EUGENE PARK ULTRA LONG HAUL NETWORKS
WITH ULTRA LONG-HAUL COHERENT PLUGGABLES EXPANDING IP-OVER-DWDM APPLICATIONS The introduction of 400G coherent pluggable optics marked a pivotal moment, enabling the convergence of the optical transport and IP layers. This paradigm, often referred to as IP-over-DWDM, allows coherent modules to plug directly into router ports, eliminating the need for traditional transponder hardware. Hyperscalers were early drivers of this architecture and quickly capitalised on it for their metro data centre interconnects. Service providers soon followed suit, recognising the significant network cost savings.
F or instance, Bell Canada projected savings of 125 million Canadian dollars over ten years by reducing capital expenditure (CapEx) by approximately 27% through this approach and Arelion expects savings up to 66% CapEx and 95% operational expenditure (OpEx) compared to legacy, discrete solutions.” Today, hundreds of network operators have embraced this cost-saving paradigm. The widespread adoption was enabled by the availability of interoperable 400G coherent multi source agreement (MSA) modules in form factors such as QSFP-DD and OSFP, with QSFP-DD becoming the dominant choice due to its compatibility with widely adopted host platforms. Widespread adoption of disaggregated optical line systems has also played a crucial role. Open line systems enabled the insertion of wavelength transmission directly from router-based coherent MSA pluggable modules, rather than being tied to transponders from the same line system vendor. This flexibility has been a key enabler, with most network operators utilising an open line system alongside router-based optical modules. EXPANDING HORIZONS: 400G ULH PLUGGABLES FOR LONG- HAUL AND ULTRA LONG-HAUL While 400G coherent pluggables initially focused on metro and regional reaches, the industry’s continuous drive for expanded capabilities led to the development of 400G Ultra Long Haul (ULH) modules. These modules leverage advanced coherent technology,
specifically Class 3 (120+ Gbaud data) rate technology, to extend the reach of 400G from metro/regional distances to truly ultra long-haul applications. This breakthrough significantly reduces the barrier for network operators to deploy router-based coherent optics in virtually any network scenario. As shown in the following examples, the advantages of using these coherent pluggables for long haul and ultra long-haul routes are compelling. SIGNIFICANT COST SAVINGS By integrating optical functions directly into routers, operators can reduce the number of discrete devices, simplify network design, and lower power consumption. This translates directly into CapEx savings from fewer dedicated transponder shelves and OpEx savings from reduced power, cooling, and operational complexity. Arelion’s successful trial of 400G ULH modules demonstrated successful IP transmission at a spectrum of 112.5 gigahertz over 2,253 kilometres, with healthy margins, providing longer transmission distances
and higher cost savings than currently deployed transponders. Arelion stated that the 400G ULH pluggables enable a 35% reduction in CapEx and an 84% reduction in OpEx when expanding its network, providing wider reach with high capacities that support customers’ AI/ML and cloud applications. SIMPLIFIED OPERATIONS, REDUCED FOOTPRINT, AND POWER EFFICIENCY Pluggables simplify network architecture by eliminating external transponders, allowing for a more compact and streamlined deployment. This reduces rack space, cabling, and overall network complexity. The compact nature and optimised design of pluggable modules leads to lower power consumption per bit. Internet2’s trial, which achieved a 400 Gbps link over 3,000 km using 400G ULH pluggables, highlighted its efficiency, consuming less than 24 watts of power.
Low module power consumption enables 400G ULH to be supported by 400ZR/ZR+ platform ports.
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ISSUE 42 | Q3 2025
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