Definition of c band:
(N) :
In infrared optical communications, C-band (C for "conventional") refers to the wavelength range 1530–1565 nm, which corresponds to the amplification range of erbium doped fiber amplifiers (EDFAs).
(N) :
a designation by the Institute of Electrical and Electronics Engineers for a portion of the electromagnetic spectrum in the microwave range of frequencies ranging from 4.0 to 8.0 gigahertz (GHz).Peebles, Peyton Z., Jr.,, Radar Principles, John Wiley and Sons, Inc., p. 20.
(N) :
The NATO C-band is the obsolete designation given to the radio frequencies from 500 to 1000 MHz (equivalent to wavelengths between 0.6 and 0.3 m) during the Cold War period.