COLORADO SPRINGS, Colo. Luxtera Inc. has used a silicon-on-insulator (SOI) process from Freescale Semiconductor Inc. as the basis for an integrated receiver with a layered pure-germanium photodetector applied after waveguides are etched into the SOI substrate. Marek Tlalka, Luxtera vice president of marketing, predicted that successful scaling of a single-chip receiver to high volumes might spell the end of the discrete photodetector market for many applications.
"This is not a silicon-germanium process we have used," Tlalka emphasized. "We are applying pure germanium to an SoI-CMOS process."
Luxtera had demonstrated all-CMOS transceiver devices for a variety of fiber-optic communication applications in the past, but integration of germanium photodetectors will allow for long-range broadband transmission using lower power continuous-wave lasers. Transmit-path devices from Luxtera already had combined such lasers with grating couplers and fiber-attach blocks. Now the addition of photodetectors completes the receive channel as well.
In a die measuring less than 40 square microns, Luxtera can implement dual 10-Gbit XFP transceivers. The ideal configuration for many communication applications will be four-channel devices, Tlalka said, with each channel rated at 2.5, 5, or 10 Gbits/sec. The performance of the integrated germanium photodiodes have typically been 6 dB better than discrete devices, Luxtera claims.