Design Of Underwater Long Distance Gas Pipeline Leak Detection System Based On Hybrid Interferometer Distributed Fiber-optic

As the main part of the gas exploitation gathering system on thesea, underwater long distance pipeline plays an important role in t he processof offshore gas exploration. Owing to the characteristic of high pressure,flammability and explosive, once long distance gas pipeline is leaked, it willlead to serious security accidents. This dissertation is based on Mach-Zehnderand Sagnac’s interferometer principle, it develops underwater long distancegas pipeline leaking detection system by improving the configuration ofMach-Zehnder/Sagnac hybrid interferometer distributed fiber-optic assensing frame, and using PGC demodulation technology of fiber-optic signal.1. Researching the detection principle based on Mach-Zehnder/Sagnachybrid interferometer, assaying parameter of significant structures indistributed fiber-optic sensing system, and designing the configuration ofimproved hybrid interferometer distributed fiber-optic sensing which appliesto detecting leaks of underwater long distance gas pipeline.2. Through researching the principle and technology of interferometerfiber-optic signal modulation and demodulation, assaying interferometersignal demodulation principle, the advantages and disadvantages of variousdemodulation methods and the characteristics of the corresponding system,performance of each module, designing the PGC phase generated carrierdemodulation circuit which is used for demodulating the fiber-optic signal.3. By means of researching the sensing principle and location algorithmof distributed fiber-optic when a single point starts up leak, derivingdetection principle and mathematical model of the location algor ithm whentwo or multipoint turn out leaks, assaying multi-leak detection method andpositioning technology of hybrid interferometer distributed fiber-opticsensing configuration based on this dissertation designed.4. Researching performance influencing factors of interferometerdistributed fiber-optic when it’s used to detect underwater long distance gas pipeline leaks. Put forward to an improved method of increasing systemdetection performance. Solving detection system optimize correlationtechnique of hybrid interferometer distributed fiber-optic which is used todetect underwater long distance gas pipeline leaks.Use underwater gas pipeline simulator to proceed correlationexperiments of system detection performance, the underwater long distancegas pipeline leak detection system based on hybrid interferometer distributedfiber-optic which this dissertation designed can detect the leaks of underwatergas pipeline accurately with total length of10km and pipeline leak apertureof Φ≥2.5mm, the absolute positioning error for the leaks does not exceed200m. Experimental result indicates, this system can meet the underwaterlong distance pipeline detection requirements, it can be used to provide thedesign basis for real-time automatic monitoring of underwater long distancegas pipeline.