Large-scale optical backboard bus

Abstract

This paper describes an innovative high-speed optical backboard bus composed of an optical star coupler, optical-transmitter (E/O) modules, optical-receiver (O/E) modules, and optical multimode glass fibers. A highly efficient optical coupling structure with an aspherical lens and a laser diode was designed to achieve coupling efficiency of up to 90%, enabling the distribution of optical signals at up to 1 Gb/s to 32 functional boards. Embedded optical fibers in the printed circuit board are used to achieve precise control of the optical propagation delay time, and permit a high packaging density. E/O and O/E modules are placed with a pitch of about 15 mm. We developed small laser diode and photo diode modules suitable for optical coupling to the end of embedded fibers through the use of an alignment tool. A fabricated 8/spl times/8 prototype optical backboard bus was able to distribute high-speed optical signals of up to 1 Gb/s to function boards with a high packaging density.