Tapered section of multimode cladded fibers as mode filters and mode analyzers

Abstract

Mode filtering characteristics of biconical tapers in multimode fibers were examined. The insertion loss of a biconical taper for the HE₁₁ mode is 0.2 dB and the rejection ratios for higher−order modes are more than 20 dB. The mode conversion in a biconical taper is sufficiently small except for the HE_1n modes. It is found that a linearly tapered section can be used as a mode analyzer for multimode fibers.