Long-Haul Mode Multiplexing Transmission Enhanced by Interference Cancellation Techniques Based on Fast MIMO Affine Projection

In space division multiplexing (SDM) transmission utilizing mode division multiplexing (MDM) technologies, transmission performance of each spatial channel is highly dependent on a spatial mode that delivers information symbols over few-mode fibers (FMFs) or multi-mode fibers (MMFs). This still remains as a dominant barrier to realize a future deployable long-haul MDM transport systems. In this article, we review the transmission issues we face when transmitting MDM signals over long distances. We also present the review of key techniques that we have recently developed to overcome mode-relevant linear phenomena. By developing the projection technique for a signal detection application in multiple-input multiple-output (MIMO) systems, a novel linear filtering adaptation technique is proposed to enhance the performance of our interference canceling scheme with decreased complexity. Experimental evaluation using dense SDM transmission results over multicore FMFs verifies a fast convergence property brought by the proposed projection technique.