Mode coupling in FM-EDFAs caused by fiber bending: theory and experiments

Abstract

Refractive index perturbation caused by erbium-doped fiber (EDF) bending is inevitable in the fabrication of erbium-doped fiber amplifiers (EDFAs). The resulting mode coupling might bring about the deviation of theoretical results from experimental data. We present a theoretical model of FM-EDFAs with mode coupling due to fiber bending and carry out a proof-of-concept experiment by a 3.2-m-long EDF stretcher. Our experiments show that the fluctuation of modal gain due to fiber bending is about 1.5 dB for LP01 and LP11e modes, and about 2.5 dB for LP11o mode, and the theoretical model is more useful for the FM-EDFA design in the presence of fiber bending.

Investigating changes in the electric field profiles of transverse modes in fibres due to bending

“…Most of the previously presented articles have focused on analysing bending loss, which differs from the approach taken in this article to examine the effects of bending on fibres. Bending loss typically considers mode energy loss due to bending [38][39][40][41][42], whereas this work focused on analysing the behaviour and distribution of mode fields during propagation in a fibre with a bent geometry based on the concepts of normalised propagation constant and effective refractive index.…”