Improvement Of The Performance Of BOTDA By Gain-Profile Tracing Method

High spatial resolution is one of the important directions of BOTDA technology.Gain-Profile Tracing method develop from differential pulse technology,its spatial resolution is determined by falling-edge of pulse,but not the pulse width.By BOTDA system with 50 km sensing distance,temperature and strain sensing properties of GPT – BOTDA is researched.Main contents and innovation points include follow.Based on corresponding relation between Brillouin frequency shift with the intensity,the temperature and strain,we deduced steady coupled wave equations of SBS in BOTDA sensing system with single light source.Focused on some performance parameters like spatial resolution,temperature/sensing sensitivity of strain,measuring time and so on,signal features and demodulation principle of short(<1km)and middle(20-50km)distance sensing fiber's GPT-BOTDA system is researchd,and discussed subtraction-methods to process the experimental data of GPT signal.Fiber optical sensor system based on single light source,sensing distance 50 km and centimetre level spatial resolution GPT-BOTDA distributed sensing system is designed and to calculate the spatial resolution,temperature and strain sensing resolution and measurement time.This thesis discusses the characteristics of GPT sensor signal,the spectrum characteristics of temperature and strain sensing signal and the influence of the pulse down along the envelope on the spatial resolution.The GPT-BOTDA distributed sensing system is designed to realize the temperature and strain distributed detection and get the temperature and strain sensitivity 1.17MHz/?and 0.046MHz/??.Temperature and strain sensing resolution is 6.1?/209??.Sensor system based on single ligbuted detection with sensing distance 50 km and submeter spatial resolution is achieved.Compared with the theoretical simulation results,the errors of temperature and strain sensitivity are 2.5% and 4.2%.GPT technology medium distance BOTDA sensing system for single light source with 50 km spatial resolution and sub-meter spatial resolution is researched.The experiment achieved 50 km sensing distance and spatial resolution of 50 cm in distributed detection of temperature and stress.