基于线型腔拉曼光纤激光器的长距离光纤布拉格光栅传感

Long-Distance Fiber Bragg Grating Sensor System Based on Linear-Cavity Fiber Raman Laser

提出了一种基于线型腔拉曼光纤激光器的长距离分布式光纤布拉格光栅(FBG)传感解调系统,并进行了理论分析和实验验证。传感光纤布拉格光栅构成拉曼光纤激光器腔镜的一端,受一维调节器调节控制的匹配光纤布拉格光栅构成腔镜的另一端。一维调节器与步进电机相连,步进电机由计算机(PC)通过可编程逻辑控制器(PLC)进行控制,一维调节器通过调节匹配光纤布拉格光栅的周期来控制激光器的输出。实验结果表明,传感解调系统能很好地实现长距离分布式传感及传感信号的检测。30 km非归零色散位移光纤(NZDSF)用于拉曼增益可以产生信噪比大于40 dB的稳定拉曼激光输出,在4.2 nm范围内系统解调精度为0.05 nm。

A scheme of long-distance fiber Bragg grating （FBG） sensor system based on linear-cavity fiber Raman laser is proposed and demonstrated. The cavity of the laser consists of the sensing FBG and the tunable FBG, of which the Bragg period is tunable through a one-dimensional （1D） adjustor. The 1D adjustor, which is connected with a step motor that is controlled by a programmable logic controller （PLC）, can control the Bragg period of the tunable FBG to match the Bragg period of the sensors, which decide the wavelength of the laser output. The tuning module, the optical/electrical circuit, the detecting-and-controlling system and the fiber Raman laser construct a close loop, which performs the wavelength demodulation. Experimental results show that the demodulation sensor system can accomplish sensing and detecting of long-distance distributed sensing signal. Signal-to-noise ratio of stable Raman laser output is greater than 40 dB with 30 km non-zero dispersion shifted fiber （NZDSF）, and the precision of the proposed system is about 0. 05 nm in a demodulation range of 4.2 nm.