FEATURE: NEXT GENERATION NETWORKS Te companies involved with hyperscale


networks want small 400ZR components that are available from multiple vendors. Consequently, 400ZR IAs are in process for coherent optics and soſtware management interfaces. Tese are perfect examples of the OIF’s


industry role, according to Karl Gass, optical vice chair of its physical and link layer working group. ‘OIF’s goal in all its work is to identify gaps in the market that are not being served with definitions that will allow multivendor interoperability,’ he explained. ‘As an organisation, that is truly member-contribution- driven. ’Tese two projects reflect the needs of


membership, which represents a cross section of the leading component and optic suppliers, equipment providers, test and measurement companies, and network operators that make up the telecom, cloud and enterprise markets that OIF serves.’ At OFC, the OIF demonstrated two aspects


of 400ZR, explained Jeffery Maki, chair of OIF’s physical layer user group working group. One, a static demo, outlined a framework for future demonstrations of a 400ZR data centre use case. Tis ‘will continue to be fleshed out with operational products as they become available’ said Maki. A second, active demo accompanied this, showing error vector magnitude (EVM) measurements. Tis demonstrated the maturity of a test methodology established for characterising transmiters for coherent applications as an extension of the International Telegraph Union Telecommunication Standardization Sector’s (ITU-T) 100G work. ‘Te measurement methodology demo provides a future platorm to showcase our Integrated Coherent Transmit-Receive Optical SubAssembly (IC-TROSA),’ he said. Yet the technology supporting the IAs remains at an early stage.


Solid progression Nathan Tracy, president at OIF, said the OFC demos ‘did not imply or otherwise communicate that 400ZR is ready to be introduced’. ‘Te challenge of defining interoperable


coherent optics is not a simple task, but it is proceeding forward solidly. Te objective of the demo at OFC was to communicate OIF technical progress, EVM measurements, and details of the interoperable coherent application use case.’ Te form factors determining the size and


shape of the 400ZR transceivers able to plug into sockets found in switches are important. But 400ZR IA contributor firms have defined it to be ‘form-factor agnostic’, Tracy said. Te aim is to fit the solution into mechanical


form factors such as the quad small form factor pluggable double density (QSFP-DD), Consortium for On Board Optics (COBO) and octal small form factor pluggable (OSFP). Targets include minimising power consumption and volume, while maintaining link distance. ‘We understand the size and power


restrictions for “targeted” module form factors,’ www.fibre-systems.com @fibresystemsmag Issue 24 n Summer 2019 n FiBRE SYSTEMS 15


Tracy said. ‘It should be assumed that different form factors, built to the 400ZR implementation agreement, should communicate with each other over the full reach.’ Beyond hardware, OIF is defining the


standardised soſtware management interface specification for 400ZR modules that is also critical to support multiple vendors on a common system. ‘While form-factor agnostic, OIF tries to look at the ecosystem and ensure all the aspects are ready for deployment,’ said Maki. At the moment only one form factor suitable for 400ZR – the form-factor pluggable- digital coherent optics (CFP2-DCO) – has standardised soſtware registers to support coherent modulation, he added. ‘Tis will change soon.’


Working together In order to ensure interoperability, IAs must consider the data plane, according to Tracy. Here, they must enable a receiver to understand bits from a different vendor’s transmiter, decode the forward error correction (FEC) used, and correct errors. Digital Signal Processing (DSP) is central to this, especially when the components doing the DSP at each end of a link are different, he explained. Tese DSP systems will be produced


using the latest 7nm CMOS lithographic processes, making them fast enough to meet the specifications for 400ZR modules. Te biggest challenge to 400ZR interoperability is preservation of performance, including reach. Tracy said that defining vendor interoperability over a specified reach is a crucial aspect of OIF’s efforts. In the first instance, Ciena is designing


products to fit into a QSFP-DD form factor, Xenos said. However, if customers need OSFP or other packages, Xenos is confident that Ciena can fit the same capabilities into those formats. She stressed that the firm has both the coherent DSP and electro-optical technology to achieve the necessary performance level. Tese are embodied in the company’s WaveLogic 5 range, which it announced at OFC. In particular, WaveLogic 5 Nano ‘will be


IT SHOULD BE ASSUMED THAT DIFFERENT FORM FACTORS, BUILT TO THE 400ZR IMPLEMENTATION AGREEMENT, SHOULD COMMUNICATE WITH EACH OTHER OVER THE FULL REACH


optimised to deliver the smallest footprint low-power solutions’, Xenos said. ‘It’s going to be a range of solutions from 100 to 400G, and one of these would be the 400ZR pluggable solution. Target availability for 400ZR is mid- 2020.’ It’s important to move to 7nm to deliver


higher quality DSP that consumes less electrical power. ‘Te transistors are smaller and they’re closer together,’ said Xenos, ‘so there’s less energy required to perform the logical functions. For 400ZR, specifically it allows us to perform the functions that we need to get this 400G wavelength into the smallest size and consume the lowest power possible.’ In its WaveLogic 5 range, Ciena pairs this


coherent DSP technology with silicon photonics electro-optics. Xenos highlighted the company’s experience in advanced packaging that brings all these functions in this very small form factor. Ciena will also offer the important ability ‘to be able to deliver these products, and the ZR in particular, in volume,’ she says.


Full support Also at OFC, NeoPhotonics showed off its own silicon photonics offering targeting 400ZR. ‘We demonstrated live operation of


400ZR is intended to span 80km links optically, then connect with hosts via Ethernet interfaces


g


OIF


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