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Abstract

This invention is a dynamic gain equalizer for fiber optic communication systems with a spectral output that can be changed dynamically as needed by adjusting one or more variable power lasers providing optical pumping. The proposed dynamic gain equalizer can adjust power inequalities in WDM signals resulting from the gain properties of EDFA's. The dynamic gain equalizer uses erbium ions in a system that has not been pumped by a laser, or pumped only to a small extent, with the result that passing radiation can be absorbed by the erbium ion. For a given erbium doped fiber, with a given fiber length, the spectral absorption of the fiber is dependent on the signal power entering the erbium doped fiber for each of the signal wavelengths. In order to vary the absorption spectrum of the filter, the erbium doped fiber is pumped by a laser at a low power, to levels where the excited state population inversion either has not occurred or is insufficient to achieve total gain. By choosing the adequate type of Erbium fiber and by altering the pump level of the dynamic filter it is possible to reach a very large dynamic range of gain for a given EDFA This filter can be used as a stand alone device or in conjunction with a dichroic filter, or any other filter, and can be an important contributor for dynamic gain equalization in erbium doped fiber amplifiers.

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