Signal Transport Mechanism

1:26 AM | Posted by Fiber Optic 101


Physics of Total Internal Reflection 

Consider a ray of light passing between two media of different refractive indexes n1 and n2 as shown in figure 3. If n1> n2 the light ray as it passes from one media to the next will bend away from an imaginary line (the normal) perpendicular to the media’s mating surface. Conversely if n1 < n2 then the ray will bend towards the normal. Total internal reflection occurs when n1 > n2 and the incident ray of light makes an angle, Θc, such that it does not enter the adjacent medium but travels along the interface. At angles greater than Θc the ray will be reflected back into medium 

Total Internal Reflection

Ray Theory 

Light is confined within the core of the optical fiber through total internal reflection. To understand the phenomenon of total internal reflection and how it is responsible for the confinement of light in an optical fiber consider a ray of light incident on the fiber core as shown in figure 4. Light enters the core of the optical fiber and strikes the core/cladding interface at an angle Θ . If this angle is greater than the critical angle (i.e.Θ ≥ Θcw h e r eΘ c= a r c s i n ( n2/n1)) then the ray will reflect back into the core thus experiencing total internal reflection. This ray of light will continue to experience total internal reflection as it encounters core/cladding interfaces while propagating down the fiber

Light propagates through a fiber due to total internal reflection
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