Patent ID: 9571203
Date: 2017-02-14
CPC Classifications: G02F,H04B,H04J

Claim:
1. An optical modulator comprising: a first substrate that includes: a Mach-Zehnder optical waveguide that is formed on the first substrate having an electro-optical effect; a signal electrode and a ground electrode that are disposed along a pair of branching waveguides positioned between an optical branching unit and an optical coupling unit of the Mach-Zehnder optical waveguide; plural optical modulating units that are disposed in parallel, and respectively modulate a light beam propagating in the Mach-Zehnder optical waveguide; and an output optical coupling unit that couples modulated light beams output from the optical modulating units; a second substrate that is disposed separately from the first substrate and has plural first signal line paths corresponding to the optical modulating units; a flexible circuit board having plural second signal line paths corresponding to the optical modulating units, wherein first input ends of input electrodes of the optical modulating units on the first substrate are each supplied the electrical signal and are disposed side by side on one side face of the first substrate, when base points are independently set such that each optical path length from the output optical coupling unit in the branching waveguide disposed along the signal electrode of the branching waveguides of the optical modulating units to the base points is equivalent, each electrical length from an input end of each signal electrode to each respective base point differs, second input ends of the first signal line paths on the second substrate are respectively supplied the electrical signals respectively corresponding to the optical modulating units and are disposed side by side on one side face of the second substrate, and second output ends electrically connected to the first input ends are disposed side by side on another side face of the second substrate, third input ends of the second signal line paths on the flexible circuit board are respectively supplied the electrical signals respectively corresponding to the optical modulating units and are disposed side by side on one side face of the flexible circuit board, and third output ends electrically connected to the third input ends are disposed side by side on another side face of the flexible circuit board, electrical lengths from the third input ends of the second signal line paths to the third output ends thereof respectively differ, and electrical lengths of signal paths respectively corresponding to the optical modulating units are equivalent, the electrical lengths are the signal paths that are from the third input ends to the base points on the signal electrodes.