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The "copper cliff" is the biggest bottleneck in the data center today, but a new startup with a weird name thinks they’ve found a way to bridge the gap between heavy copper and expensive optics. In this video, we’re looking at Point2 Technologies and their E-Tube system—a hybrid interconnect that uses plastic waveguides to send millimeter-wave RF signals.
This was a very interesting listen. It sounds like it won't scale as high bandwidth-wise as fiber long term, but it finds a potential sweet spot in cost vs. distance and bandwidth inbetween copper and fiber.
The problem isn't so much long-term, it's real soon now...
Each "e-tube" carries two RF carriers at around 80GHz and 170GHz, each PAM4 modulated with 112Gbps, so 224Gbps per "e-tube" -- meaning, 8 "e-tubes" for 1.6T. There's no obvious way to scale this, doubling the RF frequencies is very difficult, higher modulation than PAM4 will run into SNR/BER problems.
That could be used to transport 8x224G down 8 "e-tubes" with a simple 1:2 reverse MUX at the input and MUX at the output. It's then competing against a 8x226G optical transport, which can use 8 fibres -- or 1 fiber with CWDM, which it can't do. If the 1.6T is 4x448G then you need 4:1 muxes but 8 "e-tubes". For 32T (8x448G) you need 16 "e-tubes". The problem rapidly becomes one of multiway connectors, as well as running out of bandwidth...
If copper still works, that's will carry on being the solution -- until it isn't. At that point you need so switch to something which is scaleable with increasing data rates without running out of connector poles in a few years time, which means optical and then WDM, and also means going CPO to avoid having to get all that data from the switch chip/GPU/AI chip to pluggable modules.
In theory they could take the same approach and move inside the package, but they'll very quickly hit the problem of connecting up large and increasing numbers of "e-tubes" because each one can only carry about the same amount of data as one optical carrier, but they can't be multiplexed together onto one fiber using WDM.
