Ultimate Spectral Efficiency Limits in DWDM Systems

The overall capacity (b/s) of a DWDM transmission system is governed by the available bandwidth (Hz) and by the achievable spectral efficiency (b/s/Hz). Ultimate limits to the spectral efficiency are determined by the information-theoretic capacity per unit bandwidth. While closely approaching these limits may require exponentially increasing complexity and delay, establishing accurate estimates of the limits can yield insights useful in practical system design. This paper summarizes current knowledge of spectral efficiency limits in amplified DWDM systems, and briefly review technologies required to approach these limits.