  Operators are constantly faced with the need to increase optical-network
capacity to accommodate rapid traffic growth while minimizing the cost-per-bit
and power-per-bit. The drastic reduction of power consumption of IP routers and
ZR/ZR+ pluggable transponders seen in the last years has renewed the interest
in "opaque" optical-network architectures, where no optical bypassing is
allowed. In this work, we aim to quantify and compare the power consumption of
four "IP over Wavelength Division Multiplexing" (IPoWDM) transport network
architectures employing ZR/ZR+ modules vs. long-haul muxponders, considering
different grooming, regeneration, and optical bypassing capabilities. We first
propose a power consumption model for different IPoWDM node architectures with
ZR/ZR+ modules and long-haul muxponders. Then, to obtain the power consumption
of different architectures, we propose a compact auxiliary-graph-based
network-design algorithm extensible to different network architectures.
Moreover, we investigate how the continuous decrease in the power consumption
of ZR/ZR+ and IP routers can impact the power consumption of different
architectures through a sensitivity analysis. Illustrative numerical results on
networks of different sizes show that, despite drastic reductions of power
consumption at IP layer, optical bypassing is still the most power-efficient
solution, reducing consumption by up to 48%.
