Optical Subassembly Modules Using Light Sources Butt-Coupled With Silica-Based PLC

We have fabricated DML/EML-based subassembly modules based on chip-to-chip optical butt-coupling with straight waveguides between a silica AWG chip and commercial directly modulated laser (DML) or electro-absorption modulated laser (EML) chips. By properly inducing external optical feedback on the DML chips, we experimentally demonstrate that 3-dB bandwidths of the DML-based subassembly module can be increased by 5 ~ 9.5 GHz compared with those of commercial 28-Gbaud DML chips. The EML-based subassembly module exhibits optical characteristics insensitive to the external optical reflection with a side mode suppression ratio (SMSR) of over 50 dB, revealing excellent optical eye patterns under 112-Gbps PAM4 operations.