This book presents some of the recent developments in the field of optical-wireless coherence communication. The factors affecting the coherence detection sensitivity are analyzed and the approach to approximate the coherence detection limit is discussed. The wavefront distortion caused by atmospheric turbulence is analyzed, and the influence of the wavefront distortion on the coherence detection performance is examined. A new concept of vortex-beam coherence-detection is proposed, and the problem of signal light decomposition into partially coherent light detection is analyzed. This book can benefit researchers, engineers, and graduate students in the field of telecommunications. It is suitable for engineering and technical personnel engaged in applied optics and communications engineering, university teachers, graduate students, and senior undergraduates.