WO2020034558A1 - 一种面向分布式光纤拉曼传感器的高精度温度解调方法 - Google Patents

一种面向分布式光纤拉曼传感器的高精度温度解调方法 Download PDF

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WO2020034558A1
WO2020034558A1 PCT/CN2019/000087 CN2019000087W WO2020034558A1 WO 2020034558 A1 WO2020034558 A1 WO 2020034558A1 CN 2019000087 W CN2019000087 W CN 2019000087W WO 2020034558 A1 WO2020034558 A1 WO 2020034558A1
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stokes light
fiber
light
stokes
sensing
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PCT/CN2019/000087
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French (fr)
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张明江
李健
张建忠
乔丽君
王涛
王云才
靳宝全
王宇
王东
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太原理工大学
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Priority to US17/252,995 priority Critical patent/US11808639B2/en
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    • 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
    • G01K11/324—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 using Raman scattering
    • 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
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K15/00—Testing or calibrating of thermometers
    • G01K15/005—Calibration

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  • the invention relates to the field of temperature demodulation in a distributed optical fiber sensing system, in particular to a high-precision temperature demodulation method for a distributed optical fiber Raman sensor.
  • Optical fiber sensing technology has a wide range of continuous monitoring, precise positioning of the processing space, timely and accurate diagnosis of faults, and good expansion and upgrade capabilities, which can meet the complex manufacturing requirements and the ever-changing functions of intelligent manufacturing. Due to the complicated wiring of the traditional electronic sensing system, the system is susceptible to various problems such as electromagnetic interference, lightning strikes, and wet weather during the use of the system. Therefore, it has not been widely used in many key areas of intelligent manufacturing, and continuous precision measurement cannot be popularized. Therefore, new fiber-optic sensing technology has become the key technology for realizing the network of intelligent manufacturing and industrial production chains.
  • temperature measurement accuracy is one of the important parameters of system performance.
  • the temperature measurement accuracy of distributed optical fiber Raman sensors is basically maintained at ⁇ 1 ° C.
  • some industrial monitoring fields have put forward higher requirements for the temperature measurement accuracy of fiber optic sensing systems, such as petrochemical reactors.
  • the temperature measurement accuracy is required to reach ⁇ 0.1 ° C.
  • the temperature demodulation method is the key technology to achieve high-precision online monitoring of the temperature along the fiber.
  • the commonly used temperature demodulation method is to use Stokes backscattered light as a reference channel, anti-Stokes backscattered light as a signal channel, and then use the ratio of the intensity of these two kinds of backscattered light to demodulate the temperature along the fiber.
  • the Stokes and anti-Stokes scattering signals in the fiber are very weak, and the scattered information is almost completely submerged in noise.
  • the system separates the anti-Stokes and Stokes signals through a Raman wavelength division multiplexer (WDM). If WDM cannot achieve the filtering function well, then some Rayleigh scattered light will be doped in the Raman scattered light.
  • WDM Raman wavelength division multiplexer
  • the anti-Stokes signal strength is too weak, the residual Rayleigh scattered light component will become a serious noise interference in the system.
  • Raman wavelength division multiplexers used in actual projects can usually provide isolation of 35 to 40 dB, which has basically reached people's requirements for high isolation.
  • the intensity is several orders of magnitude weaker than the Raman scattered light after passing through the wavelength division multiplexer. It is difficult to cause interference to the temperature information extraction of the system, which can be ignored, so this part is not
  • the Rayleigh scattered light filtered by WDM will be output with anti-Stokes scattered light and passed through the photodetector and data acquisition card.
  • the data collected by the system actually contains two components: anti-Stokes scattered signal and Rayleigh. Scattered signals.
  • using the data detected by the system to directly perform temperature demodulation will obviously be affected by Rayleigh light noise.
  • There is a certain degree of error from the real situation making it difficult to achieve temperature measurement accuracy of ⁇ 0.1 ° C.
  • a targeted data processing algorithm must be proposed. Therefore, eliminating the interference of Rayleigh noise has become a key technical issue to achieve high-precision detection along the optical fiber.
  • the present invention proposes a high-precision temperature solution for the distributed optical fiber Raman temperature sensing system. Adjust the method to make the temperature measurement accuracy reach ⁇ 0.1 °C.
  • a temperature demodulation method for an optical fiber Raman temperature sensing system includes the following steps:
  • Step 1 Set up the above-mentioned high-precision temperature detection device for distributed fiber Raman sensing system
  • the device includes a pulse laser, WDM, 2 APDs, 2 LNAs, a data acquisition card, and a computer; wherein the output end of the pulse laser is connected to the input end of the WDM; the two output ends of the WDM are respectively connected to the first APD and the second The input of the APD is connected; the output of the first APD is connected to the input of the first LNA; the output of the second APD is connected to the input of the second LNA; the output of the first LNA and the second LNA are connected to the data acquisition card The input end of the data acquisition card is connected to the input end of the computer; the public end of the WDM is connected to the input end of the sensor fiber under test.
  • Step 2 Signal processing of Stokes light and anti-Stokes light in the calibration phase
  • the laser pulse emitted by the pulse laser is incident on the sensing fiber under test through WDM.
  • the laser pulse is spontaneously Raman scattering when it propagates in the multimode sensing fiber, thereby causing the Stokes light and anti-Stokes light; where the backward Stokes light and anti-Stokes light generated in the fiber first reach the first APD, the first LNA, the second APD, and the second LNA respectively through WDM for photoelectric conversion and amplification, and finally enter the high-speed acquisition
  • the card and computer perform data acquisition to obtain the position and intensity information of Stokes light and anti-Stokes light along the fiber.
  • K s, K a and K r is related to the fiber end sections scattering coefficient
  • V s, V a and V 0 is the Stokes light, the incident light and the anti-Stokes frequency
  • h is the Planck constant and Boltzmann constant
  • ⁇ v is the Raman frequency shift of the fiber is 13.2 THz
  • ⁇ s , ⁇ a , and ⁇ 0 are Stokes light, anti-Stokes light, and Rayleigh scattered light, respectively.
  • Attenuation coefficient per unit length in the fiber T c0 represents the temperature value of the sensing fiber to be measured during the first calibration phase
  • l represents the distance between this position and the front end of the multimode sensing fiber
  • P 0 is the incident light strength.
  • the back-scattered light intensity curve of anti-Stokes light and Stokes light was obtained in the second calibration phase of the data acquisition card.
  • the light intensity ratio is expressed as:
  • T c1 represents the temperature value of the sensing optical fiber to be measured in the second calibration stage.
  • the backscattered light intensity curve of anti-Stokes light and Stokes light is obtained during the measurement phase of the data acquisition card.
  • the ratio of the light intensity is expressed as:
  • T represents the temperature value at the sensing fiber 1 to be measured in the measurement stage.
  • Step 4 High-precision temperature demodulation method for distributed fiber Raman sensing system
  • Equation (3) is subtracted from equation (1) to get:
  • Equation (3) is subtracted from equation (2) to get:
  • Equation (6) can be obtained after solving
  • the self-calibrated temperature detection device and temperature demodulation method for the optical fiber Raman sensing system according to the present invention have the following advantages:
  • the present invention creatively uses two calibration data and temperature measurement data to demodulate temperature without adding any devices, avoiding the effect of Rayleigh noise on the temperature measurement result, and it is expected to achieve temperature measurement accuracy.
  • the calibration phase of the present invention is performed in the early stage of the measurement phase. After the calibration is completed, the subsequent measurement period does not need to be repeatedly calibrated, which speeds up the process of the distributed optical fiber sensing system that is more convenient for industrialization.
  • the invention has a reasonable design and effectively solves the problem of low temperature measurement accuracy of the system due to Rayleigh optical crosstalk in the existing distributed optical fiber Raman temperature measurement system. It is expected to make the temperature measurement accuracy within ⁇ 0.1 ° C, which is suitable for distributed Fiber Raman temperature measurement system.
  • FIG. 1 shows a schematic diagram of a high-precision detection device for a distributed optical fiber Raman sensing system in the present invention.
  • a high-precision temperature demodulation method for distributed fiber Raman sensing systems is implemented by the following devices.
  • the device includes a 1550nm high-power pulsed laser, a wavelength division multiplexer (WDM), two avalanche photodiodes (APD), two low-noise amplifiers (LNA), a sensing fiber under test (ordinary multimode fiber), and data acquisition. Card and computer.
  • WDM wavelength division multiplexer
  • APD avalanche photodiodes
  • LNA low-noise amplifiers
  • sensing fiber under test ordinary multimode fiber
  • Step one build a high-precision temperature detection device for distributed fiber Raman sensing systems
  • the fiber-optic Raman thermometer includes a pulse laser, WDM, two APDs, two LNAs, a data acquisition card, and a computer; wherein the output of the pulse laser 1 is connected to the input of the WDM 2.
  • the input end of the sensing optical fiber 3 to be tested is connected to the common end of the WDM 2.
  • the two output terminals of WDM 2 are connected to the input terminals of the first APD 4 and the second APD 5 respectively; the output terminal of the first APD 4 is connected to the input terminal of the first LNA 6; the output terminal of the second APD 5 is connected to the second The input terminals of the LNA 7 are connected; the output terminals of the first LNA 6 and the second LNA 7 are connected to the input terminal of the data acquisition card 8; the output terminal of the data acquisition card 8 is connected to the input terminal of the computer 9.
  • the pulse laser has a wavelength of 1550 nm, a pulse width of 10 ns, and a repetition frequency of 8 KHz.
  • the working wavelength of WDM is 1550nm / 1450nm / 1663nm.
  • APD has a bandwidth of 100 MHz and a spectral response range of 900 to 1700 nm.
  • the bandwidth of the LNA is 100MHz.
  • the number of channels of the data acquisition card is 4, the sampling rate is 100M / s, and the bandwidth is 100MHz.
  • the sensing fiber under test is a common multimode fiber.
  • Step 2 Signal processing of Stokes light and anti-Stokes light in the calibration phase
  • the fiber-optic Raman thermometer is started, and the laser pulse emitted by the high-power pulsed laser is incident on the sensing optical fiber through WDM; the laser pulse is spontaneously Raman scattering when it propagates in the sensing optical fiber to be measured, thereby making multi-mode sensing Stokes light and anti-Stokes light are generated at various positions of the optical fiber.
  • the Stokes light is incident on the data acquisition card through the WDM, the first APD, and the first LNA, and the data acquisition card performs analog-to-digital conversion on the Stokes light, thereby obtaining the light intensity curve of the Stokes light.
  • the anti-Stokes light is incident on the data acquisition card through WDM, the second APD, and the second LNA in turn.
  • the data acquisition card performs analog-to-digital conversion on the anti-Stokes light, thereby obtaining the intensity curve of the anti-Stokes light.
  • K s, K a and K r is related to the fiber end sections scattering coefficient
  • V s, V a and V 0 is the Stokes light, the incident light and the anti-Stokes frequency
  • h is the Planck constant and Boltzmann constant
  • ⁇ v is the Raman frequency shift of the fiber is 13.2 THz
  • ⁇ s , ⁇ a , and ⁇ 0 are Stokes light, anti-Stokes light, and Rayleigh scattered light, respectively.
  • Attenuation coefficient per unit length in the fiber T c0 represents the temperature value of the sensing fiber to be measured during the first calibration phase
  • l represents the distance between this position and the front end of the multimode sensing fiber
  • P 0 is the incident light strength.
  • the back-scattered light intensity curve of anti-Stokes light and Stokes light was obtained in the second calibration phase of the data acquisition card.
  • the light intensity ratio is expressed as:
  • T c1 represents the temperature value of the sensing optical fiber to be measured in the second calibration stage.
  • the backscattered light intensity curve of anti-Stokes light and Stokes light is obtained during the measurement phase of the data acquisition card.
  • the ratio of the light intensity is expressed as:
  • T represents the temperature value at the sensing fiber 1 to be measured in the measurement stage.
  • Step 4 High-precision temperature demodulation method for distributed fiber Raman sensing system
  • Equation (10) is subtracted from equation (8) to get:
  • Equation (10) is subtracted from equation (9) to get:
  • Equation (13) can be obtained after solving

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  • General Physics & Mathematics (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)
  • Investigating, Analyzing Materials By Fluorescence Or Luminescence (AREA)

Abstract

一种面向分布式光纤拉曼温度传感***的温度解调方法，包括如下步骤：步骤一、搭建面向分布式光纤拉曼传感***的高精度温度检测装置；步骤二、定标阶段Stokes光和anti-Stokes光的信号处理；步骤三、测量阶段Stokes光和anti-Stokes光的信号处理；步骤四、面向分布式光纤拉曼传感***的高精度温度解调方法。本方法有效解决了现有分布式光纤拉曼测温***中的由于瑞利光串扰导致***的测温精度低的问题，有望使其测温精度达到±0.1℃以内，适用于分布式光纤拉曼测温***。

Description

一种面向分布式光纤拉曼传感器的高精度温度解调方法 技术领域
本发明涉及分布式光纤传感***中的温度解调领域，具体是一种面向分布式光纤拉曼传感器的高精度温度解调方法。
背景技术
分布式光纤传感器是工业数据的来源，是实现智能化转型升级的基础。光纤传感技术具备大范围连续监测、加工空间精确定位、故障及时准确诊断以及良好的扩展升级能力，可应付结构复杂、功能日新月异的智能制造需求。由于传统电子传感***接线繁复，***使用过程中易受电磁干扰、雷击、潮湿天气干扰等各种问题，所以在诸多智能制造关键领域未能被广泛应用，连续精密测量亦无法普及。故此，新型光纤传感技术已经成为实现智能制造与工业生产链条网络化的关键技术。
在分布式光纤拉曼测温***中，测温精度是***性能的重要参数之一。目前分布式光纤拉曼传感器的测温精度基本维持在±1℃，但是随着科学技术的发展，一些工业监控领域对光纤传感***的测温精度提出了更高方面的要求，例如石化反应堆、智能电网、隧道渗水的温度监测领域，要求测温精度需达到±0.1℃。在分布式光纤拉曼测温***中，温度解调方法是实现光纤沿线温度高精度在线监测的关键技术。目前常用的温度解调方法是利用Stokes后向散射光作为参考通道，利用anti-Stokes后向散射光作为信号通道，然后利用这两种后向散射光的光强比值来解调光纤沿线的温度信息。但是光纤中的Stokes和anti-Stokes散射信号非常微弱，散射信息基本完全淹没在噪声中。***是通过拉曼波分复用器(WDM)将anti-Stokes和Stokes信号分离出来，如果WDM不能很好地实现滤光作用，那么会有部分的瑞 利散射光掺杂在拉曼散射光中，由于anti-Stokes信号强度过于微弱，残留的瑞利散射光成分将会成为***严重的噪声干扰。目前，实际工程中使用的拉曼波分复用器通常能提供35～40dB的隔离度，已经基本达到人们对高隔离度的要求。对于光纤中的布里渊散射光，经过波分复用器后，其强度比拉曼散射光弱了好几个数量级，对***的温度信息提取已经难以造成干扰，可以忽略不计，因此这部分未被WDM滤掉的瑞利散射光会和anti-Stokes散射光一同输出，并通过光电探测器和数据采集卡，此时***采集到的数据实际包含两种成分：anti-Stokes散射信号和瑞利散射信号。这种情况下，使用***检测的数据直接进行温度解调显然会受到瑞利光噪声的影响，与真实情况存在一定程度的误差，使其测温精度难以达到±0.1℃，要想进一步提高***的测温精度，必须提出针对性的数据处理算法，因此，消除瑞利噪声的干扰已经成为实现光纤沿线高精度检测的关键技术问题。
基于此，有必要发明一种全新的温度解调方法，以解决瑞利噪声对光纤拉曼传感***温度解调的影响，导致***测温精度降低的问题。
发明内容
本发明为了解决现有分布式光纤拉曼传感***由于瑞利噪声干扰等现象导致***测温精度急剧下降的问题，提出了一种面向分布式光纤拉曼温度传感***的高精度温度解调方法，使其测温精度有望达到±0.1℃。
本发明是采用如下技术方案实现的：
一种面向光纤拉曼温度传感***的温度解调方法，包括如下步骤：
步骤一、搭建上述面向分布式光纤拉曼传感***的高精度温度检测装置
该装置包括脉冲激光器、WDM、2个APD、2个LNA、数据采集卡、 计算机；其中，脉冲激光器的输出端与WDM的输入端连接；WDM的2个输出端分别与第一APD和第二APD的输入端连接；第一APD的输出端与第一LNA的输入端连接；第二APD的输出端与第二LNA的输入端连接；第一LNA和第二LNA的输出端与数据采集卡的输入端连接；数据采集卡的输出端与计算机的输入端连接；WDM的公共端与待测传感光纤的输入端连接。
步骤二、定标阶段Stokes光和anti-Stokes光的信号处理
脉冲激光器发出的激光脉冲经WDM入射到待测传感光纤，激光脉冲在多模传感光纤中传播时发生自发拉曼散射，由此使得多模传感光纤的各个位置均产生的Stokes光和anti-Stokes光；其中在光纤中产生的后向Stokes光和anti-Stokes光经WDM首先分别到达第一APD、第一LNA和第二APD、第二LNA进行光电转换和放大，最后进入高速采集卡和计算机进行数据采集得到光纤沿线的Stokes光和anti-Stokes光的位置和光强信息。
在测温前，需将全部传感光纤放置在恒温下进行定标处理，定标阶段总共进行两次定标过程。数据采集卡第一次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000001
式中，K s、K a和K r为与光纤散射端截面有关的系数，V s、V a和V 0为斯托克斯光、反斯托克斯光和入射光的频率，h、k分别为普朗克常数和玻尔兹曼常数，Δv为光纤的拉曼频移量为13.2THz，α s、α a、α 0分别为Stokes光、anti-Stokes光和瑞利散射光在光纤中单位长度下的衰减系数；T c0表示第一次定标阶段待测传感光纤的温度值；l表示该位置与多模传感光纤的前端之间的距离，P 0为入射光的强度。
数据采集卡第二次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000002
式中，T c1表示第二次定标阶段待测传感光纤的温度值。
步骤三、测量阶段Stokes光和anti-Stokes光的信号处理
数据采集卡测量阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000003
式中，T表示测量阶段待测传感光纤1处的温度值。
步骤四、面向分布式光纤拉曼传感***的高精度温度解调方法
公式(3)减去公式(1)可得：
Figure PCTCN2019000087-appb-000004
公式(3)减去公式(2)可得：
Figure PCTCN2019000087-appb-000005
公式(4)与公式(5)做比值可得：
Figure PCTCN2019000087-appb-000006
公式(6)化解后可得
Figure PCTCN2019000087-appb-000007
与现有分布式光纤传感***相比，本发明所述的面向光纤拉曼传感***的自校准温度检测装置及温度解调方法具有如下优点：
第一、本发明在无增加任何器件的基础上，创造性的利用两次定标数据和测温数据进行温度解调，避免了瑞利噪声对测温结果的影响，有望使其测温精度达到±0.1℃以内。
第二、本发明的定标阶段在测量阶段的前期进行，定标完成后，后续测量时期无需重复进行定标，加快了分布式光纤传感***更加便捷的面向工业化的进程。
本发明设计合理，有效解决了现有分布式光纤拉曼测温***中的由于瑞利光串扰导致***的测温精度低的问题，有望使其测温精度达到±0.1℃以内，适用于分布式光纤拉曼测温***。
附图说明
图1表示本发明中面向分布式光纤拉曼传感***的高精度检测装置示意图。
图中：1-脉冲激光器，2-WDM(波分复用器1550nm/1450nm/1650nm)，3-待测传感光纤，4-第一APD(雪崩光电二极管)，5-第二APD(雪崩光电二极管)，6-第一LNA(低噪放大器)，7-第二LNA(低噪放大器)，8-高速数据采集卡，9-计算机。
具体实施方式
下面结合附图对本发明的具体实施例进行详细说明。
一种面向分布式光纤拉曼传感***的高精度温度解调方法由以下装置来实现。该装置包括1550nm大功率脉冲激光器、波分复用器(WDM)、2个雪崩光电二极管(APD)、2个低噪放大器(LNA)、待测传感光纤(普通多模光纤)、数据采集卡和计算机。
具体方法分为以下四个步骤。
步骤一、搭建面向分布式光纤拉曼传感***的高精度温度检测装置
如图1所示，光纤拉曼测温仪包括脉冲激光器、WDM、2个APD、2个LNA、数据采集卡、计算机；其中，脉冲激光器1的输出端与WDM 2的输入端连接。待测传感光纤3的输入端与WDM 2的公共端连接。WDM 2的2个输出端分别与第一APD 4和第二APD 5的输入端连接；第一APD 4的输出端与第一LNA 6的输入端连接；第二APD 5的输出端与第二LNA 7的输入端连接；第一LNA 6和第二LNA 7的输出端与数据采集卡8的输入端连接；数据采集卡8的输出端与计算机9的输入端连接。
具体实施时，脉冲激光器的波长为1550nm、脉宽为10ns、重复频率为8KHz。WDM的工作波长为1550nm/1450nm/1663nm。APD的带宽为100MHz、光谱响应范围为900～1700nm。LNA的带宽为100MHz。数据采集卡的通道数为4、采样率为100M/s、带宽为100MHz。待测传感光纤为普通多模光纤。
步骤二、定标阶段Stokes光和anti-Stokes光的信号处理
启动光纤拉曼测温仪，大功率脉冲激光器发出的激光脉冲经WDM入射到待测传感光纤；激光脉冲在待测传感光纤中传播时发生自发拉曼散射，由此使得多模传感光纤的各个位置均产生的Stokes光和anti-Stokes光。
其中，Stokes光依次经WDM、第一APD、第一LNA入射到数据采集卡，数据采集卡对Stokes光进行模数转换，由此得到Stokes光的光强曲线。
anti-Stokes光依次经WDM、第二APD、第二LNA入射到数据采集卡，数据采集卡对anti-Stokes光进行模数转换，由此得到anti-Stokes光的光强曲线。
在测温前，需将全部传感光纤放置在恒温下进行定标处理，定标阶段总共进行两次定标过程。数据采集卡第一次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000008
式中，K s、K a和K r为与光纤散射端截面有关的系数，V s、V a和V 0为斯托克斯光、反斯托克斯光和入射光的频率，h、k分别为普朗克常数和玻尔兹曼常数，Δv为光纤的拉曼频移量为13.2THz，α s、α a、α 0分别为Stokes光、anti-Stokes光和瑞利散射光在光纤中单位长度下的衰减系数；T c0表示第一次定标阶段待测传感光纤的温度值；l表示该位置与多模传感光纤的前端之间的距离，P 0为入射光的强度。
数据采集卡第二次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000009
式中，T c1表示第二次定标阶段待测传感光纤的温度值。
步骤三、测量阶段Stokes光和anti-Stokes光的信号处理
数据采集卡测量阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
Figure PCTCN2019000087-appb-000010
式中，T表示测量阶段待测传感光纤l处的温度值。
步骤四、面向分布式光纤拉曼传感***的高精度温度解调方法
公式(10)减去公式(8)可得：
Figure PCTCN2019000087-appb-000011
公式(10)减去公式(9)可得：
Figure PCTCN2019000087-appb-000012
公式(12)与公式(11)做比值可得：
Figure PCTCN2019000087-appb-000013
公式(13)化解后可得
Figure PCTCN2019000087-appb-000014
最后所应说明的是，以上实施例仅用以说明本发明的技术方案而非限制，尽管参照本发明实施例进行了详细的说明，本领域的普通技术人员应当理解，对本发明的技术方案进行修改或者等同替换，都不脱离本发明的技术方案的精神和范围，均应涵盖本发明的权利要求保护范围中。

Claims (2)

  1. 一种面向分布式光纤拉曼传感器的高精度温度解调方法，其特征在于：包括如下步骤：
    步骤一、搭建面向分布式光纤拉曼传感***的高精度温度检测装置，包括脉冲激光器(1)，脉冲激光器(1)的输出端与WDM(2)的输入端连接；WDM(2)的2个输出端分别与第一APD(4)和第二APD(5)的输入端连接；第一APD(4)的输出端与第一LNA(6)的输入端连接；第二APD(5)的输出端与第二LNA(7)的输入端连接；第一LNA(6)和第二LNA(7)的输出端与数据采集卡(8)的输入端连接；数据采集卡(8)的输出端与计算机(9)的输入端连接；WDM(2)的公共端与待测传感光纤(3)的输入端连接；
    步骤二、定标阶段Stokes光和anti-Stokes光的信号处理
    脉冲激光器发出的激光脉冲经WDM入射到待测传感光纤，激光脉冲在多模传感光纤中传播时发生自发拉曼散射，由此使得待测传感光纤的各个位置均产生的Stokes光和anti-Stokes光；其中在光纤中产生的后向Stokes光和anti-Stokes光经WDM首先分别到达第一APD、第一LNA和第二APD、第二LNA进行光电转换和放大，最后进入高速采集卡和计算机进行数据采集得到光纤沿线的Stokes光和anti-Stokes光的位置和光强信息；
    在测温前，将全部待测传感光纤放置在恒温下进行定标处理，定标阶段总共进行两次定标过程；数据采集卡第一次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
    Figure PCTCN2019000087-appb-100001
    式中，K s、K a和K r为与光纤散射端截面有关的系数，V s、V a和V 0为 斯托克斯光、反斯托克斯光和入射光的频率，h、k分别为普朗克常数和玻尔兹曼常数，Δv为光纤的拉曼频移量为13.2THz，α s、α a、α 0分别为Stokes光、anti-Stokes光和瑞利散射光在光纤中单位长度下的衰减系数；T c0表示第一次定标阶段待测传感光纤的温度值；l表示该位置与待测传感光纤的前端之间的距离，P 0为入射光的强度；
    数据采集卡第二次定标阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
    Figure PCTCN2019000087-appb-100002
    式中，T c1表示第二次定标阶段待测传感光纤的温度值；
    步骤三、测量阶段Stokes光和anti-Stokes光的信号处理
    数据采集卡测量阶段得到anti-Stokes光和Stokes光的后向散射光强曲线，其光强比值表示为：
    Figure PCTCN2019000087-appb-100003
    式中，T表示测量阶段待测传感光纤l处的温度值；
    步骤四、面向分布式光纤拉曼传感***的高精度温度解调方法
    公式(3)减去公式(1)可得：
    Figure PCTCN2019000087-appb-100004
    公式(3)减去公式(2)可得：
    Figure PCTCN2019000087-appb-100005
    公式(4)与公式(5)做比值可得：
    Figure PCTCN2019000087-appb-100006
    公式(6)化解后可得
    Figure PCTCN2019000087-appb-100007
  2. 根据权利要求1所述的一种面向分布式光纤拉曼传感器的高精度温度解调方法，其特征在于：所述脉冲激光器的波长为1550nm、脉宽为10ns、重复频率为8KHz；
    所述WDM的工作波长为1550nm/1450nm/1663nm；
    所述APD的带宽为100MHz、光谱响应范围为900～1700nm；
    所述LNA的带宽为100MHz；
    所述数据采集卡的通道数为4、采样率为100M/s、带宽为100MHz；
    所述待测传感光纤为普通多模光纤。
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