Cross talk and ghost talk in a microbeam free-space optical interconnect system with vertical-cavity surface-emitting lasers, microlenses, and metal-semiconductor-metal detectors

A diffraction-based beam-propagation model is used to study optical cross t alk in microbeam free-space optical interconnection (FSOI) systems. The sys tem consists of VCSEL's, microlenses, and metal-semiconductor-metal (MSM) d etectors, with the detectors modeled as amplitude gratings with low contras t ratio (based on experimental results). Different possible cross-talk sour ces are studied. Results show that, in an optimized system, the cross talk caused by diffractive scattering is not an issue. However, in such systems the principal reflection from a MSM detector surface creates two problems: VCSEL coupling and ghost talk. The coupling of the reflected beam into the VCSEL's may cause power oscillation (and increase the bit error rate), wher eas ghost talk will limit the distance-bandwidth product of the interconnec t system. This optical system is also abstracted in HSPICE together with th e laser driver and receiver circuits to analyze ghost talk in this system. Results show that at high speed (1 Gbit/s or more) these effects negatively affect system performance. (C) 2000 Optical Society of America. OCIS codes : 200.4650, 250.7260.