The performance of an optical fiber depends to a great extent on the conditions of the process being used to draw the fiber from a glass preform. To get fibers with higher strength and lower transmission loss, the parameters of the draw process must be optimized and the geometric uniformity of the fiber must be maintained with high precision. To increase the geometric uniformity of the fiber the online fiber diameter measuring accuracy must be improved. The coating concentricity and uniformity also play an important role in fabricating quality fiber. As the fiber drawing speed goes higher and higher, which is the trend of modern fiber fabrication processes, the uniformity of fiber diameter and coating concentricity becomes even tougher to maintain. The main objective of this research has been to understand and develop an optical fiber drawing process that produces fiber with improved dimensional uniformity, higher strength and lower transmission loss. Particular emphasis has been given to the accurate measurement of on-line fiber diameter, which is the first and most important step in obtaining uniform fiber. / Master of Science