The growing Internet traffic has imposed strong demands on current fiber optical communications. Mode division multiplexing (MDM) transmission based on few mode fiber (FMF) has attracted worldwide research interests, due to the potential for overcoming the capacity crunch of standard single mode fiber (SSMF). It is expected that N spatial modes in the FMF can achieve a capacity N times higher than that of the SSMF. We review the recent progress of MDM techniques including mode division multiplexer/demultiplexer, FMF design and fabrication, few-mode fiber amplifiers for long-haul transmission, and the latest outstanding transmission demonstrations. Finally, we outline the prospects and future challenges in this research topic.

mode division multiplexing  /  few-mode fiber  /  optical fiber communication  /  high capacity optical transmission