Abstract
The demand for advanced interconnects to satisfy market requirements on bandwidth, cost, and power is ever increasing with the expansion of data centers. An interconnect called E-TUBE is presented as a cost-and-power-efficient all-electrical-domain wideband waveguide solution for high-speed high-volume short-reach communication links. The E-TUBE achieves an unprecedented level of throughput-distance product, bending radius, and channel density without requiring complex manufacturing process. The E-TUBE link demonstrates nearly 25 GHz bandwidth at a carrier frequency of 70 GHz and exhibits a frequency-independent insertion loss of 5 dB/m with a frequency-independent group delay of 4 ns/m. Such loss and delay characteristics independent of frequency enabled broadband data transmission over extended reach compared to conventional waveguide links. The E-TUBE link transmits 25 Gbps NRZ data over 3 m distance using a 70 GHz RF CMOS transceiver IC, which is the state-of-the-art throughput-reach product. This new interconnect is expected to overcome the limitations of existing electrical and optical interconnects and to replace them in high throughput links, including but not limited to, 100/400 Gbps board-to-board communications.
Highlights
The demand for advanced interconnects to satisfy market requirements on bandwidth, cost, and power is ever increasing with the expansion of data centers
A low-cost low-loss broadband dielectric waveguide solution referred to as an E-TUBE is proposed as an advanced alternative to existing electrical and optical interconnects in high-speed short-reach communication links
The E-TUBE implemented with low-loss dielectric core laminated with low-roughness, high-conductivity metal films overcomes the functional limitations of conventional waveguides and demonstrates low-loss, low-group velocity dispersion (GVD) characteristics even in the strictly bended condition
Summary
The metal-clad dielectric waveguide, E-TUBE, connects the transmitter and receiver boards. The connector is designed to couple the signal vertically to the board, which increases the area efficiency of the E-TUBE link defined as throughput/footprint Such 90-degree redirection achieves low-profile board-edge connection of the E-TUBE. These new boundary conditions lead to a relatively constant group delay over the passband (Supplementary Note 2), which is a significant improvement over conventional designs enabling higher-speed and extended-reach signal transmission. The closed cell foams consist of enclosed, tiny and closely packed air pockets leading to the overall foams more flexible and resilient compared to the open cell foams These characteristics enable the dielectric core to achieve high dimensional stability after compression, bending, or twisting during the manufacturing process. The measured BER is less than 1 0–12 for the channel reach less than 3 m
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