You can use fiber optics as an optical delay line too! About 60KB/km at 100Gbps. https://en.wikipedia.org/wiki/Delay-line_memory https://en.wikipedia.org/wiki/

You can use fiber optics as an optical delay line too! About 60KB/km at 100Gbps. https://en.wikipedia.org/wiki/Delay-line_memory https://en.wikipedia.org/wiki/Delay-line_memory