基于3×3耦合器的环型Sagnac干涉仪管道监测系统实验研究

Experimental study on pipeline security monitoring system based on ring-structure Sagnac interferometer with 3×3coupler

利用基于3×3耦合器的Sagnac光纤干涉仪分布式光纤振动传感器,构建管道安全监测系统,实现对长距离输油气管道沿线进行实时安全监测,判断管道沿线是否有威胁管道安全的行为发生并进行定位。监测系统采用环型结构Sagnac光纤干涉仪,利用3×3耦合器对光信号相位有调制作用的特点,无需进行特定的相位调制和解调,优化了光路,提高了信号处理精度。给出了光波的相位调制和理想状态下外扰动行为的定位表达式,阐述了系统的工作和定位原理。根据光路设计和定位理论建立了Sagnac环型结构实时监测实验系统,开发了监测系统实验软件,利用选定的扰动信号源,通过外扰动行为产生的不同频率扰动信号对光信号产生调制,并对所接收的干涉光信号进行分析和定位的实验研究,实验结果表明,对100~500 Hz的外扰动信号,定位计算结果最大相对误差为1.23%。本文构建的管道监测系统不仅能迅速地监测到高频的外扰动信号,还能有效地监测到低频的外扰动信号,为管道沿线进行实时安全监测和对扰动位置的实时定位提供有效的技术保障。

A distributed optical fiber sensor system based on the principle of Sagnac optic interferometer with 3 × 3 coupler is developed for long-distance pipeline security monitoring. By using this system, the disturbance which may threat the security of pipeline can be identified and located in real time. The sys tem using ring-structure Sagnae interferometer does not need the phase modulation and demodulation, because the 3 × 3 coupler can modulate the phase of optic signal, and then improve the signal disposal precision. The principle of the monitoring in ideal condition, the phase demodulation and location of the possible damage action point are analyzed and formulated. Based on the theory, the ring structure Sagnac interferometer real-time monitoring system and the disturbance signal resource are set, the data collection software is designed, the interference signals demodulated by different frequencies of disturbance signals are collected,and then the data are demodulated and calculated to analyze the disturbance position. The results validate that the largest average absolute error of location is 1.23% when the disturbance frequency is between 100 Hz and 500 Hz. The system and indicate that the system can detect the low frequency signal resulting from the damage action and locate the action point accurately over a long distance.