Abstract

We report here a well performing fiber–optic high relative humidity (75−99 % RH) sensor with sensitivity as high as ~ 1.1dBm/%RH and ultra-fast response (~125 ms). Controlled chemical etching, extremely responsive gelatin overlay and most importantly appropriately designed quasi-adiabatic transition region to launch at an angle that has a potential to selectively excite the desired coating mode is the key reason for this manifold increase in the sensitivity, high stability and fast detection. The structural parameters yielding optimized transmission characteristics are obtained from our devised hybrid theoretical ray- and wave-optic model.

© 2016 Optical Society of America