Synthesis and characterization of multilayered sol–gel based plastic-clad fiber optic pH sensor

The fabrication and characterization of an optical fiber pH sensor for the detection range 3–11 are described. The sensing element consists of a combination of indicators encapsulated in mesoporous surfactant based hybrid matrix, which are deposited onto an uncladed plastic optical fiber. Stable, dense and uniform sol–gel cladding with more than 90% transparency in the visible range are observed. Roughness value 9.7–6.57 nm is obtained by AFM. Film thickness, refractive index, and porosity are found to vary with number of coatings, 70% porosity is determined with 116 nm thickness. The response of the sensor with third layer is observed in acid and basic medium.