Optical fiber pH sensor fabrication by means of indium tin oxide coated optical fiber refractometers

In this work, the fabrication of a novel optical fiber pH sensor is described. This optical fiber pH sensor is based on the utilization of a pH sensitive polymeric coating fabricated onto indium tin oxide coated optical fiber refractometers. The pH of the external medium modifies the thickness of the polymeric coating and hence the effective refractive index. Thus, ITO coated optical fiber refractometers based on electromagnetic resonances are used as suitable transducers in order to monitor the variations of the pH in the surrounding medium. The fabricated devices permit wavelength based pH detection in the near infra-red region, showing high sensitivity (17.5 nm/pH unit) and fast response.