A 12.5+12.5Gb/s full-duplex plastic waveguide interconnect

S. Fukuda, Y. Hino, S. Ohashi, T. Takeda, S. Shinke, M. Uno, K. Komori, Y. Akiyama, K. Kawasaki, and A. Hajimiri

This paper presents a 12.5+12.5Gb/s full-duplex plastic waveguide interconnect solution based on millimeter-wave signal transmission. The plastic waveguide is simply a long solid piece of plastic that provides a very simple, versatile, flexible, and low-cost transmission medium that has the main advantages of optical fiber in isolation and bandwidth, without the need for costly EO and OE. The dielectric waveguide does not need to be connected electrically like the wire or aligned to micron-level accuracy like optical fibers. It can be bent and twisted without significant impact on the signal. Compared to the wireless link discussed earlier, it offers additional signal isolation and confinement. Thus, it can be extended over much longer distances due to the low attenuation in the waveguide (as opposed to free space) and multiple independent lines can be run in parallel to increase the bandwidth. In our proposed plastic waveguide link, the TXs and RXs are fully integrated in CMOS, and the waveguide couplers can be fabricated in a conventional resin package without additional cost. In our existing setting there are a transmitter and a receiver operating at different carrier frequencies on each side of the waveguide, making it possible to realize a full-duplex solution. Because of the smaller fractional bandwidth for the millimeter-wave transmission, no equalization circuit is required.