Modulation format-dependence of crosstalk fluctuations in homogeneous multi-core fibers

Abstract

Homogeneous single-mode multi-core fibers (MCF) offer the potential for a dramatic increase of the per-fiber capacity in long-haul optical communication systems [1, 2]. Inter-core crosstalk, resulting from unwanted core coupling can limit the achievable data rates and transmission distance [3]. It has been found that short-term average crosstalk (STAX) may vary randomly over time and frequency by more than 20 dB [4, 5], potentially requiring an additional OSNR margin to guarantee a certain performance. Fig. 1 (a) shows an experimental comparison between the STAX power variation when using continuous wave (CW) and amplified spontaneous emission (ASE) noise within a 0.2 nm bandwidth as crosstalk source. The STAX variation is strongly reduced for ASE compared to CW. This dependence of the STAX variation on the spectral characteristics of the crosstalk-inducing signal is critical for the design of MCF transmission systems but is yet to be explained. This paper presents a numerical analysis of the crosstalk behavior when using modulated signals and its dependence on the propagation delay between cores, referred to as skew.