For strong pumpimg ( ) and small signal power ( ), the inversion factor almos becomes 1 in case of 980 nm pumping whereas for 1480 nm pumping the best one gets is about 1.6.
5.
Gain :
The ratio of the output signal power to input signal power is the gain of an amplifier. It is conventional to specify gain in the logarithmic dB unit
Gain of EDFA depends on the pump power as well as on the pump wavelength.
The figure alongside shows typical gain characteristics as a function of wavelength for two different levels of pump power. It may be seen that for small pumping power, the gain spectrum has a maximum at about nm. However, as pump power increases, the gain becomes roughly independent of pump wavelength. The gain can be increased by reducing the temperature. at liquid nitrogen temperatures, the gain for a pumpingb power of 100 mW is approximately 30 dB.
) and small signal power ( 
), the inversion factor almos becomes 1 in case of 980 nm pumping whereas for 1480 nm pumping the best one gets is about 1.6.
nm. However, as pump power increases, the gain becomes roughly independent of pump wavelength. The gain can be increased by reducing the temperature. at liquid nitrogen temperatures, the gain for a pumpingb power of 100 mW is approximately 30 dB. 
