We have developed a high‐speed and simultaneous photon beam diagnostic system using optical cables at SPring‐8. The system is composed of blade type X‐ray beam position monitors (XBPM) in front ends, optical cables spread over the experimental hall and multi A/D converters at the photon beam diagnostic station. Analog data of the beam positions are transferred through the optical cables. The multi A/D converter allows us to browse and process the data from the main control room in real time. The features of the system are the wide band‐width, the ability of full‐time observation with XBPMs and the compatibility to the monitoring system of electron beam position monitors in the storage ring. The system has been routinely used for high‐speed and simultaneous measurements of photon beam and electron beam.
