Optical Connections Magazine Spring 2023



With traffic volumes, data densities and pressures on service provider costs continuing to ramp up, the attractions of 800G and beyond optical networking have become compelling for many different areas of application, writes John Williamson .

A s outlined by Helen Xenos, Senior Director of Portfolio Marketing at Ciena, these attractions include significant reduction in footprint, lower power and transport costs, and fewer wavelengths to deploy and manage. “Furthermore, 800G technology enables optical network evolution to the high-bandwidth ubiquitous 400GbE connectivity that is required to interconnect modern 400G routers,” she adds. 800G is well established in the general communications networking domain. “800G is pervasive in most parts of the network now. In addition to subsea and long haul, 800G solutions are increasingly being deployed in metro and regional networks,” asserts Robert Maher, Infinera CTO. He notes that the barriers to 800G use are falling, as most optical line systems use flexible wavelength selective switches and low noise Raman amplification, enabling long distance transmission of these higher speed wavelengths. “As demonstrated by Infinera and others, the more advanced 800G solutions are capable of transmission distances of 1,000km or more, making the technology viable for a large portion of operators’ networks.”

difficulties, and much depends on how easily it can be introduced and operationalised into the network. Xenos says the key issues are around the availability of all the requisite elements for widespread deployment. This includes support across multiple platforms to meet diverse customer requirements; the ability to supply products in volume; link engineering and design tools; support of photonic line systems; operational integration into a multi-layer domain controller; and open APIs. LONG DISTANCE INFORMATION Nor was getting 800G to run over extended distances a shoo-in. Serge Melle, Nokia’s Director of IP-Optical Product Marketing, describes how, using the earlier generation of coherent transport, some solutions operating at 90 to 100Gbaud could operate at “headline” capacities up to 800Gbps, but that the physics of coherent transmission limited operation of those systems at 800Gbps only out to several hundreds of kilometres. “For longer distances, and certainly anything over 1,000km, the coherent wavelength speed needs to ratchet down to 600Gbps or 400Gbps in order to go longer distances such as in regional and long-haul networks or subsea links,” he points out. “While current 90 to100 Gbaud coherent solutions are great for enabling 400GE

over ’any distance’, they cannot efficiently transport 800GE services in such a fashion. So it’s difficult to get 800G to run over very long distances? “Very,” emphasises Xenos. Even though very difficult, given the spans currently being achieved by the like of Ciena, Infinera, Nokia and others, stretching the reach of 800G is clearly now a fact of life. Pointing out that the symbol rate, or baud, of coherent design influences the highest throughput per wavelength that can be achieved for a specific distance, Xenos observes that the higher the baud or symbol rate, the better the performance. “Achieving a higher-baud design is dependent on advanced CMOS technology, as well as access to high-speed, high- bandwidth design elements that may not be available in the market yet,” remarks Xenos. This includes high-bandwidth electro-optics with the appropriate passband to process the new signal and digital-to-analogue and analogue-to- digital converters (DACs/ADCs) that can operate at an appropriate sampling rate. Also, in the Ciena ‘go-further’ 800G mix are sophisticated Forward Error Correction (FEC) algorithms, and further improvements in electro-optic miniaturisation, leveraging photonic integration with silicon photonics, Indium Phosphide (InP) and other materials. Melle says that new sixth-generation super-coherent optics, that leverage the

Needless to say, the larger scale commercialisation of 800G has its


| ISSUE 32 | Q1 2023


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