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171 km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33 dB。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11 pm/℃。

A remote fiber Bragg grating (FBG) sensors system based on the self-heterodyne detection and wavelength-sweeping technique is proposed and experimentally demonstrated. In this system, the heterodyne signal produced by the reflected sensing signal and the local reference beam is detected by a balanced photodetector. With frequency-shift and pulse-modulation of the acousto-optic modulator, the detection sensitivity and sensing distance are improved effectively. The system is able to detect the two multiplexed FBGs placed 171 km away, offering a signal-to-noise ratio of 33 dB without amplification. In addition, this system can scan the reflection spectra of FBGs accurately. Applying this system to remote temperature detection, the results show the typical liner behavior of both FBGs, shifting their reflected Bragg wavelengths in 11 pm/℃.