Co-Packaged Optics (CPO) Introduction

What is Co-Packaged Optics (CPO)?

Currently,  data centers are overgrowing, which also means a vast increase in data demand. The performance and network bandwidth of existing data centers are already struggling to handle these enormous data transfer demands. As the heart of the data center, switch designs need to evolve to meet growing data center traffic challenges and support more enormous network demands. To address some of the obstacles traditionally associated with avoiding high-speed optoelectronics, including thermal management, power consumption, bandwidth, and port density, Microsoft and Facebook have formed the Co-Packaged Optics (CPO) Collaborative.

Co-Packaged Optics (CPO) technology is designed to enable more extensive scale and faster integration by placing the electro-optical conversion process as close as possible to the computing, switching, or ASIC chip to achieve higher bandwidth and energy efficiency. The active device and the optical transceiver are mounted on the same substrate, eliminating all losses and distortions caused by copper wires on the motherboard. The electrical signal from the chip is converted to an optical signal by an optoelectronic integrated circuit (PIC) (also called an optical chip) located at the periphery of the substrate and coupled to an optical fiber. These fibers are terminated to high-density optical connectors that can be mounted on I/O panels.

Currently, in the data center market, major equipment manufacturers and large data center users are actively developing Co-Packaged Optics (CPO) products based on silicon optical engines. Authorities predict that Co-Packaged Optics (CPO) will become the dominant enabling technology for cloud provider data centers by 2030 and will lead to an enormous application market.

What are the advantages of Co-Packaged Optics (CPO)?

• Compared to traditional Pluggable optics, Co-Packaged Optics based on integrated silicon photonics brings the optics closer to the host switching ASIC. It can be manufactured in volume to reduce costs effectively.
• Power consumption is a significant challenge in today’s data centers. Co-Packaged Optics (CPO) power consumption can be significantly reduced because SERDES or switching chips do not require high power I/O drivers. It can save up to 30% of the total system power.
• Higher system reliability because the signal is distributed among many independent laser sources. Failure of a single laser will not bring the system down.
• It increased bandwidth scalability.
• Increased I/O port and overall system density. Optical pluggable devices may have reached their density limit.
• Reduces chip-to-I/O loss/distortion.

What are the disadvantages of Co-Packaged Optics (CPO)?

There are always two sides to co-packaged optics (CPO), and there are certain disadvantages.

• The complexity of optical connections inside the Co-Packaged Optics (CPO) switch. The shift from front-board pluggable transceivers to Co-Packaged Optics (CPO) can present two major challenges for optical connectivity within data center switches. One is the increase in the total number of fibers per unit, and the other is the added complexity of routing fibers from each Co-Packaged Optics (CPO) optical engine (OE) to the front panel.

• Because of the unique structure of the Co-Packaged Optics (CPO) switch, it is complicated to repair or replace the CPO switch once it fails. The ASIC baseboard of the switch is soldered to the OE. If a single fiber is damaged during installation, the entire Co-Packaged Optics (CPO) switch can be challenging to repair. This replacement risk can negatively impact the total cost of ownership of the data center.

Final Words

Pluggable optical modules remain the most widely deployed data center optics to date because of their superior flexibility, interoperability, and rich multi-vendor ecosystem. However, technology is constantly advancing. It may be difficult for COBO or Co-Packaged Optics (CPO) to replace existing pluggable optical modules in the next 5 to 8 years. But as the technology matures, Co-Packaged Optics (CPO) will likely begin to compete with pluggable optical modules. CPO technology has the potential to change the shape of communications equipment dramatically and the industry chain. One case in point: the first generation of Co-Packaged Optics (CPO) designed for 100Gb/s electrical and optical channels, targeting the 51.2 T switch generation entering the market.

References
https://www.connectorsupplier.com/co-packaged-optics-are-on-the-horizon
https://www.photonics.com/Articles/Microsoft_Facebook_Form_Co-Packaged_Optics/a64508
https://www.linkedin.com/pulse/co-packaged-optics-switch-what-challenges-placed-optical-ninomiya
http://www.copackagedoptics.com