A kind of fiber PH sensor coated with PANI (polyaniline) on the surface of LPFG (long-period fiber grating) has been developed in the work. PANI film was nurtured in the solution by in-situ chemical oxidative polymerization and the growth process of the PH sensitive film was traced by an optical spectrum analyzer to optimize the response of the sensor. The RI and optical properties of PANI change regularly in the PH range of 2-12, which is the basic principle of LPFG coated with PANI sensing material for PH measurement. Though the experiment, the sensor can achieve a high sensitivity of 152pm/ph. Besides, other performances of the sensor, such as response time, temperature stability, reversibility and long-term stability were studied in the experiment. As a result, The PANI-LPFG sensor has such advantages as fast response speed, excellent temperature stability, low cost, easy to be used, and continuous measurement of the environment.
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