@devinplombier Fibre optical cables are made of glass and can be very long; cheap too.Fibre is used to transmit data across large distances reliably,
Glass cannot carry analog noise that is in the network, a network is likely ethernet cable based for the most part, like my home network. I use fibre cable as the last bit before the DAC.
I think jitter is another matter to be concerned with, but most competent DACs (low cost) can handle jitter these days. I do not know how that relates to streaming. I do not care since the DACs can deal with it.
Toslink is likely also made of glass, but it is a different type of cable and cannot travel long distances. Toslink also has some issue related to digital transmission that I do not know enough to explain.
I do use Toslink in my office system for 1 DAC input and SPDIF for another DAC input. The Toslink is for my noisy computer (YouTube and sports) and the SPDIF is for CD/SACD's. The SPDIF sounds great, as good as the streaming. The Toslink is not that great, nor is the source.
I am just some person spewing an opinion here however, there are some heavy-duty DAC designers that are stating the same thing. PlayBack Designs Andreas Koch for one.
BTW - Lumin were the first DAC company to support fibre natively, they actually did this after reading posts on an online forum years ago about the advantages of fibre.