Final industry reflections from ECOC 2025. Here Professor Polina Bayvel, Dr Sanjai Parthasarathi, Lisa Huff, and Jörg-Peter Elbers share their thoughts.
Polina Bayvel, Royal Society Research Professor & Professor of Optical Communications & Networks Head, Optical Networks Group, Department of Electronic & Electrical Engineering, UCL
ECOC this jubilee year (1975-2025) felt like a party. The large number of exhibitors reinforced the excitement, as did the technical conference attendees numbering approximately 2,000.
Unfortunately, I had to leave halfway through the conference and follow the rest online. The Sunday workshops were packed – especially the one on modulator technologies, with people lining the gangways, along the walls, and sitting on the stairs.
The availability of reliable, high-frequency modulators, especially for coherent transmission, is definitely a challenge. Thin-film lithium niobate is winning as a technology, but there are too few suppliers of low-loss commercial devices capable of bandwidths well beyond 100GHz. Broadband modulators, spanning several wavelength bands, are also clearly missing.
In terms of new developments, work on hollow-core fibre continues to impress, with several low-loss results and the promise of broadband operation over hundreds of nanometres. The post-deadline papers on hollow-core fibre by the Microsoft, Southampton, and Linfiber Technology teams were impressive – especially the long-haul transmission with a fully loaded C-band from the team led by Ben Puttnam (Microsoft).
One of the key promises of hollow-core fibre is the absence of non-linearities and the possibility of using high-power lasers. However, given operators’ caution about allowing high-power (above 20dBm) in their networks, I wonder whether high-power will ever come into practical use? And what about the availability of really high-power amplifiers across various bands? Something for researchers to think about!
Despite the excitement in the field, I felt disappointed and somewhat shocked by how the entire field is being dominated, and its direction shaped, by the hyperscalers.
This development has an impact on the development of optical technologies and on fibre companies. The increasing dominance of coherent pluggables over embedded systems overlooks that both are the result of an enormous amount of research on digital communications and digital signal processing (DSP), and that they are not separate technologies but represent a continuum of optimisation.
The plenary talk by Edward Lee from Nvidia brought this into sharp focus. The push to develop optical networks for AI factories overlooks the fact that these networks consume at most 10 per cent of the power in these data centres. The push to reduce this by halving it to 5 per cent is having an effect, changing the direction of the entire field to serve these goals. The end-goal is to use the savings in power to monetise the graphics processing units (GPUs) with the GPU-as-a-service model. More GPUs will make more money but for whom, though?
Money talks, of course, but are we missing opportunities to develop groundbreaking science, devices, and algorithms in the future if the entire field is now being encouraged to work on co-packaged optics and its applications for short-term gains? At least Nvidia seems to have discovered wavelength-division multiplexing, citing it as an exciting ‘future alternative’ technology!
In the Sunday workshops, numerous speakers from fibre companies cited cost as the biggest challenge. Optical fibre companies, who have led the developments enabling the communications over four orders of magnitude in distance (1km to 10,000km), now appear as ‘poor relatives’ to the hyperscalers, being demoted to the level of ‘commodity’ providers. This was shocking to see.
This may stem from the short-term approach to optical networks, which are made up of fibre links. These are viewed as ‘dumb pipes’ or ‘optical plumbing’ rather than offering intelligent access to bandwidth that more adaptive, intelligent and educable networks could provide. These networks will, in the future, operate on land, in space, and under the sea. Maximising network throughput and focussing on the design of networks resilient to changes in topology, traffic patterns, and service requirements could bring much greater benefits in the long term.
I encourage all optical comms researchers & professionals to think beyond the current co-packaged optics & AI hysteria, as hard as it is to resist the AI tsunami. But all tsunamis eventually pass.
Dr Sanjai Parthasarathi, Chief Marketing Officer at Coherent
ECOC 2025 once again confirmed the incredible momentum driving the data centre and communications industries, and highlighted how photonics innovation is evolving to meet the scale and complexity of the AI era.
The prime time for 1.6 terabit is coming! The demand is booming in both scale-out and scale-across applications: we saw a lot of effort at all levels of the value chain (optics, electronics, and integration) to be ready for the expected ramp-up in 2026.
The appetite for bandwidth remains relentless, despite some concerns about long-term uncertainties; demand shows no signs of easing. This sustained growth is driving innovation in areas such as higher bit-per-lane transmission. One area of particular focus was 400 gigabit-per-lane transmission, which underscores the industry’s commitment to pushing the boundaries of speed, efficiency, and cost-effectiveness in next-generation optical interconnects.
Co-packaged optics (CPO) was one of the most discussed topics on the show floor. The conversation has clearly shifted from concept to manufacturability. Turning co-packaged optics into a large-scale reality will require a coordinated effort across the entire ecosystem, encompassing demand from cloud operators and solutions not just at the laser and integration levels, but also down to the passive optics element and fibre assembly.
Alternative architectures are also generating strong interest. Our “slow-and-wide” approach, demonstrated through a 2D VCSEL array and detector configuration, drew considerable attention and thoughtful questions. We see this as a promising pathway for scalable implementation: one that could complement the traditional co-packaged optics roadmap.
A key theme emerging from many discussions was scale-across: a concept gaining traction as data centres evolve into distributed, geographically diverse engines powering AI. The enthusiasm surrounding this idea points to a new wave of market potential as global AI infrastructure matures.
I was also pleasantly surprised by the strong interest in quantum key distribution (QKD).
The joint demo we participated in attracted more attention than expected, boosted by growing momentum from government programmes.
ECOC 2025 highlighted how innovation in photonics, from co-packaged optics manufacturability to new scaling paradigms, will continue to shape the future of AI connectivity and high-performance networks.
Lisa Huff, Chief Analyst, Optical Components, Data Centres and Connectivity at DC Tech Analysis
Just like OFC 2025, ECOC was all about AI networks and how the optics industry can support them. I expect this trend to continue for years to come as cloud service providers struggle to build their massive AI infrastructure.
At ECOC 2025, I observed two significant technological advancements.
- Progress towards the realisation of co-packaged optics/ near-packaged optics from both Meta and Broadcom. The reliability data shown by both companies highlight that the promise of the technology may be realisable. While co-packaged optics has seen slow, incremental advancements, this seems to be a much larger one. Whether this can be commercialised and deployed into production data centres remains to be seen, but it’s a monumental milestone along this path.
- 400 gigabit-per-line electrical interfaces are progressing much faster than anticipated. Just six months ago, at OFC, most companies were struggling to show any kind of signal integrity for any type of PAM encoding, and especially PAM4. At ECOC 2025, the OIF demonstrated a 400-gigabit open eye using PAM4 – a significant milestone, marking great progress in six months.
From one of the workshops, I learned that the fight between VCSELs and silicon photonics is alive and well. I believe it will continue into 1.6-terabit devices and probably beyond that.
Jörg-Peter Elbers, Senior Vice President, Advanced Technology, Standards and IPR, Adtran
ECOC 2025 was held in the beautiful city of Copenhagen. The event was very well organised and attracted over 8,000 visitors from across the world.
For me, the most exciting themes were “AI for Optics” and “Optics for AI.”
The former theme focused on leveraging agentic AI and large language models to automate and improve efficiency in network operations.
The vision is to apply a divide-and-conquer strategy, breaking down complex tasks and workflows so that specialised agents—think of AI-based ‘junior engineers’ trained through knowledge input and feedback—can solve them more effectively.
The theme of Optics for AI resonated throughout the conference and show-floor discussions. A highlight was Nvidia’s Edward Lee keynote, which showed the massive scale of next-generation AI factories and explained why Gigawatts are the new currency of data centres.
While copper remains dominant in scale-up configurations, optical technologies are essential for scale-out and front-end connectivity and are expected to play an increasingly important role in future. Near-packaged optics and co-packaged optics promise reduced power consumption at the electrical interface, though pluggable transceivers continue to be vital for interface flexibility and inter-data centre reach.
There is growing industry consensus around OSFP as the preferred format for pluggable 800 gigabit and 1.6 terabit transceivers, which demands equipment capable of dissipating 40W per OSFP in a compact equipment form factor. The 200 gigabit per lane speed currently represents the sweet spot at which electrical and optical lanes can operate comfortably without the need for ‘gearbox’ ICs. The jury is still open on whether next-generation 3.2Tb/s interfaces will adopt 400- gigabit lane speeds or require increased parallelism.
Looking ahead to a data centre landscape where AI accelerators and compute clusters demand petabit-per-second connectivity and ultra-compact, low-power optical short-reach interfaces, our Starfall project anticipated a post-IPoWDM era in which transponders would experience a renaissance.
We envisioned “one box – one band” solutions, where pizza-box-style integrated terminals provide interface conversion from short-reach to dense WDM data centre interconnect optics in a rack-and-stack configuration for a full wavelength band. It was gratifying to see this concept echoed in Benny Mikkelsen’s (Cisco/Acacia) keynote talk, which proposed a full C-/L-band transponder in a box using multi-channel integration.
Another hot topic was the advancement of hollow-core fibers. Pre-show announcements, such as the collaboration between Microsoft/Lumenisity and Corning, signal that the industry is becoming serious about addressing scalability challenges in production and making these fibers more widely available. Insertion losses continue to improve, and operational challenges are being actively addressed.
ECOC 2025 will likely be remembered not only for its 50th anniversary (51st edition) but also for the drone sightings over Copenhagen Airport prior to the event and the European leaders’ summit at the Bella Center on the final conference day.