Trickle bed reactors (TBRs) are widely employed in various industries, such as chemical and petrochemical, due to their simplicity in operation under high-temperature and high-pressure conditions, resulting in low energy consumption. However, they face challenges like rapid deactivation and liquid maldistribution, leading to potential issues like hot spots and reactor runaways. Understanding local liquid saturation in multiphase flow reactors is crucial for pressure drop, residence time, and heat transfer coefficient parameters. Advanced techniques, like the two-tip optical fiber probe (OFP) developed at Missouri University of Science and Technology, offer reliable measurement of gas and liquid volume fractions locally, aiding in reactor design and scale-up. OFP, based on light reflection variations, has successfully studied hydrodynamics and dynamic flow parameters in various multiphase flow reactor systems. Validation against x-ray digital radiography and syringe pump techniques confirms its reliability. Moreover, some other parameters, such as local gas and liquid velocities and evaluating channeling or bypassing locally along bed height, can also be measured by processing different concepts. Successfully, OFP was used to study the effects of bed height, gas flow rate, liquid flow rate, and catalyst shape (using different industrial catalyst shapes such as trilobe, quadralobe, cylindrical, and spherical particles) on the liquid saturation and local gas and liquid velocities diametrical profiles studied to evaluate performance in the pilot plant trickle bed reactor.