Altera optical FPGA in 100 Gigabit Ethernet traffic demo
Altera is demonstrating its optical FPGA at OFC/NFOEC, being held in Los Angeles this week. The FPGA, coupled to parallel optical interfaces, is being used to send and receive 100 Gigabit Ethernet packets of various sizes.
The technology demonstrator comprises an Altera Stratix IV FPGA with 28, 11.3Gbps electrical transceivers coupled to two Avago Technologies' MicroPod optical modules.
"FPGAs are now being used for full system level solutions"
Kevin Cackovic, Altera
The MicroPods - a 12x10Gbps transmitter and a 12x10Gbps optical transceiver - are co-packaged with the FPGA. "All the interconnect between the serdes and the optics are on the package, not on the board," says Steve Sharp, marketing program manager, fiber optic products division at Avago. Such a design benefits signal integrity and power consumption, he says: "It opens up a different world for FPGA users, and for system integration for optic users."
Both Altera and Avago stress that the optical FPGA has been designed deliberately using proven technologies. "We wanted to focus on demonstrating the integration of the optics, not pushing either of the process technologies to the absolute edge," says Sharp.
The nature of FPGA designs has changed in recent years, says Kevin Cackovic, senior strategic marketing manager of Altera's transmission business unit. Many designs no longer use FPGAs solely to interface application-specific standard products to ASICs, or as a co-processor. "FPGAs are now being used for full system level solutions, things like a framer or MAC technology, forward error correction at very high rates, mapper engines, packet processing and traffic management," he says.
Having its FPGAs in such designs has highlighted for Altera current and upcoming system bottlenecks. "This is what is driving our interest in looking at this technology and what is possible integrating the optics into the FPGA," says Cackovic. Applications requiring the higher bandwidth and the greater reach of optical - rack-to-rack rather than chip-to-module - include next-generation video, cloud computing and 3D gaming, he says.
Altera has still to announce its product plans regarding the optical FPGA dsign. Meanwhile Avago says it is looking at higher-speed versions of MicroPod.
"The request for higher line rates is obviously there," says Sharp. "Whether it goes all the way to 28 [Gigabit] or one of the steps in-between, we are not sure yet."
Altera unveils its optical FPGA prototype
Altera has been showcasing a field-programmable gate array (FPGA) chip with optical interfaces. The 'optical FPGA' prototype makes use of parallel optical interfaces from Avago Technologies.
Combining the FPGA with optics extends the reach of the chip's transceivers to up to 100m. Such a device, once commercially available, will be used to connect high-speed electronics on a line card without requiring exotic printed circuit board (PCB) materials. An optical FPGA will also be used to link equipment such as Ethernet switches in the data centre.
"It is solving a problem the industry is going to face," says Craig Davis, product marketing manager at Altera. "As you go to faster bit-rate transceivers, the losses on the PCB become huge."
What has been done
Altera's optical FPGA technology demonstrator combines a large FPGA - a Stratix IV EP4S100G5 - to two Avago 'MicroPod' 12x10.3 Gigabit-per-second (Gbps) optical engines.
Avago's MicroPod 12x10Gbps optical engine deviceThe FPGA used has 28, 11.3Gbps electrical transceivers and in the optical FPGA implementation, 12 of the interfaces connect to the two MicroPods, a transmitter optical sub-assembly (TOSA) and a receiver optical sub-assembly (ROSA).
The MicroPod measures 8x8mm and uses 850nm VCSELs. The two optical engines interface to a MTP connector and consume 2-3W. Each MicroPod sits in a housing - a land grid array compression socket - that is integrated as part of the FPGA package.
"The reason we are doing it [the demonstrator] with a 10 Gig FPGA and 10 Gig transceivers is that they are known, good technologies," says Davis. "It is a production GT part and known Avago optics."
Why it matters
FPGAs, with their huge digital logic resources and multiple high-speed electrical interfaces, are playing an increasingly important role in telecom and datacom equipment as the cost to develop application-specific standard product (ASSP) devices continues to rise.
The 40nm-CMOS Stratix IV FPGA family have up to 32, 11.3Gbps transceivers, while Altera's latest 28nm Stratix V FPGAs support up to 66x14.1Gbps transceivers, or 4x28Gbps and 32x12.5Gbps electrical transceivers on-chip.
Altera's FPGAs can implement the 10GBASE-KR backplane standard at spans of up to 40 inches. "You have got the distances on the line card, the two end connectors and whatever the distances are across a 19-inch rack," says Davis. Moving to 28Gbps transceivers, the distance is reduced significantly to several inches only. To counter such losses expensive PCBs must be used.
One way to solve this problem is to go optical, says Davis. Adding 12-channel 10Gbps optical engines means that the reach of the FPGAs is up to 100m, simplifying PCB design and reducing cost while enabling racks and systems to be linked.
The multimode fibre connector to the MicroPod
Developing an optical FPGA prototype highlights that chip vendors already recognise the role optical interfaces will play.
It is also good news for optical component players as the chip market promises a future with orders of magnitude greater volumes than the traditional telecom market.
The optical FPGA is one target market for silicon photonics players. One, Luxtera, has already demonstrated its technology operating at 28Gbps.
What next
Altera stresses that this is a technology demonstrator only.
The company has not made any announcements regarding when its first optical FPGA product will be launched, and whether the optical technology will enter the market interfacing to its FPGAs' 11.3Gbps, 14.1Gbps or highest-speed 28Gbps transceivers.
The undersideof the FPGA, showing the 1,932-pin ball grid array