US Patent 9941973 Phase modulator with reduced residual amplitude modulation

A phase modulator with reduced Residual Amplitude Modulation includes a main path; a correction path; a first coupler configured to split, at a first ratio, an input to the main path and the correction path; and a second coupler configured to combine outputs from the main path and the correction path and to split the combined outputs, at a second ratio, with a first output comprising an output of the phase modulator with the reduced Residual Amplitude Modulation. The correction path can include a correction signal with a proper amplitude and phase that, when combined with an output signal from the main path by the second coupler, cancels the Residual Amplitude Modulation from the output signal.