Hybrid FBG–LPG sensor for surrounding refractive index and temperature simultaneous discrimination

In this work, we propose a configuration of a hybrid fiber Bragg grating together with a long period grating sensor used for simultaneously detect surrounding refractive index and temperature to be applied in aqueous environment and to reveal pollution. We present the simulation of such sensor and analyze the reflected wavelength and amplitude variations of the fiber Bragg grating spectrum to obtain the temperature and the external refractive index variations, respectively. The results show that the fiber Bragg grating reflected amplitude change depends on the variation of the long period grating transmission spectrum with the surrounding refractive index modification and the reflected wavelength shift depends on the temperature of the aqueous solution.

► The amplitude of the FBG reflected power depends on the LPG transmission spectrum.
► The amplitude of the FBG reflectivity was used to discriminate the SRI.
► The wavelength of the FBG reflectivity was used to discriminate the temperature.
► The FBG response can be used for simultaneous measurement of temperature and the SRI.