OFC 2024 industry reflections

Gazettabyte is asking industry figures for their thoughts after attending the recent OFC show in San Diego. In particular, what developments and trends they noted, what they learned and what, if anything, surprised them. Here are the first responses from Huawei, Drut Technologies and Aloe Semiconductor.

Maxim Kuschnerov, Director R&D, Optical & Quantum Communication Laboratory at Huawei.

Some ten years ago datacom took the helm of the optical transceiver market from legacy telecom operators to command a much larger volume of short-reach optics and extend its vision into dense wavelength division multiplexing (DWDM).

At OFC, the industry witnessed another passing-of-the-torch moment as Nvidia took over the dominant position in the optics market where AI compute is driving optical communication. The old guard of Google is now following while others are closely watching.

Nvidia’s Blackwell NVL72 architecture was the talk of the conference and its exclusive reliance on passive copper cables for intra-rack GPU-to-GPU interconnects dampened the hopes of Wall Street optics investors at the show.

Since the copper backplane is using 224-gigabit serdes, last year’s hot topics of 100 gigabit-based linear pluggable optics or dense optical interconnects based on 16x100 gigabits suddenly felt dated and disconnected from where the market already is. It is also in no shape to respond to where the compute market is rapidly going next: 400-gigabit-per-lane signalling.

Here, the main question is which type of connectivity for the GPU scale-up in the intra-rack domain would be employed and whether this might be the crossover point to go to optical cables? But as often is the case in the optical business, one should never fully bet against CMOS and copper.

The long-term evolution of AI compute will impact optical access and this was also a theme of some of the OFC panels.

6G is envisioned to be the first wireless network supporting devices primarily, not humans, and it’s fair to assume that a majority of those distributed devices will be AI-enabled. Since it will be uneconomical to send the raw training or inference bandwidth to the network core, the long term evolution of AI compute might see a regionalisation and a distribution towards the network edge, where there would be a strong interdependence of 6G, fronthaul/ backhaul & metro edge networks, and the AI edge compute cloud.

While a majority of coherent PON presentations failed to quantify the market driver for introducing the more expensive technology in future access networks, AI-data powered 6G fronthauling over installed optical distribution networks will drive the bandwidth need for this technology, while residential fibre-to-the-home - “PON for humans” - can still evolve to 200 gigabit using low cost intensity modulation direct detection (IMDD) optics.  

The times are over where the talk of cheaper datacom ZR optics dominated the show and commanded attendance at the Market Watch sessions. Don’t misunderstand, the step to 1600ZR is technologically important and market-relevant, but since coherent doesn’t have “AI” written all over it, the ZR evolution was more a footnote of the exhibition. However, in a necessary move away from electro-absorption-modulated lasers (EMLs), 400-gigabit-per-lane optics for intensity modulation direct detection will share similar Mach-Zehnder modulator structures as coherent optics.

Thus, start-ups crowding the thin-film lithium niobate modulator market in the US, Europe and China are going for both: the coherent and the intensity modulation direct detection dollar.

Meanwhile, the established silicon photonics ecosystem will have to wrap its head around what their value-add in this domain will be since silicon photonics would be just the carrier of other materials enabling lasers, modulators and photodetectors.       

Bill Goss, CEO of Drut Technologies

The last time I attended OFC, the conference was in Los Angeles at the Staples Center.

One thing I found super interesting at this year’s event was the number of companies working on optically-connected memory solutions. But the biggest noteworthy item to us was a number of presentations on using optical circuit switching (OCS) for AI/ML workloads. 

Nvidia and some universities presented projects using OCS in the data centre and Coherent actually showed a new 300x300 switch in their booth. There also seemed to be a feeling that the world has been waiting on co-packaged optics for years.   

One thing evident in talking with optical companies that typically focus on service provider networks, is that they all want to get inside the data centre.  That is where the big market explosion is going to be in the next decade and companies are thinking about how to gain share in the data centre with optical solutions. 

You could almost feel the gloom around service provider capital expenditure and the companies that normally play in this market are looking at all the spending going on inside the data centre and trying to figure out how to access this spend. 

Drut Technologies did not exhibit at OFC. Instead, we used the show to listen to presentations and talk to suppliers and customers.  Surprises were the amount of pluggable optics available. 

Walking through the show floor, it seemed like a sea of pluggables and I had multiple meetings with companies looking to put coherent optics inside the data centre.  Visually too, the amount of pluggables was noticeable. 

I was also surprised at the absence of certain companies.  It seems companies opted for a private meeting room rather than a booth.  I do not know what that means, if anything, but if the trend continues, the show floor is going to be half-filled with private meeting spaces. It will be like walking through a maze of white walls.

I was not surprised with all the AI excitement, but the show did not seem to have a lot of energy.    

Chris Doerr, CEO of Aloe Semiconductor

The first most noteworthy trend of this OFC was the acceleration of pluggable module data rates.  There were demonstrations of 1.6-terabit pluggables by almost every module vendor. This was supposed to be the year of 800 gigabit not 1.6 terabit. 

Digging into it more, most of the demonstrated 1.6 terabit modules were not fully operational - the receiver was not there, all the channels not running simultaneously, etc. - but some EML-based modules were complete.

The second most noteworthy trend was supply constraint and the subsequent driving of new technology. For example, it was said that Nvidia bought up all the VCSEL supply capacity. This is driving up VCSEL prices and seems to be allowing a surge of silicon photonics in the lower speed markets that were previously thought to be done and closed, such as active optical cables.   There was an increasing polarity in opinion on linear pluggable optics, with opposing opinions by well-known technologists.

It seems that Nvidia is already deploying 100 gigabit per lane linear pluggable optics, and Arista will be deploying it soon. For 200 gigabit per lane, it seems the trend is to favour half-linear pluggable optics, or linear receive optics (LRO), in which the transmit is still retimed.  

Large-scale co-packaged optics (not to be confused with small-scale CPO of a coherent ASIC and coherent optics) was exhibited by more vendors this year. It seems very little, if any, is deployed. Large-scale CPO is inevitable, but it on a significantly slower time scale than previously thought.

For 200 gigabit per lane, there were many demonstrations using EMLs and quite a few using silicon photonics. Most of the silicon photonics demonstrations seemed to require driver ICs to overcome the reduced modulation efficiency, sacrificed to achieve the higher bandwidth. Consequently, most companies appear to be throwing in the towel on silicon photonics for 200 gigabaud (GBd) applications, instead moving toward indium phosphide and thin-film LiNbO3 (TFLN). This is surprising.

This author strongly believes in the trend usually followed by silicon electronics in that innovation will allow silicon photonics to achieve 200GBd. It is unreasonable to expect indium phosphide or TFLN to meet the volumes, density, and pricepoints required for 3.2-terabit modules and beyond.  

There is no widely accepted solution for 400-gigabit-per-lane intensity modulation direct detection. Proposals include two wavelengths x 200 gigabit, going for 200GBd early, and dual-polarization intensity modulation direct detection.  

There was significant discussion about optoelectronic interposers, with start-ups LightMatter and Celestial AI receiving large funding in this area. However, the end customers do not seem to have a need for this technology, so it is unclear where it is headed.

OFC was highly noteworthy this year, driven by the surging demand for high-performance computing interconnects. Probably the biggest takeaway is the amount of uncertainty and polarised views, including linear pluggable optics, silicon-photonic’s future, and optoelectronic interposers.