Higher order optical pam modulation using a mach-zehnder interferometer (mzi) type optical modulator having a bent optical path

A method, comprising:

• receiving an n-bit input digital signal;
• converting the n-bit input digital signal to a pulse amplitude modulated (PAM) analog signal having 2n levels, where n is greater than or equal to 2;
• generating from said PAM analog signal a plurality of drive signals;
• and
• applying each drive signal to PN junction phase shifter of an optical waveguide, each PN junction phase shifter extending along a portion of said optical waveguide.

An optical modulator, comprising:

• an optical waveguide having:
• an input waveguide;
• and
• an optical splitter to split the input waveguide into a first waveguide arm and a second waveguide arm, said first and second waveguide arms being parallel to each other;
• a first PN junction phase shifter positioned on the first waveguide arm;
• a second PN junction phase shifter positioned on the first waveguide arm;
• a third PN junction phase shifter positioned on the second waveguide arm parallel to the first PN junction phase shifter;
• a fourth PN junction phase shifter positioned on the second waveguide arm parallel to the third PN junction phase shifter;
• a digital to analog converter configured to receive an n-bit input digital signal and output a pulse amplitude modulated (PAM) analog signal having 2n levels, where n is greater than or equal to 2;
• a first driver having an input configured to receive the PAM analog signal and an output configured to generate first drive signals for application to control operation of the first and second PN junction phase shifters;
• and
• a second driver having an input configured to receive the first drive signals and an output configured to generate second drive signals for application to control operation of the third and fourth PN junction phase shifters.