Graphene oxide based optical fiber humidity sensor having a linear response throughout a large dynamic range and optimum sensitivity

The main objective of the present research is to develop an optical fiber relative humidity (RH) sensor with a high sensitivity, linear response over a wide dynamic range, and optimum response/recovery times by employing the simplest optical fiber sensing configuration. An optical fiber RH sensor that exploits the intensity modulation scheme through evanescent wave absorption spectroscopy and fulfills the objective is reported here. The fiber sensor employs graphene oxide (GO) diffused silica nanostructured thin sensing film as the cladding on the centrally decladded straight and uniform multimode optical fiber. Detailed experimental investigations are carried out to analyze the response characteristics of the proposed sensor. In comparison to other GO based optical fiber RH sensors, a linear response over the widest dynamic range (15.0%-95.3%RH) and shortest (fastest) response/recovery times (0.1436 s/0.1547 s) are observed for the proposed sensor. The linear sensitivity for the developed sensor is observed to be 0.1036 dB/%RH. In addition, the proposed sensor exhibits a very good degree of reversibility, reliability, and repeatability.