One of the huge problems of requiring lossless photon transmission through fiber: This will break all currently known approaches to DWDM. It is not economical for inter-city transport between ISPs to require its own dark strand pair, no WDM of any type, in most scenarios. There's a reason why people want to be able to do things like 100/200/400GbE coherent frequencies in a 80-channel DWDM bandplan.