Research|Optics: ECOC 2026 Takeaways, NPO Gains Momentum as Slow and Wide Takes Shape

We attended ECOC 2026 in Málaga last week. The debate between slow and wide and fast and narrow was a recurring topic in presentations and plenary sessions. Companies presented microLED and micro-VCSEL designs and discussed their performance, manufacturing challenges and production timelines. NPO was also in focus, with live NPO demos on the show floor and more discussion of how and when it ramps.

This note covers our takeaways from the presentations, demos and conversations with companies, including developments in NPO, scale-in, external lasers, retimers, DSPs, coherent-lite and test and measurement.

1. Theme

Slow and wide means many lanes at a low rate, typically 2-50 Gbps NRZ, using microLEDs or micro-VCSEL arrays instead of a few 200G or 400G PAM4 lanes. Lumentum, Coherent, ams OSRAM, Credo, Marvell, Avicena and even Nvidia’s research team all presented hardware or concepts at ECOC.

Companies at the Sunday workshop used different definitions of slow. OpenAI used less than 50 Gbps, while Marvell used slow and wide for 2-50 Gbps micro-emitters and flat optics for 50-100 Gbps.

The other debate was the choice between microLEDs and micro-VCSEL arrays. Credo’s first Active Light Cable uses microLEDs, but when we talked to the company, it told us it is working on both. Lumentum, Coherent and ams OSRAM presented micro-VCSEL approaches. Coherent also included a microLED architecture credited to Avicena in its slides. Avicena also had a microLED demo at its booth.

2. Why the industry cares

Power remains the main constraint. Marvell places slow and wide in scale-in and describes it as having the lowest total pJ/bit. Coherent showed GaAs VCSEL NPO/CPO at 1.2 pJ/bit with no external laser module. NRZ also offers simpler electrical signaling than high-baud PAM4 SerDes.

A separate slide at ECOC summed up the case for VCSELs as the lowest energy per bit, the lowest cost per lane, dense parallel arrays with sparing, simple coupling in and out of multimode fiber, manufacturing at massive scale across different supply chains, wafer-level test and burn-in and error-free low-latency NRZ.

Image 1. The case for high-speed VCSELs

Reach is another reason operators are interested. Credo’s presentation uses 72 GPUs as copper’s limit and says its ALCs can extend a GPU domain to more than 300 GPUs in one optical hop. Binbin Guan, a member of the technical staff at OpenAI, said copper remains the best choice for short in-rack links, with pluggable optics used when copper can no longer meet the link budget. He also said slow and wide could be used for direct GPU-to-GPU links, while fast and wide could work for both in-rack and cross-rack links, including OCI.

The choice of material also seems to be driven by supply chain challenges. Lumentum and Coherent already have high-volume GaAs VCSEL capacity. These arrays would use GaAs manufacturing rather than the InP lines facing shortages. Cignal AI’s slide at the light sources workshop linked worldwide shortages to demand for InP.

Image 2. Cignal AI’s datacenter module outlook

Scale-in also came up many times across ECOC. Keysight’s slide at the Optica forum describes scale-in as within the node, where chiplets are densifying the package today and optical I/O to the die is on the horizon. Avicena mentioned that XPU makers want HBM taken out of the package and made replaceable since a failing HBM stack can take down the XPU. We also heard that XPU roadmaps are already set for the next two years, which puts the earliest opportunity for optics in the package in late 2028 or 2029. Our read is that microLEDs take the shortest links, while VCSELs cover the longer reaches within scale-in.

Image 3. Keysight’s scaling stack, from scale-across to scale-in

Recent industry research is consistent with what we heard in our discussions and across presentations at ECOC, pointing to strong demand for 800G and 1.6T optical transceivers in 2027 as more links move from copper to optics. DSP availability, especially for 1.6T, is expected to constrain shipments, while both CW lasers and pump lasers were also highlighted in some of our discussions as being in tight supply. Smaller and secondary suppliers could benefit by filling the gaps in CW and pump laser supply.

NPO is gaining momentum. Almost every conversation we had across the supply chain added more detail on architectures, technologies and customer engagement, which gives us more confidence that NPO will arrive sooner rather than later.

Several transceiver makers, including InnoLight / TeraHop, are also working on 3.2T/6.4T NPO projects. Optical engine volumes across the industry are expected to reach single-digit millions in 2027 and tens of millions in 2028. Nvidia’s NPO project remains in sampling, with firmer orders potentially emerging toward year-end or in the first half of 2027.

Two main NPO architectures are being evaluated. In the first, the laser sits at the faceplate of the chassis, much like CPO. In the second, the laser sits inside the box next to the optical engines, which means lower-power CW lasers and lower laser pricing. In our discussions at ECOC, CW laser powers between 70 and 150 mW came up for that version, with Coherent at the low end of that range.

Arista’s openness to NPO came up several times in our conversations at ECOC and was also discussed in the Cignal AI webinar the week before the show, where TeraHop presented its Diablo-1 6.4 Tbps NPO with an integrated laser. At ECOC, a 12.8 Tbps XPO demo ran at 224 Gbps per lane on an Arista switch. One investor we spoke with described the split as Nvidia’s ecosystem leaning toward CPO while the CSP ecosystem leans more toward NPO. With Arista remaining open to NPO and XPO demonstrations already running on its switches, we expect both approaches to coexist.

Image 4. A 12.8T XPO demo running 64 channels at 224 Gbps per lane

Image 5. The liquid-cooled XPO module and cable at the same demo

3. Counterarguments

Packaging and reliability remain difficult. Higher fiber counts, optical alignment and flip-chip assembly are still open challenges for slow and wide. VCSEL-based slow and wide also faces electrical crosstalk and fiber attachment challenges, separate from the cost of the fibers themselves. VCSELs have a history of reliability issues in datacenter deployments, which has left some hyperscalers cautious, while Lumentum’s flip-chip assembly is still in development. MicroLEDs also have no field reliability record in this application yet, and GaN on sapphire can be more sensitive to electrical overstress, which can shorten emitter lifetime.

Individual emitter control allows arrays to include spare lanes to replace failed ones. Avicena said its coming product will switch these lanes on automatically when an active lane starts to degrade.

Temperature is another open question. It came up repeatedly in our ECOC conversations as one of the biggest challenges for micro-emitters in scale-in, even with liquid cooling.

MicroLED reach and bandwidth are limited by dispersion. In the Q&A, Mohsen Asad of Credo said chromatic dispersion can be compensated, but modal dispersion is the bigger problem and in practice limits an LED to around 2 Gbps per lane. Avicena’s booth demo ran at 3 Gbps per lane over 5 meters, so we would not treat 2 Gbps as a universal limit. Lumentum also said microLEDs cannot meet 50-meter links. These are company claims from the respective workshops rather than a common set of test results.

Cost is another issue. Passive copper costs next to nothing, so any optical replacement has a high bar to clear. VCSELs operating at 850-1060 nm typically require multimode fiber, which in these early applications is expected to be more expensive than single-mode fiber and also comes with yield considerations, particularly with OM4 and OM5. MicroLEDs face a similar cost challenge. Their low per-lane data rates require hundreds of parallel optical paths, increasing the amount and complexity of the fiber.

The main counterargument from Chris Cole of Applied Materials was timing. Speaking in a personal capacity, he said 200G serial is ramping and that options such as 4x50G arrived too late for the 200G market window. He called fast and narrow the only real option for 400G optics and said the packaging required for slow and wide is 4-6 years away. In that view, hardware designed today would be obsolete by the time the required packaging is ready.

Image 6. Chris Cole’s framing of the 400G serial question

Peter Winzer, VP of Systems Architecture at Ciena, also expects high-speed SerDes to remain necessary through the 400G generation. In his framework, systems that still use copper stay with SerDes and Open CPX. OCI and slow and wide are for systems with no copper remaining.

Deployment evidence remains limited for now. OpenAI said simpler electrical signaling still needs reliability proof, while Nvidia described its VCSEL design as an exploratory concept rather than a product plan. We do not expect a named slow and wide deployment before the second half of 2027.

From talks with industry peers, we still expect active cables beyond copper’s reach to be the first use case for slow and wide. For scale-in, we still expect adoption at the switch and XPU package only after the 400G-per-lane generation.

4. Individual companies

The companies below are ordered by how directly slow and wide could impact revenue. Other ECOC takeaways are included under the relevant company.

Credo

We see Credo as the clearest listed near-term beneficiary of slow and wide. Among the companies discussed here, it already has a named product, an OCP demonstration date and an initial revenue target.