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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 3 × 3 coupler-based Sagnac fiber-optic interferometer distributed optical fiber vibration sensor was used to build a pipeline safety monitoring system to monitor real-time safety along the long-distance oil and gas pipelines and determine whether pipelines threaten pipeline safety. Positioning. The monitoring system adopts the ring type structure Sagnac optical fiber interferometer and utilizes 3 × 3 coupler to modulate the optical signal phase without the need of special phase modulation and demodulation to optimize the optical path and improve the signal processing accuracy. The phase modulation of light wave and the positioning expression of external disturbance under the ideal state are given. The working principle and positioning principle of the system are expounded. Based on the optical path design and positioning theory, a real-time monitoring system of Sagnac ring structure was established. The experimental system of monitoring system was developed. The selected disturbance source was used to modulate the optical signal with different frequency disturbance signals generated by external disturbance. The experimental results show that the maximum relative error of the result of localization calculation is 1.23% for the 100 ~ 500 Hz external disturbance signal. The pipeline monitoring system constructed in this paper not only can quickly detect high-frequency external disturbance signals, but also can effectively detect low-frequency external disturbance signals, providing effective technical support for real-time safety monitoring along the pipeline and real-time positioning of disturbance locations .