Cisco Systems, Fujitsu and operator KDDI recently turned on a metro network in Japan that uses an open architecture combining the IP layer and optical transmission layer to smooth operations and reduce power consumption by up to 40%. The network shows continued momentum toward an all-photonic network (APN) architecture.

The network uses Cisco’s NCS5500 series routers to directly transmit and receive optical signals for wavelength-division multiplexing (WDM) across Fujitsu’s 1Finity open line system (OLS). This connection is through an open interface.

Bill Gartner, SVP and GM for Cisco’s Optical Systems and Optical Business Unit, explained in an interview with SDxCentral that the vendor’s part of the network was to integrate the previously used WDM equipment into its router, which reduced the needed footprint and power.

“You take those chassis that we're carrying transponders out of the solution and for space-constrained environments that's an important consideration,” Gartner said. “Overall, it's just a simpler solution. You're putting a pluggable into a router rather than having to deploy a chassis or chassis-based solution when you want to deploy more capacity.”

These efforts are also being pushed by the growing use of open interfaces. This move de-couples the layer-zero physical fiber from the layer-one components that send traffic over that fiber.

“Customers get the benefit of being able to have multivendor solutions out there now,” Gartner said. “DWDM [dense wavelength-division multiplexing] was sort of the last bastion of networking that was not standard and with this new generation of pluggable optics, it’s opening up the layers — layer-zero, layer-one — and this new generation of optics is opening what was a proprietary solution for many years.”

The simplified nature of the KDDI/Cisco/Fujitsu work also leads to increased efficiency.

“As the capacity goes up, the total power goes up too, but the power-per-bit has to come down. Customers look at the cost-per-bit and the power-per-bit and we have to continue to drive that down,” Gartner said. “We are very focused on driving down the power of a bit and the cost-per-bit and the space-per-bit. The total power might go up as you go from 10-gig to 100-gig, but the power-per-bit has to be going down.”

Gartner added that the work with KDDI and Fujitsu is with 100 Gb/s and 200 Gb/s connections, but that operators can see even more savings as they ramp up speeds. “We've seen upwards of 90% when we're at 400 gigs, so there's a significant amount no matter how they look at it,” he said.

The move toward more efficient equipment architecture is becoming increasingly important for operators as they look to expand the reach and capacity of their networks.

Chris Sambar, EVP for technology at AT&T, labeled his carrier’s sustainability work as “green G.” He explained during the recent Brooklyn 6G Summit that “the older stuff uses between six and eight times as much power, so we're constantly trying to turn off the old stuff and migrate to the new stuff as soon as possible.”

KDDI plans to deploy this newly architected metro network across Japan by the end of fiscal 2028.

The carrier is also using this work as the first step toward APN. This goal would see optical light-based wavelength signals transmitted without having to convert that transmission into an electrical signal for routing. That optical light transmission can instead remain a light signal throughout the length of its journey.

KDDI earlier this year struck a deal with in-country telecom rival NTT to work toward global standardization of optical and photonic networking technology. This work is tapping into the Innovative Optical and Wireless Network (IOWN) Forum, which NTT helped form in 2019.