Fujitsu Corporation

Shigeki Kawaai

Manabu Yamazaki

Hirotomo Izumi

Yoshiharu Yoshizawa

Daisuke Usui

A Mach-Zehnder optical modulator includes: a Mach-Zehnder interferometer that includes first and second arms formed on a silicon substrate, and a controller that controls bias current of the first and second arms. The controller controls the bias current of the first and second arms respectively to be a first offset value. The controller repeatedly executes a current adjustment process to increase the bias current of the first arm until a gradient of a phase shift amount of the first arm with respect to the bias current of the first arm reaches a target value. The controller controls the bias current of the second arm to be a second offset value that is smaller than the first offset value. The controller repeatedly performs the current adjustment process to increase the bias current of the first arm until a phase difference of the Mach-Zehnder interferometer reaches a target phase difference.

Mach-zehnder optical modulator

An optical transmitter includes an optical modulator that includes a first phase shifter for a most significant bit, a second phase shifter for a least significant bit, and a third phase shifter for fine adjustment, the first phase shifter, the second phase shifter, and the third phase shifter are disposed along an optical waveguide, and a drive circuit that includes a first driver that drives the first phase shifter, a second driver that drives the second phase shifter, and a third driver that drives the third phase shifter, wherein a drive polarity of the third driver is adjustable in a positive direction and a negative direction, and the third phase shifter adjusts an amount of phase change of the optical modulator in a positive direction or a negative direction based on a drive voltage inputted from the third driver.

Growing community of inventors

Kawasaki, Japan

Shigeki Kawaai