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提出并实验证明了一种基于自外差探测和波长扫描技术的光纤布拉格光栅远距离传感系统。该系统将远程光纤光栅阵列的反射信号光与本地参考光进行差频探测,并通过声光调制器对探测光的频移及脉冲进行调制,有效地提高了系统的探测灵敏度和传感距离。在没有放大的情况下,在171km的探测距离处,光纤光栅传感器的反射布拉格波长信号的信噪比达到33dB。该系统可以准确地绘制出远端光纤光栅阵列的反射谱,实验结果显示两个光纤光栅的布拉格波长与温度均成良好的线性关系,且传感灵敏度为11pm/℃。
A fiber Bragg grating remote sensing system based on heterodyne detection and wavelength scanning technology is proposed and experimentally proved. The system detects the difference between the reflected signal light and the local reference light of the remote FBG array and modulates the frequency shift and pulse of the probe light through the acousto-optic modulator, which effectively improves the detection sensitivity and the sensing distance of the system. Without magnification, the signal-to-noise ratio of the FBG’s reflected Bragg wavelength signal reaches 33 dB at a detection distance of 171 km. The experimental results show that the Bragg wavelengths of the two FBGs are in good linear relationship with the temperature and the sensing sensitivity is 11 pm / ° C.