Filter Bank Multi-Sub-Band Transmission for Optical Systems with Mode Multiplexing

Abstract

Mode-multiplexed optical transmission is subject to mode coupling and potentially large differential mode delays. In most recent implementations, these effects are compensated for at the receiver by complex adaptive multiple-input multiple-output (MIMO) equalizers. Although frequency-domain MIMO equalization requires a moderate complexity compared to time-domain equalization, the long required fast Fourier transforms may face implementation issues. In this paper, we evaluate an alternative transceiver architecture based on sub-band partitioning, implemented by filter banks, which enables concurrent time-domain equalization. Single-carrier (SC) and multi-sub-band (MSB) mode division multiplexing transmission are simulated using frequency-domain equalization and time-domain equalization, respectively. Their performance is compared in terms of static transmission performance, channel tracking capability, phase noise tolerance, and computational complexity. The results indicate that compared with an equivalent SC solution, the MSB architecture provides a high degree of parallelism at the cost of a penalty of 0.7-1.3 dB for a laser linewidth of 25-100 kHz and a moderate increase in complexity.