Modal domain analysis has gained special attention over the years due to its immense value both in fiber-optic sensor technology and communication systems. This presentation is aimed at reviewing the research done in that area so far and at describing a data acquisition system that can be used extensively for such analysis. This work primarily concentrates on the capabilities of the PN-2304 OPTOMATION II system in the study of mode coupling and transient distance analysis in graded-index optical fibers, as well as microbending loss measurements and phase modulation effects in a fiber guiding four modes. While the results of these measurements have been useful in themselves, the performance of the data acquisition system has been exploited to a great extent thus rendering a sophisticated tool for modal distribution studies. The system has been found useful in fiberdyne measurements and speckle pattern analysis thus leading to information on the propagating modes. Chapters I and 2 give a brief introduction to fiber optic systems and mode theory while Chapter 3 reviews the work already done in that area. Chapter 4 describes the PN-2304 OPTOMATION II and its capabilities in modal analysis and Chapter 5 reports the various measurements made using the system and their results. / M.S.