Key chips arrive for both faces of 40/100G

Karen Liu/Ovum
06 Jun 2011

Two established merchant CMOS suppliers announced critical PHY chips this week: PMC-Sierra announced a solution for 40G DWDM line-side ports, while AppliedMicro announced a solution for 100GbE client interfaces. What do they have in common? Both are eagerly awaited because they address weak points in the supply chain for next-generation line cards.

Their arrival signals a positive turn in the roadmap, away from the increasing confusion arising from too many formats toward convergence on a long-term solution. 40G coherent is one of too many 40G approaches, but it is the one which aligns with the clear choice for 100G. Until now, 100GBase-LR4 has been a poster child for the disproportionately high cost of optics at these speeds, leading to industry fragmentation by the nonstandard 10×10 MSA alternative. Yet it is acknowledged as best aligned with IC roadmaps when 100G hits full stride.

DWDM line-side ports, capable of transmitting across hundreds and thousands of km, are the most visible features of optical transport equipment. But this type of equipment also has so-called client ports which take in the information that needs to be transported. These ports need only connect across a central office or at most a city, under a km to a few tens of km. They connect to switches and routers, which also need the same optical technology.

At 40Gbps and 100Gbps, both sides are challenging. Lack of readily available technology has fragmented the market into multiple solutions with different trade-offs. At 40Gbps the issue is most severe on the line side, while at 100Gbps the client-side options have been characterized as “confusing.” This week’s announcements address the hotspots on the line side of 40Gbps and the client side of 100Gbps.

PMC-Sierra’s chip goes into a 300-pin transponder module that supports 40G DWDM coherent transmission. It performs critical digital signal processing (DSP) that is the “magic” behind the coherent approach’s ability to receive data despite corruption suffered during transmission. A mature supply for the chip is necessary for eventual widespread deployment of 40G transport technology, which is still early in its lifecycle compared to the 10G incumbent.

Until now, 40G coherent systems have been shipping only from its originator, Ciena-Nortel. Other major OEMs, Alcatel-Lucent, Cisco, Fujitsu, and Nokia Siemens Networks, started bringing their products online in late 2010. Systems can be built from discrete components rather than transponders but OEMs typically redesign with a multisourced (MSA) transponder for cost-reduced volume deployment.

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