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20 April 2012
Silicon photonics firm Kotura has unveiled its 100Gbps optical transceiver. Referred to as an optical engine, the 100Gbps chip is implemented as a 4x25Gbps design. The optical engine consumes 5W and has a reach of at least 10km, making it suitable for all likely requirements in the data centre including the 100 Gigabit Ethernet 100GBASE-LR4 standard.
Kotura demonstrated its optical engine to select customers at the recent OFC/ NFOEC show.  "We are not announcing the product yet," said Arlon Martin, vice president of marketing at Kotura.
Optical engines are used in several applications including pluggable modules on a system's face plate, the optics at each end of an active optical cable, and for board-mounted embedded applications.  
For such embedded applications, the optical engine is mounted deeper within the line card, close to high-speed chips, for example, with the signals routed over fibre to the face-plate connector. Using optics rather than high-speed copper traces simplifies the printed circuit board design. Embedded optical engines will also be used for future optical backplane-based platforms.
Kotura's silicon photonics-based optical engine integrates all the functions needed for the transmitter and receiver on-chip. These include the 25Gbps optical modulators and drivers, the 4:1 multiplexer and 1:4 demultiplexer and four photodetectors. To create the lasers, an array of four gain blocks is coupled to the chip. Each laser's wavelength, at around 1550nm, is set using on-chip gratings.
The 100Gbps chip, measuring about 5x6mm, is small enough to fit in the QSFP+ and future CFP4 optical modules, says Martin. The QSFP+ is likely to be the first application for Kotura's 100Gbps optical engine, where it will be used to connect switches within the data centre. 
By Roy Rubenstein