ABSTRACT
This chapter describes the optical propagation and signal propagation inside an optical fiber. In terms of materials, optical fibers can be classified as silica fibers and plastic fibers, whereas in terms of structure, they can be categorized as multimode fibers and single-mode fibers. In single-mode fibers, the frequency dependence of group delay of fundamental mode causes pulse broadening. The classification of the modes of the distributed index fibers is the same as that described so far; however, as the refractive index is not uniform inside the core, the electromagnetic field distribution inside the core cannot be expressed by the Bessel function. When optical pulses are propagated in optical fibers, they will undergo changes that are roughly classified into two categories. One is attenuation, wherein the pulse amplitude is weakened by loss inside the optical fiber, and the other is pulse width broadening caused by dispersion inside the optical fiber.
