Highly Sensitive Optical Fiber Temperature Sensor Based on Microwave Photonic Filter With Enhanced Vernier Effect

A highly sensitive optical fiber temperature sensor based on microwave photonic filters (MPFs) with enhanced Vernier effect has been proposed and experimentally demonstrated. The enhanced Vernier effect is achieved through a parallel configuration structure that precisely controls the delay time difference and filter coefficient of two dual-tap MPFs with a common sensing arm. So, the free spectral range (FSR) of the two MPFs varies in opposite directions with temperature, which results in a more pronounced envelope shift and increased sensitivity. Experimental results demonstrate that the temperature sensitivity is improved to 902.51 kHz/°C by using the enhanced Vernier effect, which is around 69 and 71 times the individual MPFs, respectively.