Tag Archives: silicon photonics

Road to 100Gb/sec…Innovation Required! (Part 3 of 3)

Physical Layer Innovation: Silicon Photonics

So in two previous posts, I discussed the innovations required at the transport, network, and link layer of the communications protocol stack to take advantage of 100Gb/s networks . Let’s now talk about the physical layer. A 100Gb/sec signaling rate implies a 10ps symbol period.

Frankly, this is just not possible on a commercial basis with current technology. It is not practically feasible on copper nor on optical interfaces. At this rate the electrical and optical pulses just can’t travel any useful distance without smearing into each other and getting corrupted.

So there are two possible solutions.  The first is to use 4 parallel connections each running @25Gb/sec. The second is to use a single channel with a 25Gb/sec symbol rate but to send four bits per symbol. This can be done either through techniques like Pulse Amplitude Modulation (PAM4) or optically by sending four different colors of light on a single fiber using Wavelength Division Multiplexing (WDM) techniques. Continue reading

Silicon Photonics: Using the Right Technology for Data Center Applications

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.



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