FR4 printed circuit board design for Giga-bits embedded optical interconnect applications

As the demand of high data rate increases, electrical interconnects on the board becomes a bottleneck for the overall system performance because of crosstalk, transmission line effects, clock skew, and timing jitter [4]. Thus, considerable effort has been made to investigate alternatives to board-level electrical interconnect, such as optical interconnects. However, current board-level optical interconnects still have limitations such as board fabrication cost, optical loss, and alignment tolerance. In this paper we discuss an optical board-level interconnect that uses optoelectronic devices embedded in an optical waveguide, to provide a solution to for Giga-bit data range interconnect, on FR4 printed circuit board (PCB) [I]. FR4 PCB is an attractive candidate because it is low-cost and widely used technology. However, the design of electrical interfaces to the optical interconnect still faces all the challenges of FR4 PCB design [12]. Therefore, careful design of electrical path by EM/Schematic co-simulation is inevitable to use the FR4 PCB for 10 giga-bit per second (Gbps) applications even with optical interconnect. From the results of the measurements and simulations provided in this research, we see that fully embedded optical interconnect is a feasible solution to replace the current board-level electrical interconnect in high speed digital systems, however, the design of the optical electrical interfaces remains a challenging part of the interconnect problem.