Ultra-Sensitive Temperature Sensor of Cascaded Dual PDMS-Cavity Based on Enhanced Vernier Effect

In this article, an ultra-sensitive temperature sensor based on the enhanced Vernier effect is presented. It consists of a double-groove cavity (DGC) and an open cavity (OC) filled with polydimethylsiloxane (PDMS). The length of DGC is limited by two single-mode fibers (SMFs), and the length of OC is not limited. The two sensing cavities are affected by the thermal optic effect (TOE) and thermal expansion effect (TEE). Their interference dip of the spectra shifts to opposite directions, respectively, which realizes the enhanced Vernier effect. The sensitivity of the sensor can be further improved, and the interference caused by the reference cavity can be also eliminated. The experimental results show that the sensor exhibits a high temperature sensitivity of 11.93 nm/°C. Compared to the traditional sensors based on the Vernier effect using TOE (3.33 nm/°C) or TEE (8.62 nm/°C) alone, the sensitivity increased by 264.8% and 38.4%, respectively. As such, we believe that the proposed sensor has great application potential in biochemical detection, aeronautical engineering, and environmental monitoring.