US Patent 6,636,666
United States Patent and Trademark Office
University of Iowa Research Foundation (Iowa City, IA, US)
The methods and apparatus according to the invention equalize the power of at least one frequency in a multi-wavelength optical signal, or limit the power contained in a single or multi-frequency signal. More particularly, the optical power equalizer according to the invention is a filter with separably variable wavelength dependent transmission coefficients, wherein each coefficient decreases with increasing power for each respective wavelength coupled to the equalizer. Thus, the highest power wavelength output from an EDFA will be filtered more than the lower power wavelengths, making the output power from the EDFA more evenly distributed among the wavelengths. Such an equalizer can be placed downstream from each EDFA without destabilizing the optical network so that no changes need to be made to the EDFA or to the other components in the system.
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Chan, Winston K and Andersen, David R Optical power equalizer. US Patent 6,636,666 filed May 14, 2001 and issued October 21, 2003. https://ir.uiowa.edu/patents/342