That capacity travels over a single fiber pair because dense wavelength-division multiplexing places each coherent carrier at a different optical frequency.

This distinction is important. Thirty-two 800G interfaces do not require 32 separate long-distance fiber pairs. With a properly designed DWDM system, they can share the same pair.

This distinction matters.

Coherent’s new POLS product targets interconnects from approximately 2 to 200 km. That does not mean an 800G ZR+ coherent module stops working at 200 km.

Current 800G ZR+ implementations from major vendors support substantially longer distances when paired with an appropriate amplified DWDM system. Cisco, for example, specifies more than 1,000 km for its 800G ZR+ module under suitable line-system conditions. Nokia likewise offers 800G ZR+ implementations targeting regional and long-haul networks.

Cisco, Juniper and other routed-optical vendors report substantial reductions in equipment, facilities and operating cost when coherent pluggables replace external transponders. Exact savings vary too much by topology to treat any vendor percentage as a universal enterprise benchmark.

In the old architecture, a router mostly had to provide an Ethernet client signal. The optical transport equipment worried about wavelength tuning, dispersion, modulation and coherent transmission.

In an IP-over-DWDM architecture, much of that functionality is visible directly through the coherent optic hosted in the router.

Modern platforms can expose optical parameters such as receive power, transmit power, chromatic dispersion, FEC performance and wavelength settings through the router’s own management interfaces.

For many enterprises, the most interesting application is not a continental backbone. It is two or three major facilities in the same metro or neighboring region.

Examples include a primary data center connected to a disaster-recovery site, two colocation facilities, an enterprise campus connected to a cloud on-ramp facility, or two AI-compute locations separated by tens or hundreds of kilometers.

Packing 25.6 Tbps onto one fiber pair is an extraordinary utilization of physical infrastructure.

It is also an extraordinary amount of capacity to lose to one backhoe.

At this scale, a resilient DCI design should normally be discussed in terms of physically diverse routes rather than simply two logical links.

Simplifying the electronics can free budget for something much harder to replicate: physically diverse fiber.

For example, an enterprise planning 6.4 Tbps between two facilities could use eight 800G wavelengths on one route. A more resilient design could place another eight wavelengths on a geographically separate route.

That doubles optical equipment and dark-fiber requirements, but it protects the business against the failure that coherent pluggables cannot solve: a physical cable cut.

Not necessarily.

One of the benefits of ZR+ is that the newest modules can support multiple operating modes. Depending on vendor and platform, an 800G-capable coherent optic can operate at lower line rates to gain additional reach or improve optical margin.

That creates a useful lifecycle strategy: install an 800G-capable router and coherent optical ecosystem, then choose the capacity/reach tradeoff appropriate for the actual fiber path.

800G is the capacity headline. The architectural story is convergence.

At 400G, the industry demonstrated that coherent DWDM technology could move from specialized transport shelves into familiar switch and router pluggables. The OpenZR+ ecosystem was created specifically to extend that architecture beyond the original 400ZR point-to-point DCI envelope.

800G extends the same model to twice the wavelength capacity. Coherent’s pluggable line-system work now asks the next question: if the transponder can be turned into a module, how much of the line system can become modular too?