networkZONE Products for the week of July 24, 2006
Quake Technologies Says…
Quake's 10GbE Transceiver Dramatically Reduces Cost of 10 Gigabit Ethernet
SFP+ PHY Technology To Speed 10G Deployment to the Enterprise
Quake Technologies Inc. announced the availability of the QT2035S, the industry's first integrated physical layer IC for all SFP+ 10 Gigabit Ethernet (10GE) applications. The advanced signal processing technology in the Quake chip will reduce the cost of 10G optics to less than a quarter the price of today's solutions.
The rapid growth of data-intensive applications and the broad adoption of Gigabit Ethernet have led to a greater demand for 10GE switch ports, uplinks and server connections. Despite the demand, 10GE still carries a significant price premium over Gigabit Ethernet. SFP+ pluggable optical modules are increasingly recognized as a technology necessary to bring the cost of 10GE more in line with that of Gigabit Ethernet.
"Today, the wholesale cost for a typical XFP module for short-reach 10G Ethernet is approximately $350. Using Quake's new QT2035S and SFP+ technology, the cost of a module for this same reach can be reduced to below $100," said Mitch Kahn, Quake's vice president of marketing. "At this new price point, 10G Ethernet becomes very compelling for a range of high-volume applications."
In order to facilitate the shift to SFP+, Quake has overcome the significant technological challenges associated with signal integrity at 10Gbps. These challenges require advanced signal-processing capabilities and Quake's QT2035S is the first silicon device to integrate a standard XAUI-interface 10G Ethernet PHY, with complete SFP+ signal processing support.
"The signal processing problem for SFP+ presents a significant challenge," said Stan Blakey, Quake's director of product architecture. "For SFP+, the PHY must provide equalization not only for various grades of installed-base fiber, but also for circuit board impairments. The programmable Electronic Dispersion Compensation engine in our QT2035S device is the first solution to provide the performance headroom required in SFP+ applications."
"An additional benefit of the EDC performance of the QT2035S is that is allows us to use lower performance transmit optics, such as those for 4 or 8G FibreChannel, and run them at 10G," continued Kahn. "The EDC engine compensates for the limited transmitter bandwidth; enabling a 10G short-reach SFP+ module with a cost very close to that of a 4G FibreChannel SFP. At around $50, that's a 10x savings over today's technology."
Quake demonstrated EDC compensated short-reach optics in conjunction with Picolight at Interop 2006. In the demonstration, a prototype linear 850nm VCSEL-based SFP+ established an error-free 10Gbps link over more than a kilometer of multimode fiber.
Technology Backgrounder
SFP+: Maximum performance, minimum cost
Approximately 80% of 10G Ethernet ports shipping today make use of XENPAK or X2 form factor optical modules. As the demand for higher-density and lower-cost switches grows, OEMs have looked to smaller, lower-power form factors for a solution.
XFP modules offer a partial solution that enables somewhat higher density, but not a significant savings in terms of power or cost. With an XFP-based design, Ethernet switches of up to 32 ports are possible in a standard rack-mount chassis, but this is still well short of the 48-port designs available with 1G Ethernet technology. XFP modules also make use of redundant, power-hungry, signal-conditioning circuitry rendered obsolete by modern signal-processing techniques.
SFP+ modules offer the optimum solution for 10G Ethernet optics by every metric. SFP+ modules, by virtue of being 40% smaller than XFP modules, allow for full-density 48-port designs. Elimination of redundant electronics in the module reduces power consumption by at least 500mW per port while dramatically lowering end-user costs.
SFP+ is not an entirely new technology; rather it is the natural evolution of SFP small form factor optics developed for 1G Ethernet and 1G, 2G, and 4G FibreChannel. SFP+ has been defined to support both 8G FibreChannel and 10G Ethernet. This will drive the same economies of scale that allowed for significant cost savings in the previous generation of 1/2/4G FibreChannel and 1G Ethernet.
Advanced Signal Processing the Key
Migration of the SFP form factor from 4Gbps to 10Gbps in SFP+ is no simple matter. Significant signal-integrity challenges at 10Gbps require advanced signal processing in both receive and transmit directions. Quake's new QT2035S device is the first silicon solution to integrate a standard, XAUI-interface, 10G Ethernet PHY with complete SFP+ signal processing support.
In the receive path, the QT2035S includes a sophisticated SFP+ receiver that is capable of compensating for impairments due to both installed-base, low-bandwidth, multimode fiber as well as connector and printed circuit board effects. The heart of the receiver is an advanced mixed-signal Electronic Dispersion Compensation (EDC) engine that provides the adaptive signal processing required for SFP+. The EDC engine uses a novel re-programmable architecture that optimizes both power and performance.
In the transmit direction the QT2035S provides programmable waveshaping of the transmit waveform, effectively eliminating circuit board and connector impairments. By pre-compensating for these impairments, the SFP+ module receives a clean 10Gbps signal ready for optical transmission. This eliminates the need for equalizers or retimers in the module, saving both power and cost.
The QT2035S supports all current 10G serial optical standards, including 10GBase-SR, 10GBase-LR, 10GBase-LRM and 10GBase-ER. In addition, the EDC performance QT2035S enables emerging standards making use of lower-grade transmit optics, which promise to move the cost of 10GE even closer to that of 1GE.
EN-Genius Says . . .
When I visited Quake in the Fall of 2005, I was treated to a visit to their lab where I saw their QT2022 transceiver (reviewed here) coupled to their QT1006 equalizer on an evaluation board. The chips were blazing away at 10 Gbit/s across a long run of some pretty funky low-grade multi-mode fiber, well in excess (I can't recall the exact length) of what one would expect them to be capable of handling. When I remarked on what nice performance the two chips produced and asked about what it would take to integrate the two, they told me they were "working on it" and that they'd have a product ready when they felt there would be "sufficient demand to support high volume production." Apparently Quake feels that this is the time, because they've just rolled out a lovely little device which should help slash the cost of 10G NICs and line cards.
While it supports nearly any kind of 10G media and module form factor, the QT2035S 10G transceiver has arrived just in time to latch on to the emerging market for SFP/SFP+ modules which will be instrumental in bringing 10GbE within 2x - 4x the cost of GbE rather than the 10x+ pricing that's more typical today.
This is especially true for 10G SR (multimode 25 - 350 - 100 m, depending on fiber) applications which are well-suited for the emerging SFP+ module standard that's on track for ratification later this year. Once approved, SFP+ should enable manufacturers to run slightly modified 4G FibreChannel laser/detector assemblies (which wholesale for around $40 today) at 10Gbit/s for huge cost savings in short-haul applications. Even with the added cost of a modified TIA (changed from limiting to linear mode) the economies of scale should keep prices low enough to jump-start the market.
 The SFP/SFP+ form factor moves all electronics off-chip for higher density, lower cost, lower power but it also raises some challenges which the QT2035S has been specifically designed to handle. For one thing, the transmit path includes a pre-distortion scheme to deliver clean signals to the SFP module after a trip across the PCB traces, without the need for a CDR device. To overcome the reflections and severe attenuation in the path it looks over multiple bit times to calculate the proper pre-emphasis or de-emphasis required for the next outgoing bit.
The transmitter's pre-distort equalizer is not adaptive, and relies on weighted tables programmed into its on-chip registers. These values can be determined empirically but the chip's on-board processor can be programmed to use the receive slicer (horizontal and vertical) circuitry to analyze the link and provide them automatically. The same slicers can be used like a digital sampling scope to provide you with a digitized image of the receive eye via one of the devices I/O ports, a really useful feature for design and development -- not to mention manufacturing test and field debug. Likewise, the QT2035S on-chip BERT logic makes a great engineering production and field diagnostic tool. And while the promotional literature makes no mention of it, Quake informed me of a quiet feature that allows the chip to insert PRBS patterns in the data stream's inter-packet gap to perform in-band diagnostics on live systems.
As the release above indicates, the QT2035S receive-side circuitry compensates for the optical dispersion that plagues longer reaches of multi-mode fiber using adaptive EDC techniques. Conversations with Quake reveal that they actually use a combo adaptive/predictive equalizer to help the receiver compensate on the fly for both the optical dispersion and varying modal response of the fiber link. While I can't reveal all the details here, they will allow me to say that it's a hybrid DFE/FFE scheme with large chunks of EQ circuitry implemented in analog and a digital control processor managing it.
Other nice amenities include a system-side XAUI interface which has a simpler, but effective pre-emphasis and equalization circuit and an integrated clock multiplier that support low cost, low-frequency reference oscillators (52 MHz or 156.25 MHz in LAN mode and 55 MHz or 155.52 MHz WAN Mode).
The result is a low-cost high-performance device that supports every 10G PHY standard in the known universe with lots of margin. Its power consumption is equally impressive with a nominal rating of 1.3 W in LRM applications and around 900 mW in non-LRM applications.
Quake has shown excellent foresight by stepping up to the plate with a part that has the potential to drive 10GbE to commodity status, something that should help it win a dominant market share of the emerging applications that will drive volume sales. Despite its aggressive performance claims, the QT2035S earns a respectably low Vapor Index Rating because of its past track record and the fact that I've seen most of the chip's elements operating in separate chips at Quake's Ottawa-based development facility.
The QT2035S is sampling in August 2006. An evaluation board and SFP+ reference design will also be available with full production anticipated for Q1 2007. Quake has not formally announced a price but was willing to go on record that the QT2035S volume pricing would be "about $10 higher than a standard SFP PHY" ($50 - $55).
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