3 ms·

USB 4 (opt) is ... optical? Or optional?

by a3w 4y ago

willis936 4y ago
It would have a longer max length if the data lanes were optical.
- johnwalkr 4y ago
  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.
  - mschuster91 4y ago
    > 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.
    - johnwalkr 4y ago
      That’s a good point although optical usb3 and thunderbolt3 cables tend to be advertised with electrical isolation as a feature and suggest using an external hub to provide power.[1] [1] https://www.corning.com/optical-cables-by-corning/worldwide/en/products/usb-optical-cables.html https://www.corning.com/optical-cables-by-corning/worldwide/...
      - mschuster91 4y ago
        Whoa, that pricing is quite a bit.
        johnwalkr 4y ago
        Yeah that must be the real reason it didn’t catch on as a default. Light peak did have cheaper cables though, the optical part was in the connector, not the cable. The connector was a usb-a connector if I remember correctly.. and the history is actually pretty interesting! Apparently that connector was deemed proprietary and frowned upon by the usb folks for causing consumer confusion[1]. Kind of hilarious now, seeing how thunderbolt 1/2 ended up barely being adopted outside of Apple and usb itself is a confusing mess these days. [1] https://www.theverge.com/2011/10/14/2490694/how-sony-accidentally-did-the-right-thing-with-light-peak https://www.theverge.com/2011/10/14/2490694/how-sony-acciden...
        mschuster91 4y ago
        > Kind of hilarious now, seeing how thunderbolt 1/2 ended up barely being adopted outside of Apple Which is to a large degree the fault of Intel restricting the TB spec to hell and back.
masklinn 4y ago
According to the wiki table (https://en.wikipedia.org/wiki/USB4#Support_of_data_transfer_modes https://en.wikipedia.org/wiki/USB4#Support_of_data_transfer_...), it's "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.

USB 4 (opt) is ... optical? Or optional?

by a3w 4y ago

USB 4 (opt) is ... optical? Or optional?

willis936 4y ago

It would have a longer max length if the data lanes were optical.

johnwalkr 4y ago
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.
- mschuster91 4y ago
  > 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.
  - johnwalkr 4y ago
    That’s a good point although optical usb3 and thunderbolt3 cables tend to be advertised with electrical isolation as a feature and suggest using an external hub to provide power.[1] [1] https://www.corning.com/optical-cables-by-corning/worldwide/en/products/usb-optical-cables.html https://www.corning.com/optical-cables-by-corning/worldwide/...
    - mschuster91 4y ago
      Whoa, that pricing is quite a bit.
      - johnwalkr 4y ago
        Yeah that must be the real reason it didn’t catch on as a default. Light peak did have cheaper cables though, the optical part was in the connector, not the cable. The connector was a usb-a connector if I remember correctly.. and the history is actually pretty interesting! Apparently that connector was deemed proprietary and frowned upon by the usb folks for causing consumer confusion[1]. Kind of hilarious now, seeing how thunderbolt 1/2 ended up barely being adopted outside of Apple and usb itself is a confusing mess these days. [1] https://www.theverge.com/2011/10/14/2490694/how-sony-accidentally-did-the-right-thing-with-light-peak https://www.theverge.com/2011/10/14/2490694/how-sony-acciden...
        mschuster91 4y ago
        > Kind of hilarious now, seeing how thunderbolt 1/2 ended up barely being adopted outside of Apple Which is to a large degree the fault of Intel restricting the TB spec to hell and back.

masklinn 4y ago

According to the wiki table (https://en.wikipedia.org/wiki/USB4#Support_of_data_transfer_modes https://en.wikipedia.org/wiki/USB4#Support_of_data_transfer_...), it's "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.