1. The problem statement, all variables and given/known data I need to find the refractive indexes of the core and cladding of an optical fibre by using the specs found here http://www.photonics.byu.edu/FiberOpticConnectors.parts/images/smf28.pdf Then I'm suppose to calculate the Numerical aperture and compare it with the one listed. 2. Relevant equations None that I'm aware of 3. The attempt at a solution I have tried reading the specs but can't seem to find any that would help me solve the index of refraction. Does anyone have an idea?