The hydrodynamic properties significantly influence the performance of bubbling fluidized bed reactors. For this reason, it is necessary to conduct hydrodynamic measurements for which several different measurement techniques are available. However, many of them are limited by their range of application concerning the temperature and the reactive conditions. In the course of this study, an optical measurement technique was applied to investigate a bubbling fluidized bed. The optical measurement technique is designed in a way to withstand temperatures of up to 400 degrees C under reactive conditions. However, all experiments were conducted at ambient temperature since one general objective of the present study was to demonstrate the applicability of the sensor for hydrodynamic measurements. A new algorithm was developed to extract the bubble events out of the signal that is generated by the optical sensor. In the scope of the measurement campaign, the fluidization number, the absolute pressure and both the vertical and radial measurement positions were varied. Some trends on the influence of these parameters on the bubble properties like the pierced chord length, the bubble rise velocity or the hold-up could be identified and explained. (C) 2018 Elsevier B.V. All rights reserved.