基于光相干外差检测的布里渊散射DOFS的研究

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

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 25km光纤的分布式温度和应变传感,达到 3℃的温度分辨率、100με的应变分辨率和 10m的空间分辨率.

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 experimentally, which adopts optical heterodyne detection to measure Brillouin scattering signal. In detail, a DFB-LD with less than or equal 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°C in temperature resolution, 100 με in stress resolution and 10 m in spatial resolution.