Tapered no-core optical fibre for oxygen sensing

In this paper a tapered no-core (TNC) optical fibre sensor coated with methylene blue (MB) is proposed and experimentally investigated for oxygen sensing at the near infra-red (NIR) wavelength range of 993.5 nm. The influence of no-core tapering diameter and the coating thickness of MB sol-gel on the sensitivity of the sensor are investigated. The sensor with tapering diameter of 2 µm and coating thickness of MB sol-gel of 0.86 µm has a maximum sensitivity of 0.19 dB/O2 % within the oxygen concentration range of 0 - 37.5 % with a response time of 4 mins.