Multiplexing is a method of combining multiple analog or digital signals into one signal over a shared medium. The main types of multiplexing are space-division, frequency-division, time-division, polarization-division, and orbital angular momentum multiplexing. Each type has advantages such as efficient use of bandwidth but also disadvantages such as added complexity, cost, or signal degradation.

1. Multiplexing
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2. Multiplexing
 In telecommunications and computer networks,
multiplexing (sometimes contracted to mixing) is a method by
which multiple analog or digital signals are combined into one
signal over a shared medium.
 A device that performs the multiplexing is called
a multiplexer (MUX), and a device that performs the reverse
process is called a demultiplexer (DEMUX or DMX).

3. Types OF Multiplexing
 Space-division multiplexing
 Frequency-division multiplexing
 Time-division multiplexing
 Polarization-division multiplexing
 Orbital angular momentum multiplexing

4. Space-division multiplexing
 There are several possible methods for increasing transmission capacity over
fixed bandwidth. There are two basic strategies for achieving spatial separation
within a fiber
 These include modulation employing different amplitude levels, two orthogonal
subcarriers and polarization.
 In fact, the only remaining unused dimension is Space.
 Multi-core and multi-mode operation.

5. SDM
Space-division multiplexing

6. SDM
Advantage of SDM
 Two different signals then can use
the same frequency.
 One transmitting a vertically
polarized signal and the other
transmitting a horizontally polarized
signal.
 It is usually combined with other
multiplexing techniques to better
utilize the individual physical
channels.
Disadvantage of SDM
 Some of the disadvantages of SDMA
is the fact that the number of
switches.
 There are also high insertion losses
since each input must have the
capability to be split to any output.
 Reverse link may be a problem:
interference problems

7. Frequency-division multiplexing
 In FDM, signals generated by each sending device modulate different carrier
frequencies. These modulated signals are then combined into a single Composite
signal that can be transported by the link.
 Carrier frequencies are separated by sufficient bandwidth to accommodate the
modulated signal.
 These bandwidth ranges are the channels through which the various signals
travel.

8. FDM
Frequency-division multiplexing

9. FDM
Advantage of FDM
 This method is highly accurate, since
it uses fine mesh.
 It is the only widely used method in
time domain for solving general
problems.
 Simple to implement than MOM or
FEM.
Disadvantage of FDM
 Meshing is inflexible
 Uncertainty about precision of
boundaries
 Frequency domain finite difference
formulation are available but never
become popular for general
problems.

10. Time-division multiplexing
 Time-division multiplexing (TDM) is a method of transmitting and receiving
independent signals over a common signal path by means of synchronized
switches at each end of the transmission line so that each signal appears on the
line only a fraction of time in an alternating pattern.
 It is used when the bit rate of the transmission medium exceeds that of the signal
to be transmitted.
 This form of signal multiplexing was developed
in telecommunications for telegraphy systems in the late 19th century, but found
its most common application in digital telephony in the second half of the 20th
century.

11. TDM

12. TDM
Advantage of TDM
 we can transmit more number of
signals through a single channel.
 It is immune to amplitude non-
linearities
 Most suitable technique for digital
Disadvantage of TDM
 It is not much suitable for continues
 Extra guard time are necessary
 Synchronization is necessary.

13. Polarization-division multiplexing
 Polarization-division multiplexing uses the polarization of electromagnetic
radiation to separate orthogonal channels. It is in practical use in both radio and
optical communications, particularly in 100 Gbit/s per channel fiber optic
transmission systems.
 It is used in microwave links such as satellite television downlinks to double the
bandwidth by using two orthogonally polarized feed antennas in satellite dishes.

14. PDM

15. PDM
Advantage of PDM
 optical networks are commonly
found in such applications as cable
television, video-on-demand,
interactive services data
transmission, multimedia signals,
fields employing optical instruments,
as well as many other technologies.
 Data transmission via optical
networks is advantageous because it
has low delay and offers large
bandwidth.
Disadvantage of FDM
 A disadvantage of optical networks
is the relatively high cost associated
with the installation of these
networks.
 Since the high cost of optical data
transmission must be passed on to
subscribers or users of services, cost
is a drawback to service providers
that consider implementing optical
networks.

16. Orbital angular momentum multiplexing
 Orbital angular momentum multiplexing is a relatively new and experimental
technique for multiplexing multiple channels of signals carried using
electromagnetic radiation over a single path.
 It can potentially be used in addition to other physical multiplexing methods to
greatly expand the transmission capacity of such systems.
 This is a controversial subject in the academic community, with many claiming it
is not a new method of multiplexing, but rather a special case of space-division
multiplexing.

17. OAM
Advantage of OAM
 High data capacity: Higher when
combined with other multiplexing
methods
 Enhanced security
Disadvantage of OAM
 Capacity limited by atmospheric
turbulence
 Unable to use in long haul fiber
communication systems