The optical fiber probe technique has been widely used in the analysis of gas-solid fluidized bed phenomena owing to the small size, quick response and flexibility of the probe as well as wide ranges of applicability of the technique as a whole. With potentially equal applicability to gas-liquid and gas-liquid-solid flow systems, this technique has recently witnessed its important role in the multiphase flow research. No systematic, fundamental explanations/guidelines for the usage of the fiber optics, however, are available to our knowledge in the pertaining research field. In this article, we introduce the basic probestructures, characteristics of the obtained signals, the data processing techniques and the range of applicability to further encourage the use of optical fiber techniques “tailored” to the multiphase flow analysis.