The QSFP combines a package size similar to the XFP (including a similar latching mechanism) with internal mechanics reminiscent of the POP4 parallel module to create a z-pluggable device that offers high density and low power consumption-1 W, in the case of Zarlink’s offering.
“This delivers the highest gigabits per centimeter or per inch of bezel area and also gigabits per square inch of board space of any transceiver,” asserts Stan Swirhun, senior vice president and general manager, Zarlink Optical Solutions. “In addition, it’s by far the lowest power dissipation per channel per gigabit/second of any fibre-optic transceiver.”
The first two devices will come in 4×2.5 Gbit/s and 4×5 Gbit/s configurations, respectively, to match the existing single- and double-data-rate specifications of InfiniBand, an interconnect technology popular in the data center and high-performance computing worlds. With system vendors in this space moving to the double-data-rate configuration this year, Zarlink sees an opportunity to offer an alternative to the bulky, less efficient copper cables now commonly used. Copper cabling generally can support connections of no more than 15 m at the single data rate and struggle to reach 10 m at the double data rate, the Zarlink sources say. The QSFP transceivers will handle reaches of 150 m over MPO/MPT multimode cable at InfiniBand’s double data rate, and as much as 300 m in other applications.
Zarlink also has a 4×10 Gbit/s transceiver on its roadmap. The company believes that a parallel approach to such high speeds offers advantages over serial transceivers. “Compared to 40-gig serial, for example, even though 10 gig today is still a complex challenge, it is obviously far more straightforward to try to do 10 gig than to look at 40 gig,” explains Marco Ghisoni, QSFP product manager, Zarlink Optical Solutions. “From a cost-effectiveness point of view, 40-gig solutions-be they WDM-based or be they direct 40 gig-will face significant cost challenges.”
As an example of potential cost differences, Zarlink claims that use of the QSFP’s parallel-optics technology offers a power savings of 50% and board and edge density savings greater than 60% versus the use of standard SFPs to support an equivalent number of channels.
Because of these factors, Swirhun sees the QSFP reaching not only into other data rates, but into other market spaces as well. “It will be the platform to deliver four-channel optical interconnect, not only through InfiniBand but it will do XAUI extension. It will almost certainly in the future be delivered for Gigabit Ethernet, 10-Gigabit Ethernet extensions,” he says. “It’s the first of a new generation of high-density parallel fibre-optic transceivers that are better matched than the existing serial transceivers to the new densities of integrated circuits.”
In addition to its first-to-market position, Swirhun and Ghisoni believe Zarlink’s use of in-house 850-nm VCSEL technology and IC expertise gives it an advantage over future competitors. While Swirhun professes not to know which companies might follow Zarlink into the market, the MSA membership roster includes such transceiver vendors as Avago Technologies, BeamExpress, EMCORE, Fiberxon, Finisar, JDSU, Merge Optics, OCP, Opnext, Picolight, and XLoom Communications.
Zarlink has delivered samples of the SDR and DDR modules to first customers; evaluation boards and a graphical user diagnostic interface also are available. The company expects preproduction parts will be available in early 2007, with full-production releases by mid-year. Zarlink plans to have the “complete range” of modules in production over the next 12 months.
Swirhun believes that other markets will join InfiniBand and embrace the new modules. “This is a pretty important technology milestone because more communications, storage, and computing systems have blades and boards that have 80-gig, 160-gig capacities. And this is the kind of product that’s required to I/O those systems,” he concludes.