LOCAL SUPERMODE ANALYSIS OF TAPERED FIBER SENSOR

The authors investigate the performance of an evanescent-field fibre s ensor made from standard single-mode optical fibre with a tapered clad ding region, upon which a thin attenuating material coating is deposit ed. The authors' method involves calculating the supermodes of the com plete core-cladding-coating-air structure locally at each point along the taper and studying the evolution of the supermode guided power alo ng the sensor. Results are compared with those from a numerical finite difference scheme; and also used to interpret experimental results ob tained for a taper with a thin layer of sulphur deposited by electrica l discharge in an atmosphere of SF6.