Q15.26Multiple choice
- (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 Io is the intensity at x = 0 and α is the attenuation constant. Show that the intensity reduces by 75 per cent after a distance ln 4 of α
- (ii)Attenuation of a signal can be expressed in decibel (dB) I according to the relation dB =10 log10 . What is the Io attenuation in dB/km for an optical fibre in which the intensity falls by 50 per cent over a distance of 50 km?