  Two-photon interference with independent classical sources, in which
superposition of two indistinguishable two-photon paths plays a key role, is of
limited visibility of interference fringes with a maximum value of 50%. By
using a random-phase grating to modulate the wavefront of a coherent light, we
introduce superposition of multiple indistinguishable two-photon paths, which
enhances the two-photon interference effect with a signature of visibility
exceeding 50%. The result shows the importance of phase control in the control
of high-order coherence of classical light.
