Method for setting drive voltage of optical modulator and optical modulator set drive voltage

摘要

PROBLEM TO BE SOLVED: To provide a method for deriving the drive voltage of a semiconductor optical phase modulator that reduces the loss fluctuation of optical power even when the amplitude of a modulation amplitude voltage fluctuates and minimizes the loss of optical power.SOLUTION: The present invention is a method for deriving a drive voltage in an optical modulator provided with two arm waveguides having a semiconductor on a substrate in core and a phase modulation electrode formed on the top surface of each of the two arm waveguides and to each of which is applied a modulation voltage in which a bias voltage of the same value and a modulation amplitude voltage having AC components that are 180 degrees out of phase are synthesized, the method comprising the steps of: setting the amplitude of a modulation amplitude voltage to a reference value; finding a loss difference of optical power between the reference value plus or minus a desired value and a value that is added or reduced; calculating a loss difference in terms of absolute value while varying a bias voltage and deriving the value of the bias voltage in which the loss difference is minimal; and setting the bias voltage of a modulation voltage applied to the phase modulation electrode to the value of the derived bias voltage.SELECTED DRAWING: Figure 4