Excess loss caused by the outer layer in a multimode step-index optical fiber: theory.

An equation has been derived using an electromagnetic theory for evaluating excess loss caused by the outer layer (jacket) coated around the cladding in a multimode step-index fiber. Using the derived equation for the LP modes, numerical calculations have been made by varying parameters such as fiber and jacket parameters, wavelength, and mode power distribution. The calculations have revealed that the excess loss is especially influenced by the refractive index of the jacket, cladding thickness, and mode power distribution in the fiber.