The present invention concerns an apparatus for transmission of optical signals between a rotating part and a stationary part of a machine, particularly a computer tomograph, in which an optical transmitter is arranged on a first of the two parts and an optical receiver with an optical detector is arranged on a second of the two parts, via which optical signals emitted by the optical transmitter are received, whereby the optical receiver comprises an optical concentrator with an at least approximately horn-shaped geometry that concentrates incident optical radiation via internal reflection on side surfaces of the concentrator onto a detection area of the detector. The optical concentrator is formed from a material filling the entire inner volume of the concentrator and optically transparent for at least one wavelength with which the transmitter transmits. A signal-to-noise ratio improved relative to that of known apparatuses for data transmission can be achieved with the present apparatus.