12-Channel × 20-Gbps on-board parallel optical modules using multi-chip visual alignment technique

We have developed 12-channel × 20-Gbps optical transmitter/receiver modules with 9 × 14-mm footprints. To achieve stable optical coupling efficiency, we also developed a precise multi-chip mounting technique. The three dies of 4-channel vertical-cavity surface-emitting laser (VCSEL)/photodiode (PD) arrays are mounted at the same time. The accuracy of the Z-axis can be controlled by monitoring the dies' positions for the optical reference plane. The coupling losses were less than 1.5 dB in the 12-channel transmitter/receiver modules. The standard deviations of the coupling losses were less than 1.0 dB in all samples. Error-free transmissions at a data rate of 20 Gbps were also demonstrated. A reliability test indicated that the modules are repairable and reliable.