“…It should be outlined that a thermal coefficient of around 1.5 × 10 −4°C−1 for the core and cladding refractive indices, respectively, has been reported by several authors 11,19,20,25 but having a negligible influence on the frequency response (and so on the high-order resonances) for the temperature ranges considered, and simulations with the model reported here are consistent with this fact. In contrast, for a similar temperature range, deviations of around units (in percentage from the nominal value)of the graded index exponent α,due to the influence of temperature on the silica properties, have been reported.…”