With many vendors now introducing fifth-generation coherent interfaces, which will support 400G to 600G on one wavelength, some industry executives predict line rates of 400G and higher will become more power efficient in 2019 and 2020, driven by by the 400G-ZR standard.
"We will see the underlying technology move into 400G applications beyond the original ZR definition," Harald Bock, vice president of Network & Technology Strategy at Coriant, told Broadband World News.
There are multiple drivers to deploy higher speed wavelengths, including lower cost per bit, lower power consumption and higher capacity of the transmission system. The 400Gbit/s line interfaces also push C-band capacity from about 20Tbit/s per fiber pair to about 40Tbit/s, Bock said.
"Right now, the best cost and power consumption for coherent detection interfaces is achieved by the latest generation 16 nm electronic integration," he said, noting these are implemented in the latest 200G/wavelength products.
Many scenarios in core optical networks and submarine networks also will improve due to the new standard's system scalability, Bock predicted. Although speeds may differ from the improvements operators see on core detection interfaces, submarine networks -- which carry more than 97% of global data traffic, with the remaining 3% or so traversing via satellite systems, according to ResearchandMarkets -- will also enjoy faster performance.
While applications in submarine networks may not be 400Gbit/s to 600Gbit/s, "those interfaces also provide much better reach at for example, 150Gbit/s or 200Gbit/s, extending the use case of 200Gbit/s to trans-Pacific reach," said Bock. "[Another plus is] the lower complexity of managing wavelengths and equipment in the network," he added.
"These interfaces will be used in long-reach applications, providing a significantly improved trade-off between reach and single carrier line rate versus older generations. They will be used in subsea applications and long terrestrial links to increase overall fiber capacity and remove the need for regeneration," Bock said. "We expect both higher capacity as well as longer reach use cases to be the triggers for the first deployments, with increased programmability becoming a driver for deployment later on as network automation is enhanced by network operators."
Moving the focus to data center interconnect (DCI), benefits include maximum scalability, capacity per fiber and minimum power consumption and footprint.
"As a result, data centers are using 200G line speed today for high capacity interconnect." Bock noted. "200G 16QAM, using the latest electronic integration, provides the lowest power DCI -- besides enabling highest capacity per fiber. As a next step, those connections needing very high capacity will move to 400G-600G line rates with power targets only met by the newest interfaces using the latest generation CMOS integration."
Newer generations of 400Gbit/s wavelengths triggered by the 400G ZR standard will improve power efficiency and "become the standard deployment model, particularly for shorter reach applications," said Bock.
Today's high-speed interfaces are not fixed-rate interfaces but do have flexible capabilities for modulation rate and modulation depth. This makes them ideal for submarine as they offer unprecedented tenability to trade off reach versus capacity/spectral efficiency.
"400G transmission on a submarine link will be possible for regional installations while trans-Pacific installations will likely move to 200G per wavelength or even a bit beyond," he said. "Overall, the latest generation of terrestrial interface technology can be very easily adopted by subsea applications. This further reduces the need for the dedicated development of subsea line interfaces."
These new interfaces' programmability is directly tied with the level of network automation achieved today. Applying software-defined networking (SDN) in a DCI environment is the natural extension of data centers (DC) linking of automation to their interconnecting networks. This approach enables automated provisioning and monitoring of the DCI network in the same way as the DC itself: With its open, standardized northbound interfaces (NBI), SDN can easily be integrated into Data Center Orchestration (DCO).
And, when integrated with SDN, providers can use the flexibility of modern packet optical networks to adapt DCI bandwidths and topologies according to real business needs, such as time of day, special events and faults.
Implementation requirements include Network Orchestrator with open NBIs, programmable SDN Controller solution that adapts to the specific network situation and use cases, and integration of the SDN solution in the DC orchestration.
Proprietary SDN solutions have some advantages like early availability and tailoring to the suppliers’ environment, but they also have challenges -- higher integration efforts due to proprietary approaches and technologies instead of standards-based integration that can be used off-the-shelf with little effort, for example.
"Redoing or at least verification of one of the involved systems with every release update is another challenge, and they are not future-proof as proprietary solutions may end up moving in a different direction than standards-based solutions.," Boch said. "Interoperating in a multi-vendor environment then poses challenges when operators are locked in with non-standard solutions."
Whilst the industry still faces many challenges, 400Gbit/s speeds will be appropriate across all network segments wherever use cases demand high capacity and multiple opportunities emerge as new technologies become available. The use of 400G is particularly appropriate for high-speed DCI and high-capacity core networks. The industry as a whole is moving in the direction of open solutions that eliminate the downsides of vendor lock-in; just like other systems, proprietary SDN solutions are simply not viable. Operators don't -- and won't -- buy them, and vendors that embrace open systems and standards are listening to their customers to deliver what they want.
— Logan Armendone-Mowbray is content marketer at KNect365.