Tilted FBGs coated with ZnO nano coatings for the development of VOC sensor

The sensing properties of zinc oxide (ZnO) combined with tilted fiber Bragg gratings have been studied in this work for the development of organic vapor optical fiber sensors. ZnO has been deposited onto tilted optical fiber Bragg gratings by drop casting technique to obtain coatings with thickness below 100nm. For a title angle of 4°, cladding modes up to 4 dB peak to peak amplitude were obtained and, as a consequence, the fundamental mode strength dropped below 0.5dB. The sensing features were evaluated by exposing the sensor to saturated atmospheres of three different alcohols and acetone. A negligible change was registered for methanol but in the case of ethanol and isopropanol a 24pm red shift was observed; in the case of acetone, the shift was 96pm which is of the order of spectral width of certain cladding modes. For all cases, the shifts were reversed once the organic vapors were removed. Ongoing studies are focused on the optimization of the sensing layer as well as the tilted angle to enhance the spectral response of the sensor.