Contents 1. Introduction
A coupled multi-core fiber (MCF) is an attractive space division multiplexing (SDM) fiber for high capacity transmission since it has a much smaller core pitch and accommodates larger number of cores than those of uncoupled MCFs. The coupled MCF has unique properties owing to the random mode coupling in the MCF such as the narrow group delay spread specified by the spatial mode dispersion (SMD) coefficient in the ps/√km unit [1]. The lower nonlinearity of the coupled MCF has been experimentally confirmed in a 4-core transmission by comparing the single mode fiber (SMF) with the comparable fiber loss and effective area of the core mode [2]. Although the advantage of the nonlinear performance of the coupled MCF has theoretically been investigated [3], [4], a measurement method for the nonlinear property of the coupled MCF has not yet been investigated, which is mandatory for fabricated fiber characterization and transmission system design.
