This document discusses different multiplexing techniques, including frequency division multiplexing (FDM), which divides a carrier's bandwidth into logical channels that do not overlap, with each user assigned an independent channel frequency. It also describes time division multiplexing (TDM), a digital technique where each transmitter is assigned a time slot, and wavelength division multiplexing (WDM), an analog optical networking method that combines multiple wavelengths of light into a single optical fiber.

2.  It is a technique which allows to send multiple signals
over a single data link.
 Multiplexer
 It is a device that combine multiple signals into one
signal.
 Demultiplexer
 It is a device that separate the multiplexed signal.

5.  When the carrier is frequency, FDM is used. FDM is an
analog technology. FDM divides the spectrum or
carrier bandwidth in logical channels and allocates one
user to each channel. Each user can use the channel
frequency independently and has exclusive access of it.
All channels are divided in such a way that they do not
overlap with each other. Channels are separated by
guard bands. Guard band is a frequency which is not
used by either channel.

7.  Time Division Multiplexing TDM is a digital
multiplexing. Every transmitter is assigned a
time slot to transmit its signals.
 TDM has further two types.
1. Synchronous TDM
2. Asynchronous TDM

9.  It is an analog technique. It combine multiple
wavelength of optical signal to transmit in a
single optical fiber.