An optical phase modulator includes an input source that is configured to receive a light source. There is an output operative to provide a phase modulated output signal based on the received light source. There is a first optical coupler configured to split the light source into a first optical path of a Mach Zehnder Interferometer (MZI) and a second optical path of the MZI. A static phase shifter is configured to provide a static phase shift to the first optical path. There is a phase modulator in the second optical path. There is a second optical coupler configured to combine the first optical path and the second optical path. The first and second optical couplers are tuned such that the phase modulated optical signal at the output provides a substantially constant amplitude that is independent of a change in loss introduced by the phase modulator.