A comparative analysis of short-and long-wavelength multi-chip optical transmitter modules for optical PCBs applications

Optical interface multichip modules promise to alleviate the bottlenecks of electrical interconnection. Two kinds of optical transmitter multichip module were fabricated for optical printed circuit board (OPCB) based interconnections for performance analysis. Each of the modules consist of 1 x 4 bottom-emitting VCSELs flip-chip bonded on a CMOS driver array IC for optical interconnection; among them one is an 850nm short-wavelength and the other is a 1310nm long-wavelength VCSEL. The short- and long-wavelength VCSELs have -3dB bandwidth of about 3.6 GHz and 2.6 GHz, respectively. Four-channel driver array which has been fabricated in a 0.18μm Si-CMOS technology requires 1.8V of power supply, is used for the both multichip transmitter modules. Short- and long-wavelength multichip modules are bumped with Au/Sn solder and gold stud bump wire respectively using the flip-chip bonding technology. The multichip modules have a dimension of 1.1mm x 1.2mm x 0.5mm for the four channels. The multichip module employing flip-chip bonding technology reduces unwanted crosstalk due to bond wires. The two modules showed BER less than 10-12 and clear eye openings at 2.5 Gbps. We measured the frequency response and crosstalk of long-wavelength multichip module and will compare them with the short-wavelength multichip module to evaluate which module is preferable for the optical interconnection applications on optical PCBs.