A multimode, step-profile fibre has a core radius of 50 microns, a core index of 1.52 and a cladding index of 1.50.
(a) If the fibre end-face is excited by a source with a wavelength of 850nm, what is the maximum number of bound modes that can be excited?
(b) What is the minimum number of bound modes that will be excited regardless of the wavelength of the source?
(c) If the fibre in (a) is now illuminated simultaneously by 2 sources that emit light at wavelengths of 1,300 and 1,550nm, respectively, what is the total number of different modal states that can be excited?