Despite the Hydrodynamics of Trickle Beds Experiencing Pilot Size, on the Contrary, the Possibility of Measuring Hydrodynamic Parameters Locally and for Large Scale and Finding an Indicator to Pinpoint the Flow Regime from Trickling to Pulsing Remains Obscure, to Assess the Feasibility of Getting Such Information the Reactor Bed Was Randomly Packed with Equal-Sized Spherical Beads of 3 Mm Diameter. Gas and Liquid Holdup Measurements and Flow Regime Identification Were Achieved at Various Flow Conditions from Trickling to the Pulsing Regime by an Optical Probe Method using Time Series Processing Method. This Method is Shown to Be Simple and Efficient Provides Quantitative Information About the Gas and Liquid Holdup Variation in Different Flow Regime. the Various Experimental Results Were Compared to Available Literature Models and Correlations for Confrontation and Recommendations. the Trickle-To-Pulse Flow Transition Boundary Shifted towards Higher Gas and Liquid Superficial Velocities, Aligning with the Findings on a Variation of Holdup Along the Axial Direction Confirmed to Broaden the Trickle Flow Domain. [Correction Added after Online Publication June 26, 2015: to Unify the Adjective Everywhere in This Manuscript, Optic Fiber Probe Was Changed to Optical Probe.]