Design tradeoffs of few-mode step index fiber for next generation mode division multiplexing optical networks

Next generation few mode fibers (FMF) promise to substantially increase the spectral efficiency of existing state-of-the-art optical communication networks by an order of magnitude [1]. In FMF, individual propagating modes are considered as independent optical communication channels that carry separate streams of data. The performance of these communication streams however, suffers from inter channel interference (ICI) that depends on the physical characteristics of the optical fiber. The ICI mainly results of two impairments, namely the mode coupling and the differential mode delay. It is known that step index (SI) FMF is the less expensive and the easiest to fabricate in addition to having a limited number of physical design parameters, i.e., step refractive index and core diameter. Our objective here is first to investigate the design trade-offs of SI-FMF and then identify the parameters intervals that minimize the inter channel interference by reducing: the mode coupling and the differential mode delay. Our numerical simulation identifies the desired design regions that minimize these impairments separately. Our analysis also illustrates the challenge to minimize both impairments simultaneously and get compromising design solutions.