Have you ever heard of Co-packaged Optics (CPO) technology? It tightly integrates optics and electronics, which increases data rates and reduces latency, while also combining high performance with low power consumption. This integration has the potential for wide-ranging applications. Next, we’ll take a closer look at CPO.
What is Co-Packaged Optics(CPO Meaning)
Co-packaged Optics (CPO) is a technical architecture that combines optics and electronic components within a switching or processing system. This integration enhances the bandwidth, density, and power efficiency of data center networks and processing. Cloud computing giants such as AWS, Microsoft, Meta, and Google, network equipment and chip leaders such as Cisco, Broadcom, Marvell, etc., have laid out CPO technologies and products.
Current Packaging Technology
Foundation Stage: Pluggable; Transition Phase: NPO; Ultimate Form: CPO.
Applications of Co-Packaged Optics
Co-Packaged Optics in the Network
Data centers primarily use co package optics in front-end networks that connect servers. Encapsulating the optical module and chip in the same package greatly reduces the connection length and distance, thereby improving communication efficiency. This technology enables data centers to implement functions such as high-speed network switching, server interconnection, and distributed storage, further improving overall performance. With these advantages of high bandwidth, low latency, and high energy efficiency, copackaged optics is a promising solution for next-generation optical Ethernet technology for network applications. Some domestic cloud computing giants and data center operators have started adopting CPO technology in their self-developed data center networks. This technology allows them to package optical modules and chips in the same package, thereby enhancing the speed and quality of the network.
OIO (HPC for AI/ML)
To handle AI/ML workloads, the optics industry is working on a new architecture powered by OIO, called AI backend networking. The traditional siloed HPC architecture lacks flexible resource allocation in computing. Additionally, due to the long-standing limitation of data transfer rates, it suffers from obvious bandwidth capacity bottlenecks and inefficient processing of diverse workloads. As central processing units (CPUs) and graphics processing units (GPUs) advance rapidly, the existing I/O infrastructure finds it difficult to keep pace. This often leads to inefficient processing units frequently waiting for data.
As the demands of AI/ML workloads continue to escalate, this dilemma is becoming more and more severe, requiring a network fabric with high speed, low latency, lossless data transmission, and scalability. The evolving HPC disaggregated architecture aims to address the limitations of the “siloed” model. The evolving HPC disaggregated architecture separates memory, compute, and storage into clusters, and then interconnects them using cutting-edge OIOs to achieve this. This strategic shift enables dynamic resource allocation and addresses the inefficiencies of traditional architectures when handling a wide variety of data center workloads.
Challenges in Co-Packaged Optics Development
Thermal management
Placing photonic integrated circuits (PICs) in electrical packages increases the chance of thermal crosstalk. The heat source and laser source within the photonic die generate thermal power. This thermal power influences the temperature profile of the package. Additionally, the heat produced by the electrical die and the overall system’s heat dissipation mechanism also have an impact on the thermal behavior of the PIC. We require a complete thermal analysis that spans from the die to the system level.
Signal Integrity and Power Integrity
We need to perform transient simulation of the entire system to ensure signal and power integrity. This requires self-consistent electrical and photonic circuit simulation. Additionally, it necessitates considering the additional parasitics introduced by the different types of electrical interconnects at the packaging stage.
Scalability and Bandwidth Density
Because fibers are typically edge-coupled, a key metric for CPO and OIO is bandwidth density along the edge of the chip. The minimum fiber spacing requirement limits the number of fibers for a given substrate size. Given the large difference between waveguide and fiber size, fan-out is an inherent challenge for edge coupling solutions. If a V-groove is used to orient the fiber vertically, an edge-coupled solution can be achieved without fan-out. In addition, grating-based microlens coupling and other innovative solutions are being studied.
Fiber Optic Connection
Efficiently coupling optical signals from fiber arrays to packages is a challenging task. Considerations include fiber alignment, which can be achieved through passive or active alignment methods, as well as tilt. Additionally, there are factors such as structural and thermal management, manufacturability, and maintainability. Therefore, designers need to carefully model and optimize their opto-coupled designs.
Co-Packaged Optics Summary
To sum up, CPO technology, as a new type of optical packaging technology, has broad application prospects and great significance. With the development of artificial intelligence, big data, and cloud computing, the demand for data center bandwidth capacity and high-speed data transmission rate is increasing. CPO technology is expected to become one of the main solutions for data centers to introduce ultra-high-bandwidth silicon-based data interconnection.
