1. Introduction
Space division multiplexing (SDM) using multi-core fibers (MCFs) is considered to be a promising means to overcome the capacity exhaustion issue of conventional optical fibers [1]–[2] [3] [4]. Many researchers are intensively working for improvement of MCF performance. Among all, the inter-core crosstalk (XT) has been the most important concern about MCFs. It will be valuable, then, if we can characterize XT properties of MCFs quickly and accurately from only short samples: Preparing a multiple kilometers of MCF sample on every trial would be costly, and also it would inevitably require the MCF to be wound on a bobbin and suffer significant bend-induced effect [5].