基于光相干外差检测的布里渊散射DOFS的研究

对布里渊散射分布式光纤传感器(DOFS)检测原理进行了分析, 针对布里渊散射光信号的特点, 应用光相干和外差技术来检测布里渊散射光信号. 具体采用微波电光调制产生频率可调的参考光, 和布里渊散射光进行相干检测, 根据布里渊频移特性取出布里渊散射光信号, 从而得到分布式传感信号. 分别实现了25 km光纤的分布式温度和应变传感, 达到3℃的温度分辨率、100 με的应变分辨率和10 m的空间分辨率.

Study on the Technique of Brillouin Scattering Distributed Optical Fiber Sensing Based on Optical Interferometric Heterodyne Detection

The detecting mechanism and scattering optical signal′s characters of Brillouin scattering distributed sensor are analyzed first, then a novel detecting scheme is presented and demonstrated experimently, which adopts optical heterodyne detection to measure Brillouin scattering signal. In detail, a DFB LD with <1 MHz line width is used as light source, the source is divided into two part, one part is used as pump light which is modulated into optical pulse(100 ns); the other part acts as reference light which is modulated by microwave electric optical modulator to produce frequency adjustable light. Then Brillouin back scattering light is heterodyne detected with the reference right, the detecting photoelectric signal is first converted into digital signal by hi speed A/D, then the digital signal is stored and added, and at last the distributed sensing signal with better S/N ratio is gained. The distributed detecting of temperature and strain are gotten, and a 25 km distributed sensor is achieved with 3℃