Several deep-packet inspection chips and test instrumentation applications are using next-generation speed-rate IO application-specific integrated circuit (ASIC) chips. These chips combine several circuits in one and are customized for a particular use.
This is different than what the current server and switch markets are typically using. These developers are experienced with the 200+ per lane technical issues and are working to solve them.
In this article, we’ll take a mid-year look at some of the key interconnect developments happening in the industry. Specifically, we’ll cover the newer 212G per-lane copper connector and cable links.
Passive DACs
The Ethernet IEEE-802.3df 212G per-lane PHY committee meetings have been reviewing passive DAC link budgets — with a focus on the 26 and 27 AWG Twinax copper cables that are one meter long.
The latest revisions mean the 1-lane SFP, 2-lane SFP-DD, and 4-lane QSFP cables are, in general, fit for electrical and mechanical use. However, there are also high-volume applications for the 8-lane QSFP-DD, 16-lane double-stack QSFP-DD, 8-lane OSFP, and 16-lane OSFP-XD, which are relying on 32 Twinax cables with 64 wire conductors.
Unfortunately, a single, large cable bundle rarely works well for the rack-routing of higher-lane count cable assemblies. Such assemblies typically require four to eight cable-leg bundles in a single-link assembly or fanout.
New developments in Twinax raw cables are offering greater flexibility to support such assemblies. A couple of examples include Luxshare-Tech’s Optimax and ColorChip’s Hairtail. These are extremely flexible Twinax cables.
The one-meter links might require a middle-of-rack cluster switch topology if the application has a limited reach. This is an alternative to the top-of-rack (ToR) switches.
Next, we’ll cover some of the current (and past) link electrical elements and parameters, with cost and analysis.
The TE chart below illustrates various test points, connectivity types, reach section lengths, and budget segment values.
The next chart demonstrates three different packaging structure options, with a performance comparison, particularly of the IL for TP0 to TP5. TE shared this insight at a recent IEEE802.3df meeting.
It’s clear that using the optical CPC interconnect offers the ideal link budget number option.
The Amphenol HFFS model below shows the cable assembly insertion loss that supports a DAC 27 AWG one meter, using a 27 AWG Twinaxial cable. This was also shared in a public folder at the recent IEEE802.3df meeting. Expect more insight at the next meeting in September.
These channel link budget charts are ideal for guiding development teams working on the 200G+ links. It’s also worth following the OIF CEI spec developers for their 224G interconnect progress.
Here’s a temporary Annex clause, indicating the key dB loss maximum per-reach segments, with the respective standard test points.
Active DACs
Most OEMs and data-center operators use 200+G per-lane topologies that require longer reaches than the one-meter maximum passive DAC. The active DAC or ADAC one-meter cables are likely the preferred choices to gain a smaller cable diameter and better routing and airflow. These cables also offer lower weights with a better supply chain.
Marvell’s cloud-optimized Active Electrical Cable (AEC) 800G PAM4 DSP chips are a popular copper-link extender solution. Marvell and Spectra7 are developing updated technology to support the latest 200+G per-lane solutions, likely based on the new IEE802.3df spec clauses.
Samtec’s Active Linear Direct Drive solution ideally supports 100G+ signaling applications. So, it’s likely the company’s also developing the next-generation 200G+ solutions.
Observations
The larger, exascale data centers of the near future will require fast cable and connector installations with smart robotic add-in/removal functions. Robotically installed pluggable modules and DAC/ADACs must be equipped with mechanical alignment and sensing capabilities that exceed what’s currently available.
Such smart robot solutions are already in the works and might affect the specifications of most pluggable connectors and cages. They’ll likely also affect the cost.
Currently, there’s at least some relief for copper-cable assembly suppliers and customers. The Copper Index price is down 20% and at a 20-month low.
The lowest cost and rate of power consumption will likely be the primary factor when choosing DACs, ADACs, AOCs, OBOs, and CPOs interconnection media types for high-volume users.
Considerations
Will the upcoming optical and wireless network connectivity options compete with or complement those currently used in data centers? Will there be an impact on the product lifecycles of the copper pluggable types?
By 2025, it’s predicted that optical OBOs and CPO types with passive external cable options will account for an annual total link of TAM 25%, globally. This is instead of external ADACs and AOCs.
The top interconnect suppliers might be wise to invest in copper and optical internal and external link products running at 200G+ per lane.
Participation in the Innovative Optical and Wireless Network’s (IOWN) Global Forum is also a good idea (learn more at www.iowngf.org). This is a new infrastructure initiative supported by several Japanese and Taiwanese companies, including Ericcson, Intel, Microsoft, and others.
IOWN focuses on the cloud, data centers, and global telecom systems and is driving advances in several optical and wireless networks. This includes fiber-to-silicon photonic devices and board-to-board, box-to-box, and system-to-system direct link applications. Future optical transceivers, modules, connectors, cables, and related components will likely be based on IOWN specifications.
Aside from the IOWN Technology Working Group, keep up with the latest Ethernet IEEE-802.3df and OIF CEI 224G specs.
This leads to another question: will IOWN technology complement the major other types of connectivity used in InfiniBand, FibreChannel, and PCIe interfaces?
Conclusions
Active DAC links that offer three and five-meter reach lengths and smaller wire-gauge diameters are more feasible for 212G per-lane links. They’ll likely be implemented for MoR and ToR applications as newer, smaller, and lower-powered embedded extender chips are released.
Active DAC, AOC, pluggable-module heat generation, cooling methods, and thermal-circuit design are critical for 200G+ applications.
It’s a challenging task to measure individual ROI for 212+G DAC, ADAC, AOC, OBO, and multiple CPO types. The same goes for internal copper and optical jumper cables. As a result, communication and technical support from suppliers are necessary, even if complex. Certainly, the supply chain and global commerce challenges are not helping matters.
Keep updated with the latest online insights and connectivity projects from OSFP-XDmsa, QSFP-DDmsa, CXL, and OCP. Check with EA, IB, UNH-IL, plug fest compliance, interoperability test data, and supplier certifications.
Filed Under: Connector Tips
