Distributed optical fiber sensor systems: application to natural gas pipeline monitoring

Distributed fiber optic sensing is a cutting-edge technology that has found extensive applications in the monitoring of pipelines. Among them, distributed acoustic sensors, phase-sensitive optical time domain reflectometry (Φ-OTDR) is a versatile technology that can continuously detect external perturbations and provide spatial and real-time information along the kilometer lengths of sensing fiber. Considering the low backscattering level of standard single-mode fiber as fiber under test, a Rayleigh-enhanced optical fiber embedded within the tight-buffered cable is demonstrated in field testing. We analyzed the increased backscattering fiber cable's vibration performance to the conventional single-mode telecom fiber using a custom-built Φ-OTDR interrogator system. Thereafter, using a 4-inch steel pipeline with a flow rate of 5, 10, 15, and 20ft/s and a fixed pressure level of 1000psi, we field-tested the sensor system for monitoring natural gas pipeline acoustic vibrations. We also field-tested the Brillouin optical time domain analysis (BOTDA) system for pipeline hoop strain monitoring under various pressure conditions. The pilot-scale testing results presented in this study suggested that pipeline operators can accurately perform flow monitoring, leak detection, and pressure monitoring for pipeline integrity monitoring.