Temperature characterization of Long Period Gratings written in three different types of optical fibre for potential high temperature measurements

The characteristics of Long Period Gratings (LPGs) written in a range of Bi–Ge, Sn–Er–Ge and Sb–Er–Ge specialist fibres were investigated in light of their application to high-temperature sensing and to compare their performance with previously published work. The results show that the LPG written in Bi–Ge fibre has shown a temperature sensitivity of 0.10 nm/°C over the temperature range of 25–500 °C whereas by contrast the LPGs written in Sn–Er–Ge and Sb–Er–Ge fibre have shown a lower temperature sensitivity of 0.05 nm/°C over the temperature ranges of 25–600 °C and 25–350 °C respectively. When compared to the Fibre Bragg Gratings (FBGs) written in the same fibres, the operational temperature range of the FBGs is higher but the LPGs have shown nearly five times higher temperature sensitivities than comparable FBGs, making them better suited to a number of optical fibre sensor applications.