This blog is Part 2 in a 3-part series on Mellanox’s high-speed interconnect products. My first blog covered Direct Attach Copper (DAC) cables which are the least expensive way to create a high-speed 25G/50G/100Gb/s interconnect, but have a maximum reach of about 3-5 meters. Active Optical Cables (AOCs) pick it up from there and can reach up to 100-200 meters and are the least expensive, optical links available. They are widely used in HPCs and more recently became popular in hyperscale, enterprise and storage systems.
Optical transceivers convert electrical data signals into blinking laser light which is then transmitted over an optical fiber. Optical transceivers have an optical connector to disconnect the fiber from the transceiver. AOCs bond the fiber connection inside the transceiver end, creating a complete cable assembly much like a DAC cable, only with a 3-200-meter reach capability. AOCs main benefit is the very long reach of optical technology, while acting like a simple, “plug & play” copper cable.
Compared to less expensive DAC cables, AOCs offer:
Compared to more expensive optical transceivers, AOCs offer:
Permanently attaching the fibers is a seemingly simple change but yields a surprisingly large number of technical benefits and cost advantages; enough to create an entirely new category of interconnect products. Since the optics is contained inside the cable, designers do not have to comply to IEEE or IBTA industry standards for transceiver interoperability with other vendors. Hence, customers can pick and choose the lowest cost, best performing technology. Here are some of the results this simple change enables:
An AOC uses two optical transceivers with integrated fiber. So, how on earth can it cost less than a single optical transceiver with an optical connector?
While AOCs reaches can extend to the limits of the optical technology used (100-200 meters), installing a long 100-meter (328 foot) cable, complete with an expensive transceiver end, is difficult in crowded data center racks so the average reach typically used is between 3-30 meters. Only one “oops” per cable allowed. Damaging the cable means replacing it as it cannot be repaired. AOCs are typically deployed in open access areas such as within racks or in open cable trays for this reason.
Mellanox’s InfiniBand AOCs started out in about 2005 with DDR (4 x 5Gb/s) for use in the Top10 HPCs and quickly became the preferred solution for the large InfiniBand HPCs in the Top100. Today, it is the norm for QDR, FDR and EDR and in 2017 the newly announced LinkX® 200G HDR announced at SC’16 event in November.
The power and cost savings caught the eye of the Ethernet hyper scale and enterprise data center builders and has since become a popular way to link Top-of-Rack switches upwards to aggregation layer switches such as End-of-Row and leaf switches. Several hyperscale companies have publically stated their preferred use of AOCs for linking Top-of-Rack switches. Additionally, single channel (SFP) AOCs have become very popular in storage subsystems and some hyperscale builders who often run 10Gb/s or 25Gb/s AOCs from a Top-of-Rack switch to subsystems at reaches greater than DAC limits of 3-7 meters.
Here is an example of how AOCs are typically used inside systems racks to link subsystems together and between switches and systems in rows:
Here is a more detailed view in Ethernet configurations showing the LinkX® 10Gb/s and 25Gb/s based AOCs, Spectrum switches and ConnectX-3, 4, 5 QSFP and SFP network adapters.
Here is an example at the Texas A&M HPC center and as you can see, nothing but orange AOCs and open access!
Newly Announced 200Gb/s HDR InfiniBand AOCs
At the HPC supercomputer conference SC’16 in Salt Lake City Utah, Mellanox announced its 40-port, 200Gb/s HDR InfiniBand line of Quantum-based switches and dual-port ConnectX®-6 host bus adapters. To link them all together, we also announced, a line LinkX® Direct Attach Copper (DAC) cables and splitters and Mellanox’s own design, Silicon Photonics-based, HDR200 Active Optical Cables (AOCs) running at a whopping 200Gb/s in a QSFP56, 4x50Gb/s configuration!
These will be available in Low-Smoke, Zero-Halogen (LSZH) jackets and reaches from 3 meters up to 100 meters. Available in mid 2017, watch our new LinkX® website for more detailed information coming!
Mellanox LinkX® AOC cables offer the lowest-cost optical links with the lowest-power and latency in the industry. This enables the most cost efficient, highest ROI, lowest Capex and Opex interconnect solution. The full portfolio of 10Gb/s, 25Gb/s and 50Gb/s line rates and SFP and QSFP form-factors enable customers the ability to build a wide variety of configurations that meet every application in both InfiniBand and Ethernet. Everything is manufactured by Mellanox and uses Mellanox-designed Silicon Photonics and control ICs.
Check out the Mellanox LinkX® website and Mellanox Academy for more detailed DAC, AOC and transceiver white papers and articles in the future. LinkX® is Mellanox’s brand name for its cables and transceivers product line.
Contact your Mellanox sales representative for availability and pricing options and stay tuned to my blog more interconnect news and tips.