Investigation of power oscillations along tapered monomode fibers

Abstract
An abruptly tapered fiber can be essentially divided into three different regions: one beating region in its central, quasi-cylindrical part, lying between two coupling regions, where the slopes are large. In this paper we report two experiments which help to visualize and analyze the beating region. We show that, in this region, there are principally two modes present, HE11 and HE12, both excited with large amplitudes.