Extending propagation distances from short range to tens of kilometers requires compensation for atmospheric turbulence. Free-space laser communications, in which a laser beam is sent directly through the air instead of through a fiber, is already being used successfully over short distances when fiber links are either physically or economically impractical. Recently, the idea of extending the range to tens of kilometers has been explored. However, as the path length that a laser beam must propagate increases, performance becomes increasingly susceptible to several deleterious effects caused by atmospheric turbulence. These effects decrease the receiver signalto-noise ratio, ultimately resulting in a large bit-error rate (BER).
展开▼
