[alfie2]

Internet backbone uses OC192s FO connections, there is plenty of Bandwith for expansion.
To get an idea of how FAST is OC192:

T-1 - 1.544 megabits per second
OC-192 - 9.6 gigabits per second ( or 6400 X T1)

remember this: one backbone router, alone can contains 5-7 OC192s boards.
large backbone providers have hundreds of this routers running as of now.

ADSL lines from your home goes to a DSLAM which handles a set numbers of homes/lines
the aggregate total of all the ADSL lines is shared on one to two T3(about 28x T1) - 43Mbps which handles 200-400 ADSL lines depends on service provider.
which means,in actuality, about 10-30 ADSL lines share one T1 speed or worse.

fiber optic/communications companies:
alcatel-lucent
jds uniphase
nothern telecom or nortel

router company:
ciso
juniper networks