Quasi-distributed fibre-optic chemical sensing using telecom optical fibre

Quasi-distributed chemical sensing using telecommunications grade fibre is reported for the first time. Using graded index fibre, an etched cavity at each fibre tip is filled with sol-gel-derived-silica in which an analyte-sensitive reagent is entrapped. A standard optical time domain reflectometer system, interrogating three such sensors based on a pH sensitive NIR absorbing dye was used to prove the principle of this approach