Fully embedded board-level guided-wave optoelectronic interconnects

A fully embedded board-level guided-wave optical interconnection is present ed to solve the packaging compatibility problem. All elements involved in p roviding high-speed optical communications within one board are demonstrate d. Experimental results on a 12-channel linear array of thin-film polyimide waveguides, vertical-cavity surface-emitting lasers (VCSEL's) (42 mu m), a nd silicon MSM photodectors (10 mu m) suitable for a fully embedded impleme ntation are provided. Two types of waveguide couplers, tilted gratings and 45 degrees total internal reflection mirrors, are fabricated within the pol yimide waveguides. Thirty-five to near 100% coupling efficiencies are exper imentally confirmed. By doing so, all the real estate of the PC board surfa ce are occupied by electronics, and therefore one only observes the perform ance enhancement due to the employment of optical inter-connection but does not worry about the interface problem between electronic and optoelectroni c components unlike conventional approaches. A high speed 1-48 optical clock signal distribution network for Cray T-90 s upercomputer is demonstrated. A waveguide propagation loss of 0.21 dB/cm at 850 was experimentally confirmed for the 1-48 clock signal distribution an d for point-to-point interconnects. The feasibility of using polyimide as t he interlayer dielectric material to form hybrid three-dimensional intercon nects is also demonstrated. Finally, a waveguide bus architecture is presen ted, which provides a realistic bidirectional broadcasting transmission of optical signals. Such a structure is equivalent to such IEEE standard bus p rotocols as VME bus and FutureBus(+).