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USB 4 (opt) is ... optical? Or optional?
* "USB4 20 Gbit/s Transport" (= USB4 20Gbps = USB4 Gen 2x2) is required for host to support
* "USB4 40 Gbit/s Transport" (= USB4 40Gbps = USB4 Gen 3x2) is not
Also USB4 apparently only requires support for tunneling "SuperSpeed USB 10Gbps" (USB 3.2 Gen 2×1), "SuperSpeed USB 20Gbps" (USB 3.2 Gen 2x2) is optional.
> May 05, 2025 The article is dated May 5, 2025. I've long been wondering about the future of USB.
Some of the entries seem incorrect: "USB 3.2 (USB 3.2 Gen 2x2) and "USB 4" (USB 4 USB4 Gen 2×2) should have the same nominal data rate of 2500MB/s, they're 2 lanes (x2) of 10GB/s. Though they are apparently coded differently electrically, so they're distinct protocols. The tables would benefit from mentioning the coding (8/10 or 128/132) as IMO it's one of the most confusing bits when you see the effective data rates…
Suggestion: maybe include all the USB-C-plug Thunderbolt versions too. My personal policy these days is to just buy reputable Thunderbolt cables for all my USB-C needs. Maybe I'm doing the wrong thing? Also, I think there's a difference between active and passive USB-C cables, or something like that.
If you're happy with it then probably not.
The main possible issues are that it's more expensive and you get shorter and thicker (less flexible) cables, a passive non-optical TB (or USB4) cable will top out around 1m.
Less capable cables can be longer and thinner which is convenient for e.g. mice and such small devices. But otherwise may not matter overly much.
Earlier quoted context omitted.
It would have a longer max length if the data lanes were optical.
You can actually get optical usb3 and thunderbolt (all generations) cables. Thunderbolt was originally called light peak and shown off by Intel and Apple in demos as optical, and Sony had a line of laptops with optical light peak connectors to connect to external GPUs. But ultimately the default became non-optical because it can carry power too.
There's no problem in making a cable with two fibre leads for data and two (at higher lengths thicker to reduce issues with voltage drop) power lines.
I have 2 different generations of USB-C hosts, and they behave quite differently when approaching max cap, especially with high-quality low-latency audio (USB-C was supposed to be de-facto replacement for FireWire).
While I get the technical reasoning about high frequency/attenuation etc that limits cable length as speeds go higher, there are obviously some practical limits to how short cables can be.
How would that be solved, I don't know.