The invention relates to an optical data carrier (2) for bi-directional communication with a read/write device that optically reads the optical data carrier. Said optical data carrier has data tracks (12) that carry data and can be optically read and/or optically modified by the read/write device. The aim of the invention is to create a simple, cost-effective option for bi-directional communication. To achieve this, the optical data carrier has optical receiving means (4) for receiving the data emitted from the read/write device, the optical data carrier has processing means (6) for processing the received data and the optical data carrier has optical emission means (8) for emitting data to the optical sensor.
