Optomechanical design considerations are presented in the development of a fiber-delivered three degree-offreedom displacement measuring interferometer. The tool can be used to simultaneously calibrate the linear motion and rotational errors of a translating stage using a single measurement beam incident on a plane mirror target. This novel interferometer incorporates a quadrant photodiode to measure four spatially separated interference signals all within a single optical interference beam, otherwise known as differential wavefront sensing. In post processing, a weighted phase average is created over symmetrically adjacent pairings of detector elements to decouple and measure displacement and changes in pitch and yaw. Design considerations include a custom displacement interferometer architecture, mechanical analyses and qualification testing of a working prototype. This interferometer has the potential for providing multi-DOF calibrations for precision motion stages.