An optical fibre communication system works on a wavelength of $1.3 \mu m$. The number of subscribers it can feed if a channel requires $20 \ kHz$ is:

$A$ message signal of frequency $50 / \pi \text{ kHz}$ and peak voltage of $5 \text{ V}$ is used to modulate a carrier of frequency $1 \text{ MHz}$ and peak voltage $20 \text{ V}$. The modulation index is

An amplitude modulated wave is modulated to $50\%$. What is the saving in power if the carrier as well as one of the sidebands are suppressed?

The antenna current of an $AM$ transmitter is $8 \ A$ when only the carrier is sent,but it increases to $8.96 \ A$ when the carrier is modulated by a sine wave. The percentage of modulation is: (in $\%$)

$A$ modulating signal $2 \sin (6.28 \times 10^{6} t)$ is added to the carrier signal $4 \sin (12.56 \times 10^{9} t)$ for amplitude modulation. The combined signal is passed through a non-linear square law device. The output is then passed through a band pass filter. The bandwidth of the output signal of the band pass filter will be $MHz$.

Consider an optical communication system operating at $800 \, nm$. Suppose,only $1\%$ of the optical source frequency is the available channel bandwidth for optical communication. How many channels can be accommodated for transmitting audio signals requiring a bandwidth of $8 \, kHz$?