Localization mechanisms and location methods of the disturbance sensor based on phase-sensitive OTDR

The mathematic models of the disturbance sensor based on phase-sensitive optical time-domain reflectometry (OTDR) are established. On the basis of the models, the localization mechanisms of the conventional location techniques for phase-sensitive OTDR are simulated. The simulation results indicate that the frequency characteristics of the backscattered signal at disturbance region are different from other regions. According to the results, a novel location method relied on power spectrum analysis is described. The experiment is then conducted over a monitored length of 9 km with a spatial resolution of 100 m, which demonstrates that the described location approach can significantly enhanced signal-to-noise ratio (SNR) to 19.4 dB.     

A Strain Sensor Based on OTDR for Gas Trunk Pipelines

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Input Power Conditions for Distributed Fiber Optic Temperature Sensors in Raman Optical Time-Domain Reflectometry

The critical power of the input pulse in which spontaneous Raman scattering is not seriously disturbed by stimulated Raman scattering in a fiber optic temperature sensor has been investigated experimentally and theoretically. The critical power determines the critical distance, which is nearly equal to the distance where optical time-domain reflectometry (OTDR) signal of the stimulated Raman scattering becomes maximum. From this fact, a new method to determine the critical input power with the OTDR system has been proposed, which may be applicable to most distributed fiber optic temperature sensors. It has been determined that the critical power of the input pulse is 4 watts for an infinitely long silica fiber.Presented at the International Commission of Optics Topical Meeting, Kyoto, 1994.     

光纤分子背向散射的温度效应及其在 分布光纤温度传感网络上应用 研究的进展

讨论了光纤分子瑞利(Rayleigh)背向散射精细结构谱和光纤分子喇曼(Ra man)背向散射光谱及其温度效应,以及在分布型光纤温度传感网络上应用研究的进展。