Simultaneous refractive index and temperature sensing based on a fiber surface waveguide and fiber Bragg gratings

An optical fiber sensor based on a fiber surface waveguide and Bragg grating is proposed for a simultaneous refractive index (RI) and temperature sensing. The device consists of two fiber Bragg gratings fabricated by a femtosecond laser, one of which is situated in the fiber core for temperature sensing; the other is located in the fiber surface waveguide for both temperature and RI measurements. The RI and temperature sensitivities achieved are 10.3 nm/RIU and 9.94 pm/°C, respectively. The device is featured with a compact structure, high robustness, and convenient operation.