Aloe Semiconductor

Vijay Vusirikala, Distinguished Lead, AI Systems and Networks, and Andy Bechtolsheim, Chief Architect, at Arista Networks.

OFC 2025 wasn’t just another conference. The event felt like a significant momentum-gaining inflexion point, buzzing with an energy reminiscent of the Dot.com era optical boom.

This palpable excitement, reflected in record attendance and exhibitor numbers, was accentuated for the broader community by the context set at Nvidia’s GTC event held two weeks before OFC, highlighting the critical role optical technologies play in enabling next-generation AI infrastructure.

This year’s OFC moved beyond incremental updates, showcasing a convergence of foundational technologies and establishing optics not just as a supporting player but a core driver in the AI era. The scale of innovation directed towards AI-centric solutions – tackling power consumption, bandwidth density, and latency – was striking.

Key trends that stood out were as follows:

Lower Power Interconnect technologies

The overarching topic was the need for more power-efficient optics for high-bandwidth AI fabrics. Legacy data centre optics are impacting the number of GPUs that fit into a given data centre’s power envelope.

Three main strategies were presented to address the power issue.

First, whenever possible, use copper cables, which are far more reliable and cost less than optics. The limitation, of course, is copper’s reach, which at 200 gigabit-per-lane is about 1-2m for passive copper cables and 3-4m for active redriven copper cables.

Second, eliminate the traditional digital signal processor (DSP) and use linear interface optics, including Linear Pluggable Optics (LPO), Near Package Optics (NPO), and Co-Packaged Optics (CPO), all of which offer substantial (60%) power savings, lower latency, and higher reliability compared to traditional DSP solutions.

The biggest difference between linear pluggable optics and co-packaged optics is that linear pluggable optics retains the well-known operational advantages of pluggable modules: configurability, multi-vendor support, and easy field serviceability (hot-swapping at module level), compared to fixed optics like co-packaged optics, which require chassis-level RMAs (return materials authorisation). It remains to be seen whether co-packaged optics can overcome the serviceability issues.

Third, developments in a host of new technologies – advances in copper interconnects, microLED-based interconnects, and THz-RF-over-waveguides – promise even lower power consumption than current silicon photonics-based interconnect technologies.

We look forward to hearing more about these new technologies next year.

Transition from 200 gigabit-per-lambda to 400 gigabit-per-lambda

With the 200 gigabit-per-lambda optical generation just moving into volume production in 2025-26, attention has already turned to the advancement and challenges of 400 gigabit-per-lambda optical technologies for future high-speed data transmission, aiming towards 3,200 gigabit (8×400 gigabit) modules.

Several technical approaches for achieving 400 gigabit-per-lambda were discussed, including PAM-4 intensity modulation direct detection (IMDD), PAM-4 dual-polarisation, and optical time division multiplexing (OTDM). The technology choices here include indium phosphide, thin-film lithium niobate (TFLN), and silicon photonics, which are compared based on RF (radio frequency) loss, integration, cost, and high-volume readiness.

For 400 gigabit lambda optics, indium phosphide and thin-film lithium niobate are strong candidates, as silicon photonics will struggle with the high bandwidth.

At this point, it is impossible to predict which platform will emerge as the high-volume winner. Delivering power and cost-effective 400-gigabit lambda optics will require a concerted industry effort from optical component suppliers, connector suppliers, and test and measurement vendors.

Multi-core fibre

A new pain point in large AI data centres is the sheer number of fibre cables and their associated volume and weight. One way to solve this problem is to combine multiple fibre cores in a single fibre, starting initially with four cores, which would offer a 4:1 reduction in fibre count, bulk, and weight.

Hollow-core fibre

Innovation continues in the foundational fibre itself. Hollow-core fibre generated significant buzz, with its potential for lower latency and wider bandwidth attracting intense interest.

The maturing hollow-core fibre ecosystem, including cabling and interconnection progress, suggests deployments beyond niche applications like high-frequency trading may be approaching, reaching areas like distributed AI processing.

AI-driven network evolution

AI isn’t just driving network demand, it is increasingly becoming a network management tool.

Numerous demonstrations showcased AI/machine learning applications for network automation, traffic prediction, anomaly detection, predictive maintenance – e.g., analysing optical time-domain reflectometer (OTDR) traces, configuration management, and resource optimisation. This represents a fundamental shift towards more efficient, reliable, self-configuring, self-healing, and self-optimising networks.

Along with the many technical talks and tutorials, show floor demos, and customer and supplier meetings, OFC attendees also had a chance to combine technology with some light-hearted fun at the rump session.

This year’s topic was rebuilding global communication infrastructure after an alien invasion, and three teams came up with thought-provoking ideas for this theme.

Chris Doerr, CEO of Aloe Semiconductor

The best way to describe OFC 2025 is a giant Mars dust storm that raged for days. The swirling sand made it difficult to see anything clearly, and the sound was so loud you couldn’t think.

Acronyms ending in “O” were hitting you from all sides: LPO, LRO, NPO, CPO, OIO. The wind blew away sand that had buried old technologies, such as lithium niobate, electro-optic polymer, and indium-phosphide modulators, and they joined the fray.

Only now that the storm has somewhat subsided can we start piecing together what the future holds.

The main driver of the storm was, of course, artificial intelligence (AI) systems. AI requires a vast number of communication interconnects. Most interconnects, at least within a rack, are still copper. While copper keeps making incredible strides in density and reach, a fibre-optic interconnect takeover seems more and more inevitable.

The Nvidia announcements of co-packaged optics (CPO), which go beyond co-packaged optics and deserve a new name, such as optical input-output (OIO) or system-on-chip (SOC), created a great deal of excitement and rethinking. Nvidia employs a silicon interposer that significantly increases the electrical escape density and shortens the electrical links. This is important for the long-term evolution of AI computing.

The CPO/OIO/SOC doesn’t mean the end of pluggables. Pluggables still bring tremendous value with attributes such as time-to-market, ecosystem, replaceability, etc.

Most pluggables will still be fully retimed, but 100 gigabit-per-lane seems comfortable with linear pluggable optics (LPO), and 200 gigabit-per-lane is starting to accept linear receive optics (LRO).

For 200 gigabit per lane, electro-absorption modulated lasers (EMLs) and silicon photonics have comfortably taken the lead. However, for 400 gigabit per lane, which had two main demos on the show floor by Ciena and Marvell, many technologies are jockeying for position, mostly EMLs, thin-film lithium niobate (TFLN), indium phosphide, and silicon photonics.

Many companies are abandoning silicon photonics, but this author feels this is premature. There were demos at OFC of silicon photonics attaining near 400 gigabit-per-lane, and the technology is capable of it.

An important thing to remember is that the new OIO/SOC technology is silicon photonics and comes from a CMOS foundry. Putting non-CMOS materials such as thin-film lithium niobate or indium phosphide in such a platform could take years of expensive development and is thus unlikely.

In summary, OFC 2025 was very active and exciting. Significant technology improvements and innovations are needed.

The dust is far from settled, so we must continue wading into the storm and trying to understand it all.

Jörg-Peter Elbers, Senior Vice President, Advanced Technology, Standards and IPR, Adtran

OFC 2025 marked its largest attendance since 2003 with nearly 17,000 visitors, as it celebrated its 50th anniversary.

Discussions in 1975 centred around advances in fibre technology for telecommunications. This year’s hottest topic was undoubtedly optical interconnects for large-scale AI clusters.

Following an insightful plenary talk by Pradeep Sindhu from Microsoft on AI data centre architecture, sessions were packed in which co-packaged optics (CPO) and associated technologies were discussed. The excitement had been fueled by Nvidia’s earlier announcement of using co-packaged optics in its next generation of Ethernet and Infiniband switches.

The show floor featured 800 gigabit-per-second (Gbps), 1.6 terabit-per-second (Tbps), and the first 3.2Tbps interconnect demonstrations using different interface standards and technologies.

For access, 50G-PON was showcased in triple PON coexistence mode, while interest in next-generation very high-speed PON spurred the technical sessions.

Other standout topics included numerous papers on fibre sensing, stimulating discussions on optical satellite communications, and a post-deadline paper demonstrating unrepeated hollow-core fibre transmission over more than 200km.

OFC 2025 was fun too. When else do you get to reimagine communications after an alien attack, as in this year’s rump session?

No visit to San Francisco is complete without trying one of Waymo’s self-driving taxis. Having been proud of Dmitri Dolgov, Waymo’s CEO, for his plenary talk at OFC 2019, it was thrilling to see autonomous driving in action. I love technology!

Daryl Inniss, Omdia Consultant, Optical Components and Fibre Technologies

I worked on commercialising fibre technology for emerging applications at OFS – now Lightera – from 2016 to 2023. I spent the prior 15 years researching and analysing the optical components market.

Today, I see a market on the cusp of a transition due to the unabated bandwidth demand and the rise of computing architectures to support high-performance computing (HPC) and artificial intelligence (AI).

Even optical fibre, the fundamental optical communications building block, is under intense scrutiny to deliver performance suitable for the next 30 to 50 years. Options include hollow-core and multi-core fibre, two of the three fibre technologies that caught my attention at OFC 2025.

The third, polarisation-maintaining fibre arrays for co-package optics, is one part of the conference’s biggest story. OFC 2025 provided a status update on these technologies.

Hollow-core fibre

OFC’s first day hollow-core fibre workshop (S2A) illustrated its niche status and its potential to remain in this state until the fibre is standardised. The industry ecosystem was well represented at the session.

Not surprisingly, challenges highlighted and summarised by Russ Ellis, Microsoft’s Principal Cloud Network Engineer, included manufacturing, field installation, field splicing, cabling, and termination inside the data centre. These are all expected topics and well understood.

I was surprised to hear Microsoft report that the lack of an established ecosystem was a challenge, and I’ll explain why below.

Coming into OFC, the biggest market question was fibre manufacturing scalability, as most reported draws are 5km or less. Supplier YOFC put this concern to rest by showcasing a +20 km spool from a single fibre draw on the show floor. And Yingying Wang, CEO of Linfiber, reported that 50 to 100km preforms will be available this year.

In short, suppliers can scale hollow-core fibre production.

From a field performance perspective, Microsoft highlighted numerous deployments illustrating successful fibre manufacturing, cabling, splicing, termination, installation, and testing. The company also reported no field failures or outages for cables installed over five years ago.

However, to my knowledge, the hollow-core fibre ecosystem challenge is a consequence of a lack of standardisation and discussion about standardisation.

Each fibre vendor has a different fibre design and a different glass outer diameter.  Microsoft’s lack-of-an-ecosystem comment mentioned above is therefore unsurprising. Only when the fibre is standardised can an ecosystem emerge, generating volumes and reducing costs,

Today, only vertically integrated players benefit from hollow-core fibre. Until the fibre is standardised, technology development and adoption will be stunted.

Multi-core fibre

I was pleasantly surprised to find multiple transceiver vendors showcasing modules with integrated fan-in/fan-out (FIFO). This is a good idea as it supports multi-core fibre adoption.

One vendor is targeting FR4 (TeraHop for 2x400G), while another is targeting DR8 (Hyper Photonix for 8x100G). There is a need to increase core density, and it is good to see these developments.

However, we are still very far from multi-core fibre commercialisation as numerous operational factors, for example, are impacted. The good news is that multi-core fibre standardisation is progressing.

Polarisation-maintaining fibre

According to Nick Psaila, Intel’s principal engineer and technology development manager, polarisation-maintaining fibre arrays remain expensive.

The comment was made at Optica’s February online Industry Meeting and verified in my follow-up conversation with Psaila.

Using an external laser source is the leading approach to deliver light for co-packaged optics, highlighting an opportunity for high-volume, low-cost polarisation-maintaining fibre arrays.

Co-packaged optics were undoubtedly the most significant topic of the show.

Coherent showcased a 3Tbps concept product of VCSELs to be used in co-packaged optics. Given that multimode fibre is used in the shortest optical connections in data centres and that VCSELs have very low power consumption, I’m surprised I’ve not heard more about their use for this application.

Testing of emerging photonic solutions for HPC and AI devices has been identified as a bottleneck. Quantifi Photonics has taken on this challenge. The company introduced an oscilloscope that provided quality results comparable to industry-leading ones and is designed for parallel measurements. It targets photonic devices being designed for co-packaged optics applications.

Multiple channels, each with wavelength-division multiplexing lasers, must be tested in addition to all the electrical channels. This is time-consuming, expensive process, particularly using existing equipment.

Polymer modulators continue to be interesting because they have high bandwidth and the potential to be inexpensive. However, reliability is their challenge. Another vendor, NLM Photonics, is targeting this application.

The many vendors offering optical circuit switches was a surprising development. I wonder if this opportunity is sufficiently large to justify the number of vendors.  I’m told that numerous internet content providers are interested in the technology. Moreover, these switches may be adopted in telecom networks. This is a topic that needs continual attention, specifically regarding the requirements based on the application.

Lastly, Lightmatter provided a clear description of its technology. An important factor is the optical interposer that removes input-output connectivity from the chip’s edge, thereby overcoming bandwidth limitations.

I was surprised to learn that the laser is the company’s design, although Lightmatter has yet to reveal more.