Determination of the stress in optical fibers by means of a polariscope

A polariscope has been built for studies of the stresses in optical fibers. The stress optic coefficient has been determined for five different fibers and for one of the preforms from which one of the fibers was drawn. It was found that the coefficient of the preform was larger than that of the fiber from which it was drawn. Calculations based on measurements on a Corning B fiber indicate that the residual stress in the cladding is compressive. The polariscope has also been used in conjunction with a fiber-drawing machine and a diameter-measuring instrument to determine the relationship between the tension of a Vycor-clad quartz fiber, as it is being drawn, and the diameter of the fiber.