INTRODUCTION TO OPTICAL FIBER
An optical fiber is a dielectric wave guide that operates at optical frequencies. This fiber-wave-guide is normally cylindrical form.
Physically, an optical fiber is a very thin and flexible medium having a cylindrical shape, consisting of three section, core, cladding and protective jackets as follows:
(i) The Core
(ii) The Cladding
(iii) The Protective Jacket
Thus an optical fiber can be considered as a transparent coaxial cable having core of higher refractive index and cladding, the external cable of lower refractive index. In low and medium loss fiber, the core material is generally glass which is surrounded by plastic cladding.