Transmission of light in FOC

Only if a FOC is installed absolutely straight do some light beams pass through the core without hitting the "side walls".

 

 

However, most light beams do not pass parallel to the core and would leave the core. Because of the reflective layer they are reflected on the side walls and continue to pass in the core. In this manner the light beams pass virtually without loss in a type of "zigzag course" through the FOC.