On Digital Subcarrier Multiplexing under A Bandwidth Limitation and ASE Noise

TL;DR

This paper compares digital subcarrier multiplexing and single-carrier systems under bandwidth limitations and ASE noise, revealing that DSM requires more complex pulse shaping and does not outperform SC in net data rate in long-haul scenarios.

Contribution

It demonstrates that DSM's complexity is higher and it does not provide higher net data rates than SC under ASE noise in practical long-haul conditions.

Findings

DSM requires more complex Nyquist pulse shaping than SC.

DSM does not achieve higher net data rates than SC with ASE noise.

Optimized waterfilling and entropy loading do not favor DSM over SC.

Abstract

We show that digital subcarrier multiplexing (DSM) systems require much greater complexity for Nyquist pulse shaping than single-carrier (SC) systems, and it is a misconception that both systems use the same bandwidth when using the same pulse shaping. Through back-to-back (B2B) experiments with realistic transmitter (TX) modules and amplified spontaneous emission (ASE) noise loading, we show that even with optimized waterfilling and entropy loading, DSM does not achieve a larger net data rate (NDR) compared to SC when only ASE noise exists in the channel in long-haul transmission scenarios.