PMD Layer Chip Set

The complete 2.5/3.125Gbps Physical Media Dependent (PMD) layer chip-set manufactured in standard Complementary Metal Oxide Semiconductor (CMOS) process technology enables manufacturers to build low-cost 2.5/3.125Gbps fiber optic modules. The chip-set consists of a preamplifier, a limiting amplifier, and a laser driver. Using proprietary circuit designs, the company can manufacture chips using the standard CMOS process that meet or exceed standard specifications. The preamplifier and limiting amplifier utilize proprietary Broadband Cascade Amplifier (BCA) technology. BCA allows CMOS to achieve broadband performance previously attained only through bipolar or GaAs processes.

The CN3000TV laser driver provides up to 40mA of modulation current at both 2.5 Gbit/s and 3.125 Gbit/s that could support either a short wavelength Vertical Cavity Surface Emitting Laser (VCSEL) or a long wavelength edge-emitting laser such as the Fabry-Perot (FP) or the Distributed Feedback (DFB) Laser. The CN3000TV features on-chip circuitry for automatic control of the laser's average power and modulation level. The laser driver's modulation current has a programmable temperature coefficient that allows customers to compensate for changes in laser diode's slope efficiency with temperature.

The CN3000RL limiting amplifier employs BCA technology to achieve more than 40dB gain and better than 5mV sensitivity and hosts on-chip Loss of Signal (LOS) circuitry. The CN3000RT preamplifier, also utilizing BCA technology, features on-chip automatic gain control circuitry that attains an optical dynamic range better than 26dB. All devices in the chip set operate with a +3.3V supply and are currently available in sample quantities.

Cognet Microsystems/Cognet, Inc., 11500 West Olympic Blvd., Suite #611, Los Angeles, CA 90064. Tel: 310-231-8242; Fax: 310-231-0702.