An optical crossbar switch for optically coupling optic fibers comprising: at least one first fiber (21) and a plurality of second fibers (22); a moveable fiber-end carriage (41) coupled to an end of the at least one first fiber and constrained to move along a predetermined trajectory; at least one moveable slack-control carriage (42) coupled to the body of the at least one first fiber and constrained to move along a predetermined trajectory; and at least one moving device (70, 80) controllable to move the carriages; wherein to optically couple a first fiber of the at least one first fiber to a second fiber of the plurality of second fibers, the at least one moving device moves the fiber-end carriage of the first fiber along its trajectory to a position at which the end of the first fiber is optically coupled to an end of the second fiber and moves the at least one slack-control carriage to take up slack in the first fiber generated by movement of its fiber-end carriage.