(i) The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation I = Ioe–αx, where I o is
the intensity at x = 0 and α is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance of (ln 4/α)
(ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation dB =10 log10 (I/I0). What is the attenuation in dB/km for an optical fibre in
which the intensity falls by 50 per cent over a distance of 50 km?
(i) The decrease in the intensity is reduced by 75%.
(ii) The attenuation of the given optical fibre = 0.0602 dB/km
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