Temperature Independent on Plastic Optical Fiber Evanescent Wave Sensor

We have developed a fiber optic evanescent wave sensor which is capable of monitoring the concentration of liquids by eliminating the changes in the temperature of the surrounding medium. This evanescent technique is based on the evanescent field interactions between the propagating light and the analyte under consideration. A step index polymer optical fiber is manually side polished such that the cladding gets exposed to the solution. Samples of different concentrations of D-Glucose anhydrous (Dextrose anhydrous) procured from Nice Chemicals Pvt Ltd. serves as the analyte. The optoelectronic system consisted of a 650nm narrowband laser, photo detector from Holmarc for light launching and detection respectively. In order to make the measurements independent of temperature effects of the surrounding environment, the POF, after polishing was treated to several cycles of heating and cooling in high temperature oil (Silicone oil). The POF (Plastic optical fiber) was jacketed in a PTFE tube with diameter 3mm during the heat-cool cycles to prevent the ingress of oil into the sensing region. Later, the solution concentration was again monitored and the results show the independency in the photocurrent output on temperature.