Detector and mode subset selection for DSP based multimode fiber links

Single-mode fibers have traditionally been the choice for medium and long haul optical links over the past two decades, with wavelength division multiplexing (WDM) offering large amounts of bandwidth. However, the recent growth in demand for bandwidth has necessitated a further expansion of optical fiber capacity. This has prompted the development of new solutions, ranging from new fiber media to digital signal processing (DSP) techniques to enhance data rates. In this paper, we briefly review some of these new developments, particularly modern multimode fibers, few-mode fibers and the DSP techniques that enable data enhancements with these fibers. We also consider the issue of decoding complexity and analyze the effect of choosing only a subset of modes or detectors at the receiver to decode with a reduced complexity, while still preserving the data rate enhancements obtained through multiplexing.