A data trunk between two buildings of a desert observatory uses a step-index fibre…

PHYSICS · Multi-part · Fermi University Physics · Optics & Photonics · Beams, resonators and guided-wave photonics · Beams, resonators and guided-wave photonics

Optics and Photonics, Ch Optical fibres in communication and endoscopy

Problem

A data trunk between two buildings of a desert observatory uses a step-index fibre with core index

n_1 = 1.47

and cladding index

n_2 = 1.45

, terminating in air, with attenuation

0.2

dB km

^{-1}

. ((a)) Find its numerical aperture and acceptance angle

\theta_a

in air. ((b)) Find the modal pulse spread per kilometre. ((c)) Over the

50

km run, what fraction of the launched power arrives?

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