Comment by octoberfranklin

The dark fiber glut wasn't caused by DWDM suddenly appearing out of nowhere.

The telcos saw DWDM coming -- they funded a lot of the research that created it. The breakthrough that made DWDM possible was patented in 1991, long before the start of the dotcom mania:

  https://patents.google.com/patent/US5159601

It was a straight up bubble -- the people digging those trenches really thought we'd need all that fiber even at dozens of wavelengths per strand.

They believed it because people kept showing them hockey-stick charts.