question_answer 34)

    The intensity of a light pulse travelling along a communication channel decreases exponentially with distance x according to the relation where  is the intensity at x = 0 and  is the attenuation constant. Show that the intensity reduces by 75 percent after a distance of (ii) Attenuation of a signal can be expressed in decibel (dB) according to the relation  What is the attenuation in dB/km for an optical fibre in which the intensity falls by 50 percent over a distance of 50 km?

Answer:

                    (i) Given,    or                        or     When %decrease in intensity (ii) Let be the attenuation in dB/Km. If x is the distance travelled by signal, then                   Given      Or  or