At the 2025 Optica Executive Forum in San Francisco, top industry voices from Ciena, Acacia, Coherent, Eoptolink, and TeraHop explored the current state and future direction of photonic-enabled modules. With AI scaling exerting unprecedented pressure on data center architecture, panelists described a fast-evolving landscape where pluggable transceivers and co-packaged optics must adapt rapidly to higher bandwidth, power constraints, and deployment complexity.
Helen Xenos of Ciena emphasized that the lines between coherent and IMDD optics are blurring, especially as industry demonstrations of 3.2T interconnects push boundaries. Tom Williams of Acacia connected the dots between AI-driven architecture shifts and the widespread adoption of coherent pluggables, now reaching 800G and aiming for 1.6T. Julie Eng from Coherent highlighted the growing tradeoffs between power efficiency and flexibility in pluggables versus co-packaged optics, while Eoptolink’s James Zhang and TeraHop’s Rangchen Yu pointed to accelerating demand for 800G and 1.6T modules—powered by multi-vendor ecosystems and maturing DSP technology.
Key Points from the Panel:
• Ciena (Helen Xenos):
• Demonstrations at OFC 2025 showcase 448G signaling and 3.2T IMDD links.
• Industry trend: convergence of IMDD and coherent use cases at high line rates.
• Full technology stack—pluggables, DSPs, and electro-optics—needed to meet diverse needs.
• Acacia (Tom Williams):
• AI is driving scale-up (copper-to-optics) and scale-out transitions across data centers.
• Pluggable coherent optics (400ZR, 800ZR, OpenZR+) are now mainstream in service provider and cloud networks.
• Coherent light gaining traction for campus interconnects (2–20 km) with 20% cost/power premium over IMDD.
• Early use cases at 1.6T and 3.2T will test coherent’s viability in new intra-DC applications.
• Coherent (Julie Eng):
• Pluggables dominate today due to serviceability, flexibility, and multi-vendor interoperability.
• Co-packaged optics are ideal for power-sensitive, high-density scale-up environments.
• Industry pushing toward 400G/lane and beyond using new form factors (e.g. 2D connectors).
• Multiple tech paths: silicon photonics, indium phosphide, and thin-film lithium niobate all have roles.
• Eoptolink (James Zhang):
• 800G modules entering mass deployment; 1.6T modules next.
• DSPs shifting from 5nm to 3nm, cutting power by ~20%.
• Industry exploring 3.2T feasibility, with potential for new modulation schemes like PAM6 or PAM8.
• Multimode (VCSEL-based) products slightly lagging but progressing in 2025.
• TeraHop (Rangchen Yu):
• Data center complexity rising—campus interconnects and hyperscale growth driving need for fiber-efficient, power-optimized optics.
• Silicon photonics now logging 10 billion cumulative device hours with strong reliability.
• Half-retimed configurations can save 40% power at 1.6T; 3.2T coming in 2–3 years.
• Multicore fiber and native multicore transceivers proposed to reduce fiber bulk.
From the Q&A Session:
• IMDD vs. Coherent for Campus Links:
• All panelists agreed coherent optics are inevitable beyond 2–3 km due to chromatic dispersion limits.
• IMDD remains dominant where it meets reach and cost targets; some are exploring dispersion compensation to extend it.
• Hollow-Core and Multicore Fiber:
• Hollow-core fiber could favor IMDD by reducing dispersion, but mass deployment remains years away.
• Multicore fiber seen as promising for reducing fiber count in gigawatt-scale data centers.
• Technology Pathways for 1.6T and Beyond:
• Debate continues on silicon photonics vs. indium phosphide vs. thin-film lithium niobate for 400G/lane.
• Coherent implementations will vary by vendor strength and integration capability.
• Co-Packaged Optics Market Outlook:
• Early deployments remain custom and proprietary; standardization may come if hyperscalers demand it.
• Open ecosystems may emerge via modular designs (e.g., socketable CPO) but face industry inertia.
- IMDD (Intensity Modulation Direct Detection) and coherent optics are two key approaches used in optical transceivers. IMDD is a simpler and more power-efficient method where data is transmitted by varying the light intensity and detected directly without phase or frequency information. It’s commonly used for shorter-reach applications (typically under 10 km) due to its lower cost and complexity. In contrast, Coherent optics encodes information using both the amplitude and phase of the light signal, enabling advanced digital signal processing (DSP) at the receiver. This allows for much higher spectral efficiency and longer transmission distances—currently used for metro, long-haul, and increasingly, campus-scale interconnects under the term “Coherent-Lite.”
