Abstract: Phase shifts of light in orders of diffraction grating for the interference linear displacement sensor are considered. Using the phase diffraction grating with given geometric parameters of the surface relief allows one to stabilize phase relations in optical signals and in resulting signals outputted from the displacement sensor. Based on the mathematical simulation data, technically feasible parameters of the grating relief are proposed for creating the required phase shifts between diffracted beams leading to quadrature modulation. It helps reaching the required measurement accuracy with nanometric resolution.