Optical fiber humidity sensor using a nano Fabry-Perot cavity formed by the ionic self-assembly method

The ionic self-assembly monolayer process was utilized to fabricate a novel optical fiber humidity sensor based on a nano interferometric cavity. A wide operation range, from 11.3% to 100% relative humidity with a maximum variation of 4.77 dB, was experimentally demonstrated. Due to the short length of the interferometric cavity, less than 400 nm, an LED was used as the light source instead of a laser. The fast response time of this humidity sensor, less than 1.5 s, makes it possible to monitor human breathing. (C) 1999 Elsevier Science S.A. All rights reserved.