A method of controlling deflection of an optical beam at a beam steering element. The method comprises receiving switching instructions indicative of a target one of a plurality of potential transmit or receive elements; determining a control signal associated with the target transmit or receive element; and applying the control signal to the beam steering element, thereby to cause deflection of the optical beam. Deflection of optical beams on the basis of the determined control signal allows greater pointing accuracy. Also, a port card, comprising a plurality of optical transmitter elements operative to produce respective optical beams from the input optical signals; and an array of beam steering elements operative to controllably orient the optical beams into respective transmit directions. The port card also comprises a controller for controlling the beam steering elements of the array using, for example, the above method.