Polymer cables could replace Thunderbolt & USB, deliver more than twice the speed

An Apple Thunderbolt 3 Pro cable

Presented at the February IEEE International Solid-State Circuits Conference, the research aims to develop a connection type that offers far better connectivity than current methods. In part, it aims to accomplish this by replacing copper wiring with something else.

Copper is typically used for wires like USB and HDMI to handle data transfers, but it requires a lot of power to work for high levels of data transmission. "There's a fundamental tradeoff between the amount of energy burned and the rate of information exchanged," said MIT alumni and lead author Jack Holloway.

While the "increasingly bulky and costly" copper could be replaced by fiber optic cables, that introduces its own issues. As silicon chips have difficulty dealing with photons, this makes the interconnection between the cable and the computers more challenging to optimize.

According to Holloway, "there are all kinds of expensive and complex integration schemes, but from an economics perspective, it's not a great solution," which led to developers creating their own version.

Combining the benefits of copper and fiber optic conduits, a plastic polymer is used by the researchers. This makes it cheaper to manufacture than copper wires, which could be an attractive proposition for cable producers.

The polymer can also use sub-terahertz electromagnetic signals, which is more energy-efficient than copper at high data loads. It is believed this efficiency brings it close to that of fiber optic systems, but crucially with better compatibility with silicon chips.

Low-cost chips are paired with the polymer conduit that can generate the high-frequency signals powerful enough to transmit into the conduit directly. As such, the system is expected to be manufactured with standard methods, which also makes it cost-effective to produce.

The cables themselves can also be extremely thin, with the cross-sectional area of the interconnect measuring 0.4 millimeters by a quarter millimeter, smaller than typical copper variants.

That small hair-like cable can be used to transport data over three different parallel channels, enabling it to achieve a total bandwidth of 105 gigabits per second. Bundling conduits together could bring the cables into the terabit-per-second range, while still remaining at a reasonable cost.

Echoes of Thunderbolt

The system, using chips on either end of a cable, uses a relatively similar concept to Thunderbolt cables, albeit with a different conduit in use. In each case, chips inside the cable are used to manage data being fed into the cable at one end and out the other, while also handling interfacing with the conduit itself.

It seems plausible that such a system could be employed for a future Thunderbolt-style connection, allowing it to go far beyond the current 40Gbps upper limit.

Another connection to Thunderbolt is its research funding. While Thunderbolt was developed by Intel and Apple, the unnamed polymer research was also funded by Intel, alongside Raytheon, the Naval Research Laboratory, and the Office of Naval Research.