Cascaded FPI-FBG hybrid fiber sensor based on gold nanofilm mirror for simultaneous measurement of refractive index and temperature

A miniature hybrid FPI-FBG optical fiber sensor based was proposed to measure refractive index (RI) and temperature simultaneously. The integrated FPI-FBG composite fiber sensor is constructed by cascading an FP interference cavity at one end of the FBG, where the FPI is used to measure the liquid refractive index and the FBG to measure temperature and compensate for FPI. In this paper, Monte Carlo method is used to simulate the sputtering yield of three commonly used metal high reflection films (aluminum, silver and gold). Au film perform as the reflective mirror of the FPI due to its high sputtering yield and high stability. Owing to the different sensitivities, two-dimensional matrix method was constructed to calculating the refractive index (RI) and temperature synchronously. Experimental results show that the temperature and RI sensitivity of spectral dip wavelength for FPI are 0.338 nm/°C and 1669.5 nm/RIU, respectively. The FBG is insensitive to RI and temperature sensitivity of sensor is 9.8 pm/°C.