Adaptive divergence and power for improving connectivity in free-space optical mobile networks.
A significant challenge for free-space optical (FSO) links is the restrictive alignment requirements, especially when the transceivers are moving. For moderate distances and rapid unpredictable motion, the receiver's field of view and the positioning system's dynamics become factors. We explore the use of adaptive transmitter power and beam divergence to improve the likelihood of maintaining a mobile FSO link by using Gaussian beam propagation theory and link budgets. We calculate the allowable misalignment between the transceivers' optical axes as a function of power, divergence, and transceiver distance. The maximum allowable error is independent of the distance, except when the field of view is a limiting factor. Certain combinations of divergence and power, while suboptimal for one distance, provide a relaxed misalignment limit for many distances. Based on the calculations, we make initial suggestions for system design.
LoPresti
Peter
P
Department of Electrical Engineering, University of Tulsa, OK 74104, USA. peter-lopresti@utulsa.edu
Refai
Hazem
H
Sluss
James
J
Varela-Cuadrado
Iker
I