Design Of Sagnac Optic-Fiber Pipeline Prealarm System

pipeline transportation has been widely acknowledged and used transportation way. Pipeline transports oil and gas such flammable media.Once the pipeline leaked,environment and human's life and wealth will surf from huge damage.Even it make explosion occur.My issue was begun under such a background.Distributed sensing system has been widely recognized as the effective method in the forewarning system of pipeline safety with long distance. The thesis establishes the forewarning system of pipeline safety based on Sagnac interference principle. A single optical-fiber is used as the sensing fiber, which has lower cost and less difficulty in paving. My issue aim at the major technology question of the Sagnac Optic-fiber pipeline safty and prealarm system. My job finished as following:1. Established the Sagnac optical-fiber distributed forewarning system, elaborated the principle of work and locating. The phase sensitivity of the system and other parameters are analyzed on all sides.2. Analyze the phenonmenon of polarization-fading in the Sagnac optic-fiber pipeline prealarm system. Established the optic-transmission modeling of the Sagnac optic-fiber prealarm system. And then, the quantitative contrast between the optical-fiber loop and FRM is made. Through the experiment'sdata demonstrate that the system using FRM as the reflective device has a stronger ability of anti-polarization.3. The noise model of the distributed the all optical-fiber distributed forewarning system of pipeline safety is established. Through experiment ,quantitative the background noise is calculated.4. In my paper, the phase demodulation algorithm of the interference signal of Sagnac optic-fiber pipeline prealarm sysytem and the algorithms of the envelope extraction and position are finished. Through the positioning experiment,demonstrate the Sagnac optic-fiber prealarm's feasibility of finding and positioning the intrusion.