Crosstalk analysis of planar and multi-chip transmitter modules for optical PCB applications

As the speed of integrated circuits increases, inductive coupling becomes an issue for the packaging interconnect technologies. Two transmitter modules (planar and multichip) have been fabricated for crosstalk analysis. The modules are prepared using 1×4 VCSELs and driver integrated circuit (IC) fabricated in a 0.18 µm Si-CMOS technology. The planar module has been fabricated using the conventional wire-bonding technology for interconnect between the vertical cavity surface emitting laser (VCSEL) and the driver chip while the multichip module has been prepared using flip-chip bonding process. The modules showed clear eye openings at 2.5 Gb/s with bit error rate less than 10⁻¹². This work focuses on the crosstalk effect due to the electrical interconnects between the driver chip and VCSEL chip. Crosstalk improvement of the multichip module over the planar module is shown analytically and by field simulation. Equivalent circuit model of the interconnects has been extracted based on RLC line model.