Optical modulator and optical transmission module

An optical modulator comprising a plurality of Mach-Zehnder optical modulation units,

• wherein each of the plurality of Mach-Zehnder optical modulation units includes a pair of arm waveguides extending in a first direction, a pair of first signal wirings, a pair of first signal electrode pads, a pair of second signal electrode pads, a pair of first ground wirings, a pair of first ground electrode pads, and a pair of second ground electrode pads,
• the plurality of Mach-Zehnder optical modulation units are arrayed in a second direction perpendicular to the first direction,
• each of the pair of first signal wirings includes a pair of first signal wiring portions, a pair of second signal wiring portions connected to one ends of the pair of first signal wiring portions, and a pair of third signal wiring portions connected to the other ends of the pair of first signal wiring portions,
• the pair of first signal wiring portions is provided on the pair of arm waveguides, and extends in the first direction,
• the pair of second signal wiring portions extends from the one ends of the pair of first signal wiring portions so as to separate gradually in the second direction from a center line in the second direction of each of the plurality of Mach-Zehnder optical modulation units with a distance from the pair of first signal wiring portions in the first direction increases,
• the pair of third signal wiring portions extends from the other ends of the pair of first signal wiring portions so as to separate gradually in the second direction from the center line of each of the plurality of Mach-Zehnder optical modulation units with a distance from the pair of first signal wiring portions in the first direction increases,
• the pair of first signal electrode pads is connected to the pair of second signal wiring portions,
• the pair of second signal electrode pads is connected to the pair of third signal wiring portions,
• the pair of first ground wirings extends in the first direction, provided on both sides of the pair of first signal wirings in the second direction, and opposed to the pair of first signal wirings,
• the pair of first ground electrode pads is located close to the pair of first signal electrode pads, and connected to the pair of first ground wirings,
• the pair of second ground electrode pads is located close to the pair of second signal electrode pads, and connected to the pair of first ground wirings,
• the first signal electrode pads of the plurality of Mach-Zehnder optical modulation units are disposed on a first straight line extending in the second direction,
• the pair of first ground electrode pads is displaced in the first direction from the pair of first signal electrode pads, and separates from the pair of first signal electrode pads in the first direction,
• the pair of first ground electrode pads is displaced in the second direction by less than a first interval from the pair of first signal electrode pads so as to separate from the center line of each of the plurality of Mach-Zehnder optical modulation units, and
• the first interval is an interval in the second direction between centers of the pair of first signal electrode pads.