What is the structure of the EDFA?

Basic structure of erbium-doped fiber amplifier:

There is an isolator at the input and output for the one-way transmission of the optical signal. The pump oscillator wavelength is 980 nm or 1480 nm and is used to provide energy. The function of the coupler is to couple the input optical signal and the pump light into the erbium-doped fiber, and transfer the energy of the pump light to the input optical signal through the erbium-doped fiber to realize the energy amplification of the input optical signal.

In order to obtain a larger output optical power and a lower noise figure and other parameters, the actually used erbium-doped fiber amplifier uses two or more pump source structures with an isolator to isolate each other. In order to obtain a wider and flatter gain curve, a gain flattening filter is also added.

The EDFA is mainly composed of five parts: an erbium-doped fiber (EDF), an optical coupler (WDM), an optical isolator (ISO), an optical filter, and a pumping supply.

Commonly used pump sources include 980 nm and 1480 nm. These two pump sources have higher pumping efficiency and are therefore more used.The 980 nm pump source has a lower noise figure; the 1480 nm pump source is more efficient and can achieve higher output power (about 3 dB higher than the 980 nm pump source). 

The 980 nm pump source has a lower noise figure; the 1480 nm pump source is more efficient and can achieve higher output power (about 3 dB higher than the 980 nm pump source). www.civillaser.com