Differential Mode Delay Managed Transmission Line for WDM-MIMO System Using Multi-Step Index Fiber

We proposed a mode group delay managed transmission line for a WDM-MIMO system consisting of fibers with positive and negative DMDs to compensate for the total DMD. We show numerically that the multi-step index fiber can flexibly tune the DMD. We fabricated fibers for use in a C-L band WDM-MIMO system, and realized a 20.4 km-long DMD compensated transmission line with a total absolute DMD of less than 111 ps over the entire C-L band. Finally, we achieved a 2 $,\times,$ 2 WDM-MIMO transmission within the C-L band by using equalizers with a small tap number.