All-Optical Humidity Sensor Using SnO_(2) Nanoparticle Drop Coated on Straight Channel Optical Waveguide

The straight channel optical waveguide coated with the SnO_(2) nanoparticle is studied as an all-optical humidity sensor.The proposed sensor shows that the transmission loss of the waveguide increases with increasing relative humidity(RH)from 56%to 90%with very good repeatability.The sensitivity to changes in relative humidity is~2 dB/%RH.The response time of the humidity sensor is 2.5 s,and the recovery time is 3.5 s.The response to humidity can be divided into 3 different regions,which are correlated to the degree of water adsorption in the SnO_(2) nanoparticle layer.Compared with the previous all-optical humidity sensor based on SnO_(2),the proposed sensor exhibits more rapid response,simpler fabrication process,and higher sensitivity.The proposed sensor has a potential application in the long distance,remote agriculture,and biological humidity sensing.