An Ultrahigh Sensitivity Point Temperature Sensor Based on Fiber Loop Mirror

An ultrahigh sensitivity point temperature sensor is presented by inserting a section of low birefringence photonic crystal fiber (LB-PCF) inside the fiber loop mirror structure. The sensor head is configured by applying a mechanical lateral force on the LB-PCF, whose birefringence is sensitive to environmental temperature change due to stress optic effect. The sensor has the merits of simple and robust structure. Experiment shows only the small sensor head is sensitive to temperature change while the guiding PCF is insensitive to environmental temperature, so it can be used as a point temperature sensor. The proposed sensor has a linear response to the temperature change with an ultrahigh temperature sensitivity of $\text{30.33}\ \text{nm}/^\circ \text{C}$ .