Q1. Write a brief bullet-point-style essay (maximum 2 A4 pages) ab...

Let us start with basic, in introducing the idea of modulation; we stressed its importance as a process that ensures the transmission of a message signal over a prescribed channel. There is another important benefit, namely, multiplexing, that results from the use of modulation. Multiplexing is the process of combining several message signals for their simultaneous transmission over the same channel. Three commonly used methods of multiplexing are as follows:
i) Frequency- division multiplexing (FDM)
ii) Time-division multiplexing (TDM)
iii) Code-division multiplexing (CDM)
iv) Wave-length division multiplexing (WDM)
In FDM the message signals overlap with each other at the channel input; hence the system may suffer from crosstalk
In TDM the message signals use the full passband of the channel, but on a time-shared basis.
In CDM the message signals are permitted to overlap in both time and frequency across the channel.
Hence all multiplexing from i) to iii) have a sort of problems arises while deploying them,
Its WDM having rare problems is the special multiplexing for optical fibers and widely adopted in telecom industries.
Wavelength-division multiplexing (WDM):
WDM is the act of combining light by using different wavelengths.
Wavelength-division multiplexing is a method of combining multiple message signals on laser beams at various infrared (IR) wavelengths for transmission along fiber optic media. Each laser is modulated by an independent set of signals. Wavelength-sensitive filters, the IR analog of visible-light color filters, are used at the receiving end for demodulation. WDM signals are assigned a wavelength. That way the signals can be retrieved upon reception.