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Comment by CoastalCoder | Hacker News Reader

Not my area of expertise, but maybe some (unrealistic) options include using fiber optics for the data lines, or adding more data lines.

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There already exists some fiber-optic USB cables that come in lengths >50m and with support for USB 3.1 so it doesn't seem like a very unrealistic option.

That sounds more like fiber optic adapters/converters that fit into usb-ports and talk usb, rather than USB-cables that can be 50+ meters.

I think GP is thinking of fiber optic Thunderbolt cables probably.

Seems like you can get 3m optical usb-c cables. Oculus sells an official "Full featured USB active optical cable. USB 3.2 Gen 1 Type-C" for tethered play.

That's what the cheatsheet says so maybe that's part of the spec.

Some USB4 / Thunderbolt cables are like that, but with copper in the middle. The drivers on the device end wouldn't be able to maintain signal integrity over that size of cable, so there's a pair of transceivers in each end of the cable to convert the signal into a format that'll survive transmission.

What's the difference between talking USB and being USB?

https://www.amazon.com/FIBBR-Female-Active-Extension-Optical... provides USB-to-fibre-to-USB in a single cable, and a copper pair in parallel for power.

$169+47 shipping for those curious

Can't say it's not unique and cool, to be fair

Redmere chips also proved HDMI can go very, very far with a little extra investment. I've run 4K signals hundreds of feet with them. We've seen this problem solved several times, I can't imagine it's physically impossible with USB-C.

I guess at some point optical will be the only way forward.

Having more data lines in a serial bus is interesting, as the whole reasoning to go from parallel lines (e.g. Centronics, ATA/SCSI or ISA/PCI buses) to serial (SATA/SAS, PCIe, USB) was that coordinating multiple data lines got impossible due to physical limitations where e.g. minimal differences in cable lengths started to matter).

Multiple serial busses, each with its own clocking and buffer, so that the combined data is extracted synchronously at the end. The crosstalk is still a problem but there are ways around that: different twist rates for different pairs for instance.

> I guess at some point optical will be the only way forward.

Maybe. Though Infiniband's currently at 100Gbps per lane on a 1.5 meter passive cable. And active cables can give you a moderate boost while still on copper.

that's a giant QSFP+ cable (I think mine are at least 3/8") with tons of shielding and a terrible bend radius though.

And my cables all have a "10 plug/unplug cycle lifespan" sticker on them - it undoubtedly will go for longer in practice but it's not designed for USB-style usage where you might plug and unplug your phone a dozen times a day as you charge it.

Commercial design concerns are very different from consumer design concerns, basically. Phones would probably be easier if we had a 1/2" x 1/2" x 1.5" connector with a shielded connector body! ;)

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