We review a bidirectional optical link scheme for memory-interface applications. A driver-receiver combined optical
transceiver (TRx) modules was demonstrated on an optical printed-circuit board (OPCB) platform. To select the
bidirectional electric input/output signals, a driver-receiver combined TRx IC with a switching function was designed in
0.18-μm CMOS technology. The TRx IC was integrated with VCSEL/PD chips for optical link in the TRx module. The
optical TRx module was assembled on a fiber-embedded OPCB, employing a 90°-bent fiber connector for 90° deflection
of light beams between the TRx module and the OPCB. The TRx module and the 90° connector were passively
assembled on the OPCB, using ferrule-type guide pins/ holes. Employing these constituent components, the bidirectional
optical link between a pair of TRx modules has been successfully demonstrated up to 1.25 Gb/s on the OPCB.