In the past few years tech like 100G Coherent DWDM have reduced latency by 10-20% on longhaul fiber links, as dispersion compensation fiber is no longer needed.

In the past few years tech like 100G Coherent DWDM have reduced latency by 10-20% on longhaul fiber links, as dispersion compensation fiber is no longer needed. Other companies have simply opted to pull out the slack in the fiber to decrease latency. It's basically "you get what you pay for"