Co-axial dual-core resonant leaky fibre for optical amplifiers

TL;DR

This paper introduces a co-axial dual-core resonant leaky optical fibre design that enables efficient mode control and gain equalization in optical amplifiers through resonant coupling and wavelength-dependent leakage loss.

Contribution

It presents a novel fibre design that leverages resonant coupling to enhance single-mode operation and suppress unwanted emissions in optical amplifiers.

Findings

Resonant coupling increases differential leakage loss for mode control.

Design enables effective single-mode operation in large-core fibres.

Wavelength-dependent leakage loss can be used for gain equalization.

Abstract

We present a co-axial dual-core resonant leaky optical fibre design, in which the outer core is made highly leaky. A suitable choice of parameters can enable us to resonantly couple power from the inner core to the outer core. In a large-core fibre, such a resonant coupling can considerably increase the differential leakage loss between the fundamental and the higher order modes and can result in effective single-mode operation. In a small-core single-mode fibre, such a coupling can lead to sharp increase in the wavelength dependent leakage loss near the resonant wavelength and can be utilized for the suppression of amplified spontaneous emission and thereby gain equalization of an optical amplifier. We study the propagation characteristics of the fibre using the transfer matrix method and present an example of each, the large-mode-area design for high power amplifiers and the wavelength tunable leakage loss design for inherent gain equalization of optical amplifiers.