A time domain analysis of electrical signals provided by an optical fiber probe was conducted in order to characterize the local flow dynamics of a short circulating fluidized bed riser with a height of 2.42m and ID of 82mm. Experiments were carried out with air, and the bed materials were FCC particles (Geldart A). Probability and standard deviation distribution of signals measured locally at five radial positions and four axial positions are presented. The probability distribution can indicate the uniformity of the flow in terms of solids holdup distribution and can reveal the formation of clusters. Probability distributions indicate that the flux is more uniform in the core region of the reactor and that clusters appear near the wall. The highest value obtained in the standard deviation of the radial distribution suggests greater interaction between particles at that radial position. It was found that for the two lower axial positions, this phenomenon occurs near the wall, and for the two higher positions, the interactions between particles occur both near the wall and in the center due to the exit configuration of the reactor.