Optical communication question
时间：04-04
整理：3721RD
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Sorry but please help me with this sticky question, I feel really confused about this one and this question freaks me out.
A step index, multimode, silica fibre is found, from measurements, to have a maximum acceptance (cone half angle) of 6.5o. 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.
A step index, multimode, silica fibre is found, from measurements, to have a maximum acceptance (cone half angle) of 6.5o. 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.
i googled acceptance angle and got this
https://www.rp-photonics.com/accepta...er_optics.html
it looks like it can help with the other parts of your question
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