Full-Duplex Bidirectional Optical Data Transmission over 50 μm-Core Graded-Index Multimode Fiber with Monolithically Integrated Transceiver Chips

For a wide range of interconnect applications, bidirectional optical data transmission in the Gbit/s range is very desired. Monolithically integrated transceiver (Tx/Rx) chips for 850 nm wavelength operation have recently been presented [1], which consist of a verticalcavity surface-emitting laser diode (VCSEL) and a metal–semiconductor–metal photodiode (MSM PD) and are suited for coupling to a 100μm core diameter fiber. Nevertheless, owing to the applied lithographic process, they are not well suited for standard gradedindex multimode fibers (MMFs) with smaller core. A new generation of chips (Fig. 1) presented in this article is based on a completely revised and simplified process technology. Due to a significant reduction of the VCSEL diameter, the detection area is increased and a centered laser diode can be realized for Tx/Rx chips with 110μm diameter, which drastically enhances coupling tolerances between chip and fiber. Even quasi error-free full-duplex 1Gbit/s bidirectional data transmission over a 500m-long MMF with 50μm core diameter is possible and shows the high potential of the given approach for various low-cost datacom applications.