Investigation of the effects of grating length, Bragg wavelength and wavelength shift on temperature sensitivity in fiber Bragg grating-based sensing systems

In optical fiber sensing systems based on fiber Bragg gratings (FBGs), there are numerous parameters that significantly limit the overall sensing performance. In this study, the effects of FBG parameters such as grating length, Bragg wavelength, and reflection rate on temperature sensitivity have been investigated considering there are no strain effects along the length of the grating. For this purpose, the OptiSystem program has been utilized to design an FBG-based sensing system, which is a relevant approach for simulating and analyzing the performance of FBGs. For temperature variations in the range of 1–120 °C, variations of wavelength shift and grating length have been obtained between 14 and 1680 pm and between 0.1 and 100 mm, respectively. It has been observed that the grating length changes have no direct impact on the temperature sensitivity. On the other hand, a 1 °C variation in temperature causes a wavelength change of ~ 14 pm. Furthermore, temperature sensitivities have been found to be   3.66 pm/°C, 4.58 pm/°C, 5.50 pm/°C, 9.2 pm/°C, 14 pm/°C and 18.4 pm/°C for the Bragg wavelengths of 400 nm, 500 nm, 600 nm, 1000 nm, 1550 nm and 2000 nm, respectively. Moreover, the change in temperature sensitivity depending on Bragg wavelength has been computed as ~ 9.15 × 10^–3 pm/°C(nm)⁻¹. For the reflection rate variations in the range of 0.001–0.99%, temperature sensitivity has taken the value of ~ 14 pm/°C at 100 °C whilst the reflected powers have varied from 11.1 to 42 dBm. Moreover, a change in temperature sensitivity with reflection rate has been acquired as ~ 0.021 pm/°C(%)⁻¹.