Comment by amiga386

I used to work for a telco equipment provider around the time everyone was replacing PDH with SONET. Telcos were gagging to buy our stuff, the main reason being basic hardware advances.

Telephone Exchanges / Central Offices have to be in the centre of the lines they serve, meaning some very expensive real estate, and datacenter-level HVAC in the middle of cities is very, very expensive.

They loved nothing more than to replace old 1980s switches with ones that took up a quarter to a tenth of the floorspace, used less than half the electricity, and had fabrics that could switch fibre optics directly.