Coherent 100G Starts Getting Pluggable
Coherent 100Gbit/s modules are moving down into pluggable transceiver formats, as seen in pre-OFC/NFOEC announcements this week.
Pieces of the coherent 100Gbit/s landscape are coming together this week, with a few announcements made in advance of the conference and more likely to come.
Oclaro Inc. kicked it off by being the first vendor to announce a pluggable, coherent module for 100Gbit/s -- a device in the CFP2 form factor that was announced Tuesday. Production volumes are expected in mid-2014. (See Oclaro Intros Coherent CFP2.)
Sumitomo Electric Device Innovations USA, Inc. is following suit. It's using chips from ClariPhy Communications Inc. that are being announced Wednesday; combined with Sumitomo's own optics, the eventual result will be a Sumitomo CFP2 module that should get launched later this year, according to ClariPhy Chief Strategy Officer Paul Voois.
The chips in question are the analog-to-digital and digital-to-analog converters (ADC and DAC); they'll be shown, along with Sumitomo's coherent optical subsystem, at OFC/NFOEC in Anaheim next week.
CFP2 is a smaller version of the CFP pluggable module that's being used for 100Gbit/s interfaces on the client side -- that is, interfaces that link to other equipment such as routers.
It's the line-side 100Gbit/s interfaces, those that point out towards the network, that are using coherent detection, per the OIF framework. Those interfaces haven't been in pluggable form so far; they've been big transponder modules that the systems vendors have mostly built themselves.
The significance of the Oclaro and ClariPhy/Sumitomo announcements, then, is that the coherent 100Gbit/s technology is shrinking into pluggable form -- not a surprising step, but a crucial one, in that it means the interfaces will be smaller (allowing for more on a line card) and less power-hungry. A CFP module (original version, not CFP2) consumes 32 W of power compared with 80 W, or usually much more, for a non-pluggable coherent transponder, Voois says. "This advances what's been a growing demand among carriers for coherent in the metro."
Chips will be a key factor in advancing coherent 100Gbit/s. One gating factor, for instance, has been the very high-end digital signal processor (DSP) used on the receiving end of a coherent link. Most systems vendors designed their own DSPs for the first generation of coherent 100Gbit/s transponders. Among merchant semiconductor vendors, only NTT Electronics Corp. (NEL) has been shipping this part.
ClariPhy's announcement Wednesday doesn't include a coherent 100Gbit/s DSP, but the company should announce one later this year, Voois says. Everybody knows it's going to build one anyway. (Put it this way: Every module vendor that Light Reading asks points out that they expect ClariPhy to do a 100Gbit/s DSP. MultiPhy gets an occasional shout-out, too, but Light Reading hasn't yet contacted that company to see what its plans are.)
NEL already has a second generation of its DSP available, meanwhile. It's been in customer labs for about six months, says George Jones, vice president of marketing and business development for AppliedMicro Inc..
"There's a number of customers who are on a redesign cycle to get cost and power out" of coherent 100Gbit/s designs, Jones says, because the first generation is "kind of clunky, to be frank. The existence of the second-generation NEL chip is making that possible, and we like to think the existence of our chip is making that possible, too."
That chip would be a multiplexer called the S28032, AppliedMicro's contribution to the transmission side of a 100Gbit/s coherent transponder. That chip, which started shipping last year, is being used by eight of the top 10 module and systems manufacturers, as AppliedMicro announced Wednesday. (See AppliedMicro Pushes 100G.)
One of the chip's customers is startup Acacia Communications Inc., which will show off its 100Gbit/s transponder module in the AppliedMicro booth.
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