基于光纤Sagnac环滤波器的高稳定光纤布拉格光栅传感解调技术

Fiber Bragg Grating Sensor Demodulation Technology with High Stability by Using Sagnac Loop Filter

光纤Sagnac环滤波器用于光纤布拉格光栅（FBG）传感器波长解调时受环境温度影响很大,为此提出一种可消除温度影响的高稳定解调新方法,介绍了系统光路和解调器的工作原理。将带有一段保偏光纤的Sagnac环作为边缘滤波器,分布反馈（DFB）激光器的单波长激光作为参考光,对FBG波长信号和参考光信号同时进行滤波。在同一时间探测经Sagnac环滤波器输出的透射光强度和反射光强度,进行光强信号归一化处理并采用差动检测方法分析。理论分析和实验结果表明,该解调方法基本消除了Sagnac环滤波器的温度效应,提高了解调系统的稳定性。在1302~1318nm波长范围内,解调装置的温度漂移为2.4×10^-4 nm/℃,是未封装补偿无参考光的Sagnac环滤波器透射谱温度漂移的1.8×10^-4倍。

The fiber Sagnac loop filter for wavelength demodulation of fiber Bragg grating（FBG）sensor is greatly influenced by environmental temperature.A new stable demodulation method is proposed to eliminate the influence of temperature.The principle of wavelength demodulation is introduced,and the optical configurations are presented.Using apolarization maintaining fiber Sagnac loop as the edge filter and a distributed feedback（DFB）single wavelength laser as a reference light,FBG signal and reference lights are demodulated.Optical intensities of the transmission and reflection outputs from Sagnac loop filter are detected simultaneously,which are normalized and analyzed by the differential detection method.Theoretical analysis and experimental results show that using this technology,the temperature influence on the Sagnac loop filter is sufficiently eliminated,and the stability of the demodulator is improved.When the Bragg wavelengths range from1302 nm to 1318 nm,the wavelength shift of the demodulator due to temperature is small as 2.4×10^-4 nm/℃,which is as 1.8×10^-4 times as that of an uncompensated Sagnac loop filter without the DFB reference light.