CN106482805A - A kind of can real time fail monitoring multi-channel optical fibre liquid level measuring system and fault monitoring method - Google Patents
A kind of can real time fail monitoring multi-channel optical fibre liquid level measuring system and fault monitoring method Download PDFInfo
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Abstract
本发明提供了一种可实时故障监测的多路光纤液位测量系统，包括：探测光源、掺铒光纤放大器、第一光纤耦合器、光环形器、1×N光分路器、液位传感器和光电探测器；掺铒光纤放大器的输入端与探测光源的输出端连接，第一光纤耦合器的输入端与掺铒光纤放大器的输出端连接，环形器的第一端口与第一光纤耦合器的第一输出端连接，环形器的第二端口与1×N光分路器的输入端口连接，1×N光分路器具有多个输出端口，分别与多个不同长度的光纤延时线的第一端口相连，光纤延时线的第二端口与液位传感器相连；光电探测器的第一输入端与光环形器的第三端口相连，光电探测器的第二输入端与第一光纤耦合器的第二输出端连接；数据采集处理设备的输入端与光电探测器的输出端连接。
The invention provides a multi-channel optical fiber liquid level measurement system capable of real-time fault monitoring, including: a detection light source, an erbium-doped optical fiber amplifier, a first optical fiber coupler, an optical circulator, a 1×N optical splitter, and a liquid level sensor and photodetector; the input end of the erbium-doped fiber amplifier is connected with the output end of the detection light source, the input end of the first fiber coupler is connected with the output end of the erbium-doped fiber amplifier, and the first port of the circulator is connected with the first fiber coupler The first output port of the circulator is connected to the input port of the 1×N optical splitter, and the 1×N optical splitter has multiple output ports, which are respectively connected to multiple fiber delay lines of different lengths The first port of the optical fiber delay line is connected to the liquid level sensor; the first input end of the photodetector is connected to the third port of the optical circulator, and the second input end of the photodetector is connected to the first optical fiber The second output end of the coupler is connected; the input end of the data acquisition and processing device is connected with the output end of the photodetector.
Description
技术领域technical field
本发明属于液位测量领域，更具体地，涉及一种可实时故障监测的多路光纤液位测量系统及故障监测方法。The invention belongs to the field of liquid level measurement, and more specifically relates to a multi-channel optical fiber liquid level measurement system capable of real-time fault monitoring and a fault monitoring method.
背景技术Background technique
液位测量技术在工业上有广泛且重要的应用。例如在石油化工领域，常常需要测定容器中的液位高度；在抗洪防汛方面，也需要对江河水位进行密切监测。传统的液位传感器主要有浮子式、电容式、电阻式、压力式和雷达式等。随着光纤传感技术的发展，应用与液位测量的光纤传感器越来越多，相比传统液位传感器，具有体积小、重量轻、绝缘性好、安全性好、抗电磁干扰、耐腐蚀等优点。Liquid level measurement technology has extensive and important applications in industry. For example, in the petrochemical field, it is often necessary to measure the liquid level in the container; in flood control and flood control, it is also necessary to closely monitor the water level of the river. Traditional liquid level sensors mainly include float type, capacitive type, resistive type, pressure type and radar type. With the development of optical fiber sensing technology, more and more optical fiber sensors are used for liquid level measurement. Compared with traditional liquid level sensors, they have the advantages of small size, light weight, good insulation, good safety, anti-electromagnetic interference, and corrosion resistance. Etc.
常见的光纤液位传感器主要有光纤微结构液位传感器、光纤光栅液位传感器、光纤法布里-珀罗液位传感器等。这些光纤液位传感器受制于光纤微结构长度、光栅栅区长度、法布里-珀罗干涉腔长度等因素，测量范围较小。已报道的光纤液位传感器及液位传感系统通常测量范围只能达到几十毫米，且只能对单点的液位进行测量。此外，由于光纤液位传感器通常要浸没在待测液体中，这些液体通常成分复杂甚至具有腐蚀性，光纤的断裂易于发生；在复杂的光纤传感系统中，光纤的故障排查十分耗时耗力；因此对光纤液位传感系统进行故障监测和故障定位就显得尤为重要。传统的光纤液位传感系统通常缺乏故障监测与定位功能。Common optical fiber liquid level sensors mainly include optical fiber microstructure liquid level sensors, optical fiber grating liquid level sensors, optical fiber Fabry-Perot liquid level sensors, etc. These optical fiber liquid level sensors are limited by factors such as the length of the optical fiber microstructure, the length of the grating region, and the length of the Fabry-Perot interference cavity, and the measurement range is relatively small. The reported optical fiber liquid level sensors and liquid level sensing systems usually have a measurement range of only tens of millimeters, and can only measure a single point of liquid level. In addition, because the optical fiber liquid level sensor is usually immersed in the liquid to be measured, these liquids are usually complex in composition and even corrosive, and the breakage of the optical fiber is prone to occur; in a complex optical fiber sensing system, troubleshooting of the optical fiber is time-consuming and labor-intensive ; Therefore, it is particularly important to carry out fault monitoring and fault location on the optical fiber liquid level sensing system. Traditional fiber optic liquid level sensing systems usually lack fault monitoring and location capabilities.
发明内容Contents of the invention
针对现有技术的缺陷，本发明的目的在于提供一种可进行实时故障监测的多路光纤液位测量系统及故障监测方法，旨在解决传统光纤液位传感系统测量范围小、只能进行单点液位测量，且难以对测量系统进行故障监测与定位的问题。Aiming at the defects of the prior art, the purpose of the present invention is to provide a multi-channel optical fiber liquid level measurement system and a fault monitoring method capable of real-time fault monitoring, aiming to solve the problem that the traditional optical fiber liquid level sensing system has a small measurement range and can only perform Single-point liquid level measurement, and it is difficult to monitor and locate faults in the measurement system.
本发明提供了一种可实时故障监测的多路光纤液位测量系统，包括：环腔型探测光源、掺铒光纤放大器、第一光纤耦合器、光环形器、1×N光分路器、液位传感器和光电探测器；所述掺铒光纤放大器的输入端与所述环腔型探测光源的输出端连接，所述第一光纤耦合器的输入端与所述掺铒光纤放大器的输出端连接，所述环形器的第一端口与所述第一光纤耦合器的第一输出端连接，所述环形器的第二端口与所述1×N光分路器的输入端口连接，1×N光分路器具有多个输出端口，分别与多个不同长度的所述光纤延时线的第一端口相连，所述光纤延时线的第二端口与液位传感器相连；所述光电探测器的第一输入端与所述光环形器的第三端口相连，所述光电探测器的第二输入端与所述第一光纤耦合器的第二输出端连接；所述数据采集处理设备的输入端与所述光电探测器的输出端连接。The invention provides a multi-channel optical fiber liquid level measurement system capable of real-time fault monitoring, including: a ring-cavity detection light source, an erbium-doped optical fiber amplifier, a first optical fiber coupler, an optical circulator, a 1×N optical splitter, Liquid level sensor and photodetector; the input end of described erbium-doped fiber amplifier is connected with the output end of described ring cavity type detection light source, the input end of described first optical fiber coupler is connected with the output end of described erbium-doped fiber amplifier connected, the first port of the circulator is connected to the first output end of the first fiber coupler, the second port of the circulator is connected to the input port of the 1×N optical splitter, 1× The N optical splitter has a plurality of output ports, which are respectively connected to the first ports of the optical fiber delay lines of different lengths, and the second port of the optical fiber delay lines is connected to the liquid level sensor; the photoelectric detection The first input end of the device is connected to the third port of the optical circulator, and the second input end of the photodetector is connected to the second output end of the first optical fiber coupler; the data acquisition and processing device The input end is connected with the output end of the photodetector.
更进一步地，所述第一光纤耦合器为90：10的光纤耦合器，所述第一光纤耦合器的第一输出端输出90％的光信号，所述第一光纤耦合器的第二输出端输出10％的光信号。Further, the first fiber coupler is a 90:10 fiber coupler, the first output of the first fiber coupler outputs 90% of the optical signal, and the second output of the first fiber coupler output 10% of the optical signal.
更进一步地，所述环腔型探测光源包括：半导体光放大器、光隔离器和第二光纤耦合器；所述半导体光放大器的输出端连接所述光隔离器的输入端，所述光隔离器的输出端连接所述第二光纤耦合器的输入端，所述第二光纤耦合器的第一输出端连接半导体光放大器的输入端，形成环腔结构，第二光纤耦合器的第二输出端则作为环腔光源的输出。Furthermore, the ring cavity type detection light source includes: a semiconductor optical amplifier, an optical isolator and a second fiber coupler; the output end of the semiconductor optical amplifier is connected to the input end of the optical isolator, and the optical isolator The output end of the second optical fiber coupler is connected to the input end of the second optical fiber coupler, and the first output end of the second optical fiber coupler is connected to the input end of the semiconductor optical amplifier to form a ring cavity structure, and the second output end of the second optical fiber coupler Then it is used as the output of the ring cavity light source.
更进一步地，第二光纤耦合器为80：20的光纤耦合器；所述第二光纤耦合器的第一输出端输出20％的光信号；所述第二光纤耦合器的第二输出端输出80％的光信号。Furthermore, the second optical fiber coupler is an 80:20 optical fiber coupler; the first output end of the second optical fiber coupler outputs 20% of the optical signal; the second output end of the second optical fiber coupler outputs 80% light signal.
更进一步地，所述液位传感器包括：第一单模光纤、无芯光纤、第二单模光纤和光纤全反镜；所述无芯光纤的两端分别与所述第一单模光纤的一端和所述第二单模光纤的一端连接，所述第二单模光纤的另一端连接所述光纤全反镜，所述第一单模光纤的另一端连接光纤延时线的第二端口；所述无芯光纤部分浸没在待测液体中，当液位发生变化时，所述无芯光纤被浸没的长度也随之改变，所述无芯光纤中包层模式的泄漏也会发生变化，影响其传输光强。Furthermore, the liquid level sensor includes: a first single-mode optical fiber, a coreless optical fiber, a second single-mode optical fiber, and a fiber optic mirror; both ends of the coreless optical fiber are connected to the first single-mode optical fiber One end is connected to one end of the second single-mode fiber, the other end of the second single-mode fiber is connected to the optical fiber mirror, and the other end of the first single-mode fiber is connected to the second port of the fiber delay line ; The coreless optical fiber is partially immersed in the liquid to be measured, and when the liquid level changes, the immersed length of the coreless optical fiber also changes, and the leakage of the cladding mode in the coreless optical fiber also changes , affecting its transmitted light intensity.
更进一步地，所述第一单模光纤与所述无芯光纤的纤芯直径不匹配，所述第二单模光纤与所述无芯光纤的纤芯直径不匹配。Furthermore, the core diameter of the first single-mode optical fiber does not match the coreless optical fiber, and the core diameter of the second single-mode optical fiber does not match the coreless optical fiber.
本发明还提供了一种基于上述的多路光纤液位测量系统的故障监测方法，包括下述步骤：The present invention also provides a fault monitoring method based on the above-mentioned multi-channel optical fiber liquid level measurement system, comprising the following steps:
(1)探测光源输出的光经过放大后分为两路，一路作为参考光被光电探测器接收后获得第一电信号，另一路作为探测光；(1) The light output by the detection light source is amplified and divided into two paths, one path is used as the reference light and received by the photodetector to obtain the first electrical signal, and the other path is used as the detection light;
(2)所述探测光被1×N光分路器分为N路，并分别进入各个传感支路；(2) The detection light is divided into N paths by a 1×N optical splitter, and enters each sensing branch respectively;
(3)每个传感支路的探测光经过液位传感器后，反射光再经过光环形器被光电探测器接收后获得第二电信号；(3) After the detection light of each sensing branch passes through the liquid level sensor, the reflected light passes through the optical circulator and is received by the photodetector to obtain the second electrical signal;
(4)将所述第一电信号和所述第二电信号进行相关运算后，获得每条支路的传感点的位置信息和液位信息；并通过传感点的位置信息判断该支路的光纤是否出现断裂故障。(4) After correlating the first electrical signal and the second electrical signal, the position information and liquid level information of the sensing point of each branch are obtained; and the branch is judged by the position information of the sensing point Whether the optical fiber of the road is broken or not.
更进一步地，所述参考光为10％，所述探测光为90％。Furthermore, the reference light is 10%, and the detection light is 90%.
更进一步地，在步骤(4)中，根据公式进行所述相关运算；其中，x(t)为参考光信号(强度随时间变化的序列)，x(t-τ)为探测光信号(强度随时间变化的序列)，Rx(τ)为计算后得出的相关曲线。Furthermore, in step (4), according to the formula Carry out the correlation operation; wherein, x(t) is a reference optical signal (sequence of intensity varying with time), x(t-τ) is a detection optical signal (sequence of intensity varying with time), and R x (τ) is The calculated correlation curve.
通过本发明所构思的以上技术方案，与现有技术相比，具有以下有益效果：Compared with the prior art, the above technical solution conceived by the present invention has the following beneficial effects:
(1)本发明采用基于混沌光源的相关算法进行解调，通过互相关运算得出的相关曲线中，同时包含了传感点的位置信息和探测光强度信息，能够实现传感参量与传感点位置的同时解调，因此可进行多点的同时传感。(1) The present invention uses a correlation algorithm based on a chaotic light source for demodulation, and the correlation curve obtained through cross-correlation calculations includes both the position information of the sensing point and the detected light intensity information, which can realize the sensing parameter and sensing Simultaneous demodulation of point positions, so simultaneous sensing of multiple points is possible.
(2)当光纤链路中有断点出现时，相关曲线中会出现一个与断点位置对应的相关峰，因此能对光纤中出现的断点进行实时监测与定位，由于采用的混沌光源具有光强随机起伏的特性，定位精度可高达厘米级。(2) When there is a breakpoint in the optical fiber link, a correlation peak corresponding to the breakpoint position will appear in the correlation curve, so the breakpoint in the optical fiber can be monitored and located in real time, because the chaotic light source used has Due to the random fluctuation of light intensity, the positioning accuracy can reach centimeter level.
附图说明Description of drawings
图1为本发明实施例1的带环腔反馈的探测光源示意图。FIG. 1 is a schematic diagram of a detection light source with ring cavity feedback according to Embodiment 1 of the present invention.
图2为本发明实施例1的单模-无芯-单模光纤结构的液位传感器示意图。FIG. 2 is a schematic diagram of a liquid level sensor with a single-mode-coreless-single-mode optical fiber structure according to Embodiment 1 of the present invention.
图3为本发明实施例1的探测系统示意图。Fig. 3 is a schematic diagram of the detection system of Embodiment 1 of the present invention.
图中，1为半导体光放大器，2为光隔离器，3为80：20光纤耦合器，4为第一单模光纤，5为无芯光纤，6为第二单模光纤，7为光纤全反镜，8为探测光源，9为掺铒光纤放大器，10为90：10光纤耦合器，11为光环形器，12为1×N光分路器，13为液位传感器，14为光纤延时线，15为光电探测器，16为数据采集处理设备。In the figure, 1 is a semiconductor optical amplifier, 2 is an optical isolator, 3 is an 80:20 fiber coupler, 4 is the first single-mode fiber, 5 is a coreless fiber, 6 is the second single-mode fiber, 7 is the full Reflective mirror, 8 is the detection light source, 9 is the erbium-doped fiber amplifier, 10 is the 90:10 fiber coupler, 11 is the optical circulator, 12 is the 1×N optical splitter, 13 is the liquid level sensor, 14 is the optical fiber extension Timeline, 15 is a photodetector, and 16 is a data acquisition and processing device.
具体实施方式detailed description
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.
本发明所要解决的技术问题是提供一种光纤液位测量系统，克服传统光纤液位传感系统测量范围小、只能进行单点液位测量，并且难以对测量系统进行故障监测与定位的缺点。The technical problem to be solved by the present invention is to provide an optical fiber liquid level measurement system, which overcomes the shortcomings of the traditional optical fiber liquid level sensing system, which has a small measurement range, can only perform single-point liquid level measurement, and is difficult to monitor and locate faults in the measurement system. .
本发明提供了一种光纤液位测量系统，该光纤液位测量系统采用相关算法作为解调方法，可同时对液位信息和位置信息进行解调，此外当光纤传感系统中发生故障时，也可以通过相关算法解调出来。The invention provides an optical fiber liquid level measurement system, which adopts a correlation algorithm as a demodulation method, and can demodulate liquid level information and position information at the same time. In addition, when a fault occurs in the optical fiber sensing system, It can also be demodulated by related algorithms.
光纤液位测量系统包括：探测光源8、掺铒光纤放大器9、90：10光纤耦合器10、光环形器11、1×N光分路器12、液位传感器13、光纤延时线14、光电探测器15和数据采集处理设备16。其中，探测光源8的输出端与掺铒光纤放大器9输入端连接，掺铒光纤放大器9的输出端与90:10光纤耦合器10的输入端连接，90：10光纤耦合器10的90％输出端与环形器11的第一端口连接，环形器11的第二端口与1×N光分路器12的输入端口连接，1×N光分路器12的各个输出端口与不同长度的光纤延时线14的第一端口相连，光纤延时线14的第二端口与液位传感器13相连，光环形器11的第三端口与光电探测器15的输入端相连，90：10光纤耦合器10的10％输出端直接与光电探测器15的输入端相连，光电探测器15的输出端与数据采集处理设备16相连。The optical fiber liquid level measurement system includes: detection light source 8, erbium-doped optical fiber amplifier 9, 90:10 optical fiber coupler 10, optical circulator 11, 1×N optical splitter 12, liquid level sensor 13, optical fiber delay line 14, A photodetector 15 and a data acquisition and processing device 16 . Wherein, the output end of the detection light source 8 is connected with the input end of the erbium-doped fiber amplifier 9, the output end of the erbium-doped fiber amplifier 9 is connected with the input end of the 90:10 fiber coupler 10, and 90% of the 90:10 fiber coupler 10 outputs The end is connected to the first port of the circulator 11, the second port of the circulator 11 is connected to the input port of the 1×N optical splitter 12, and each output port of the 1×N optical splitter 12 is extended with optical fibers of different lengths. The first port of the time line 14 is connected, the second port of the optical fiber delay line 14 is connected with the liquid level sensor 13, the third port of the optical circulator 11 is connected with the input end of the photodetector 15, and the 90:10 fiber optic coupler 10 The 10% output terminal of the photodetector 15 is directly connected to the input terminal of the photodetector 15, and the output terminal of the photodetector 15 is connected to the data acquisition and processing device 16.
探测光源8包括：半导体光放大器1、光隔离器2和80：20光纤耦合器3；半导体光放大器1的输出端连接光隔离器2的输入端，光隔离器2的输出端连接80：20光纤耦合器3的输入端，80：20光纤耦合器3的20％输出端连接半导体光放大器1的输入端，形成环腔结构，80：20光纤耦合器3的80％的输出端则作为环腔光源的输出。The detection light source 8 includes: a semiconductor optical amplifier 1, an optical isolator 2 and an 80:20 fiber coupler 3; the output end of the semiconductor optical amplifier 1 is connected to the input end of the optical isolator 2, and the output end of the optical isolator 2 is connected to the 80:20 The input end of the fiber coupler 3, 20% of the output end of the 80:20 fiber coupler 3 is connected to the input end of the semiconductor optical amplifier 1 to form a ring cavity structure, and 80% of the output end of the 80:20 fiber coupler 3 is used as a ring The output of the cavity light source.
液位传感器13包括：第一单模光纤、无芯光纤、第二单模光纤及光纤全反镜；无芯光纤的两端分别与第一单模光纤和第二单模光纤连接，第二单模光纤的另一端连接光纤全反镜。The liquid level sensor 13 includes: a first single-mode optical fiber, a coreless optical fiber, a second single-mode optical fiber and an optical fiber total reflection mirror; the two ends of the coreless optical fiber are respectively connected with the first single-mode optical fiber and the second single-mode optical fiber, and the second The other end of the single-mode fiber is connected to a fiber optic mirror.
数据采集处理设备可以采用数据采集卡进行实时的采集、处理和显示，也可以用示波器将数据存储下来，然后再用电脑进行离线处理。The data acquisition and processing equipment can use the data acquisition card for real-time acquisition, processing and display, or use the oscilloscope to store the data, and then use the computer for offline processing.
以下结合实施例1提供的可实时故障监测的多路光纤液位测量系统，进一步阐述本发明：本发明实施例1的多路光纤液位测量系统结构如图3，包括探测光源8、掺铒光纤放大器9、90：10光纤耦合器10、光环形器11、1×N光分路器12、液位传感器13、光纤延时线14、光电探测器15和数据采集处理设备16。探测光源8的输出端与掺铒光纤放大器9的输入端连接，掺铒光纤放大器9的输出端与90：10光纤耦合器10的输入端连接，90：10光纤耦合器10的90％输出端与光环形器11第一端口连接，光环形器11第二端口与1×N光分路器12输入端口连接，1×N光分路器12各输出端口与不同长度的光纤延时线14的第一端口相连，光纤延时线14的第二端口与液位传感器13相连，环形器11第三端口与光电探测器15输入端相连，90：10光纤耦合器10的10％输出端直接与光电探测器15输入端相连，光电探测器15的输出端与数据采集处理设备16相连。本发明实施例1的探测光源8结构如图1，包括半导体光放大器1、光隔离器2、和80：20光纤耦合器3；半导体光放大器1的输出端连接光隔离器2的输入端，光隔离器2的输出端连接80：20光纤耦合器3的输入端，80：20光纤耦合器3的20％输出端连接半导体光放大器1的输入端，形成环腔结构，80％的输出端则作为光源的输出。本发明实施例1的液位传感器13结构如图2，包括第一单模光纤4、无芯光纤5、第二单模光纤6及光纤全反镜7。无芯光纤5的两端分别与第一单模光纤4和第二单模光纤6连接，第二单模光纤6的另一端连接光纤全反镜7。The present invention is further described in conjunction with the multi-channel optical fiber liquid level measurement system that can be monitored in real time in Embodiment 1: the structure of the multi-channel optical fiber liquid level measurement system in Embodiment 1 of the present invention is shown in Figure 3, including a detection light source 8, an erbium-doped Optical fiber amplifier 9, 90:10 optical fiber coupler 10, optical circulator 11, 1×N optical splitter 12, liquid level sensor 13, optical fiber delay line 14, photoelectric detector 15 and data acquisition and processing equipment 16. The output end of the detection light source 8 is connected to the input end of the erbium-doped fiber amplifier 9, the output end of the erbium-doped fiber amplifier 9 is connected to the input end of the 90:10 fiber coupler 10, and the 90% output end of the 90:10 fiber coupler 10 Connect with the first port of the optical circulator 11, connect the second port of the optical circulator 11 with the input port of the 1×N optical splitter 12, and connect the output ports of the 1×N optical splitter 12 with the fiber delay lines 14 of different lengths connected to the first port of the optical fiber delay line 14, the second port of the optical fiber delay line 14 is connected to the liquid level sensor 13, the third port of the circulator 11 is connected to the input end of the photodetector 15, and the 10% output end of the 90:10 optical fiber coupler 10 is directly It is connected to the input end of the photodetector 15 , and the output end of the photodetector 15 is connected to the data acquisition and processing device 16 . The detection light source 8 structure of embodiment 1 of the present invention is as Fig. 1, comprises semiconductor optical amplifier 1, optical isolator 2 and 80:20 optical fiber coupler 3; The output end of semiconductor optical amplifier 1 is connected the input end of optical isolator 2, The output end of the optical isolator 2 is connected to the input end of the 80:20 fiber coupler 3, and 20% of the output end of the 80:20 fiber coupler 3 is connected to the input end of the semiconductor optical amplifier 1 to form a ring cavity structure, and 80% of the output end as the output of the light source. The structure of the liquid level sensor 13 according to Embodiment 1 of the present invention is shown in FIG. 2 , which includes a first single-mode optical fiber 4 , a coreless optical fiber 5 , a second single-mode optical fiber 6 and an optical fiber total reflection mirror 7 . Both ends of the coreless fiber 5 are respectively connected to the first single-mode fiber 4 and the second single-mode fiber 6 , and the other end of the second single-mode fiber 6 is connected to the fiber mirror 7 .
下面结合实施例1对可实时故障监测的多路光纤液位测量系统的工作原理进行阐述。The working principle of the multi-channel optical fiber liquid level measurement system capable of real-time fault monitoring will be described below in conjunction with Embodiment 1.
在探测光源8中，半导体光放大器1的输出光经过光隔离器2，保证了光在环腔中传输的单向性。此输出光被80：20光纤耦合器3分为强度比为80：20的两部分，其中20％的光在环腔中循环后，作为反馈重新输入半导体光放大器1中，80％的光则作为环腔光源的输出光。由于部分光反馈带来的扰动，输出光呈现出动态不稳定特性，即光强随机起伏，为连续非周期信号。In the detection light source 8, the output light of the semiconductor optical amplifier 1 passes through the optical isolator 2, which ensures the unidirectionality of light transmission in the ring cavity. The output light is divided into two parts with an intensity ratio of 80:20 by the 80:20 fiber coupler 3, and 20% of the light is circulated in the ring cavity and re-entered into the semiconductor optical amplifier 1 as feedback, and 80% of the light is then As the output light of the ring cavity light source. Due to the disturbance caused by part of the optical feedback, the output light presents a dynamic instability characteristic, that is, the light intensity fluctuates randomly, which is a continuous non-periodic signal.
在液位传感器13中，由于第一单模光纤4及第二单模光纤6与无芯光纤5的纤芯直径不匹配，会在无芯光纤5中激发包层模式，无芯光纤5部分浸没在待测液体中，当液位发生变化时，无芯光纤5被浸没的长度改变，无芯光纤5中包层模式的泄漏也会发生变化，影响其传输光强；无芯光纤5的长度即为液位传感范围，可达十几厘米。光纤全反镜7则将通过光纤微结构的探测光反射回去，便于进一步的接收和处理。因此当传感点的液位发生变化时，该支路的探测光反射强度发生变化。In the liquid level sensor 13, since the core diameters of the first single-mode optical fiber 4 and the second single-mode optical fiber 6 do not match the coreless optical fiber 5, the cladding mode will be excited in the coreless optical fiber 5, and the coreless optical fiber 5 part Immersed in the liquid to be measured, when the liquid level changes, the immersed length of the coreless optical fiber 5 changes, and the leakage of the cladding mode in the coreless optical fiber 5 also changes, which affects its transmission light intensity; the coreless optical fiber 5 The length is the liquid level sensing range, which can reach more than ten centimeters. The optical fiber total reflection mirror 7 reflects back the detection light passing through the optical fiber microstructure, which is convenient for further receiving and processing. Therefore, when the liquid level of the sensing point changes, the detection light reflection intensity of the branch changes.
探测光源8的输出光经过掺铒光纤放大器9放大后，被90：10光纤耦合器10分为强度比为90：10的两部分，其中10％的光作为参考光直接被光电探测器15接收。90％的光则作为探测光，通过光环形器11后，被1×N光分路器12分为N路，进入各传感支路。每个传感支路的末端接有液位传感器13，液位高度的变化会影响探测光强度，探测光经过液位传感器13后，其反射光再经过光环形器11被光电探测器15接收。参考光和探测光分别被光电探测器15转化为电信号，输入数据采集处理设备16，经过相关运算后，得到的相关曲线可同时反映传感点的位置信息和液位信息。每条支路接有不同长度的光纤延时线14，因此传感点的位置各不相同，可通过传感点的位置信息区分不同的支路；当某一支路的光纤出现断裂时，在相关曲线上也会反映出断点的位置信息，因此可便捷地进行传感网络的健康监测。After the output light of the detection light source 8 is amplified by the erbium-doped fiber amplifier 9, it is divided into two parts with an intensity ratio of 90:10 by the 90:10 fiber coupler 10, and 10% of the light is directly received by the photodetector 15 as the reference light . 90% of the light is used as detection light, and after passing through the optical circulator 11, it is divided into N paths by the 1×N optical splitter 12 and enters each sensing branch. The end of each sensing branch is connected with a liquid level sensor 13, and the change of the liquid level height will affect the detection light intensity. After the detection light passes through the liquid level sensor 13, the reflected light passes through the optical circulator 11 and is received by the photodetector 15. . The reference light and the detection light are respectively converted into electrical signals by the photodetector 15 and input to the data acquisition and processing device 16. After correlation calculation, the obtained correlation curve can reflect the position information and liquid level information of the sensing point at the same time. Each branch is connected with an optical fiber delay line 14 of different lengths, so the positions of the sensing points are different, and different branches can be distinguished by the position information of the sensing points; when the optical fiber of a certain branch breaks, The position information of the breakpoint will also be reflected on the correlation curve, so the health monitoring of the sensor network can be conveniently carried out.
相关运算的基本原理为：探测光的输出光为连续非周期信号，具有宽频谱特性，其自相关函数具有单一、尖锐的峰，类似冲激函数(δ函数)。信号x(t)与其时移副本x(t-τ)的相关函数的一般形式：相关函数可体现两信号之间的时延差τ及信号的强度。The basic principle of the correlation operation is: the output light of the probe light is a continuous non-periodic signal with wide-spectrum characteristics, and its autocorrelation function has a single, sharp peak, similar to an impulse function (δ function). The general form of the correlation function of a signal x(t) with its time-shifted counterpart x(t-τ): The correlation function can reflect the delay difference τ between the two signals and the strength of the signal.
本发明中，探测光源8的输出光被分为参考信号和探测信号两路，参考信号直接被光电探测器15接收，相当于无时移的信号x(t)。探测信号则进入多支路液位传感网络中，经液位传感器13末端的光纤全反镜7或光纤断点反射后传回。由于各支路接有不同长度的光纤延时线14，探测光在每条支路传输的时间不一样，因此探测信号相比参考信号，为一系列与参考信号具有相同时域波形和不同时延的信号x(t-τ1)，x(t-τ2)，x(t-τ3)，……的叠加，因此进行相关运算后，由于探测光与参考光之间的时延决定了相关峰的位置，各传感点对应的相关峰的位置也各不相同，不会重叠，相关曲线中出现多个相关峰，与各支路一一对应，相关峰的位置定量地反映了各支路探测信号相对参考信号的时延。将每个支路信号的时延按照光纤中的光速换算为距离，就可以确定各支路传感点的位置。当传感点的液位发生变化时，该支路的探测光强度发生变化，对应相关峰的强度也发生相应变化，通过观测特定相关峰就可以解调出特定传感点的液位高度。故障监测的原理：故障监测实际上与传感过程是同时进行。具体监测方法是：对探测光与参考光做了相关运算之后，正常情况下(即没有光纤断点出现)，相关曲线上会有N个互不重叠的相关峰，与N个传感点一一对应；如果某一条支路出现了光纤断点，那么该支路原有的相关峰就会消失，而在断点对应的位置处就会出现一个新的相关峰，这样就可以同时知道是哪一条支路出现了断点，以及断点的具体位置。由于混沌光源的相关峰很窄，因此分辨率较高，可以达到厘米级。该故障监测的优点在于：(1)可以实时故障监测，不需要额外的操作；(2)定位精度高。本发明具有以下优点：液位测量范围较大，实现了多路液位传感并具有液位传感系统的实时故障监测与定位功能。In the present invention, the output light of the detection light source 8 is divided into two paths, a reference signal and a detection signal, and the reference signal is directly received by the photodetector 15, which is equivalent to a signal x(t) without time shift. The detection signal enters into the multi-branch liquid level sensor network, and is transmitted back after being reflected by the optical fiber total reflection mirror 7 at the end of the liquid level sensor 13 or the breakpoint of the optical fiber. Since each branch is connected with an optical fiber delay line 14 of different length, the time of detection light transmission in each branch is different, so the detection signal is a series of waveforms with the same time domain and different time domains as the reference signal compared with the reference signal. The superposition of the delayed signals x(t-τ 1 ), x(t-τ 2 ), x(t-τ 3 ), ..., so after the correlation operation, due to the time delay between the probe light and the reference light The positions of the correlation peaks corresponding to each sensing point are also different and will not overlap. There are multiple correlation peaks in the correlation curve, which correspond to each branch one by one. The positions of the correlation peaks quantitatively reflect the The time delay of each branch detection signal relative to the reference signal. By converting the time delay of each branch signal into distance according to the speed of light in the optical fiber, the position of each branch sensing point can be determined. When the liquid level of the sensing point changes, the detection light intensity of the branch changes, and the intensity of the corresponding correlation peak also changes accordingly. By observing the specific correlation peak, the liquid level height of the specific sensing point can be demodulated. The principle of fault monitoring: fault monitoring is actually carried out simultaneously with the sensing process. The specific monitoring method is: after performing correlation calculations on the probe light and the reference light, under normal circumstances (that is, no fiber breakpoints appear), there will be N non-overlapping correlation peaks on the correlation curve, which correspond to the N sensing points. One-to-one correspondence; if a fiber breakpoint occurs in a certain branch, the original correlation peak of the branch will disappear, and a new correlation peak will appear at the position corresponding to the breakpoint, so that it can be known at the same time Which branch has a breakpoint and the specific location of the breakpoint. Because the correlation peak of the chaotic light source is very narrow, the resolution is high and can reach centimeter level. The advantages of the fault monitoring are: (1) real-time fault monitoring without additional operations; (2) high positioning accuracy. The invention has the following advantages: the liquid level measurement range is large, the multi-channel liquid level sensing is realized and the real-time fault monitoring and positioning functions of the liquid level sensing system are provided.
最后所应说明的是，以上具体实施方式仅用以说明本发明的技术方案而非限制，尽管参照较佳实施例对本发明进行了详细说明，本领域的普通技术人员应当理解，可以对本发明的技术方案进行修改或者等同替换，而不脱离本发明技术方案的精神和范围，其均应涵盖在本发明的权利要求范围当中。Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that the present invention can be Modifications or equivalent replacements of the technical solutions without departing from the spirit and scope of the technical solutions of the present invention shall fall within the scope of the claims of the present invention.
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| CN110260947A (en) * | 2019-07-30 | 2019-09-20 | 南昌航空大学 | A kind of fibre optic liquid level sensor and method for sensing |
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| CN113098595A (en) * | 2021-03-12 | 2021-07-09 | 华中科技大学 | Method, system and device for measuring group delay of few-mode optical fiber differential mode |
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