Strain-independent temperature measurement using a type-I and type-IIA optical fiber Bragg grating combination

A simple and effective technique for strain-independent temperature measurement has been demonstrated using the peak wavelengths of both type-I and type-IIA fiber Bragg gratings written without hydrogen loading in the same fiber, this having been specially fabricated with a high concentration of germanium in the core composition. The device is also capable of monitoring strain and temperature simultaneously and can be used to measure temperature over the range of 25–300 °C with a strain range of 0–500 μe, achieving a temperature-dependent sensitivity of 0.53 and 0.31 pm/°C for strain-independent temperature measurement with root mean square errors of 2.4 and 4.1 °C at 25 and 300 °C, respectively.