News & Analysis
OPTICAL NETWORKS: XFP device integrates full CMOS chain, amp
Loring Wirbel
10/9/2006 9:00 AM EDT
Colorado Springs, Colo. -- Luxtera Inc., a startup that has demonstrated lasers and ring modulators in silicon-on-insulator CMOS, has packaged dual transceiver channels of lasers and photodetectors in a 20 x 12-mm package that provides all the functions of an XFP transceiver. The move carries a certain irony in that Luxtera was pushing for all-silicon processes to eliminate the need for many optoelectronic packages.
"This gives customers a chance to work with layouts they are familiar with, while still stressing the critical level of silicon integration," said Luxtera chief executive Alex Dickinson, who noted that the package includes ingredients found in a full optical XFP module, such as a transimpedance amp, Mach-Zehnder modulator and clock/data recovery circuits.
The resultant chip dissipates 1.5 watts per channel. The total footprint for the dual-channel transceiver is 12 x 35 mm when an optional mechanical-transfer registered jack package is used. The transceiver die can be put inside a traditional XFP module along with a microcontroller, or used directly in a line card or server card.
The package is being sampled today, and is also being used as the basis for a series of multiport transceivers for combining 10-Gbit links. Luxtera used similar concepts in developing parallel 40-Gbit interconnects for Sun Microsystems Inc.'s High Productivity Computing Systems project, funded in part by the Defense Advanced Research Projects Agency.
Dickinson said that Luxtera is in the second stage of its own program with Darpa, an effort within the Electronic and Photonic Integrated Circuits (Epic) program to create a prototype with 10 channels of 10-Gbit/second links. The two stages of the Epic program amount to about $6 million each, Dickinson said.
The transceivers being sampled are legitimate communication products in their own right, said Marek Tlalka, Luxtera's vice president of marketing. They use flip-chip bonding to put 1,550-nanometer lasers into the package, interfaced with 10-Gbit modulators driven by on-chip circuitry. The manufacturing process allows testing of each die on the wafer, so bad dice can be removed before packaging, increasing the lot's overall reliability and yield, Tlalka said.
Dickinson said Luxtera has worked with Cadence Design Systems Inc. on standardizing library elements for photodiodes, ring modulators, Mach-Zehnder modulators and other elements, which eases the design of newer, high-integration optical subsystems.
Dickinson said the company is ready to produce high-volume optical subsystems in CMOS at comparatively low costs. It has produced more than 150 equivalent kilometers of waveguides, has manufactured 300 million fiber-to-the-chip couplers and has applied for more than 120 patents.
