mm-Wave Links and Wireless Fiber

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As aggregate data rate requirements over wired interconnects are approaching terabit/s (Tbps) levels, current physical channels are nearing their limits, both in terms of power consumption as well as bandwidth and capacity constraints. To that end, we are investigating a high capacity, low-cost planar interconnect technology based on mm-wave dielectric/plastic waveguides.

We have explored the fundamental physical constraints (such as attenuation and dispersion) in common mm-wave dielectric waveguides, and have examined the tradeoffs in using different waveguide geometries, dimensions, and operating frequencies for achieving higher capacity at different lengths. We have shown that higher capacity in such links is primarily limited by dispersion rather than attenuation [1-2].

We have also focused on the fundamental aspects of improving the capacity of these links, mainly by revisiting the microwave excitation and the propagation properties in the guide. For example, we have proposed and demonstrated a novel planar feed structure to excite two polarization-orthogonal modes of the rectangular dielectric waveguide to double the bandwidth while simplifying the structure of the feed network and maintaining reliability and robustness [2-4]. We are continuing this work by designing the interface to mm-wave electronics and moving towards building the entire system.

We are currently investigating compact and energy-efficient equalization techniques to compensate for dispersion and to increase the single carrier bandwidth of the dielectric waveguide; and are designing a system utilizing an analog feed-forward equalizer (FFE) to achieve bandwidth increase with minimum hardware overhead.

(a) Current state of interconnects in data centers, (b) multi-mode mm-wave dielectric waveguide for high-throughput interconnects, (c) planar multi-mode coupler capable of coupling signals from CMOS devices into a dielectric waveguide.

[1] N. Dolatsha, C. Cheng, and A. Arbabian, "Loss and Dispersion Limitations in mm-Wave Dielectric Waveguides for High-Speed Links," IEEE Trans. Terahertz Sci. Tech., vol. 6, pp. 637-640, July 2016.

[2] N. Dolatsha and A. Arbabian, "Analysis and Design of a Multi-mode Dielectric Waveguide Interconnect with Planar Excitation," Proc. Progress Electromag. Res. Symp., Stockholm, 2013, pp. 234-239.

[3] N. Dolatsha, N. Saiz, and A. Arbabian, "Fully packaged millimetre-wave dielectric waveguide with multimodal excitation," Elec. Lett., vol. 51, no. 17, pp. 1339-1341, Aug. 2015.

[4] N. Dolatsha and A. Arbabian, "Dielectric Waveguide with Planar Multi-Mode Excitation for High Data-Rate Chip-to-Chip Interconnects," Proc. 2013 IEEE Int. Conf. Ultra-Wideband, 2013, pp. 184-188. Best Student Paper Award