Polyaniline-coated tilted fiber Bragg gratings for pH sensing

In this paper, we report an optical fiber pH sensor based on a polyaniline coating deposited on the surface of a tilted fiber Bragg grating. The pH-sensitive film was synthesized by in situ chemical oxidative polymerization keeping track of the deposition time in order to optimize the sensor response. As a result, the sensor reacts to pH changes in the range of 2–12 with a fast response and its sensitivity is directly related to the film thickness. The main advantages of this PAni-TFBG pH sensor are its biochemical compatibility, temperature independence, long-term stability and remote real-time multipoint sensing features.