Optomechanically Mode-Locked Laser Sensor for High-Accuracy Temperature Measurement

An optomechanically mode-locked fiber laser (MLFL) temperature sensor based on forward stimulated Brillouin scattering (FSBS) is presented. By taking advantage of the mode selection function of FSBS, longitudinal modes matched with the acoustic resonance frequency in FSBS are effectively enhanced to achieve a near-single longitudinal mode output with high side-mode suppression ratio (SMSR) for easy identification and monitoring. Beat frequency (BF) signals at 320 MHz and its higher order harmonics by using
$\text{R}_{0,7}$
FSBS acoustic mode are experimentally obtained and applied for high-accuracy temperature measurement. The results show that the sensor has a higher signal-to-noise ratio (SNR) than other laser sensors at higher frequencies. Harmonic beat signal at 1.917 GHz with an SNR of 58 dB and an SMSR of 32 dB is selected for temperature sensing, yielding a temperature sensitivity of −13.3 kHz/°C and a measurement accuracy of 0.021 °C. The proposed sensing scheme has the advantages of simple structure, good stability, high accuracy, and ease of real-time measurement, which has great potential for monitoring a variety of parameters in food storage, healthcare, and other special sensing fields.