A multi-port planar evanescent coupler having N inputs and M outputs, where both N and M are each no less than three, formed of combinations of at least one of at least one planar evanescent 2.times.2 coupler and at least one planar evanescent 3.times.3 coupler subunits, with phase shifting segments in selected waveguides disposed between the planar evanescent coupler subunits. The multi-port planar evanescent coupler can be used in phase measurement and detection devices, such as interferometers, optical receivers, and laser gyroscopes.