교류성분을 제거한다. That is, since the data measured as a function of time through the second sensing photodetector 182 includes a self interference signal generated by the sensing optical fiber 170, the AC component is removed through the low pass filter 185. do.
로우패스필터(185)는 하드웨어적으로 교류성분을 제거할 수 있게 적용되거나, 수집된 신호로부터 소프트웨어적으로 교류성분을 제거하도록 구축될 수 있음은 물론이다.The low pass filter 185 may be applied to remove the AC component in hardware or may be constructed to remove the AC component from the collected signal.
신호처리부(190)는 펄스광 생성부(110)의 펄스광의 생성을 온/오프 스위칭 제어에 의해 제어하고, 펄스광의 출력 시점이 되는 기준시점을 기준신호 광검출부(PDR)(180)에서 출력되는 신호를 이용하여 결정하고, 결정된 기준시점을 기준으로 제1센싱광검출부(181)에서 검출되는 신호를 시간상으로 수집하여 진동주파수 및 세기를 측정하고, 제2센싱광검출부(182)에서 시간상으로 검출되는 신호를 수집하여 온도를 측정한다.The signal processor 190 controls the generation of the pulsed light of the pulsed light generator 110 by on / off switching control and outputs a reference time point at which the pulsed light is output from the reference signal photodetector (PDR) 180. Determining by using a signal, by collecting the signal detected by the first sensing light detector 181 based on the determined reference time in time to measure the vibration frequency and intensity, the second sensing light detector 182 to detect in time Collect the signal to measure the temperature.
즉, 신호처리부(190)는 기준신호 광검출부(180)을 통해 검출된 펄스광 출력 기준시점을 기준으로 제1센싱광검출부(181)와 제2센싱광검출부(182)을 통해 각각 레일레이 후방산란광과 라만 후방산란광을 시간의 함수로 수집하여 처리한다.That is, the signal processing unit 190 is rearward of the Ray Ray through the first sensing light detector 181 and the second sensing light detector 182 based on the pulsed light output reference time detected by the reference signal light detector 180. Scattered light and Raman backscattered light are collected and processed as a function of time.
이러한 신호처리부(190)는 제1센싱광검출부(181)를 통해 수신된 신호로부터 진동주파수 및 세기분포를 다음과 같이 측정한다.The signal processor 190 measures the vibration frequency and the intensity distribution from the signal received through the first sensing light detector 181 as follows.
펄스광 생성부(110)에서 출력되는 펄스광의 펄스폭과 펄스반복률을 설정하면 이에 따라 위치 분해능, 샘플링 주기 N과 측정주파수 범위(N/2)가 결정된다. When the pulse width and the pulse repetition rate of the pulsed light output from the pulsed light generator 110 are set, the position resolution, the sampling period N, and the measurement frequency range N / 2 are determined accordingly.
위치 분해능은 센싱광섬유(170) 길이방향에 대한 데이터 간격을 결정한다.The position resolution determines the data interval with respect to the sensing optical fiber 170 longitudinal direction.
각각의 펄스광에 대해 센싱광섬유(170)의 길이방향에서 연속적으로 발생하여 되돌아오는 레일레이 후방산란광은 광시간 영역반사측정(OTDR: Optical Time Domain Reflectometry) 데이터로 N개의 트레이스(Trace)가 수집된다. For each pulsed light, N traces are collected as optical time domain reflectometry (OTDR) data for Rayleigh backscattered light that is continuously generated and returned in the longitudinal direction of the sensing optical fiber 170. .
이로부터 센싱광섬유(170)의 길이방향에 대해 정의된 데이터간격에 따라 결정되는 센싱광섬유(170)의 같은 위치에서 발생한 N개의 데이터를 푸리에 변환하여 신호처리부(190)는 각 위치에 대한 주파수 및 세기를 계산한다. From this, Fourier transforms N data generated at the same position of the sensing optical fiber 170 determined according to the data interval defined in the longitudinal direction of the sensing optical fiber 170, so that the signal processing unit 190 has a frequency and intensity for each position. Calculate
이때, 첫 번째 정상상태에서 수집된 OTDR Trace를 기준으로 인접한 OTDR Trace를 평균화하면 신호대비잡음비율을 높일 수 있다.At this time, by averaging the adjacent OTDR traces based on the OTDR traces collected in the first steady state, the signal to noise ratio can be increased.
이를 더욱 상세하게 설명하면, 제1 및 제2 센싱광검출부(181)(182)로부터 측정된 신호는 센싱광섬유(170) 내에서의 빛의 속도를 고려하여 거리에 대한 함수로 변환한다.In more detail, the signals measured from the first and second sensing light detectors 181 and 182 are converted into a function of distance in consideration of the speed of light in the sensing optical fiber 170.
거리의 함수로 변환된 레일레이 후방산란광의 세기는 N번의 펄스광에 대해 위치 간격 M에 따라 NxM개의 배열로 재구성하며, 각각의 위치에 대해서 N개의 데이터를 푸리에 변환하여 M개의 위치에 대한 주파수 및 크기를 분석한다.The intensity of the Rayleigh backscattered light transformed as a function of the distance is reconstructed into NxM arrays according to the position interval M for N pulsed lights, and Fourier transforms N data for each position to obtain the frequency and Analyze the size.
이때, N은 광펄스 발생 주기로서 측정하고자 하는 음원의 주파수의 2배 정도이어야 하므로 1 kHz의 음원을 검출하기 위해서는 2 kHz 이상의 주기를 갖는 펄스광의 구동이 필요하다.At this time, since N should be about twice the frequency of the sound source to be measured as the light pulse generation period, it is necessary to drive pulsed light having a period of 2 kHz or more to detect a sound source of 1 kHz.
또한, M은 음원의 위치를 구분하기 위한 최소 위치간격을 센싱광섬유(170)의 전체 길이로 나눈 값으로서 전체길이 1km에 대해 1m의 위치 간격으로 측정하는 경우 M은 1,000으로 설정된다.In addition, M is a value obtained by dividing the minimum position interval for dividing the position of the sound source by the total length of the sensing optical fiber 170. When the M is measured at a position interval of 1 m with respect to the total length of 1 km, M is set to 1,000.
한편, 신호 처리부(190)에서 제2센싱광검출부(182)를 통해 수신된 신호로부터 온도분포를 다음과 같이 측정한다.Meanwhile, the temperature distribution is measured from the signal received through the second sensing light detector 182 in the signal processor 190 as follows.
펄스광 생성부(110)에 출력되는 펄스광의 펄스폭과 펄스반복률을 설정하면 이에 따라 위치분해능, 샘플링 주기 N이 결정된다. When the pulse width and the pulse repetition rate of the pulsed light output to the pulsed light generator 110 are set, the position resolution and the sampling period N are determined accordingly.
각각의 펄스광에 대해 센싱광섬유(170) 길이방향에서 연속적으로 발생하여 되돌아오는 라만 후방산란광을 모두 합산하여 노이즈를 최대한 제거한 후, 로우패스필터(185)를 통해 교류(AC) 성분을 제거하면 온도 정보가 포함된 OTDR Trace를 얻을 수 있다. 이때, OTDR Trace 합산수가 많을수록 온도정확도가 높아지므로 진동주파수 및 세기 측정방식과는 다르게 연속적으로 합산하는 것으로 온도정보를 획득한다.For each pulsed light, the Raman backscattered light that is continuously generated and returned in the longitudinal direction of the sensing optical fiber 170 is summed to remove noise as much as possible, and then the AC component is removed through the low pass filter 185. You can get an OTDR trace with information. At this time, since the temperature accuracy increases as the number of OTDR traces increases, temperature information is obtained by continuously summing unlike vibration frequency and intensity measurement methods.
즉, 로우패스필터(185)로부터 AC 성분이 제거된 후 거리의 함수로 변환된 라만 후방산란광의 세기는 N번의 펄스광에 대해 누적하여 위치에 따른 광세기를 분석한다.That is, the intensity of the Raman backscattered light converted as a function of distance after the AC component is removed from the low pass filter 185 is accumulated for N pulsed lights, and the light intensity according to the position is analyzed.
이때, 라만 후방산란광은 N번의 펄스광에 대해 누적한 값에 연속하여 누적하도록 하며 통상 60,000회 누적한 값으로부터 온도변화를 분석하며, 측정시간을 조정하여 누적횟수를 달리할 수 있다.At this time, the Raman backscattered light is continuously accumulated to the accumulated value for N pulsed light, and the temperature change is analyzed from the accumulated value of 60,000 times, and the cumulative frequency can be changed by adjusting the measurement time.
이상에서 설명된 광섬유 음향센서(100)는 센싱광섬유(170) 내에서 발생하는 레일레이 산란광과 라만 산란광을 분리하여 동시에 신호처리함으로써 진동주파수, 세기분포, 온도분포를 함께 측정할 수 있는 장점을 제공한다.The above-described optical fiber acoustic sensor 100 separates the Ray-ray scattered light and the Raman scattered light generated in the sensing optical fiber 170 and simultaneously processes the signal to provide an advantage of measuring vibration frequency, intensity distribution, and temperature distribution together. do.

Claims (9)

  1. 제어신호에 따라 펄스광을 생성하여 출력하는 펄스광 생성부와;A pulsed light generator for generating and outputting pulsed light according to a control signal;
    상기 펄스광 생성부에서 출력되어 입력단으로 입력되는 펄스광을 제1출력단을 통해 출력하고, 상기 제1출력단에서 역으로 입사되는 광을 검출단을 통해 출력하는 광서큘레이터와;An optical circulator for outputting pulsed light output from the pulsed light generator and input to an input terminal through a first output terminal, and outputting light incident from the first output terminal through the detection terminal;
    상기 광서큘레이터의 제1출력단을 통해 출력되는 광이 전송될 수 있게 설치된 센싱 광섬유와;A sensing optical fiber installed to transmit light output through the first output terminal of the optical circulator;
    상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광을 검출하는 제1센싱광검출부와;A first sensing light detector for detecting Rayleigh backscattered light which is scattered in the sensing optical fiber and is reversed;
    상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광을 검출하는 제2센싱광검출부와;A second sensing light detector for detecting Raman backscattered light which is scattered in the sensing optical fiber and proceeds backward;
    상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 상기 제1센싱광검출부에 출력하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 분리하여 상기 제2센싱광검출부로 출력하도록 설치된 파장필터와;The Rayleigh backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is output to the first sensing light detector, and the Raman backscattered light scattered from the sensing optical fiber and propagated in the reverse direction is separated and output to the second sensing light detector. An installed wavelength filter;
    상기 펄스광 생성부의 펄스광의 생성을 제어하고, 상기 펄스광의 출력 시점을 기준으로 상기 제1센싱광검출부에서 검출되는 신호로부터 진동주파수 및 세기를 측정하고, 상기 제2센싱광검출부에서 검출되는 신호로부터 온도를 측정하는 신호 처리부;를 구비하는 것을 특징으로 하는 광섬유 음향센서.Controlling the generation of the pulsed light of the pulsed light generator, measuring the vibration frequency and intensity from the signal detected by the first sensing light detector based on the output time point of the pulsed light, and from the signal detected by the second sensed light detector And a signal processing unit for measuring a temperature.
  2. 제1항에 있어서, 상기 파장필터는 상기 센싱 광섬유와 상기 광서큘레이터 사이에 접속되어 상기 제1출력단에서 상기 센싱 광섬유로 향하는 광은 투과시키고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 제1필터링단을 통해 상기 제1출력단으로 진행되게 하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 제2필터링단을 통해 분리하여 상기 제2센싱광검출부에 출력하도록 설치되어 있고,2. The rear of the Rayray of claim 1, wherein the wavelength filter is connected between the sensing optical fiber and the optical circulator, transmits light from the first output terminal to the sensing optical fiber, and is scattered from the sensing optical fiber and is reversed. Scattered light propagates to the first output terminal through a first filtering stage, and Raman backscattered light scattered from the sensing optical fiber is reversed through a second filtering stage to be output to the second sensing light detector. There is,
    상기 제1센싱광검출부는 상기 검출단에서 출력되는 광을 검출하도록 설치되어 있고, 상기 제2센싱광검출부는 상기 제2필터링단에서 출력되는 광을 검출하도록 설치된 것을 특징으로 하는 광섬유 음향센서.And the first sensing light detector detects the light output from the detection stage, and the second sensing light detector detects the light output from the second filtering stage.
  3. 제1항에 있어서, 상기 파장필터는 상기 광서큘레이터의 검출단에 접속되어 상기 센싱 광섬유에서 산란되어 역으로 진행되는 레일레이 후방산란광은 제1필터링단을 통해 상기 제1센싱광검출부에 전송되게 하고, 상기 센싱 광섬유에서 산란되어 역으로 진행되는 라만 후방산란광은 제2필터링단을 통해 분리하여 상기 제2센싱광검출부에 출력하도록 된 것을 특징으로 하는 광섬유 음향센서.The method of claim 1, wherein the wavelength filter is connected to the detection stage of the optical circulator, the scattered back light scattered from the sensing optical fiber is to be transmitted to the first sensing light detector through the first filtering stage And Raman backscattered light which is scattered from the sensing optical fiber and proceeds in the reverse direction, to be separated through a second filtering stage and output to the second sensing light detector.
  4. 제1항에 있어서, 상기 펄스광 생성부는According to claim 1, wherein the pulsed light generating unit
    상기 신호처리부에서 출력되는 구동 제어신호에 따라 펄스를 생성하는 펄스 발생기와;A pulse generator for generating pulses according to a driving control signal output from the signal processor;
    상기 펄스 발생기에서 출력되는 펄스에 대응되게 펄스광을 출력하는 광원;을 구비하고,And a light source for outputting pulsed light corresponding to the pulse output from the pulse generator,
    상기 신호처리부는 상기 펄스 발생기에서 출력되는 펄스를 인가받아 상기 펄스광의 출력 시점을 결정하도록 된 것을 특징으로 하는 광섬유 음향센서.And the signal processor is configured to determine an output time point of the pulsed light by receiving a pulse output from the pulse generator.
  5. 제1항에 있어서, 상기 펄스광 생성부에서 출력되는 펄스광을 상기 광서큘레이터의 입력단과 기준단으로 분배하여 출력하는 광스플릿터와;The optical splitter of claim 1, further comprising: an optical splitter configured to distribute the pulsed light output from the pulsed light generator to an input terminal and a reference terminal of the optical circulator;
    상기 기준단에서 출력되는 광을 검출하여 상기 신호처리부에 제공하는 기준신호 광검출부;를 더 구비하고,And a reference signal photo detector for detecting the light output from the reference stage and providing the signal to the signal processor.
    상기 신호처리부는 상기 기준신호 광검출부에서 출력되는 신호를 이용하여 상기 펄스광의 출력 시점으로 결정하도록 된 것을 특징으로 하는 광섬유 음향센서.And the signal processor is configured to determine the output time of the pulsed light by using the signal output from the reference signal photodetector.
  6. 제1항에 있어서, 상기 펄스광 생성부는 중심파장이 1550nm이고 대역폭이 1KHz 내지 44MHz 인 광을 생성하고, According to claim 1, wherein the pulsed light generating unit generates a light having a central wavelength of 1550nm and a bandwidth of 1KHz to 44MHz,
    상기 파장필터는 1450nm와 1650nm의 라만 산란광을 분리하여 상기 제2센싱광검출부로 출력하도록 된 것을 특징으로 하는 광섬유 음향센서.The wavelength filter is an optical fiber acoustic sensor, characterized in that for separating the 1450nm and 1650nm Raman scattered light output to the second sensing light detector.
  7. 제5항에 있어서, 상기 펄스광 생성부와 상기 광스플릿터 사이에 설치되어 광을 증폭하는 어븀광증폭기;를 더 구비하는 것을 특징으로 하는 광섬유 음향센서.The optical fiber acoustic sensor of claim 5, further comprising: an erbium optical amplifier disposed between the pulsed light generator and the optical splitter to amplify the light.
  8. 제1항에 있어서, 상기 제2센싱광검출부에서 검출되는 신호에서 교류성분을 제거하여 상기 신호처리부로 출력하는 로우패스 필터;를 더 구비하는 것을 특징으로하는 광섬유 음향센서.The optical fiber acoustic sensor of claim 1, further comprising a low pass filter which removes an AC component from the signal detected by the second sensing light detector and outputs the alternating component to the signal processor.
  9. 제1항에 있어서, 펄스광 생성부는 The pulse light generating unit of claim 1, wherein the pulsed light generating unit
    광원과, 상기 광원에서 생성된 광에 대해 상기 신호처리부에 제어되어 펄스광을 생성하는 전기광학 변조기를 구비하는 것을 특징으로 하는 광섬유음향센서.And a light source and an electro-optic modulator for generating pulsed light by controlling the signal processor with respect to light generated by the light source.
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