Nokia's ICE-X 800G technology has carried 600G per wavelength over 2,841km of the Brazil-USA (BRUSA) submarine cable in a trial with cable operator Telxius, as the vendor makes its case for moving coherent pluggable optics from terrestrial networks into subsea applications.

The two companies also reported a transmission record of 400G per wavelength over 5,862km on the same system. The results give submarine cable operators concrete evidence that pluggable optics — already proven in metro and long-haul land networks — can extend to ocean routes.

Nokia laid out the argument in a blog post by Serge Melle, its Optical Networks Product & Solutions Marketing lead. He framed the commercial question directly: "Pluggable coherent optics, whether deployed in routers or in thin transponders, provide undeniable benefits for network operators in terms of lower power, greater system density and reduced cost per bit. Proven deployment in metro and long-haul networks thus has subsea cable operators asking whether these benefits can also be leveraged in subsea applications?"

What are coherent pluggables — and why do they matter?

Coherent pluggable optics are compact devices that move large volumes of data over fibre while drawing less power and occupying less space than traditional transponder equipment. Speeds have climbed from 100G and 200G to 800G as digital signal processors (DSPs) have advanced.

For subsea operators, the attraction is operational: smaller footprint in landing stations, lower energy bills and a better cost per bit on regional and medium-haul routes.

Melle said: "In many cases subsea cable operators can now also consider coherent pluggables to optimise for power, space or cost."

Where does the technology stop working?

Nokia draws a clear line between what pluggables can do today and what the longest routes still require. Traditional, more powerful optical equipment remains necessary for the most demanding spans, including cables stretching 15,000km or more.

The vendor expects future generations of the technology to support speeds of 800G or higher across ocean-spanning cables, which would push pluggables further into territory currently reserved for embedded optics.

Melle concluded: "As coherent pluggables continue evolving from terrestrial to subsea networks, they give operators a practical new option for balancing reach and capacity with lower power, greater density, simpler operations and improved cost per bit — while performance-optimised embedded optics remain essential for the most demanding routes."

What's the commercial reality behind the claims?

The BRUSA trial figures come from a vendor-run demonstration with one operator partner, so the 600G and 400G results reflect laboratory-controlled conditions on a live system rather than a commercial deployment at those speeds. The underlying shift, though, is real: DSP gains have already made pluggables the default choice in terrestrial networks, and subsea operators are an obvious next market for silicon vendors and equipment makers alike.

Nokia's positioning — pluggables for power-, space- and cost-driven routes, embedded optics for the longest spans — suggests the two technologies will coexist rather than one displacing the other.

For now, the BRUSA results mark the boundary of what pluggables can reach. Whether 800G-plus versions arrive for full ocean-spanning routes will determine how much of the subsea market the form factor can capture.