Initial alignment scheme and tracking control technique of free space optics laser beam

This paper describes the laser beam alignment techniques for free space optical communication. Bilateral laser transmission system is designed between two active free-space-optical apparatuses, which are equipped with galvanic scanners, E/O and O/E converters and are able to control laser beam discharging directions. Two alignment strategies are proposed with regard to the transient and steady state of optical signal transmission. Search method for initial alignment is established based on the Gaussian beam optics, and a tracking control system is constructed for laser beam to maintain stable telecommunication between roaming transmission equipments. Experiments reveal that the proposed techniques enable the free space optics system to locate the target receiver and to pursue the unstable transmission apparatus.