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A Comprehensive Overview of Co-Packaged Optics

Posted on Jan 17, 2024 by
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In high-speed data transmission, copper circuits result in signal degradation and distortion, which become more pronounced as the circuit length increases. Nevertheless, recent developments in silicon photonics and the emergence of co-packaged optics (CPO) for a new chip generation allow designers to directly integrate different chips onto a shared base material, saving power and expanding bandwidth. In this article, we’ll dive into what co-packaged optics is and how it develop in the future.

What Is Co-Packaged Optics?

Co-packaged optics is an innovative technology that enables the integration of optical components directly into a switch ASIC package (shown in the below figure) aimed at addressing next-generation bandwidth and power challenges.

As for transmission quality, CPO addresses the problem of overloading the number of optical modules after ultra-high computing power, and the optical engine is moved near the switching chip to reduce the transmission distance and improve the quality of high-speed electrical signal transmission.

What Is Co-Packaged Optics?

Three Key Innovations of Co-Packaged Optics

1. Save Power by Removing a Level of DSPs

As network switch system speeds and densities have increased, so has the percentage of the system power consumed by front panel pluggable optical transceivers. At 25G/lane and faster speeds, the necessity of active DSP-based retimers has driven up system power. Therefore, CPO technology moves the optics close enough to the Switch ASIC to allow the removal of a level of additional DSP (see figure below).

Save Power by Removing a Level of DSPs

2. Decrease in Failure Rates by Moving Lasers Away From ASIC

In traditional pluggable optical devices, all the sub-components of them are located within the pluggable module. However, as optical devices are getting closer to ASICs (Application-Specific Integrated Circuits), the failure rates will increase when lasers are placed in hotter environments (such as near a very hot switch ASIC).

Therefore, moving the lasers away from the high-power ASIC to cooler locations within the system chassis results in more efficiency in generating optical power, lowering system power without active components like a TEC (thermo-electric cooler).

3. Improve Efficiency With Silicon Photonics Platform

To place the optical components close to the Switch ASIC silicon die, two orders of magnitude (over 100x) of miniaturization are required over existing pluggable modules. Therefore, with the Silicon Photonics platform, separate ICs like TIA, driver, modulator, and mux/demux can be combined on a single IC to improve efficiency.

As a result of innovations, the power required for connecting the Switch ASIC to front panel pluggable optics can be reduced by up to 50%, and the total fixed system power reduction of up to 25-30%.

What Are the Major Advantages of Co-Packaged Optics?

Co-packaged optics (CPO) offers a range of advantages over traditional approaches to optical communication. Let’s delve into these advantages in more detail:

Compact Form Factor for Higher Bandwidth Density

By integrating the optical components within the same package as the electronic IC, CPO optics eliminates the requirement for large and intricate external optical modules. Resulting in a higher bandwidth density, optimizing the utilization of space in data centers and other systems.

Reduced Power Consumption & Latency

In conventional optical communication systems, there is a large power consumption associated with the electrical connections between the electronic integrated circuit (IC) and the optical components. In this condition, CPO offers a solution by integrating the optical components directly into the same package as the electronic IC, thereby reducing the necessity for long-distance electrical connections. This integration significantly decreases power consumption and latency, leading to more energy-efficient data transfer.

Improved Signal Integrity

Co-packaged optics offer superior signal integrity compared to conventional optical communication systems. Through the reduction of electrical connections and signal conversions, CPO mitigates the potential for signal degradation and interference. This leads to enhanced data transmission quality, reduced error rates, and improved system reliability. Additionally, integrating optical components within the same package decreases susceptibility to external noise and electromagnetic interference, further enhancing signal integrity overall.

Co-Packaged Optics: Promises and Challenges

Despite its many merits, co-packaged optics technology also faces challenges.

Thermal Management: The integration of optical components within the same package as the electronic IC can lead to increased heat generation.

Power Consumption: As data rates increase and bandwidth requirements grow, minimizing power consumption without affecting performance is also a challenge.

Yield Improvement: The integration of optical components within the same package introduces added complexities to the manufacturing process. To achieve high yield rates, it is necessary to implement rigorous quality control measures, precise alignment techniques, and robust packaging technologies.

Cost: Currently, co-packaged optics solutions can be more expensive than traditional optical communication approaches.

With the ongoing increase in data rates, CPO technology can readily adapt to higher speeds by utilizing advancements in optical component design and manufacturing. Integrating optical components within the same package simplifies system upgrades and enables seamless integration with emerging technologies. This scalability and future-proofing feature make CPO a practical solution for industries with ever-evolving data transmission needs.

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