Simple coupling method for enhancing Brillouin scattering signal in polymer optical fibres

A simple, efficient, and cost-effective method to enhance a Brillouin scattering signal in perfluorinated graded-index (GI-) polymer optical fibres (POFs) is proposed and demonstrated. In this method, instead of the conventional butt-coupling of a POF to a silica singlemode fibre (SMF), a multimode fibre (MMF) with a proper mode-field diameter of the fundamental mode is additionally inserted between the two fibres to improve the optical coupling efficiency from the POF to the SMF. After theoretical analysis, it is experimentally shown that the Brillouin signal in the POF is clearly enhanced simply by inserting standard MMFs, which are commercially available at affordable cost.