This invention relates to optically interconnecting opto-electric components on different integrated circuit (IC) chips, and also on the same IC chip, using a printed circuit board (PCB) on which the IC chip or chips are mounted.
Many electronics systems, including computer motherboards, include one or more IC chips mounted on PCBs. A PCB provides a surface on which the IC chips are mounted, and also provides electrical interconnections between the IC chips.
Signalling speed requirements between different IC chips in the same electronics system, and perhaps mounted on the same PCB, are ever increasing. In some cases, electrical signaling may not provide the needed, or desired, bandwidth, or may provide the bandwidth with costs. Some of the costs include a more complex design, in terms of multiplexing and demultiplexing the signals into multiple parallel lines. There may also be costs in terms of noise, both because the speed of the signaling may be nearing phyical limits and because of cross-talk between the parallel electrical interconnects.
Optical signaling, as compared to electrical signaling, offers significantly higher bandwidth and eliminates, or greatly reduces, the noise problems inherent with electrical signaling. An example where bandwidth requirements are making optical signaling between IC chips in the same system increasingly attractive, and in fact may require optical signaling, is in computer motherboards. For example, signaling between processor IC chips and memory IC chips on the same motherboard are already in some systems two gigabytes per second, and will certainly only increase in the future.
Optical signaling, however, poses design challenges not posed with electrical signaling. For example, optical signaling requires there to be an optical waveguide interconnection between the signal source and detector. In some cases, the optical interconnection between two IC chips within the same system has been provided with conventional optical fibers. However, this approach has its disadvantages. First, the optical fibers add cost to the system. Also, optical fiber connectors are typically large, and thus consume sometimes precious space, and the labor involved in providing connections to optical fibers is typically significant.
Better approaches to providing optical interconnects between IC chips within the same system, and even between opto-electronic components on the same IC chip, are therefore needed.