Back in the middle of August, Intel teased the communications and data industries by revealing some talks to be given at the Intel's Developer Forum (IDF) in San Francisco. The talks that caught my attention had to do with silicon photonics and interconnect.
I reached out to Victor Krutul, Intel's director of photonics strategy, who deftly handed me to Robert Manetta in Intel's PR department. At the time, Manetta's response was "We aren't talking right now," but he promised that I was on the list for further information. Once the IDF opened in September, we all got the updates. Intel, in cooperation with Corning, launched a multi-fiber interconnect they call MXC, along with a fiber called ClearCurve. Manetta was true to his word, and I received updates almost simultaneously to the release at the IDF. As part of my ongoing interest in the impact of optical communications on the EE profession, as well as my interest in silicon photonics, herewith is an update.
Anyone involved in datacenter design or communications is aware that interest in optical interconnect has been growing for many years. The commonly cited reasons for the less than ubiquitous conversion to optical include cost, reliability, and power consumption. Intel has been at the forefront of pursuing so-called silicon photonics -- as a possible answer to all the barriers to universal optical interconnect in datacenters.
In case you missed it, way back in January, the company announced a collaboration with Facebook and Quanta Computer to develop a "disaggregated" server architecture that would separate compute, storage, and network components by using optical interconnect between the subsystems. Intel said the companies would base the program on a system on chip (SoC) Atom processor code-named Avoton.
By June, Intel's updates were touting a 100Gbit/s IC that was a "complete integrated module that includes silicon modulators, detectors, waveguides, and circuitry." Intel also said it believed "this is the only module in the world that uses a hybrid silicon laser."
Putting all this together, Intel took the approach that, since its hybrid on chip laser solution runs at 1,310nm, it would design an interconnect system optimized for that wavelength. The new system offers several innovations. If you want even more details, you should read the joint Intel-Corning whitepaper, as well as the IDF presentation.
Here is one of the connectors, clearly displaying the multi-fiber interface.
The MXC connector will support up to 64 fibers, each operating at 25 Gbit/s. Corning says cable assemblies will be available in 8-, 16-, and 24-fiber counts in the first half of 2014 and in 32- and 64-fiber counts later.
A simplified internal view of the connector is shown below.
The connector recesses the multi-mode fibers and sends the light through a beam-expanding lens to increase the diameter, shown near the exit edge of the connector body where the light beams grow in diameter. Intel and Corning claim the larger beams offer 10x better immunity to dust particles and eliminate the tolerances required in traditional connectors. They call this arrangement a lensed ferrule.
The claims for the connector/cable combination are impressive: total aggregate bandwidth of 1.6Tbit/s for the 64-fiber version. Also, having demonstrated 25Gbit/s per fiber over 300m by the IDF in September, soon afterward the company more than doubled the distance by sending 25Gbit/s per fiber over 820m. In its press materials, Intel says the "low dispersion and low attenuation enable the fiber to carry 25Gbps data" over 300m with good margin. It also says the fiber will be bent around a 7.5mm radius, making routing easier in crowded datacenters.
In the whitepaper, Intel and Corning cite Cisco's Virtual Networking Index, which has become almost a de facto standard citation for datacenter and traffic growth. In the 2013 VNI, Cisco said mobile data traffic will exceed 10Eb/month by 2017. Eb are exabytes, 1,024 x 1,024 x 1,024Gb; the mobile data traffic is expected to exceed 10 billion gigabytes per month in 2017.
Intel says that, since most mobile traffic will be on IP networks by that time, nearly all this traffic will pass through datacenters, where it will be joined by all the nonmobile Internet traffic. Forrester Research said in a July blog post that mobile traffic may exceed nonmobile Internet traffic by this year's holiday shopping season, so we can double that figure (about 2Eb/month by end of 2013). Intel says that large datacenters have more links than several small countries' entire telecom networks, with as many as 50,000 servers and 200,000 network connections.
What does all this mean for EEs and analog designers in particular? There is no doubt that more and more optical devices will be used in computing and communication. As these devices and interconnects move on to processors, the whole game will change for all the circuits around the processors. Have you struck up a friendship with photons yet?