Signal quality in amplified systems
Transmission systems on optical fibers

As already mentioned, optical amplification and wavelength-division multiplexing are closely linked.

Simultaneous transmission of several optical carriers (or channels) enables the cost of amplification to be shared between them, and the amplifier's gain band to be used efficiently. The latter is steadily increasing: amplifiers with a bandwidth of 80 nm exist today, and 100 nm will soon be exceeded. Another obvious advantage of wavelength-division multiplexing is that it enables the transmission capacity of a given fiber to be increased considerably, and thus the capacity of an existing network to be increased without the need for new infrastructure. Figure