Refractive index sensing with long-period grating fabricated in biconical tapered fibre

A single long-period fibre grating was written in a biconical fibre taper made from standard communications step-index optical fibre, resulting in an interferometric fibre sensor device that provided a resolution of 1×10−4 for refractive indices in the range of 1.30 to 1.34, suggesting that these devices may be suitable for use with aqueous solutions.