Silicon Photonics: Using the Right Technology for Data Center Applications

Silicon Photonics

At DesignCon last week, I followed a speaker who ended his presentation with a quote from Mark Twain, “the reports of my death have been greatly exaggerated!”  The speaker was talking about copper cabling on a panel entitled, Optical Systems Technologies and Integration.”  He showed some nice charts on high speed signaling over copper, making the point that copper will be able to scale to speeds of 100 Gb/s.


As next speaker on the panel, I assured him that those of us who come from optical communications are nottrying to kill copper.” Rather, the challenge for companies like Mellanox, an end-to-end interconnect solutions company for InfiniBand and Ethernet applications, is to provide the “right technology for the application.”  I spoke about the constraints of 100 Gb/s pipes and our solutions.



At Mellanox, we design our switches and adapter cards to terminate in a common port, like the QSFP.  The Quad-SFP maximizes front panel density. For example, our SX1036 switch packs an amazing 36 ports in 1 ru (one “rack unit”).   At speeds of 56 Gb/s, this enables a switching bandwidth of 4 Tb/s! The same QSFP port supports either copper or fiber interconnects.  The switch and ports can be configured with a range of technologies.


As we move to speeds of 100 Gb/s we plan to use silicon photonics to solve a problem that copper and VCSEL solutions cannot. We want to provide 2 km of reach. This is long enough to cross even the largest data centers.  We want to re-use the existing Single Mode Fiber (SMF) which is already installed in data centers.  We want to fit everything in the tiny, 3.5W QSFP package, originally designed for much lower speeds.


Silicon photonics is one of a very few technologies that can meet all our criteria. It can support reaches of 2km over SMF; silicon integration allows us to eliminate 100s of components so that we can squeeze into the QSFP form factor; and low-power electronics allows us to do all of this in less than 3.5 watts.


This is one example where silicon photonics is solving an “end-to-end” interconnect problem in data centers that VCSELs solutions and copper solutions cannot. At Mellanox our goal is not “death” copper cabling or “death” to VCSELs.  Rather, it is to use the right interconnect technology for the application.



Arlon Martin
Author: Arlon Martin is Sr. Director of Marketing at Mellanox. At the recent DesignCon 2014 conference, his presentation entitled, “Using silicon photonics to address the address the tradeoffs of cost, power, speed and complexity,” was part of panel discussion on “Optical System Technologies and Integration.”

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