一种基于FSI和MZI并联组合的光纤温度传感器

An optical fiber temperature sensor based on paralleled of FSI and MZI

基于并联的干涉型滤波器的游标效应,设计了一种基于光纤萨格纳克干涉仪(fiber Sagnac interferometer,FSI)和马赫-曾德尔干涉仪(Mach-Zehnder interferometer,MZI)并联组成的光纤温度传感器。FSI由一个3 dB的四端口耦合器和一段6.6 m的保偏光纤(polarization maintaining optical fiber,PMF)组成,因其具有较高的灵敏度以及较好的稳定性,将其作为传感腔。MZI作为参考腔由两个3 dB的三端口耦合器自制组成,通过控制MZI两臂的长度,使这两个干涉仪的自由光谱范围(free spectral range,FSR)相接近但不相等,利用游标效应来提高该结构的温度灵敏度,然后通过改变温度来测量单个FSI与并联FSI、MZI这两种结构的波长漂移情况,从而探究温度灵敏度的放大情况。实验结果表明,单个FSI的温度灵敏度仅为-1.65 nm/℃,并联系统可以将其放大到12.9 nm/℃,增益系数为7.82,与理论结果相符,表明在相同温度下,并联结构能够明显提高温度传感器的灵敏度。该传感器能在较小的温度变化时呈现明显的波长漂移,适用于生物和工业领域的温度精细检测。

Based on the vernier effect of the parallel interference filter,we propose a fiber optic temperature sensor based on the paralleled structure of the fiber Sagnac interferometer(FSI)and the Mach-Zehnder interferometer(MZI).The FSI consists of a 3 dB four-port coupler and a 6.6 m polarization maintaining optical fiber(PMF).Because of its higher sensitivity and better stability,it is used as a sensing cavity.MZI as a reference cavity consists of two 3 dB three-port couplers self-made,by controlling the length of the two arms of MZI,so that the free spectral range(FSR)of the two interferometers is close but not equal,the vernier effect is used to improve the temperature sensitivity of the structure,and then by changing the temperature to measure the wavelength drift of a single FSI and paralleled FSI,MZI,so as to explore the amplification of temperature sensitivity.Experimental results show that the temperature sensitivity of a single FSI is only-1.65 nm/℃,and the paralleled system can amplify it to 12.9 nm/℃with a gain coefficient of 7.82,which is consistent with the theoretical results,indicating that the paralleled structure can significantly improve the sensitivity of the temperature sensor at the same temperature.And the proposed sensor has significant wavelength drift while a smaller temperature changing which is suitable for fine temperature detection in biological and industrial fields.