Highly Sensitive Fiber Temperature Sensor Based on Photopolymer Probe and Vernier-Like Effect

A highly sensitive fiber temperature sensor based on the Vernier-like effect and composite Fabry-Perot interferometers (FPIs) constructed with a photopolymer probe is proposed. The composite FPIs consist of two photopolymer probes, forming a cascaded polymer-cavity FPI and an air-cavity FPI. The two sides of the air cavity are composed of photopolymer. As a result, the response of the air cavity FPI to temperature changes is opposite to that of the polymer cavity FPI. When the free spectral ranges (FSRs) of the two FPIs are close enough to meet the conditions of the Vernier-like effect, an improved sensitivity amplification effect is obtained. The experimental results show that the temperature sensitivity of the sensor was measured as high as −90 nm/°C, which is 30 times higher than the temperature sensitivity of FPI based on a single photopolymer probe. In addition, in the preparation process, the photopolymer probe of the sensor is directly attached to the end face of the fiber to form the photopolymer waveguide, which makes the sensor simpler in structure and lower in manufacturing cost.