Fiber optic amplifier is used to compensate for the wakening of information during the transmission because of fiber optic attenuation. Fiber optic repeater also can make this function but it is not good enough, it can only function on a specific wavelength and not suitable for WDM systems. That is why fiber optical amplifier play a much more important role.



Common parameter of the fiber optic amplifier include gain, bandwidth and noise performance. Gain depends on the wavelength and the power of the input fiber signal. Noise is measured by the noise figure, which shows the ratio of the input signal SNR to output signal SNR.

Erbium doped fiber amplifier is the major type of the fiber amplifier used to boost the signal in the WDM fiber optic system, as we know it is WDM that increase the capacity of the fiber communications system and it is the erbium-doped fiber amplifier that make WDM transmission possible.