Optical links for communications in local distribution

In the design of optical communication links for local distribution, two important aspects, which must be considered, are atmospheric transmission effects and detection techniques used in the receiver. Basic relationships for atmospheric absorption and scattering are reviewed, after which received signal variations observed on a Datran optical test link are briefly discussed. Direct and heterodyne detection techniques are reviewed and detailed expressions for shot-noise and thermal-noise limited cases are given. Shot-noise-limited detection is concluded to be more sensitive but is presently employed less in receivers.