Refractive index and temperature sensors based on no-core fiber cascaded with long period fiber grating

Abstract

A kind of compact fibre-optic sensor based on no-core fibre (NCF) cascaded with a strong coupling long-period fibre grating (LPFG) is proposed and experimentally demonstrated. The sensing mechanism is based on the Mach–Zehnder-like interference between the core fundamental mode and cladding mode of the fibre structure. The NCF and LPFG are used as the mode exciter and combiner, respectively. Due to the particular properties of the strong coupling LPFG, the measurements of refractive index (RI) and temperature with high sensitivity are realized by monitoring the transmission spectrum with intensity and wavelength interrogation techniques, respectively. The achieved RI sensitivity reaches −580.269 dB/RIU in the range of 1.436–1.454 and the temperature sensitivity reaches 27.2 pm/°C.

Keywords:

• Fibre-optic sensing
• long-period fibre grating
• no-core fibre
• refractive index sensor
• temperature sensor