On the energy efficiency of modulation formats for optical communications

Abstract

An information theoretic framework for performance evaluation of high-dimensional modulation formats in an optical communication link is proposed. The spectral and energy efficiency of different candidates for future coherent optical communications are analyzed to explore the advantages of exploiting different degrees of freedom for symbol coding, construction, and transmission. Our analysis demonstrates the advantage of fully utilizing both polarization states from the spectral and energy efficiency perspective. In particular, at the same spectral efficiencies of 2.5 and 2.8 b/s/Hz, dual polarization quadrature phase shift keying (DP-QPSK) has, respectively, 0.8 and 1.6 dB energy efficiency..