An apparatus comprising a first electrical driver configured to generate a first binary voltage signal according to first data, a second electrical driver configured to generate a second binary voltage signal according to second data, wherein the first data and the second data are different, and a first optical waveguide arm coupled to the first electrical driver and the second electrical driver, wherein the first optical waveguide arm is configured to shift a first phase of a first optical signal propagating along the first optical waveguide arm according to a first voltage difference between the first binary voltage signal and the second binary voltage signal to produce a first multi-level phase-shifted optical signal.