I am new to waveguides and trying to solve a homework problem based on optical communication. I will be very grateful If someone can help me with this question.

A step index, multimode, silica fibre is found, from measurements, to have a maximum acceptance (cone half angle) of 6.5°. Calculate the numerical aperture (NA) of the fibre, the coupling efficiency for light from a typical laser diode and the corresponding refractive index difference between the core and cladding regions of the fibre. A cladding region refractive index of 1.45 should be assumed where necessary.


Make an approximate estimate of the difference in phase velocity between the slowest and fastest modes in the fibre and comment on the relevance of this difference to pulse spreading.


Describe briefly, with the aid of appropriate diagrams, how the dielectric polarisation of a general material varies with frequency. Identify the contributions from the various forms of resonant absorption shown by the medium.

 

hi z,
Welcome to AAC.
As this is Homework please post your attempt at solving the problem, we can then guide you.
E

 

OK, then I'll revise it, thank you!

 

Hello,

Perhaps the attached PDF from an old navy course might help.

Bertus

 

Hello,

Perhaps the attached PDF from an old navy course might help.

Bertus

Thanks a lot, Bertus! I'll take a check for it!