Abstract: A fiber processing system includes a fiber spreader that has a spreader bar that extends in a lengthwise direction between first and second ends. The spreader bar carries at least one radiused surface between the first and second ends. At least one mechanical vibration device is operable to vibrate the spreader bar. The at least one mechanical vibration device is connected to input mechanical vibration into the spreader bar at a location between the first and second ends. A method for spreading at least one fiber bundle includes moving at least one tensioned fiber bundle over a radiused surface of the spreader bar. During the moving, mechanical vibration is input into the spreader bar at a location between the first and second ends, to transversely spread and flatten the at least one tensioned fiber bundle.