METHOD FOR BIAS CONTROL OVER OPTICAL MODULATOR AND DEVICE THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a method for bias control over an optical modulator and a device therefor that can properly correct DC biases of a plurality of optical modulation parts during normal operations of an optical modulator with simple structure even if the optical modulator has the plurality of optical modulation parts.

SOLUTION: A bias controller B for optical modulator that controls DC biases of the plurality of optical modulation parts of the optical modulator 1 having the plurality of optical modulation parts has a DC bias applying means 3 of applying the DV biases to the plurality of optical modulation parts, a low-frequency signal superposing circuit 2 which superposes a low-frequency signal fB having a specified frequency on a modulation signal (b) applied to the plurality of optical modulation parts, an optical detecting means 9 of detecting variation in the light quantity of light waves passing through a multiplexing part, and a bias control means 4 of extracting light quantity variation corresponding to the low-frequency signal from the optical detecting means and controlling the DC bias applying means according to the extracted light quantity variation.

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