Compact Hybrid-Integrated 4 × 80-Gbps TROSA Module Using Optical Butt-Coupling of DML/SI-PD and Silica AWG Chips

We have developed a compact 4 × 80-Gbps transmitter-receiver optical subassembly (TROSA) module using a chip-to-chip optical butt-coupling method. For a Tx submodule, four directly modulated laser (DML) chips precisely bonded on a silicon DML-carrier are simultaneously butt-coupled to a vertically polished silica-based arrayed waveguide grating (AWG) chip, revealing good optical characteristics insensitive to external optical feedback. A Rx submodule is realized by passive alignment between a 45°-polished AWG and four surface-illuminated (SI)-PD chips, and subsequently integrated with the Tx submodule into a single package case to form the compact TROSA module whose size is only 25 mm × 15 mm × 6.4 mm and compliant to fit into the QSFP-DD/OSFP transceiver. The fabricated TROSA module shows clear Tx optical eye patterns at 80-Gbps PAM4 signals for all channels, achieving the Rx sensitivities within -7.1∼-6 dBm at a bit error rate (BER) of 2.4 × 10-4.