Numerical calculation of temperature sensing in seawater based on microfibre resonator by intensity-variation scheme

Abstract

A seawater temperature sensing and detection method based on microfibre resonator (MR) by intensity-variation scheme is proposed, which has the advantages of high sensitivity and low detection limit. The dependences of sensitivity on probing wavelength, fibre diametre and ring diametre are studied. Results show that probing wavelength influences the sensitivity by the absorption loss predominantly. Larger absorption loss results in lower sensitivity, which is much different with resonant-wavelength-shift scheme. And sensitivity increases with the increasing ring diametre due to the decreasing bending loss and increasing Q-factor. In addition, there may exist an optimal fibre diametre, with which the sensitivity is maximized. By tuning the parameters of system, sensitivity can be tuned from 0.0784 NI/°C to 13.79 NI/°C (NI is the abbreviation of normalized intensity). Correspondingly, dynamic range changes from 11.77°C to 0.08°C. Additionally, the dependences of detection limit on wavelength, fibre diametre, and ring diametre are also investigated, which are opposite to that of sensitivity. For different temperatures, the dependences of sensitivity and detection limit at some typical temperatures are studied, which shows that high sensitivity and low detection limit are related to high temperature, and the optimal fibre diametres for high sensitivity and low detection limit are the same at different temperatures. The lowest detection limit is estimated to be 10-7°C level, which is four orders of magnitude smaller than that of the traditional method. Results shown here are beneficial to find the optimal parameters for the temperature sensors, and offer helpful references for assembling micro-photonics device used in seawater sensing and detection.