| CPC H04J 14/06 (2013.01) [G01J 4/04 (2013.01); H04B 10/2507 (2013.01); H04B 10/0795 (2013.01); H04B 10/614 (2013.01)] | 18 Claims | 

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               1. A polarization fluctuation estimation device comprising: 
            a polarization de-multiplexer configured to generate a single-polarization optical signal from an input polarization-multiplexed optical signal; 
                a photoelectric converter configured to convert the generated optical signal into an electric signal; and 
                at least one processor configured to execute an estimator configured to perform estimation of polarization fluctuation speed of the polarization-multiplexed optical signal, based on amplitude of the electric signal. 
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