Humidity Sensor Based on Hybrid Fiber Bragg Grating/Abrupt Fiber Taper

A novel fiber humidity sensor based on fiber Bragg grating (FBG) cascaded with an abrupt fiber taper is proposed and demonstrated. The evanescent wave around the abrupt fiber taper varies with humidity around the sensor, so that the power of the FBG core reflection is affected by the ambient humidity. Experimental results show that the sensor has a linear response to humidity with sensitivity of 0.10-dB/%RH in the humidity range of 50%-90% RH. Such a cost-effective, compact, and reflection power detection-based humidity sensor could be a good candidate in applications.