Optical Connections Magazine Autumn 2022

JOHN WILLIAMSON CO-PACKAGED OPTICS

CO-PACKAGED OPTICS: PUTTING THE PIECES TOGETHER

Now starting to achieve real-world deployment viability, Co-Packaged Optics (CPO) technology is considered by many optical movers and shakers to have a rosy commercial future. As an illustration, in a recent report that focuses on the demand for the technology within data centres, the analyst firm CIR Inc reckons that by 2027 the CPO market will reach US$5.4 billion in revenues, writes John Williamson .

W orking to advance the CPO cause have been industry heavyweights such as Cisco, Facebook/Meta, IBM, Intel and Microsoft, to name but some of the heaviest. In parallel, companies such as Broadcom, GlobalFoundries, Marvell, Quanta Cloud Technology, Ranovus, and SENKO – to pick out just a few – continue to deliver CPO demos and introduce CPO solutions and innovations. The chief attractions of the CPO proposition of packaging and integrating silicon and optics on a single substrate have been widely aired. These include potentially better power consumption, bandwidth density and latency metrics. “This list is the dream wish list of any modern data centre provider,” judges Lawrence Gasman, founder and president of CIR Inc. CIR states that data centre CPO deployment will be largely driven by switching evolution, which will reach speeds of 102.4Tbps in 2025. Overall, says CIR, CPO promises to reduce the power consumption by 30%, and the cost-per- bit by 40%, compared to using pluggable optics. Down at the component level, CPO has potential economies compared to Front Plate Pluggables (FPPs). For example, as instanced by Hamid Arabzadeh, chairman and chief executive officer of Ranovus: “Cost is a key factor as you eliminate the need for PAM4 IC re-timers.” Savings could also result from the lack of requirements for Clock and Data Recovery (CDR) chips and other FPP items. SERIAL NUMBERS Serializer/Deserializer (SerDes) links are a hot topic in CPO conversations. Martin Vallo, Ph.D., senior analyst Photonics, within the Photonics and Sensing Division at Yole Intelligence, believes that standardised electrical SerDes links for 224Gbps data rates are among the must-

haves to make CPO mainstream. He says these are needed to provide signalling over a multitude of link types, including Die to Die (D2D), Chip to Chip (C2C), Chip to Module (C2M), Medium-Reach Chip to Chip (MR), and Long-Reach Chip to Chip (LR).

initially hyperscale data centres and large corporate data centres. “For a while, hyperscalers will dominate but gradually corporate data centres will gain share -- there are so many of them!” reasons Gasman. “Also HPC/supercomputers have used something close to CPO for a

Meantime, Jock Bovington, Cisco and OIF Member, stresses that one of the benefits of co-packaging is to reduce the overall power consumption. In this context he refers to the fact that systems built with pluggable modules contain reasonably powerful SerDes in the ASIC, as well as the pluggable module. “When co-packaged - either on the same substrate (CPO) or on a High Density Interposer (HDI) substrate (Near Packaged Optics, NPO) - the channel will have significantly less loss,” remarks Bovington. “Which enables the use of a significantly lower power SerDes such as XSR (10dB) or XSR+ (13dB). The OIF developed both types of electrical interfaces.” WHO’S FIRST IN LINE FOR CPO? There’s much discussion about the application areas in which CPO will first make a meaningful mark. CIR Inc thinks it will be in data centres,

number of years,” he says. Arabzadeh likewise remarks on the potential of the compute space. Putting some flesh on this expectation, in March in partnership with AMD/ Xilinx, RANOVUS demonstrated a new generation CPO solution for Artificial Intelligence/Machine Learning platforms that demand power efficient, high throughput and high density optical interconnect. He believes that two main application areas for CPO will be: low capacity (< 3.2Tbps per CPO) Ethernet optical modules, and high capacity (>= 3.2Tbps per CPO) Ethernet switch and compute solutions. Vallo agrees about the High Power Computer possibilities of CPO. He suggests that before CPO achieves actual commercial status for intra- DC interconnects, it may gain more popularity in high-power computing rather than just displacing FPP.

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| ISSUE 30 | Q3 2022

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