Engineering Physics

11.1 Introduction

Optical fibre is a long, thin transparent dielectric material made up of glass or plastic, which carries electromagnetic waves of optical frequencies [visible to infrared] from one end of the fibre to the other by means of multiple total internal reflections. Thus, optical fibres work as wave guides in optical communication systems. An optical fibre consists of an inner cylindrical material made up of glass or plastic called core. The core is surrounded by a cylindrical shell of glass or plastic called the cladding. The refractive index of core (n₁) is slightly larger than the refractive index of cladding (n₂), [i.e., n₁ > n₂]. Typical refractive index values are n₁ = 1.48 and n₂ = 1.46. The core diameter is ≈ 50 µm and the ...