Observation of Brillouin gain spectrum in tapered polymer optical fiber

We report on the first observation of the Brillouin gain spectrum in a perfluorinated graded-index polymer optical fiber (POF) tapered by a heat-and-pull technique. The Stokes power was slightly enhanced by tapering probably on account of higher optical power density in the core. In addition, the Brillouin frequency shift was decreased by ∼40 MHz, which was experimentally verified to be partially caused by high heating temperature applied to the POF during the taper fabrication process. We anticipate that our findings will provide a basic principle of temperature sensing with “memory” function.