Patent ID: 7197213

Claim:
A method of controlling deflection of an optical beam at a beam steering element, comprising: I) deflecting the optical beam, said deflecting comprising the steps of: i. receiving switching instructions indicative of a target one of a plurality of potential transmit or receive elements; ii. determining a first control signal associated with the target transmit or receive element, wherein said target transmit or receive element is associated with a target orientation relative to the beam steering element, and wherein determining the first control signal comprises: determining the target orientation associated with the target transmit or receive element; wherein determining the target direction of arrival or departure relative to the beam steering element comprises consulting a lookup table comprising entries respectively associated with the potential transmit or receive elements; determining the first control signal on the basis of the target orientation associated with the target transmit or receive element; iii. applying the first control signal to the beam steering element, thereby to cause deflection of the optical beam; II) fine tuning an alignment of the deflected optical beam, wherein the target orientation associated with the target transmit or receive element is a target direction of arrival or departure relative to the beam steering element, and wherein said fine tuning comprises the steps of: i. applying a second control signal to the beam steering element to cause the deflected optical beam to undergo a degree of misalignment with respect to an optical receiver associated with the target transmit or receive element; ii. determining a pointing error associated with the deflected optical beam, the pointing error being indicative of the degree of misalignment between the deflected optical beam and the optical receiver associated with the target transmit or receive element; iii. causing a modification in the deflection of the optical beam by modifying the second control signal in accordance with the pointing error by: modifying the target direction of arrival or departure relative to the beam steering element; determining the second control signal on the basis of the modified target direction of arrival or departure; iv. monitoring a net modification to the target direction of arrival or departure relative to the beam steering element resulting from repeatedly modifying the target direction of arrival or departure relative to the beam steering element; v. updating the entry in the lookup table associated with the target transmit or receive element to reflect the net modification to the target direction of arrival or departure relative to the beam steering element.