Optical Fiber Reflection: Angle of Incidence Condition

Optical fibers guide light using the principle of Total Internal Reflection (TIR). This phenomenon occurs when light travels from a denser medium to a less dense medium.

For TIR to happen, the light ray must strike the boundary between the two media at an angle of incidence that meets a specific condition relative to the critical angle ($\theta_c$).

The condition for TIR is:

• Angle of Incidence ($\theta_i$) must be greater than the Critical Angle ($\theta_c$). Mathematically, $\theta_i > \theta_c$.

When $\theta_i > \theta_c$, the light does not refract into the less dense medium but is entirely reflected back into the denser medium (the fiber core). This process repeats along the fiber's length, effectively guiding the light.

If the angle of incidence were less than or equal to the critical angle, the light would refract out of the fiber or escape at the boundary, failing to propagate.