EUGENE PARK OPENZR+
by 400ZR. “ZR+” became the term used to specify or capture these broader modes of operation beyond 400ZR. However, due to lack of a uniform definition, the term ZR+ created industry confusion. To meet the need for hyperscale DCI links beyond 120km with QSFP-DD/OSFP form-factors, an industry effort looking at adding high-performance elements of OpenROADM to the 400ZR standard resulted in a new interoperable solution known as OpenZR+. OpenZR+ (Figure 2) maintains the simple 400ZR Ethernet-only host interface while adding support for: (1) higher coding gain oFEC from OpenROADM MSA to extend reach; (2) multi-rate Ethernet to enable 100GbE and 200GbE client multiplexing over the line-side link; (3) adjustable 100G, 200G, 300G or 400G line-side transport links (using QPSK, 8QAM, or 16QAM) to enable reach/capacity optimization over various links; and (4) higher dispersion tolerance. The higher performance of OpenZR+ can benefit hyperscale network operators by enabling a wider geographical extension of the physical connections to cover DCI Edge and regional interconnects (Figure 3). Because modules designed using OpenZR+ generally support 400ZR, as well, hyperscale operators can reduce operational complexity by having one module type. Hyperscale line systems with 75GHz DWDM grid spacing can also benefit frommodules utilizing OpenZR+. 400ZR transmission, initially targeted for 100GHz channels, might degrade over 75GHz grid spacing due to higher filtering penalties. The additional gain from oFEC in OpenZR+ can be used to compensate for these additional penalties. Carrier efforts to create a data centre OPENZR+ APPLICATIONS AND BENEFITS
Figure 3. OpenZR+ enables the expansion of a DCI network’s geographical footprint
topology, such as CORD within the Open Networking Foundation (ONF), may also benefit from OpenZR+ utilizing this Ethernet-centric coherent optical solution in a similar fashion to a hyperscale edge/ regional interconnect. Because OpenZR+ is derived from existing standards, network operators can operationally benefit from interoperability among multiple suppliers that adopt OpenZR+. Module suppliers can also benefit from OpenZR+ by supporting applications beyond 400ZR, reaching a wider range of applications. OpenZR+ utilizes a common-sense implementation of functionality, already well defined in existing standards. In support of OpenZR+, Acacia and NEL recently announced the exchange of DSP test vectors to confirm interoperability. This industry milestone paves the way for CONCLUSION
QSFP-DD/OSFP module development that supports performance and functionality beyond 400ZR. Network operators can now achieve the benefits of 400ZR with enhanced features that can expand the reach and functionality without sacrificing interoperability. Because OpenZR+ is derived from existing standards, network operators can operationally benefit from interoperability among multiple suppliers that adopt OpenZR+. Module suppliers can also benefit from OpenZR+ by supporting applications beyond
400ZR, reaching a wider range of applications.
Figure 2. OpenZR+, the logical combination of two industry standardization efforts.
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ISSUE 20 | Q1 2020
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