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13 May 2011
Altera, a vendor of field-programmable gate array (FPGA) chips, is developing optically-interconnected programmable devices to address growing demand for communications bandwidth. The vendor has yet to describe its technology demonstrator in detail, but said it will do so later this year.
“We are working with partners to develop the system and we will be demonstrating the optics-on-a-chip in Q4,” said Bob Blake, corporate and product marketing manager, Altera Europe, adding that the packaged FPGA and optical interface will support short reach links up to 100m and be based on multimode fibre.
The advent of FPGAs with optical interfaces promises to simplify high-speed connections between and within systems.  This development has been spurred by the emergence of 100 Gigabit interfaces for Ethernet and line-side optical transport and the move to a four-channel electrical interface operating at 25 to 28Gbps.  Such an increase in channel speed can be met using copper interfaces but at the expense of reduced link distances.
FPGAs can support the 10GBASE-KR 10Gbps backplane standard with a reach of 40-inches including the losses of the two end connectors. With emerging very short reach electrical interfaces at 28Gbps for line cards and electrical backplanes, the reach reduces to 4 to 6 inches of printed circuit board (PCB) trace. Moreover, the faster the link, the more energy has to be put into the signals and the higher the board losses. This complicates the line card design, raising costs and power consumption.
In contrast, an optically-enabled FPGA simplifies PCB design.  “For traditional chip-to-chip on a line card, optics does have a benefit because you can trade off the number of layers on a PCB,” said Craig Davis, senior product marketing engineer at Altera.  Such an optical-based design also offers future-proofing. “One of the advantages of using optics is that you haven’t got to throw your backplanes away as [interface] speeds increase,” said Davis.
By Roy Rubenstein