High-sensitivity optical fiber temperature sensor with cascaded configuration of MZI and FPI based on Vernier effect

A high-sensitivity optical fiber temperature sensor based on the Vernier effect is proposed, which consists of two cascaded fiber interferometers. The Fabry–Pérot interferometer (FPI) with methanol injected into the cavity is used as a sensing interferometer (SI), and the Mach–Zehnder interferometer (MZI) is used as a matching interferometer (MI) to generate the Vernier effect. As two independent interferometers, the MI can be separated from the detection environment of the SI during temperature sensing experiments. In this way, the MI is not affected by the external environment, and the accuracy of the proposed sensor is thus effectively improved. The experimental results show that the temperature sensitivity is enhanced remarkably from −555.8 pm/°C for a single FPI with methanol injected into the cavity to −6.8 nm/°C for the cascaded configuration. Owing to its advantages of simple fabrication, high temperature sensitivity, and low cost, the proposed sensor has great application prospects in several fields.