The Evolution to 800G Pluggable Modules

Abstract

The increasing bandwidth demands of hyperscale data centers are driving the development of 800G pluggable optics. This new generation of pluggables will utilize higher baud rates, standardized protocols, and advanced integration to enable 800G transmission in compact form factors. Key features like support for 800GbE, multiple client rates, interoperable modes, and low power consumption will foster adoption. With proven technologies like silicon photonics and 3D packaging, 800G pluggables are poised to be deployed at scale in 2024.

Introduction

The relentless growth in data center traffic continues to drive the development of higher capacity and more efficient optical interconnects. While 400G pluggable modules utilizing ~60 Gbaud signaling rates have been successfully deployed over the last several years, attention is now shifting to the next generation of 800G pluggable modules.

Hyperscale data centers are expected to lead the transition to 800G pluggables, with requirements for 800G ports on next-generation switching and routing platforms. Similar to the 400G generation, standards bodies are converging on common parameters to ensure multi-vendor interoperability and economies of scale. This includes doubling the baud rate to ~120 Gbaud signaling and increasing the channel spacing to 150 GHz.

Advanced technologies like silicon photonics, 3D integration, and mixed signal electronics have enabled the higher baud rates and modulation schemes required for 800G operation. With proven performance in silicon-based 400G pluggables and performance-optimized modules, these technologies can now be leveraged to develop 800G pluggables in compact form factors like QSFP-DD and OSFP.

Key features like support for 800GbE client traffic, multiple lower rate clients, interoperable modes, high transmit power variants, and low power consumption will drive adoption in a range of network applications. With both technology and standards alignment, 800G pluggables are on track for volume deployment around 2024.

Standards Convergence for 800G Optics

Industry organizations like OIF, Open ROADM, and IEEE are actively driving alignment on 800G standards to ensure multi-vendor interoperability. This includes standardization of 800G optical parameters, client protocols, and module management interfaces.

For optical transmission, OIF is defining 800ZR, an interoperable 800G coherent DWDM application with reaches up to 80 km over amplified links using Class 3 optics with ~120 Gbaud signaling and 16QAM modulation [1]. Open ROADM has specified enhanced performance modes including an interoperable probability constellation shaping (PCS) implementation for improved OSNR operating at 130+ Gbaud.

Figure 1. 2x scaling of baud rates and channel spacing for ~60+Gbaud Class 2 to ~120+Gbaud Class 3 transition. (Source: Cisco)

For client traffic, IEEE 802.3ck defines physical layer specifications for 800GbE operation over 100γ interfaces. OIF and Open ROADM also support lower rate clients like 400GbE and 100GbE using packet multiplexing over the 800G optical link. In addition, OIF’s implementation agreement for Common Management Interface Specification (CMIS) ensures interoperable module management signaling across multi-vendor pluggables. By aligning on optical, client, and management parameters, 800G standards will drive economies of scale similar to 400G while ensuring multi-vendor interoperability.

Advanced Technologies Enabling 800G Pluggables

Leveraging advanced technologies like silicon photonics, 3D integration, and mixed signal electronics has been key to developing compact and power efficient 800G pluggable modules.

Silicon photonics provides high bandwidth density WDM components like modulators, wavelength multiplexers, and photodetectors that can be integrated onto a silicon substrate. This enables scaling to higher baud rates beyond 100G in a cost effective, scalable way.

3D integration or siliconization techniques like flip chip bonding, stacked die, and high density substrate packaging co-package the photonics with CMOS electronics. This provides tight integration for improved signal integrity and power efficiency at 800G speeds.

Next generation mixed signal electronics like improved DACs and ADCs running over 112G per lane and new DSPs enable the high speed signaling and complex modulation schemes needed for 800G optical transmission.

These technologies have already been proven in 400G silicon-based pluggables and performance-optimized modules like Acacia's CIM coherent module. Their maturity makes them ready to support high volume 800G pluggable development.

Figure 2. 3D Siliconization used in (left to right) Class 2 MSA Pluggables and Class 3 performance-optimized CIM 8. Highly integrated co-packaging is going to be important for Class 3 800G MSA pluggable modules. (Source: Cisco)

Key Features for 800G Pluggable Adoption

For successful wide scale adoption, 800G pluggables will need to support several key features that address network applications and industry trends.

A primary feature is support for 800GbE client traffic. With 800G switch and router ports forecasted in 2024, pluggables will need native 800GbE capability to interconnect these platforms. Multiplexing support for lower rate clients like 400GbE and 100GbE will also be critical during the transition period when they remain prevalent in networks.

Interoperable modes are another key enabler. 800ZR will provide a baseline mode for coherent DWDM links. However, the Open ROADM PCS mode offers higher performance to match 400G-like reaches. This flexibility suits the needs of a range of network topologies and applications.

High transmit power variants are essential for operation over legacy brownfield networks utilizing existing ROADM infrastructure. Internal amplification built into pluggables provides the increased Tx power needed for these links.

And finally, low power consumption continues to be a priority. Power efficiency maximizes port density for 800G switch and router line cards. It also enables backwards compatibility with existing 400G ports. Optimized 800G pluggable designs will leverage the latest advances in silicon photonic integration and CMOS node scaling for reduced power.

Figure 3. Illustrating the key features needed for 800G MSA Pluggable modules. (Source: Cisco)

Conclusion

The industry momentum is clearly building around 800G pluggable optics as the next step in the evolution of data center interconnects. Through a combination of technology development and standards alignment, 800G pluggables are on pace for wide scale network deployment around 2024. Their availability will coincide with 800G ports on next generation switches and routers, providing a straightforward capacity increase for data center operators. 800G pluggables will build on the key lessons and technologies proven in 400G pluggable adoption to deliver the features and performance needed for next generation optical interconnects.