Simultaneous measurement of humidity and temperature by combining a reflective intensity-based optical fiber sensor and a fiber Bragg grating

A novel sensor capable of simultaneously measuring temperature and humidity has been fabricated and demonstrated using optical fiber waveguides. The sensor head is composed of a fiber Bragg grating and a low-finesse Fabry-Perot interferometric cavity. The Fabry-Perot cavity was fabricated using the electrostatic self-assembled monolayer process for the molecular-level deposition of materials of different thicknesses that form a humidity-sensitive coating on the end of the fiber, while the in-line Bragg grating fiber element is used to monitor temperature. Experimental results for a humidity range from 11% to 97% RH and for a temperature range from 10°C to 85°C are shown.