Packaging and precision testing of fiber-Bragg-grating and silicon ring-resonator thermometers: current status and challenges

In recent years photonic thermometers—temperature sensors based on optical frequency measurement which exploit the thermo-optic effect to translate thermal changes into frequency shifts—are gaining popularity as a possible alternative to their electrical counterparts: platinum resistance thermometers and thermocouples. In this work, we report our results of testing photonic thermometers based on silica fiber-Bragg-grating technology supplied by a commercial company, as well as preliminary testing results of a silicon ring-resonator thermometer developed at the National Research Council of Canada. The main purpose of showing these two examples is to highlight some of the challenges that need to be addressed if photonic thermometers are to replace thermocouples or platinum resistance thermometers in metrology laboratories and other environments where high accuracy and stability are required, namely the influence of packaging on the sensor’s performance and the need for rigorous testing to be done in a temperature metrology lab.