EDFA

Module 15 : ERBIUM DOPED FIBER AMPLIFIERS (EDFA)

Lecture : ERBIUM DOPED FIBER AMPLIFIERS (EDFA)

For a given pump power, the gain depends both on signal wavelength and the length of the EDFA section in the fibr. Typical gain spectrum against signal wavelength is shown in the figure below.

For a Ge/Er doped fiber, the gain spectrum has two peaks in the C-band, one at 1536 nm and the other at 1552 nm. ASE noise superposes the entire bandwidth. If the fiber host material is changed from silica to ZrF $_4$ , flattening of the gain spectrum takes place. Gain flattening is required if EDFAs are to be cascaded. Relative flat gain greater than 20 dB is useful for WDM applications.

$\includegraphics{edfa7}$

For a given pump power, the gain becomes maximum for an optimal value of the length $L$ and it decreases again with further increase in length. Thus to maximize gain, one needs to optimize both pumping power and the length of the fiber.