Coherent or Incoherent Optical Fiber Communications

A tutorial discussion is given on the possibilities of using coherent communications or heterodyne reception and single mode fibers in optical fiber communications to enhance the performance available now with incoherent techniques and direct detection. The paper gives some background, compares sensitivity using either direct detection or heterodyning and points out some difficulties in the latter. Coherent techniques are referred to have value in high capacity trunk communications and in CATV networks.