EUGENE PARK OPENZR+
THE RISE OF OPENZR+ THE ANSWER TO STANDARDISATION?
The move towards 400G and beyond is creating standardization issues for transceiver vendors looking to build components capable of higher speed. However, OPENZR+ looks to be the way forward, writes Eugene Park, senior technical marketing manager at Acacia Communications.
H istory has shown that adoption of optical transceiver/transponder solutions accelerates when implementable standardization and interoperability are established. Coherent optical technology, traditionally a closed-system technology with proprietary implementations, is evolving towards a similar path, which will help carriers and hyperscale data centre network operators by ensuring multiple suppliers for their critical components. This article reviews recent standardization efforts and also introduces a new 400G interoperability solution called OpenZR+. Publicly supported by numerous industry solution in a small form factor pluggable module that addresses hyperscale data centre applications for edge and regional interconnects, as well as potential future carrier applications. leaders, OpenZR+ provides an open, flexible and interoperable coherent Historically, optical transport networks were comprised of proprietary bookended carrier-centric solutions using differentiated technology to achieve high-capacity, long- reach links. When coherent technology moved into 100G pluggable form-factor solutions, there were early carrier efforts to demonstrate interoperability. Through OpenROADM MSA and the ITU, service providers drove standards that could be supported by multiple vendors, while CARRIER AND HYPERSCALE EFFORTS INTERSECTING AT 400G
In a separate effort, the carrier-focused OpenROADM MSA group chose a high performance soft-decision FEC, called openFEC (oFEC), that offered higher coding gain (comparable to proprietary long-haul bookended implementations) compared to 400ZR. The OpenROADM MSA not only defined a framing that supported 200G, 300G or 400G line rates all utilizing oFEC with greater host-board interface flexibility, but also supported multiplexing functionality and additional protocols such as OTN.
leaving opportunity for higher performance differentiated proprietary implementations. In late 2016, some network operators and a few vendors identified 400G as an intersection point for supporting coherent optics in the same form factors as emerging high-volume client optics, such as QSFP-DD and OSFP. Hyperscale network operators proposed to the Optical Internetworking Forum (OIF) a new project targeting DCI edge applications up to 120km (Figure 1), with a module power dissipation objective of ≤15W. The resulting OIF implementation agreement was known as 400ZR. OIF was quite successful in expediting this effort, with power optimization taking the highest priority in each decision. 16QAM and ~60Gbaud were adopted for the modulation format and baud rate, and a concatenated (hard-decision + soft-decision) FEC was selected.
OPENZR+: TAKING THE AMBIGUITY OUT OF “ZR+”
While the OIF focused on specifications, leading switch manufacturers successfully increased the QSFP-DD/OSFP per-port power consumption tolerance of next generation equipment beyond 15W, enabling the potential of adding features and higher performance modes not covered
Figure 1. Target application space of DCI edge for 400ZR.
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| ISSUE 20 | Q1 2020
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