JOHN WILLIAMSON CO-PACKAGED OPTICS
available to the CPO players,” he points out. “There is also FR4 standards that were developed for legacy optical technologies that are being considered to change for higher density applications using silicon photonics. This should also be there by the time CPO is ready for mass deployment for Ethernet applications.” And don’t forget Near Packaged Optics (NPO) - at least for now. Vallo argues that it is challenging with today’s technology to surround the 50T switch chip with 16 3.2Tbps optical modules, and that NPO architecture tackles this by using a high-performance PCB substrate – an interposer – that sits on the host board, in contrast to CPO where the modules surround the chip on a multi- chip module substrate. “We believe that NPO architecture is a temporary solution that tackles challenges related to the manufacturing of the CPO optical engines surrounding the chip on a multi-chip module substrate,” he says. “Ultimately, this approach will be phased out once CPO manufacturing yield is achieved.” At the same time, challenges facing the CPO industry are not trivial. “The industrial ecosystem has not yet developed,” reports Vallo. “We need to understand how to solve some complex problems related to the integration of multiple components from different vendors and need to learn how to make it cost-effective and achieve good yields.” In-situ CPO serviceability and reparability, and test and validation techniques and methodologies look to require further development. WHAT NEXT FOR CPO? Innovation in packaging is an area of interest for Broadcom. “There are new novel packing methods, ways to stack die-to-die interconnect that may even be able to provide an end-to-end KP4 FEC on a 200G/lane link without any intercode FEC,” speculates Pancholy. “Whether it be FR2, FR4, or FR8, you are going to need multiplex wavelengths to solve beach-front density issues.”
More standardisation is on the cards and is already happening. In June 2023 the OIF began a new effort to look at the next generation of energy efficient solutions, with the official launch of the Energy Efficient Interface Framework project. The objective of this initiative is to identify critical applications and their requirements for next-generation electrical and optical links. As well as CPO, targeted solutions include die-to- die, NPO and pluggables. “The effort is driven by end-users and will also include studying additional lower power configurations such as partially and non- retimed solutions,” sums up Hutchins. Yole ends on a cautious note. “To satisfy the market demands and convince end-users of CPO viability, multi-vendor business models and considerable cost and power savings must be proven,” concludes Vallo. “The full-scale deployment of CPO will only happen when pluggables run out of steam.” LINE DANCING A recent analysis from LightCounting reckons LPO/CPO ports will account for more than 30% of the total 800G and 1.6T ports deployed in 2026 to 2028. LightCounting further expects to see the first deployments of linear drive pluggable transceivers in the end of 2024. However, cautions the market intelligence firm, the deployments will be limited in scale until standards are developed and multiple vendors start offering standard products. But not everyone is entirely sold on the LPO proposition. In the view of Broadcom, once you introduce pluggability, you create connector and package losses that must be compensated for. With linear pluggables having removed the DSP, Pancholy questions how you make the physics work? He suggests that vendors can create book-ended solutions, or relax spec conditions, to make it work. “But we believe that focusing on something that compared to a 3nm DSP only saves you 2 to 3W of power and is hard to scale to 200G/lane, is not the right way to be spending resources,” he reasons.
OIF of industry’s first co-packaging standard – the 3.2T Co-Packaged Module Implementation Agreement. “Since co-packaging involves bringing so many new technologies together, end users were interested in an early co-packaging effort so that industry can learn from it, leverage a published interoperable interface and be prepared for the next generation of co-packaging,” sums up Hutchins. “OIF member companies from across the ecosystem have worked together to develop a number of new solutions. For example, new optical and electrical connectors, and module management interface extensions for supporting CPO.”
OTHER SIDE OF THE COIN? However it’s possible to get the
enthusiasm for CPO out of proportion. “A lot of companies are involved but, in many cases, they are simply keeping a watching brief on what technology platform may take them beyond 800G,” contends Gasman. “Often the first priority of transceiver vendors today is on coherent.” Nor is anyone predicting the imminent demise of pluggables at the hand of CPO deployments. Vallo states that pluggables have a well-established industrial ecosystem and a “pay as you grow” deployment model that gives flexibility and supports multiple standards. “Future CPO revenue will depend strongly on end-user demand for AI/M,” he judges. “In the AI/ML space, we see that data centre operators are making huge commitments to the AI/ML clusters they want to build – but so far, they are all based on pluggable optics modules.” Interoperability between CPO and pluggables is also a fact of data centre optical life. As observed by Hamid Arabzadeh, Ranovus Chairman, President and CEO, there’s a mandatory requirement for any CPO to be able to interoperate at the “optical link” level with pluggables. “The standard for the optical interface is already well established for DR and there are some more stringent DR+ standards
Jeff Hutchins OIF Board Member & PLL Working Group, Co-Packaging Vice Chair, Ranovus.
Martin Vallo, Ph.D. Senior Analyst, Photonics and Sensing Division, Yole Intelligence.
Hamid Arabzadeh Chairman, President & CEO, Ranovus.
Lawrence Gasman President, CIR.
Rajiv Pancholy Director, Hyperscale Strategy & Products, Broadcom
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| ISSUE 34 | Q3 2023
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