提出一种基于线偏振光干涉原理的无源波长解调系统。在普通光纤环镜中引入双折射效应。光纤环镜的反射(透射)光强是耦合器分光比K、温度t、保偏光纤长度L和两端偏振方向夹角φ的函数。在单调区间内反射(透射)光强与t存在对应关系。通过测定光强可求得t。利用矩阵光学原理建立理论模型,研究了保偏光纤长度、耦合器耦合系数、偏振光入射夹角对光纤环镜(FLM)反射(透射)光强与入射光波长关系影响的特性,设计了基于保偏光纤环镜的分辨率可控的干涉型解调仪。用自制光纤光栅作为传感头监测温度变化,数据显示该系统对温度的测量平均精度可达0.03 ℃,准确度±0.1 ℃。

A passive wavelength demodulation system based on linearly polarized light interference principle is proposed. Leading-in a section of polarization-maintaining fiber to the common fiber loop mirror (FLM) is equivalent to leading-in birefringence effect to the common FLM. As the parameters of polarization-maintaining fiber are determined, the value of effectual refractive index difference is fixed and the reflective (transmission) light intensity of the FLM becomes a function of the coupler′s prismatic ratio K, the temperature t, the length of the polarization-maintaining fiber L and the included angle of the polarization directions in the two ends. When the fabric is determined, there exists a corresponding relation between the reflective (transmission) light intensity and t in the monotonic interval. The theoretical model is established according to the matrix optics principle. The impact characteristics to the relation between the reflective (transmission) light intensity of FLM and the incidence light wavelength from the length of polarization-maintaining fiber, the coupling coefficient of coupler and the incidence included angle of the polarization light are researched. Using fiber grating as the sensing head to monitor the variation of temperature, the data show that the system′s average measuring precision of the temperature can be up to 0.03 ℃ and the veracity can be up to ±0.1 ℃.