Plastic fiber TOSLink cables -- basically everything available on Amazon -- are junk. Cheap plastic cables can barely handle the bandwidth required for 44.1/16 (for the most part not even that) forget about anything higher.
The problem stems from losses due to internal reflections. You need very fine, high-purity quartz-class conductor bundles and polished connectors to reduce reflection losses to to negligible level. Of course the quality of the receiver and transmitters play into this.
There are also high grade plastic cables out there such as the mid-level AQ and Supra cables that are supposedly the sweet spot for price-performance. I haven't compared any glass cables, but I do have a Supra cable that cost around $80, and have confirmed it competes in SQ with a filtered/isolated USB connection running off my dedicated audio PC.
The problem stems from losses due to internal reflections. You need very fine, high-purity quartz-class conductor bundles and polished connectors to reduce reflection losses to to negligible level. Of course the quality of the receiver and transmitters play into this.
There are also high grade plastic cables out there such as the mid-level AQ and Supra cables that are supposedly the sweet spot for price-performance. I haven't compared any glass cables, but I do have a Supra cable that cost around $80, and have confirmed it competes in SQ with a filtered/isolated USB connection running off my dedicated audio PC.