CN107436201A - Distributed fiber optic temperature strain sensing system and method based on Brillouin scattering - Google Patents
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Abstract
本发明公开了一种基于布里渊散射的分布式光纤温度应变传感系统及方法，采用分布式反馈激光器发出窄线宽的连续光后经光电调制器外调制成脉冲光，之后采用掺铒光纤放大器进行放大，被放大的脉冲光作为入射光进入传感光纤以获得该光纤中的布里渊后向散射信号。本发明采用单端输入的方式来获得布里渊散射信号，便于系统的安装使用；提出了采用同源外差干涉法来解调信号，避免了一般干涉法对两束光强度相近的要求，简化了测试系统；采取一定措施来加强信号，以便于后续处理；同时应用电方法来同时得到布里渊频移和强度的变化，对温度和应变进行解调，实现对二者的同时测量。
The invention discloses a distributed optical fiber temperature strain sensing system and method based on Brillouin scattering. Distributed feedback lasers are used to emit continuous light with a narrow line width, and then externally modulated into pulsed light by a photoelectric modulator, and then erbium-doped The fiber amplifier performs amplification, and the amplified pulsed light enters the sensing fiber as incident light to obtain the Brillouin backscattering signal in the fiber. The invention adopts single-ended input to obtain the Brillouin scattering signal, which is convenient for installation and use of the system; it proposes the use of homologous heterodyne interferometry to demodulate the signal, which avoids the requirement of similar intensity of two beams of light in general interferometry, The test system is simplified; certain measures are taken to strengthen the signal for subsequent processing; at the same time, the electrical method is applied to obtain the Brillouin frequency shift and the change of the intensity at the same time, and the temperature and strain are demodulated to realize the simultaneous measurement of the two.
Description
技术领域technical field
本发明涉及分布式光纤传感领域，具体是一种基于布里渊散射的分布式光纤温度应变传感系统及方法。The invention relates to the field of distributed optical fiber sensing, in particular to a distributed optical fiber temperature and strain sensing system and method based on Brillouin scattering.
背景技术Background technique
分布式光纤传感系统可以定义为：能在连续的光纤长度上，以距离的连续函数的形式传感出被测参数随光纤长度方向变化的仪器或者系统。分布式温度、应力传感系统通常是将光纤沿温度场、应力场排布，测量光在光纤中传输时产生的携带温度、应力信息的散射光，同时采用光时域反射计OTDR(Optical Time Domain Reflectometer)技术，就可以对沿光纤传输路径上的温度、应力空间分布和随时间变化的信息进行测量和监控。A distributed optical fiber sensing system can be defined as an instrument or system that can sense the change of the measured parameter with the direction of the fiber length in the form of a continuous function of distance on a continuous fiber length. The distributed temperature and stress sensing system usually arranges the optical fiber along the temperature field and the stress field, and measures the scattered light carrying temperature and stress information generated when the light is transmitted in the optical fiber. Domain Reflectometer) technology can measure and monitor the temperature, stress spatial distribution and time-varying information along the optical fiber transmission path.
基于布里渊散射的分布式传感技术研究起步较晚，但由于它在温度、应变测量上所达到的测量精度、测量范围以及空间分辨率均高于其他分布式光纤传感技术，因此这种技术在目前得到广泛关注与研究，也被很好地应用于隧道变形监测、大坝结构健康监测和大型民用工程结构健康监测等等。目前尚未有效解决的问题主要有：一是光纤单端测量系统安装方便但信号弱检测困难，而双端测量系统安装不便；二是由于光纤中光学支声子的寿命短，致使为了精确测量布里渊散射光频移则入射光的脉宽要远大于声子的寿命，这就导致低的空间分辨率；三是没有经济有效的方法来解调温度和应变两大参数。这使得基于布里渊散射的分布式传感系统性能指标无法进一步大幅提升，也使得该技术无法大规模商用化。The research on distributed sensing technology based on Brillouin scattering started late, but because its measurement accuracy, measurement range and spatial resolution in temperature and strain measurement are higher than other distributed optical fiber sensing technologies, so this This technology has received extensive attention and research at present, and has also been well used in tunnel deformation monitoring, dam structural health monitoring, and large-scale civil engineering structural health monitoring, etc. The main problems that have not been effectively solved at present are: first, the single-ended optical fiber measurement system is easy to install but difficult to detect weak signals, and the double-ended measurement system is inconvenient to install; The frequency shift of Liouin scattered light means that the pulse width of the incident light is much longer than the lifetime of the phonon, which leads to low spatial resolution; third, there is no cost-effective method to demodulate the two parameters of temperature and strain. This prevents the performance index of the distributed sensing system based on Brillouin scattering from being greatly improved, and also prevents the technology from being commercialized on a large scale.
发明内容Contents of the invention
针对现有技术中存在的不足，发明提供了一种基于布里渊散射的分布式光纤温度应变传感系统，旨在解决现有技术中布里渊散射光信号检测困难的问题，检测信号弱或安装复杂、制造成本高的问题，以及温度和应变解调成本高且不适用的问题。Aiming at the deficiencies in the prior art, the invention provides a distributed optical fiber temperature and strain sensing system based on Brillouin scattering, which aims to solve the problem of difficult detection of Brillouin scattering light signals in the prior art, and the detection signal is weak Or the problem of complicated installation and high manufacturing cost, and the problem of high cost and inapplicability of temperature and strain adjustment.
本发明的技术方案为：Technical scheme of the present invention is:
一种基于布里渊散射的分布式光纤温度应变传感系统，包括：A distributed optical fiber temperature and strain sensing system based on Brillouin scattering, comprising:
激光器、第一耦合器、光电调制器、掺铒光纤放大器、环形器、传感光纤、拉曼滤波器、第二耦合器、第一光电探测器、低通滤波器、放大器、第三耦合器、第二光电探测器、射频放大器、高通滤波器、功率分束器、第一微波探测器、第一低频放大器、频率-强度转换器、第二微波探测器、第二低频放大器和数据处理模块；Laser, first coupler, optoelectronic modulator, erbium-doped fiber amplifier, circulator, sensing fiber, Raman filter, second coupler, first photodetector, low-pass filter, amplifier, third coupler , a second photodetector, a radio frequency amplifier, a high pass filter, a power splitter, a first microwave detector, a first low frequency amplifier, a frequency-intensity converter, a second microwave detector, a second low frequency amplifier and a data processing module ;
激光器产生的入射光经第一耦合器后分为第一支路与第二支路，第一支路的出射光依次通过光电调制器、掺铒光纤放大器、环形器、传感光纤后产生后向散射光，后向散射光经过拉曼滤波器后被第二耦合器分成第三支路与第四支路；第三支路的出射光依次经过第一光电探测器、低通滤波器、放大器后由数据处理模块采集与处理，得到第一通道数据；第四支路的出射光与第二支路的出射光在第三耦合器中进行耦合，耦合出射光进入第二光电探测器中进行同源外差干涉，然后再经过射频放大器、高通滤波器后在功率分束器中进行功率分配，经功率分配后的出射光分为两路输出，第一输出的出射光进入第一微波探测器，然后经第一低频放大器后由数据处理模块采集与处理，得到第二通道数据；第二输出的出射光先经过频率-强度转换器，再经过第二微波探测器和第二低频放大器后由数据处理模块采集与处理，得到第三通道数据。The incident light generated by the laser is divided into the first branch and the second branch after passing through the first coupler. The backscattered light is divided into the third branch and the fourth branch by the second coupler after passing through the Raman filter; the outgoing light of the third branch passes through the first photodetector, low-pass filter, After the amplifier, it is collected and processed by the data processing module to obtain the first channel data; the outgoing light of the fourth branch and the outgoing light of the second branch are coupled in the third coupler, and the coupled outgoing light enters the second photodetector Carry out homogeneous heterodyne interference, and then perform power distribution in the power beam splitter after passing through the RF amplifier and high-pass filter. The outgoing light after power distribution is divided into two outputs, and the outgoing light of the first output enters the first microwave The detector is then collected and processed by the data processing module after the first low-frequency amplifier to obtain the second channel data; the outgoing light of the second output first passes through the frequency-intensity converter, and then passes through the second microwave detector and the second low-frequency amplifier Afterwards, it is collected and processed by the data processing module to obtain the third channel data.
其中，第一支路的出射光通过电光调制器与掺铒光纤放大器连接；掺铒光纤放大器和环形器的第一端口相连；环形器的第二端口一端接入传感光纤，环形器的第三端口与拉曼滤波器相连；拉曼滤波器的输出端与第二耦合器的输入端连接；第二耦合器的第一输出端依次与第一光电探测器、低通滤波器、放大器和数据处理模块；Wherein, the outgoing light of the first branch is connected with the erbium-doped fiber amplifier through the electro-optic modulator; the erbium-doped fiber amplifier is connected with the first port of the circulator; The three ports are connected with the Raman filter; the output end of the Raman filter is connected with the input end of the second coupler; the first output end of the second coupler is connected with the first photodetector, low-pass filter, amplifier and Data processing module;
第三耦合器同时接收第二耦合器的第二输出端出射光和第二支路的出射光，第三耦合器的输出端依次与第二光电探测器、射频放大器、高通滤波器和功率分束器相连，经功率分配后的出射光分为两路输出，第一输出的出射光进入第一微波探测器，然后通过第一低频放大器与数据处理模块相连；第二输出的出射光进入频率-强度转换器，然后依次通过第二微波探测器、第二低频放大器后与数据处理模块相连。The third coupler simultaneously receives the outgoing light from the second output end of the second coupler and the outgoing light from the second branch, and the output end of the third coupler is sequentially connected with the second photodetector, radio frequency amplifier, high-pass filter and power splitter. The outgoing light after power distribution is divided into two outputs. The outgoing light of the first output enters the first microwave detector, and then connects with the data processing module through the first low-frequency amplifier; the outgoing light of the second output enters the frequency -The intensity converter is then connected to the data processing module after passing through the second microwave detector and the second low-frequency amplifier in sequence.
进一步的，所述激光器为分布式反馈激光器。Further, the laser is a distributed feedback laser.
进一步的，所述第一耦合器的分光比为98:2；所述第二耦合器和第三耦合器的分光比为75:25。Further, the light splitting ratio of the first coupler is 98:2; the light splitting ratio of the second coupler and the third coupler is 75:25.
进一步的，所述光电调制器采用铌酸锂强度调制器，用于激光器输出的连续光以便得到合适的脉冲光。Further, the photoelectric modulator adopts a lithium niobate intensity modulator, which is used for the continuous light output by the laser to obtain suitable pulsed light.
进一步的，掺铒光纤放大器的工作泵浦光源为980nm波长的双向泵浦光源。Further, the working pumping light source of the erbium-doped fiber amplifier is a bidirectional pumping light source with a wavelength of 980nm.
进一步的，第一光电探测器的频率响应为125MHz以上，第二光电探测器为3kHz-12GHz。Further, the frequency response of the first photodetector is above 125MHz, and the frequency response of the second photodetector is 3kHz-12GHz.
本发明还提出了一种采用上述系统的分布式光纤温度应变传感测量方法，包括：The present invention also proposes a distributed optical fiber temperature strain sensing measurement method using the above system, including:
根据第一通道数据和第二通道数据得到布里渊散射光强度；根据第二通道数据和第三通道数据的得到布里渊频移，即得到由传感光纤感受到的温度变化或应变引起的布里渊后向散射光的强度变化和频移变化，通过布里渊散射光强度得到温度的变化值，再根据所述频移变化和温度的变化值得到传感光纤所感受的应变，实现对温度和应变的同时测量。According to the first channel data and the second channel data, the Brillouin scattered light intensity is obtained; according to the second channel data and the third channel data, the Brillouin frequency shift is obtained, which is caused by the temperature change or strain felt by the sensing fiber The intensity change and frequency shift change of the Brillouin backscattered light, the temperature change value is obtained through the Brillouin scattered light intensity, and the strain felt by the sensing fiber is obtained according to the frequency shift change and temperature change value, Realize simultaneous measurement of temperature and strain.
进一步的，所述根据第一通道数据和第二通道数据得到布里渊散射光强度包括：Further, said obtaining Brillouin scattered light intensity according to the first channel data and the second channel data includes:
根据第一通道数据和第二通道数据首先获得包括瑞利散射光强度和布里渊散射光强度在内的光电流，基于瑞利散射光、布里渊散射光的电磁场表达式，分离得出布里渊散射光强度。According to the data of the first channel and the second channel, the photocurrent including the intensity of Rayleigh scattered light and the intensity of Brillouin scattered light is firstly obtained, and based on the electromagnetic field expressions of Rayleigh scattered light and Brillouin scattered light, the distribution can be obtained by separating Rieouin scattered light intensity.
进一步的，所述第一通道数据为直流信号，第二通道数据和第三通道数据为交流信号。Further, the first channel data is a DC signal, and the second channel data and the third channel data are AC signals.
本发明的有益效果：Beneficial effects of the present invention:
与现有技术相比，本发明采用同源外差干涉方法来解调信号，并且该种方法为同源外差干涉，采用同源外差干涉避免了一般干涉对两束光强度相近的要求，简化了测试系统；使用从光源中分离出一小束与瑞利散射光同频率的光来加强后向散射光解决输入光脉冲宽度和空间分辨率的矛盾，避免使用高精度的滤光器；采用电方法来分辨布里渊散射信号的频移和强度变化，进而解调出温度和应变，相比于传统方法，可在消除光源不稳或光路扰动等外界因素影响的前提下降低成本。Compared with the prior art, the present invention adopts the homologous heterodyne interference method to demodulate the signal, and this method is homologous heterodyne interference, which avoids the requirement that the two beams of light intensities are similar in general interference by using homologous heterodyne interference , Simplify the test system; use a small beam of light with the same frequency as the Rayleigh scattered light from the light source to strengthen the backscattered light to solve the contradiction between the input light pulse width and spatial resolution, and avoid the use of high-precision filters ; Using the electrical method to distinguish the frequency shift and intensity change of the Brillouin scattering signal, and then demodulate the temperature and strain, compared with the traditional method, it can reduce the cost on the premise of eliminating the influence of external factors such as light source instability or optical path disturbance .
附图说明Description of drawings
图1是本发明实施例提供的基于布里渊散射的分布式光纤温度应变传感系统的结构图。Fig. 1 is a structural diagram of a distributed optical fiber temperature and strain sensing system based on Brillouin scattering provided by an embodiment of the present invention.
图2是本发明实施例提供的解调温度应变的电方法的电路部分结构图。Fig. 2 is a partial circuit diagram of an electrical method for demodulating temperature strain provided by an embodiment of the present invention.
图3是本发明实施例提供的系统测试结果图。FIG. 3 is a diagram of system test results provided by an embodiment of the present invention.
其中，分布式反馈激光器1、第一耦合器2、光电调制器3、掺铒光纤放大器4、环形器5、传感光纤6、拉曼滤波器7、第二耦合器8、第一光电探测器9、低通滤波器10、放大器11、第三耦合器12、第二光电探测器13、射频放大器14、高通滤波器15、功率分束器16、第一微波探测器17、第一低频放大器18、频率-强度转换器19、第二微波探测器20、第二低频放大器21和数据处理模块22。Among them, the distributed feedback laser 1, the first coupler 2, the photoelectric modulator 3, the erbium-doped fiber amplifier 4, the circulator 5, the sensing fiber 6, the Raman filter 7, the second coupler 8, the first photodetector device 9, low pass filter 10, amplifier 11, third coupler 12, second photodetector 13, radio frequency amplifier 14, high pass filter 15, power beam splitter 16, first microwave detector 17, first low frequency Amplifier 18 , frequency-intensity converter 19 , second microwave detector 20 , second low-frequency amplifier 21 and data processing module 22 .
具体实施方式：detailed description:
下面结合附图与实施例对本发明作进一步说明：Below in conjunction with accompanying drawing and embodiment the present invention will be further described:
应该指出，以下详细说明都是例示性的，旨在对本申请提供进一步的说明。除非另有指明，本文使用的所有技术和科学术语具有与本申请所属技术领域的普通技术人员通常理解的相同含义。It should be pointed out that the following detailed description is exemplary and intended to provide further explanation to the present application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
需要注意的是，这里所使用的术语仅是为了描述具体实施方式，而非意图限制根据本申请的示例性实施方式。如在这里所使用的，除非上下文另外明确指出，否则单数形式也意图包括复数形式，此外，还应当理解的是，当在本说明书中使用术语“包含”和/或“包括”时，其指明存在特征、步骤、操作、器件、组件和/或它们的组合。It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural, and it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, they mean There are features, steps, operations, means, components and/or combinations thereof.
同源外差干涉是指：使用从光源中分离出的一小束光与瑞利散射光作为同源的相干光，进行干涉，加强后向散射光，解决了输入光脉冲宽度和空间分辨率的矛盾，可以避免使用高精度的滤光器。Homologous heterodyne interference refers to: use a small beam of light separated from the light source and Rayleigh scattered light as coherent light of the same source to interfere, strengthen the back scattered light, and solve the problem of input light pulse width and spatial resolution Contradictions can be avoided by using high-precision filters.
正如前文所述的，基于布里渊散射的分布式光纤传感系统目前还存在尚未有效解决的问题主要有：一是光纤单端测量系统安装方便但信号弱检测困难，而双端测量系统安装不便；二是由于光纤中光学支声子的寿命短，致使为了精确测量布里渊散射光频移则入射光的脉宽要远大于声子的寿命，这就导致低的空间分辨率；三是没有经济有效的方法来解调温度和应变两大参数。As mentioned above, the distributed optical fiber sensing system based on Brillouin scattering still has problems that have not been effectively solved. The main problems are: first, the single-ended optical fiber measurement system is easy to install but weak signal detection is difficult, while the double-ended measurement system is installed Inconvenient; second, due to the short lifetime of the optical branch phonons in the optical fiber, in order to accurately measure the frequency shift of the Brillouin scattered light, the pulse width of the incident light is much longer than the lifetime of the phonons, which leads to low spatial resolution; There is no cost-effective way to detune the two parameters of temperature and strain.
为了解决上述问题，本发明的一种典型实施例是：In order to solve the above problems, a typical embodiment of the present invention is:
传感系统包括：分布式反馈激光器1、第一耦合器2、光电调制器3、掺铒光纤放大器4、环形器5、传感光纤6、拉曼滤波器7、第二耦合器8、第一光电探测器9、低通滤波器10、放大器11、第三耦合器12、第二光电探测器13、射频放大器14、高通滤波器15、功率分束器16、第一微波探测器17、第一低频放大器18、频率-强度转换器19、第二微波探测器20、第二低频放大器21和数据处理模块22；第一耦合器2的输入端连接激光器1，光电调制器3的输入端连接至第一耦合器2的第一输出端，掺铒光纤放大器4的输入端连接至光电调制器3的输出端，环形器5的第一端口连接至掺铒光纤放大器4的输出端，传感光纤6连接至环形器5的第二端口，拉曼滤波器7的输入端连接至环形器5的第三端口，第二耦合器8的输入端连接至拉曼滤波器7的输出端，第一光电探测器9的输入端连接至第二耦合器8的第一输出端，低通滤波器10的输入端连接至第一光电探测器9的输出端，放大器11的输入端连接至低通滤波器10的输出端，放大器11的输出端连接数据处理模块22；The sensing system includes: distributed feedback laser 1, first coupler 2, photoelectric modulator 3, erbium-doped fiber amplifier 4, circulator 5, sensing fiber 6, Raman filter 7, second coupler 8, the first A photodetector 9, a low-pass filter 10, an amplifier 11, a third coupler 12, a second photodetector 13, a radio frequency amplifier 14, a high-pass filter 15, a power beam splitter 16, a first microwave detector 17, First low-frequency amplifier 18, frequency-intensity converter 19, second microwave detector 20, second low-frequency amplifier 21 and data processing module 22; the input end of the first coupler 2 is connected to the laser 1, and the input end of the photoelectric modulator 3 Connected to the first output end of the first coupler 2, the input end of the erbium-doped fiber amplifier 4 is connected to the output end of the photoelectric modulator 3, the first port of the circulator 5 is connected to the output end of the erbium-doped fiber amplifier 4, and the transmission The sensing fiber 6 is connected to the second port of the circulator 5, the input end of the Raman filter 7 is connected to the third port of the circulator 5, and the input end of the second coupler 8 is connected to the output end of the Raman filter 7, The input end of the first photodetector 9 is connected to the first output end of the second coupler 8, the input end of the low-pass filter 10 is connected to the output end of the first photodetector 9, and the input end of the amplifier 11 is connected to the low The output end of pass filter 10, the output end of amplifier 11 is connected to data processing module 22;
第三耦合器12的第一输入端连接至第二耦合器8的第二输出端，第三耦合器12的第二输入端连接至第一耦合器2的第二输出端，第二光电探测器13的输入端连接至第三耦合器12的输出端，射频放大器14的输入端连接至第二光电探测器13的输出端，高通滤波器15的输入端连接至射频放大器14的输出端，功率分束器16的输入端连接至高通滤波器15的输出端，第一微波探测器17的输入端连接至功率分束器16的第一输出端，第一低频放大器18的输入端连接至第一微波探测器17的输出端，第一低频放大器18的输出端连接数据处理模块22；The first input end of the third coupler 12 is connected to the second output end of the second coupler 8, the second input end of the third coupler 12 is connected to the second output end of the first coupler 2, and the second photoelectric detection The input end of device 13 is connected to the output end of the third coupler 12, the input end of radio frequency amplifier 14 is connected to the output end of second photodetector 13, the input end of high pass filter 15 is connected to the output end of radio frequency amplifier 14, The input end of the power beam splitter 16 is connected to the output end of the high-pass filter 15, the input end of the first microwave detector 17 is connected to the first output end of the power beam splitter 16, and the input end of the first low frequency amplifier 18 is connected to The output end of the first microwave detector 17, the output end of the first low frequency amplifier 18 is connected to the data processing module 22;
频率-强度转换器19的输入端连接至功率分束器16的第二输出端，第二微波探测器20的输入端连接至频率-强度转换器19的输出端，第二低频放大器21的输入端连接至第二微波探测器20的输出端，第二低频放大器21的输出端连接数据处理模块22。The input end of the frequency-intensity converter 19 is connected to the second output end of the power beam splitter 16, the input end of the second microwave detector 20 is connected to the output end of the frequency-intensity converter 19, and the input end of the second low frequency amplifier 21 The terminal is connected to the output terminal of the second microwave detector 20 , and the output terminal of the second low frequency amplifier 21 is connected to the data processing module 22 .
激光器为分布式反馈激光器；第一耦合器的分光比为98:2；所述第二耦合器和第三耦合器的分光比为75:25；光电调制器选用铌酸锂强度调制器来调制激光器输出的连续光以便得到合适的脉冲光；掺铒光纤放大器结构上应选择980nm波长的双向泵浦；第一光电探测器为125MHz，第二光电探测器为3kHz-12GHz。The laser is a distributed feedback laser; the splitting ratio of the first coupler is 98:2; the splitting ratio of the second coupler and the third coupler is 75:25; the photoelectric modulator is modulated by a lithium niobate intensity modulator The continuous light output by the laser is used to obtain suitable pulsed light; the structure of the erbium-doped fiber amplifier should choose bidirectional pumping with a wavelength of 980nm; the first photodetector is 125MHz, and the second photodetector is 3kHz-12GHz.
激光器1输出的光经第一耦合器2分成第一路光和第二路光；第一路光依次通过光电调制器3、掺铒光纤放大器4、环形器5、传感光纤6后产生后向散射光，散射光经过拉曼滤波器7后被第二耦合器8分成第三路光和第四路光；第三路光依次经过第一光电探测器9、低通滤波器10、放大器11后由数据处理模块22进行数据采集与处理，为通道①数据；第四路光与第二路光在第三耦合器12中进行混合，混合光进入第二光电探测器13中进行同源外差干涉，再经过射频放大器14、高通滤波器15后在率分束器16中进行功率分配，一路直接进入第一微波探测器17，然后经第一低频放大器18后由数据处理模块22进行数据采集与处理，为通道②数据；另一路先经过频率-强度转换器19，进而经过第二微波探测器20和第二低频放大器21后由数据处理模块22进行数据采集与处理，为通道③数据。The light output by the laser 1 is divided into the first light and the second light through the first coupler 2; The scattered light is divided into the third light and the fourth light by the second coupler 8 after passing through the Raman filter 7; the third light passes through the first photodetector 9, the low-pass filter 10, the amplifier in turn After 11, the data processing module 22 performs data collection and processing, which is channel ① data; the fourth light and the second light are mixed in the third coupler 12, and the mixed light enters the second photodetector 13 for homologous Heterodyne interference, after passing through the radio frequency amplifier 14 and the high-pass filter 15, the power distribution is carried out in the rate beam splitter 16, and all the way directly enters the first microwave detector 17, and is then processed by the data processing module 22 after passing through the first low frequency amplifier 18 Data acquisition and processing is channel ② data; the other channel first passes through the frequency-intensity converter 19, then passes through the second microwave detector 20 and the second low-frequency amplifier 21, and then the data processing module 22 performs data acquisition and processing, which is channel ③ data.
在光纤中的散射光主要包括瑞利散射光、布里渊散射光和拉曼散射光。由于拉曼和瑞利散射光的中心波长差异很大，约为100nm，因此一般的光滤波器便可用于滤除拉曼散射光，这样后向散射光中只有瑞利和布里渊散射光。布里渊散射光包括斯托克斯成分和反斯托克斯成分，然而，若是自发布里渊散射光，仅仅检测布里渊频移时，利用本发明中的检测方法，无需考虑反斯托克斯成分，因为在布里渊散射光中，温度和应变变化引起的斯托克斯成分和反斯托克斯成分的移动方向是一致的；若是受激布里渊散射，在布里渊散射光中，相较于斯托克斯成分而言，反斯托克斯成分相当微弱，所以反斯托克斯成分可以被忽略。总之，12GHz的高频率探测器的交流输出端口只输出布里渊斯托克斯和瑞利散射光的干涉交流信号。The scattered light in the optical fiber mainly includes Rayleigh scattered light, Brillouin scattered light and Raman scattered light. Since the central wavelengths of Raman and Rayleigh scattered light are very different, about 100nm, general optical filters can be used to filter out Raman scattered light, so that only Rayleigh and Brillouin scattered light are included in the backscattered light. The Brillouin scattered light includes Stokes components and anti-Stokes components, however, if the spontaneous Brillouin scattered light only detects the Brillouin frequency shift, the detection method of the present invention does not need to consider the anti-Stokes Stokes components, because in the Brillouin scattered light, the Stokes components and anti-Stokes components caused by temperature and strain changes move in the same direction; if stimulated Brillouin scattering, in the Brillouin In the abyss scattered light, the anti-Stokes component is quite weak compared with the Stokes component, so the anti-Stokes component can be ignored. In short, the AC output port of the 12GHz high-frequency detector only outputs the interference AC signal of Brillouin Stokes and Rayleigh scattered light.
假设瑞利散射光的电磁场和布里渊散射(斯托克斯成份)光的电磁场如下：ER(t)＝ER cos(ωRt+φR)，EB(t)＝EB cos(ωRt+φB)……(1)其中R表示瑞利散射光，B表示布里渊散射光。鉴于频带为10KHz-12GHz的高频光探测器的光谱相应特性和频率响应特性，可以得到输出光电流为：Assume that the electromagnetic field of Rayleigh scattered light and that of Brillouin scattered (Stokes component) light are as follows: E R (t) = E R cos(ω R t + φ R ), E B (t) = E B cos (ω R t + φ B )...(1) where R represents Rayleigh scattered light, and B represents Brillouin scattered light. In view of the spectral response characteristics and frequency response characteristics of the high-frequency photodetector with a frequency band of 10KHz-12GHz, the output photocurrent can be obtained as:
这样就可以从高频探测器的交流输出端口得到与布里渊频移有关的交流信号了。In this way, the AC signal related to the Brillouin frequency shift can be obtained from the AC output port of the high frequency detector.
在本发明所采用的同源外差干涉的方法中，无论瑞利散射光还是布里渊散射光得到加强都能使得外差干涉信号加强，鉴于传感光纤中的后向散射光很弱，采用从光源中分离一小部分光来加强信号光，即用98/2的第一光耦合器1从激光器中分离出2％的光与传感光纤的后向散射光合并后进入高频光电探测器中，从而达到加强干涉信号的目的。该方法的依据是，后向瑞利散射是弹性散射，频率不变，与原光源的频率一致。In the homologous heterodyne interference method adopted in the present invention, no matter whether the Rayleigh scattered light or the Brillouin scattered light is strengthened, the heterodyne interference signal can be strengthened. In view of the weak backscattered light in the sensing fiber, Separate a small part of the light from the light source to strengthen the signal light, that is, use the 98/2 first optical coupler 1 to separate 2% of the light from the laser and combine it with the backscattered light of the sensing fiber to enter the high-frequency photoelectric detector, so as to achieve the purpose of strengthening the interference signal. The basis of this method is that the backward Rayleigh scattering is elastic scattering, and the frequency is constant, which is consistent with the frequency of the original light source.
图2是本发明实施例提供的解调温度应变的电方法的电路部分结构图。在图2中通道①数据是直流部分(α是转换系数)，通道②和③数据是交流部分。通道②数据的信号随着后向散射光强度的变化而变化，与布里渊频移的变化无关。通道③数据的信号不仅与后向散射光强度的变化有关而且与布里渊频移有关。那么，就可以在计算机中根据通道①和通道②的数据通过计算得到瑞利散射光强度ER和布里渊散射光强度EB；另一方面，可以根据通道②和通道③的数据得到不受强度变化的布里渊频移。因此，可以得到由传感光纤感受到的温度变化或应变引起的布里渊后向散射光的强度变化和频移变化，并且不受光源不稳和光路弯曲等因素的影响。而应变所引起的布里渊散射光强度的变化十分微弱，比温度引起的布里渊散射光强度的变化小3个数量级，所以可忽略应变引起的布里渊散射光强度的变化。因此可以通过布里渊散射光强度的变化得到温度的变化值，然后再根据布里渊频移的变化和温度的变化得到传感光纤所感受的应变的大小。Fig. 2 is a partial circuit diagram of an electrical method for demodulating temperature strain provided by an embodiment of the present invention. In Figure 2, the data of channel ① is the DC part (α is the conversion coefficient), and the data of channels ② and ③ are the AC part. The signal of channel ② data changes with the change of backscattered light intensity, independent of the change of Brillouin frequency shift. The signal of channel ③ data is not only related to the change of backscattered light intensity but also related to the Brillouin frequency shift. Then, the Rayleigh scattered light intensity E R and the Brillouin scattered light intensity E B can be calculated in the computer according to the data of channel ① and channel ②; Brillouin frequency shift of intensity variation. Therefore, the intensity change and frequency shift change of the Brillouin backscattered light caused by the temperature change or strain felt by the sensing fiber can be obtained, and it is not affected by factors such as light source instability and optical path bending. The change of Brillouin scattered light intensity caused by strain is very weak, which is three orders of magnitude smaller than the change of Brillouin scattered light intensity caused by temperature, so the change of Brillouin scattered light intensity caused by strain can be ignored. Therefore, the change value of temperature can be obtained through the change of Brillouin scattered light intensity, and then the strain felt by the sensing fiber can be obtained according to the change of Brillouin frequency shift and the change of temperature.
图3是基于以上步骤，对本发明的系统进行实验验证得到的温度和应变随布里渊频移变化而变化的关系，验证了该系统所用方法的可行性，也充分说明该系统可以实现温度和应变的检测，而且所得系数与前任报道的系数一致性很好。Fig. 3 is based on the above steps, the relationship between the temperature and the strain obtained by the experimental verification of the system of the present invention varies with the Brillouin frequency shift, which verifies the feasibility of the method used in the system, and fully illustrates that the system can realize temperature and strain strain detection, and the obtained coefficients are in good agreement with those reported previously.
本发明考虑了布里渊散射光频移的大小决定于声波速度，因此传感光纤感受的温度和应变会影响光纤内部的声波速度，借此我们可以通过测量布里渊频移来得到传感光纤感受的温度或应变。另一方面，布里渊散射光的强度也受温度和应变的影响，所以通过测量布里渊散射光的频移和强度变化，并且解调就可以同时测量传感光纤感受的温度和应变。The present invention considers that the frequency shift of the Brillouin scattered light depends on the speed of the sound wave, so the temperature and strain felt by the sensing fiber will affect the speed of the sound wave inside the fiber, so that we can obtain the sensing value by measuring the Brillouin frequency shift. The temperature or strain experienced by an optical fiber. On the other hand, the intensity of Brillouin scattered light is also affected by temperature and strain, so by measuring the frequency shift and intensity change of Brillouin scattered light and demodulating, the temperature and strain felt by the sensing fiber can be measured simultaneously.
本发明提出了采用同源外差干涉方法来解调信号，避免了一般干涉对两束光强度相近的要求，简化了测试系统；使用从光源中分离出一小束与瑞利散射光同频率的光来加强后向散射光解决输入光脉冲宽度和空间分辨率的矛盾，避免使用高精度的滤光器；采用电方法来分辨布里渊散射信号的频移和强度变化，进而解调出温度和应变，相比于传统方法，可在消除光源不稳或光路扰动等外界因素影响的前提下降低成本。The present invention proposes the use of the same-source heterodyne interference method to demodulate the signal, which avoids the requirement that the two beams of light intensity are similar in general interference, and simplifies the test system; uses a small beam separated from the light source and has the same frequency as the Rayleigh scattered light The light to strengthen the backscattered light solves the contradiction between the input light pulse width and spatial resolution, and avoids the use of high-precision optical filters; the electrical method is used to distinguish the frequency shift and intensity change of the Brillouin scattering signal, and then demodulate the Temperature and strain, compared with traditional methods, can reduce the cost while eliminating the influence of external factors such as light source instability or optical path disturbance.
本发明采用的是基于布里渊散射的分布式光纤传感系统，所用技术包括但不仅限于光时域布里渊分析(BOTDA)法和光时域布里渊反射计(BOTDR)法等。The present invention adopts a distributed optical fiber sensing system based on Brillouin scattering, and the techniques used include but are not limited to the Brillouin Optical Time Domain Analysis (BOTDA) method and the Brillouin Optical Time Domain Reflectometer (BOTDR) method.
以上所述仅为本申请的优选实施例而已，并不用于限制本申请，对于本领域的技术人员来说，本申请可以有各种更改和变化。凡在本申请的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本申请的保护范围之内。The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.
Claims (10)
- A kind of 1. distributed fiber optic temperature strain sensing system based on Brillouin scattering, it is characterised in that including：Laser, the first coupler, electrooptic modulator, erbium-doped fiber amplifier, circulator, sensor fibre, Raman wave filter, Two couplers, the first photodetector, low pass filter, amplifier, the 3rd coupler, the second photodetector, radio frequency amplification It is device, high-pass filter, power splitter, the first microwave detector, the first low-frequency amplifier, frequency-strength converter, second micro- Wave detector, the second low-frequency amplifier and data processing module；Incident light caused by laser is divided into tie point and the second branch road after the first coupler, the emergent light of tie point according to It is secondary by producing rear orientation light after electrooptic modulator, erbium-doped fiber amplifier, circulator, sensor fibre, rear orientation light warp Cross after Raman wave filter and the 3rd branch road and the 4th branch road are divided into by the second coupler；The emergent light of 3rd branch road passes through first successively Gathered and handled by data processing module after photodetector, low pass filter, amplifier, obtain first passage data；4th The emergent light of branch road is coupled with the emergent light of the second branch road in the 3rd coupler, and coupling emergent light is visited into the second photoelectricity Survey in device and carry out homologous difference interference, then carry out work(in power splitter after radio frequency amplifier, high-pass filter again Rate is distributed, and the emergent light after power distribution is divided into two-way output, and the emergent light of the first output enters the first microwave detector, so Gathered by data processing module and handled by after the first low-frequency amplifier, obtain second channel data；The outgoing of second output Light first passes through frequency-strength converter, then by data processing module after the second microwave detector and the second low-frequency amplifier Collection and processing, obtain third channel data.
- 2. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In,The emergent light of tie point is connected by electrooptic modulator with erbium-doped fiber amplifier；Erbium-doped fiber amplifier and circulator First port be connected；Second port one end access sensor fibre of circulator, the 3rd port and the Raman wave filter of circulator It is connected；The output end of Raman wave filter is connected with the input of the second coupler；First output end of the second coupler successively with First photodetector, low pass filter, amplifier and data processing module；3rd coupler receives the second output end emergent light of the second coupler and the emergent light of the second branch road, the 3rd coupling simultaneously The output end of device is connected with the second photodetector, radio frequency amplifier, high-pass filter and power splitter successively, through power point Emergent light after matching somebody with somebody is divided into two-way output, and the emergent light of the first output enters the first microwave detector, then passes through the first low frequency Amplifier is connected with data processing module；The emergent light of second output enters frequency-strength converter, then passes sequentially through second It is connected after microwave detector, the second low-frequency amplifier with data processing module.
- 3. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In the laser is distributed feedback laser.
- 4. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In the splitting ratio of first coupler is 98:2；The splitting ratio of second coupler and the 3rd coupler is 75:25.
- 5. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In the electrooptic modulator uses lithium niobate intensity modulator, and the continuous light for laser output is to obtain suitable arteries and veins Wash off.
- 6. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In the work pump light source of erbium-doped fiber amplifier is the two directional pump light source of 980nm wavelength.
- 7. the distributed fiber optic temperature strain sensing system according to claim 1 based on Brillouin scattering, its feature exist In the frequency response of the first photodetector is more than 125MHz, and the second photodetector is 3kHz-12GHz.
- A kind of 8. distributed fiber optic temperature strain sensing measuring method based on claim 1, it is characterised in that：Brillouin scattering luminous intensity is obtained according to first passage data and second channel data；According to second channel data and the 3rd Channel data obtains Brillouin shift, that is, after obtaining Brillouin caused by the temperature change experienced as sensor fibre or strain Strength Changes and frequency displacement change to scattering light, obtain the changing value of temperature, further according to described by Brillouin scattering luminous intensity Frequency displacement change and the change of temperature are worth to the strain that sensor fibre is experienced, and realize to being measured while temperature and strain.
- 9. according to the method for claim 8, it is characterised in that described to be obtained according to first passage data and second channel data Include to Brillouin scattering luminous intensity：Obtained first including Rayleigh scattering luminous intensity and Brillouin scattering light intensity according to first passage data and second channel data Photoelectric current including degree, the electromagnetic field expressions based on Rayleigh scattering light, Brillouin scattering, separation draw Brillouin scattering Intensity.
- 10. according to the method for claim 8, it is characterised in that the first passage data are direct current signal, second channel Data and third channel data are AC signal.
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108225387A (en) * | 2018-01-19 | 2018-06-29 | 山东大学 | System and method for is monitored for the fully distributed fiber of linear engineering safety monitoring |
| CN110160569A (en) * | 2019-04-24 | 2019-08-23 | 国网浙江省电力有限公司信息通信分公司 | For the noise-reduction method of distributing optical fiber sensing signal, system and storage medium |
| CN113654581A (en) * | 2021-08-12 | 2021-11-16 | 太原理工大学 | A distributed optical fiber coal mine roof safety monitoring system and method |
| CN113776686A (en) * | 2021-08-09 | 2021-12-10 | 北京航空航天大学 | A Gas Chamber Temperature Control System Based on Heterodyne Interference |
| CN114485748A (en) * | 2022-01-17 | 2022-05-13 | 武汉地震工程研究院有限公司 | Multi-parameter distributed optical fiber sensing method and system |
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| CN204027726U (en) * | 2013-07-03 | 2014-12-17 | 青岛派科森光电技术股份有限公司 | A kind of distributed optical fiber sensing system based on Brillouin scattering |
| CN206960011U (en) * | 2017-08-01 | 2018-02-02 | 山东大学 | Distributed fiber optic temperature strain sensing system based on Brillouin scattering |
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| CN204027726U (en) * | 2013-07-03 | 2014-12-17 | 青岛派科森光电技术股份有限公司 | A kind of distributed optical fiber sensing system based on Brillouin scattering |
| CN206960011U (en) * | 2017-08-01 | 2018-02-02 | 山东大学 | Distributed fiber optic temperature strain sensing system based on Brillouin scattering |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108225387A (en) * | 2018-01-19 | 2018-06-29 | 山东大学 | System and method for is monitored for the fully distributed fiber of linear engineering safety monitoring |
| CN108225387B (en) * | 2018-01-19 | 2024-09-17 | 山东大学 | Full-distributed optical fiber monitoring system and method for linear engineering safety monitoring |
| CN110160569A (en) * | 2019-04-24 | 2019-08-23 | 国网浙江省电力有限公司信息通信分公司 | For the noise-reduction method of distributing optical fiber sensing signal, system and storage medium |
| CN110160569B (en) * | 2019-04-24 | 2021-09-24 | 国网浙江省电力有限公司信息通信分公司 | Noise reduction method, system and storage medium for distributed optical fiber sensing signals |
| CN113776686A (en) * | 2021-08-09 | 2021-12-10 | 北京航空航天大学 | A Gas Chamber Temperature Control System Based on Heterodyne Interference |
| CN113654581A (en) * | 2021-08-12 | 2021-11-16 | 太原理工大学 | A distributed optical fiber coal mine roof safety monitoring system and method |
| CN114485748A (en) * | 2022-01-17 | 2022-05-13 | 武汉地震工程研究院有限公司 | Multi-parameter distributed optical fiber sensing method and system |
| CN114485748B (en) * | 2022-01-17 | 2023-06-23 | 武汉地震工程研究院有限公司 | Multi-parameter distributed optical fiber sensing method and system |
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