The comparative study of optical fiber coupling scheme in pigtailing of semiconductor optical amplifiers

Abstract

In this paper we present analysis on three different coupling systems, i.e., butt, single ball lens, and two ball lenses between the tips of two coupled single mode fiber in semiconductor optical amplifier (SOA) module. The coupling components inside the module can be aligned in an active alignment process and attached by means of dual beam from an Nd: YAG laser welding system. The tips of the coupled fiber are ferruled inside metallic tubes to enable the attachment to the substrates through saddle-shaped welding clips. Investigations of the variations of coupling efficiency with the with working distance for the three schemes showed that two ball lenses is more efficient with coupling efficiency of 75% followed by single ball lens at 55% and butt coupling mode at 20% maximum. In addition dual ball lens configuration have shown to have better longitudinal tolerant even with an elliptical beam profile from the source fiber. This is however not the case in single ball lens and butt coupling scheme. We also observe however the optimum separation between the two lenses at in the range between 0.35 mm - 0.45 mm. This is to ensure the coupling efficiency is the highest possible within the acceptable tolerant misalignments.