Energy efficiency in WDM fiber-optical links considering OADM/OXC nodes

In this paper, authors discuss the energy consumption for 1 bit transmission as a function of spectral efficiency (SE, bps/Hz), aggregated traffic amount (C, bps), and overall transmission distance (LP2P, km) in wavelength division multiplexing (WDM) systems with optical add-drop multiplexer/ optical cross-connect (OADM/OXC) nodes. The choice of bitrate and modulation formats was limited to three options: 10G non-return-to-zero on-off keying (NRZ-OOK), 40G NRZ differential phase-shift keying (NRZ-DPSK) and 100 dual polarization quadrature phase-shift keying (DP-QPSK). The reasons for that is the legacy in transmission networks and high energy efficiency of 3R (re-amplification, re-timing, re-shaping) regenerators and transponders, respectively. In addition, these formats are commonly used for 10-40-100G mixed-line rate solutions in core networks. It is found out that 100G DP-QPSK is the best solutions among two other considered in terms of both energy consumption per bit and spectral efficiency. Finally and foremost, it is estimated that for the WDM channels added at the OADM/OXC node, energy consumption per 1 transmitted bit could growth more than two times as compared to wavelengths transmitted over point-to-point fiber-optical links and then dropped at the receiving node.