Highly sensitive and fast surface temperature sensor based on standard single-mode fiber using double heterodyne interference technology

Abstract

Fiber optics can be ideal thermometers owing to their unique advantages. In this work, we propose a novel measurement method of double heterodyne interferometry, and construct a surface temperature sensor (STS) out of a standard single mode fiber (SMF) with high sensitivity and fast response. The STS is made of a coiled 1.2-m-long SMF, which can quickly sense small changes in ambient temperature by changing the phase of the light propagating in it. Using an oscilloscope, the proposed double heterodyne interferometry can precisely measure the phase change of the light and thus the temperature change, with a sensitivity of 4997°/°C and accuracy of ∼2 × 10−4 °C. A response time of ∼1 ms is obtained experimentally owing to the small SMF diameter, suggesting that a measurement frequency of ∼200 Hz is possible. Additionally, the sensor is characterized by its extended operating range from 0 to 200 °C.