Temperature-compensated optimized relative humidity and refractive index sensors using a hybrid fibre grating configuration

A temperature compensated Refractive Index sensor is formed using a combination of a Fibre Bragg Grating and a Long Period Grating fabricated together on a single optical fibre. The performance of the sensor was evaluated as an exemplar chemical sensor when sodium chloride concentration in water was determined. The same hybrid configuration was used to evaluate a relative humidity sensor in which the Long Period Grating was this time coated with polyimide allowing it to respond to humidity changes while the Fibre Bragg Grating was used for temperature compensation. The paper presents the results and conclusions arising from this work.