Everything You Always Wanted to Know About Optical Networking [pdf]
Is slide 6 (Fiber Works by "Total Internal Reflection") wrong? I thought that total internal reflection (TIR) happened when trying to cross from a higher refractive index (RI) medium to a lower one - not the other way around as depicted by the core-cladding boundary. Furthermore if the cladding has a higher RI, then the rays should become steeper upon transiting, not flatter like shown in the diagram.<p>I always thought fibers were single material (i.e. just the core) because the surrounding air (lower RI) lets TIR happen. It certainly seems to be the case in the next slide (Demonstration Using a Laser Pointer), TIR on Wikipedia [1], and pictures of fiber optic lamps [2].<p>[1] <a href="https://en.wikipedia.org/wiki/Total_internal_reflection" rel="nofollow">https://en.wikipedia.org/wiki/Total_internal_reflection</a>
[2] <a href="https://duckduckgo.com/?q=fiber+optic+lamp&t=canonical&iax=1&ia=images" rel="nofollow">https://duckduckgo.com/?q=fiber+optic+lamp&t=canonical&iax=1...</a><p>Okay after reading a bit more [3] I'm pretty sure it's wrong, and the cladding RI's must be lower. So my follow up question is... what's the point of the cladding? Why not just rely on the surrounding air?<p>[3] <a href="https://en.wikipedia.org/wiki/Cladding_(fiber_optics)" rel="nofollow">https://en.wikipedia.org/wiki/Cladding_(fiber_optics)</a>