The system is highly immune to background light so that alignment can be maintained even with the sun behind one of the transceivers. The invention described here provides a novel transceiver and system for performing robust, but inexpensive, tracking to maintain superior alignment between the transceivers. A controller then adjusts the active pointing mechanism accordingly to move the entire transceiver apparatus and direct the transmitted light to the receiver. The sensors detect the apparent change in position of the other transceiver (caused by numerous factors such as the wind, temperature loading, building motion, and atmosphere induced tilt). An active auto-alignment / auto- tracking system with sensors and active pointing mechanisms can be used to keep the transceivers aligned. It is, therefore, desirable in some cases to keep the communication beam narrow, in which case adequate alignment must be maintained between the transceivers at all times to ensure a reasonably high signal-to-noise ratio at the detector. Often the optical communication beams are made wider than the angular uncertainties/deviations or jitter of the beams so that the receiver always sees the transmitted beam, which of course reduces the power delivered to the receiver. 5J77J68, issued to Korevaar, is herein incorporated by reference. An example of a system for wireless optical communication application is provided in U.S. Modulated light transmitted from one transceiver propagates through the atmosphere to the other transceiver where a portion of the light is collected and detected. In a conventional terrestrial free-space/wireless optical communication application, two transceivers having a line of sight (LOS) unobstructed path between them are placed on roof-tops or in offices behind windows. H04B10/1127- Bidirectional transmission using two distinct parallel optical paths.H04B10/1123- Bidirectional transmission.H04B10/112- Line-of-sight transmission over an extended range.H04B10/11- Arrangements specific to free-space transmission, i.e. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g.
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