The Noise Figure (NF) of a Fiber Optic Amplifier (FOA) quantifies the extent to which the amplifier reduces the signal-to-noise ratio (SNR) of the optical signal it amplifies. It quantifies the amount of additional noise introduced by the amplifier during the amplification process.

In the context of fiber optic communication, maintaining a low noise figure is crucial because it directly affects the quality of the transmitted signal. The noise figure is typically expressed in decibels (dB).

The noise figure can be defined as:

A lower noise figure indicates better performance, as it implies less signal degradation and less noise added during the amplification process.