We have proposed and demonstrated that the optical coherence function can be sythesized into desired shapes by manipulating the optical frequency and the phase of the lightwave. Based upon this unique technique, the synthesis of optical coherence function, various distributed photonic sensing and optical information processing applications have been developed. In this paper, the principle of the synthesis of optical coherence function is summarized. A series of functional optical sensing systems, including fiber-optic reflectometries, distributed stress location sensors, multiplexed FBG sensors, are introduced. Fully distributed fiber optic strain sensing systems per Brillouin frequency shift are highlighted, and synthesized dynamic grating based sensor is also presented. Applications in two- or three-dimensional distributed measurements, such as optical tomography of scattering medium, are also reviewed.