Optical fiber temperature and strain sensing system based on high accuracy time delay measurement

An optical fiber temperature and strain sensing system based on phase-derived optical fiber time delay (OFTD) measurement is proposed. By detecting the phase different between probe and intrinsic microwave signals, high accuracy delay measurement can be obtained. As the OFTD in single mode fiber (SMF) changes linearly with the strain or temperature in a certain range, strain and temperature sensing can be achieved by measuring the change of OFTD with high accuracy. In the experiments, the delay measurement accuracy can reach 0.06 ps when the accuracy of phase detector is ±0.1 degree while the detecting frequency is 4.5 GHz. In addition, an accuracy of ±11 με for strain sensing with 1.5 m fiber and a resolution better than 0.24 °C for temperature sensing with 10.66 m fiber are achieved.

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