| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical modulator that generates a multi-level phase modulation signal of high signal quality, in particular, that can suppress deterioration in modulation characteristics due to an intensity difference of a signal component caused by variations in manufacturing and improve the characteristics without complicated manufacturing processes.SOLUTION: An optical modulator 1 comprises: a substrate 4 having an electrooptical effect; an optical waveguide 5 formed on the substrate; and control electrodes 61, 62, and 65 for controlling a light wave propagating through the optical waveguide. The optical waveguide includes a main Mach-Zehnder (MZ) waveguide 50 having two branched waveguides, and sub MZ waveguides 51 and 52 respectively provided on the branched waveguides. Each of the branched waveguides has light intensity adjustment means (composed of the optical waveguides 53 and 54, and control electrodes 63 and 64) provided in series on the sub MZ waveguides, and a voltage control circuit which controls a voltage applied to the light intensity adjustment means, in order to adjust the light intensities of the light waves propagating through each of the branched waveguides or a difference between the light intensities. |
