A tracker, a surgical tool system, a surgical navigation system, and a method for operating a surgical navigation system are provided. The tracker is configured to be associated with a patient or a surgical tool that is to be tracked by the surgical navigation system. The tracker comprises an optical fibre having a longitudinal extension and configured to be optically coupled to a light source such that the optical fibre transmits light emitted by the light source. The optical fibre has a lateral surface along its longitudinal extension and is configured to emit light via at least a portion of the lateral surface.
