OPTICAL MODULATOR, OPTICAL TRANSMITTER, OPTICAL TRANSMISSION/RECEPTION SYSTEM, AND CONTROL METHOD FOR OPTICAL MODULATOR

摘要

To correct and uniform phase shift at each phase modulation area in an optical modulator in operation. An optical modulation unit outputs a four-level modulated optical signal. A signal distribution circuit outputs signals based on an input digital signal. A drive circuit outputs drive signals from drivers and a calibration driver connected to phase modulation areas and calibration phase modulation areas. A control circuit calibrates amplitudes of the drive signals output from the drivers to coincide with phase shifts by the calibration phase modulation areas according to light intensity of the optical signal.

主权项

1. An optical modulator comprising:
an optical modulation unit that modulates an input light into an optical signal of n (n is an integer equal to or more than two) levels and outputs the optical signal, a plurality of phase modulation areas being formed on a waveguide in the optical modulation unit; a signal distribution circuit that outputs a signal based on an input digital signal; a drive circuit that includes a plurality of drivers connected to the plurality of phase modulation areas, respectively, and outputs drive signals according to the signal based on the input digital signal to the plurality of drivers connected to the plurality of phase modulation areas, respectively; and a control circuit that calibrates amplitude of the drive signal output from each driver connected to a phase modulation area that is a calibration objective and is other than a phase modulation area that is a calibration reference according to light intensity of the optical signal in order to coincide with a phase shift by the phase modulation area that is the calibration reference in the plurality of phase modulation areas.