A simultaneous audio and temperature sensing system based on in-line Mach–Zehnder interferometer

A system integrating audio and temperature sensing capabilities has been developed for simultaneous detection. Within this system, an in-line Mach–Zehnder interferometer (IMZI) sensor has been explored. Manufactured using the electro-discharge method, the sensor comprises a structure connecting single mode fiber (SMF) to polarization-maintaining fiber (PMF) and then back to SMF, with distinctive peanut-shaped junctions. The sensor's sensitivity to temperature and curvature has been assessed to determine its potential for simultaneous audio and temperature detection. Within the temperature range of 15 °C–48 °C and a curvature range of 0 m−1–0.06654 m−1, the peak sensitivities observed were -0.1072 nm/°C and 63.5569 nm/m−1, respectively. Experimental verification confirmed the system's audio performance using the proposed IMZI sensor. The system operates over a broad frequency range from 20 Hz to 20,000 Hz. The maximum frequency response and minimum detectable pressures (MDP) are 1804.92 mV/Pa and 11.74 μPa/Hz1/2 at 800 Hz, respectively, indicating notable acoustic sensitivity. Based on both theoretical analyses and empirical methodologies, the system successfully achieves simultaneous audio and temperature detections. This is accomplished by processing the detected data of curvature and temperature variations via high-speed sampling and dual-wavelength demodulation. Notably, this approach addresses and overcomes the sensitivity reduction experienced by acoustic sensors based on interferometers due to temperature-induced Q point drifts.