It's fiber interconnect between sites that is not actively visible to other people who are routing data around the world. Think of it as being pre-layed but not

It's fiber interconnect between sites that is not actively visible to other people who are routing data around the world. Think of it as being pre-layed but not yet turned on/made available. See: https://en.wikipedia.org/wiki/Dark_fibre https://en.wikipedia.org/wiki/Dark_fibre