Introduction
As data centers and communication networks continue to handle ever-increasing amounts of data, the demand for higher bandwidth and more efficient interconnect solutions has skyrocketed. Enter Co-Packaged Optics (CPO), a revolutionary technology that promises to revolutionize optical interconnects by integrating optics directly onto the same package as the ASIC or switch.
CPO offers several significant advantages over traditional pluggable optics, making it an attractive solution for meeting the insatiable demand for data transmission capacity.
Pros and Cons of Co-Packaged Optics
One of the primary benefits of CPO is its ability to drastically reduce the cost per bit by minimizing the number of components and interconnects required. Additionally, by eliminating the electrical interconnect power dissipation and variability, CPO offers superior power and performance characteristics compared to pluggable optics.
However, CPO also comes with its own set of challenges. The fixed configuration of CPO modules can be limiting, and the trade-off between reliability and replaceability is a concern that needs to be addressed.
Evolution from Discrete III-V to Co-Packaged SiPh
The evolution of optics has progressed from discrete III-V components to highly integrated optical engines based on silicon photonics (SiPh). This transition has been driven by the engineering and manufacturing limits in scaling conventional module designs. The integration of SiPh chiplets into packages (SCIP) represents a significant step forward, with co-packaged optics being the ultimate goal, offering highly integrated optical engines capable of supporting data rates up to 6.4T.
Key Technology and Ecosystem Demonstration
Broadcom's Humboldt 25.6T CPO demonstration is a prime example of the cutting-edge technology driving the CPO revolution. This implementation features a 32-channel photonic integrated circuit (PIC), integrated transimpedance amplifiers (TIAs) and drivers, and a detachable fiber connector, all integrated into an ODM system.
System-Level Simplification with CPO
One of the most significant advantages of CPO is the substantial reduction in board and system complexity it offers. By integrating the optics directly onto the package, the need for separate optical modules and complex fiber routing is eliminated, resulting in a simpler and more efficient system design.
CPO System Implementations
CPO connectivity offers more than 30% additional faceplate area for ventilation compared to pluggable optics solutions. This increased airflow results in a 3°C to 5°C lower pre-heating of the inlet air, enabling fan power reductions and further enhancing the overall system efficiency.
Humboldt 25.6T CPO Production Data
Broadcom's production data for the Humboldt 25.6T CPO demonstrates the impressive performance capabilities of this technology. The graphs showcase excellent receiver sensitivity, OMA-TDECQ, and optical engine temperature characteristics, meeting or exceeding the specified performance requirements.
World's First CPO System Development Timeline
The development of the world's first CPO system has been a remarkable journey, with Broadcom achieving several significant milestones in a remarkably short timeframe. From the initial public demonstration in March 2022 to the fully functional 25.6T CPO system just one year later, the rapid progress in CPO technology is truly impressive.
Critical Components of the CPO Optical Path
The CPO optical path consists of several critical components, including the front panel ports, the CPO optical engine connection, and the remote laser module (RLM) blind-mate connection. Standardization and commonality across various applications in networking and compute are crucial for driving the widespread adoption of CPO technology.
Ecosystem Opportunities and Needs
As with any new technology, the successful adoption of CPO requires a robust ecosystem to support its development and deployment. Some of the key ecosystem opportunities and needs for CPO include:
Continued investment in high-power continuous wave (CW) laser diodes
Front panel flexibility for various form factors
Emphasis on optical devices in advanced packaging (e.g., double-side attach, cleanliness)
Collaboration and standardization on stress factors for qualification and reliability
Summary
Co-Packaged Optics is a game-changing technology that promises to revolutionize high-speed optical interconnects. With its ability to significantly reduce cost, power consumption, and latency, CPO offers a compelling value proposition for data centers and communication networks.
While there are no technical showstoppers for CPO, the emerging ecosystem for integrating and deploying this technology is still evolving. The next key steps involve addressing reliability and yield challenges to fully realize the potential of CPO and achieve the lowest total cost of ownership (TCO).
As the demand for data continues to surge, Co-Packaged Optics stands poised to play a pivotal role in enabling the next generation of high-performance, energy-efficient, and cost-effective optical interconnect solutions.
Reference
[1] M. Mehta, "CPO Progress and Ecosystem Development," presented at the APC Broadcom, Jan. 2024.
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