High-sensitivity temperature and vibration sensor based on a microfiber coupler with a Sagnac loop

This study presents a compact and high-sensitivity sensor based on a reflective optical microfiber coupler (OMC) for temperature and vibration measurements. Embedding the OMC into a polydimethylsiloxane (PDMS) substrate film improves the structural stability of the sensor. The sensor leverages the strong evanescent field characteristics surrounding the OMC, the pronounced reflection effect of the Sagnac loop as the reflector, and the elevated thermo-optical coefficient of PDMS, which collectively improve its sensitivity. We theoretically analyze the optical microfiber coupler Sagnac loop (OMCSL) interference principle and the underlying mechanisms of temperature and vibration sensing. Findings from the experiments indicate that the sensor demonstrates a sensitivity of 2.43 nm/°C within the temperature interval of 35°C-41°C; moreover, it can detect vibration from 30 Hz to 4 kHz. The sensor features compactness, high sensitivity, and low cost.