One method for playing a disk, comprises illuminating a first portion of the optical article with a first laser to obtain a first optical signal, wherein the first laser has a first wavelength, illuminating a second portion with a second laser to obtain a second optical signal, wherein the second laser has a second wavelength that is different from the first wavelength, and determining if the optical article is authentic by comparing the first optical signal and the second optical signal.

 
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> Temperature control for coarse wavelength division multiplexing systems

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