PHY chips strengthen supply chain

Two established merchant CMOS suppliers announced critical PHY chips this week: PMC-Sierra announced a solution for 40G DWDM line-side ports, while Applied Micro 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 multi-sourced (MSA) transponder for cost-reduced volume deployment.

 

 

Non-coherent MSA transponders, which do not need such a chip, have been shipping in volume since 2009. The first coherent transponder, from Oclaro, became commercially available in 1Q11 but the chip suppliers have been few. Specialist DSP vendor Clariphy supplies Oclaro via a strategic agreement. Multiphy is another small DSP specialist who is developing a coherent chip. CoreOptics was a merchant supplier but was acquired by Cisco a year ago. (Semtech’s 40G chip is for non-coherent client- and line-side interfaces.) PMC-Sierra is in a different class: a broad merchant communications IC vendor with $635m in 2010 revenue. Broader availability of the DSP chip enables more vendors to supply the MSA transponder.

 

The DSP chip fits into the current-generation 300-pin module, and PMC-Sierra plans to follow up with a variant for the half-sized CFP2 module in a year, in order to enable 40G coherent to move from long-haul into metro.

 

This product line could also be extended to 100G. Ovum expects 100G systems, in very early deployment now, to start their true ramp in 2012. Unlike 40G, the line-side technology has been coherent from the start. We wrote last year about the landgrab for 100G DSP technology by both module suppliers and OEMs. It remains an open question whether merchant suppliers see enough available market at 100G. But each successive process node helps increase speed. DSP vendors like PMC-Sierra who are in the game now are well positioned for 100G and beyond.

 

The preferred telecom client interface is single-mode 100 GbE-LR4, but the transponders’ availability and cost have been a source of frustration for carrier customers. Early adopters have bought multimode SR10 or nonstandard 10×10, but each of these has drawbacks. AppliedMicro’s new chip is critical for the LR4. It is the “gearbox IC” which converts modules’ electrical interface running across 10 lanes at approximately 10Gbps to four 28Gbps signals to drive four wavelength-multiplexed lasers across the optical link.

 

AppliedMicro’s lower price for the gearbox will help the bill of materials for LR4. But just as important is the arrival of another IC vendor. Semtech was the only merchant supplier; Finisar has its own in-house supply. Though Semtech is larger than AppliedMicro, its main focus is on wireless and RF. Its gearbox is implemented in SiGe while AppliedMicro’s CMOS solution is aligned with the roadmap to denser client interfaces for which the gearbox function ultimately disappears into larger chips on the line card. The entry of CMOS IC vendors is a step towards mature 100G supply.