When we were first approached by Dr. Lucky to write this book we were
very enthusiastic about the prospect, since we had contemplated a
similar project for quite some time. The difficulty lay in how best to
digest the vast amount of data on optical propagation, reduce it to a
book of manageable size, and simultaneously form the transition from the
physics of propagation to the engineering of optical channels. This is
the intent of Optical Channels. In accomplishing our goal it was
necessary to condense the material on optical propagation and, in so
doing, we have left a large amount to be handled via references. We have
tried to make these decisions in a consistent manner so that the book
will be uniform in its treatment of this topic. We identify four
channels for consideration: the free-space channel, which: is
characteristic of a tranquil atmosphere or a space-to-space link; the
turbulent channel, which is characteristic of the atmospheric channel;
the scatter channel in two forms, clouds and water; and the fiber optic
channel. For each of these channels we have tried to reduce the
applicable propagation theory to a level that can be used for
engineering design. This has been done by example, but here again
decisions had to be made on which examples to present. We have not tried
to present any material on optical components and consequently other
references on engineering would be necessary to supplement this book.