Carrying capacity of optical cable

The throughput capacity of a single-mode fiber optic cable (1,550 nm) is 20 Tb/s (20,000 Gb/s).

Carrying Capacity (aka Shannon's Law) = W x log₂(1+s/n)

W = bandwidth (Hz) (assumed to be 12.5 THz in this case)

s/n is signal-to-noise ratio (s/n value is typically 20 dB for optical fiber, making the ratio equal to 2)

Carrying Capacity = 12.5 THz x log₂(1+2)

= 12.5 x 1.6

= 20 Tb/s

Sources: About Fiber Optics (http://www.aboutfiberoptics.com), NetClear on Shannon's Law (http://www.netclear-channel.com/shannonslaw/Default.htm)