Submitted by:- Group-6 MUKESH YADAV (2010UEC210) OM PRAKASH MALI (2010UEC211) VIKRAM BHATI (2010UEC212)

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IntroductionUnder the simplest conditions, a medium can carry only one signal at any moment in time.

For multiple signals to share one medium, the medium must somehow be divided, giving each signal a portion of the total bandwidth.

Optical Multiplexing (MUX) & De-multiplexing (DEMUX) allows for sending multiple signals through a single medium as well as for Bidirectional use of that medium.

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Multiplexing

Multiplexing• a process where multiple analog message signals or

digital data streams are combined into one signal over a shared medium

Types Time division multiplexing Frequency division multiplexing code division multiplexing (CDM)

CDM is a mathematical approach used in cell phone mechanisms. Optically

Optical Time division multiplexing Based on Time-Division Multiplexing

Wavelength division multiplexing Based on Frequency-Division Multiplexing of radio waves

MultiplexingMultiplexor (MUX)Demultiplexor (DEMUX)

Sometimes just called a MUX (multiplexer).Two or more simultaneous transmissions on a

single circuit.Multiplexing costs less.

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How does it work…??

Frequency Division Multiplexing

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•Assignment of non-overlapping frequency ranges to each “user” or signal on a medium. Thus, all signals are transmitted at the same time, each using different frequencies.

•A multiplexor accepts inputs and assigns frequencies to each device.

•All signals are sent simultaneously, each assigned its own frequency.

•Using filters all signals can be retrieved.

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•The multiplexor is attached to a high-speed communications line.

•A corresponding multiplexor, or demultiplexor, is on the end of the high-speed line and separates the multiplexed signals.

Frequency Division Multiplexing

Applications of FDM

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In FDM signals to be transmitted must be analog signals. Thus digital signals need to be converted to analog form, if they are to use FDM.

FDM is used for FM & AM radio broadcasting. Each AM & FM radio stations uses a different carries frequency .

FDM is used in television & , cable television broadcasting.

First generation AMPS cellular telephone systems also uses FDM.

This technique is the oldest multiplexing technique.

Since it involves analog signaling, it is more susceptible to noise.

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Time Division Multiplexing

Total time available in the channel is divided between several user

TDM is a digital multiplexing technique (Digital signaling is used)

In TDM, the channels is not divided on the basis of frequency but on the basic of time.

TDM

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Each time is allotted a particular a time interval called time slot during which the data is transmitted by that user. Each sending device takes control of entire bandwidth .

Synchronous Time Division Multiplexing

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The original time division multiplexing.

The multiplexor accepts input from attached devices in a round-robin fashion and transmit the data in a never ending pattern.

T-1 and ISDN telephone lines are common examples of synchronous time division multiplexing.

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If one device generates data at a faster rate than other devices, then the multiplexor must either sample the incoming data stream from that device more often than it samples the other devices, or buffer the faster incoming stream. If a device has nothing to transmit, the multiplexor must still insert a piece of data from that device into the multiplexed stream.

Synchronous Time Division Multiplexing

Synchronous TDM

Accepts the incoming data streams and creates a frame containing only the data to be transmitted

Good for low bandwidth lines Transmits only data from active workstations Example: used for LANs

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Three types popular today:

•T-1 multiplexing (the classic)

•ISDN multiplexing

•SONET (Synchronous Optical NETwork)

Statistical /Asynchronous TDM

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A statistical multiplexor transmits only the data from active workstations (or why work when you don’t have to).

If a workstation is not active, no space is wasted on the multiplexed stream.

A statistical multiplexor accepts the incoming data streams and creates a frame containing only the data to be transmitted.

Multiplexer does not allots same time slot to each device at all time . Time slots are flexible and not fixed and predefined.

If there are n input lines then there are m slots perform. m is less than n.

Statistical /Asynchronous TDM Asynchronous TDM give guarantee that full capacity

of link is used . The no of time slot in a frame is always based on

statistical analysis of no of input devices.

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Statistical Time Division MultiplexingA statistical multiplexor does not require a line over as high a speed line as synchronous time division multiplexing since STDM does not assume all sources will transmit all of the time!

Good for low bandwidth lines (used for LANs)

Much more efficient use of bandwidth!

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Optical Time Division Multiplexing (OTDM)

OTDM is accomplished by creating phase delays each signal together but with differing phase delays.

Wavelength Division Multiplexing WDM is the analog multiplexing technique.WDM is

conceptually similar to FDM, in sense that it combines different signals of different signals of different frequencies into single composite signal and transmit it on a single link.

In WDM the different signals are optical or light signals that are transmitted through optical fiber. Wavelength goes up down and vice-verse.

In WDM various waves from different sources are combined to form composite light signal that is transmitted across the channels to the different receiver.

At the receiver side, this composite light signal is broken into different light waves by demultiplexer.

This combines and splitting of light waves is not by using a prism. 18

Wavelength Division Multiplexing One prism is used at the sender side to perform

multiplexing and another prism is used at receiver side that perform demultiplexing.

The basic principal behind the usage of prism is that ,the prism bends a beam of light based on the angle of incidence and the frequency of light wave.

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Wavelength multiplexer types include:

Fiber couplers

Grating multiplexers

Wavelength demultiplexer types include:

Single mode fused taper couplers

Grating demultiplexers

Tunable filters

Grating Multiplexer Demultiplex

er

Grating

Grin Rod Lens

Fibers

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2

1 2

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Wavelength-Division MultiplexingWDM sends information through a single optical Fiber using light of different wavelengths simultaneously.WDM is the combining of light by using different wavelengthsGive each message a different wavelength (frequency)Easy to do with fiber optics and optical sources

Multiple channels of information carried over the same fiber, each using an individual wavelength

A communicates with X and B with Y as if a dedicated fiber is used for each signal ( if A & B only then WDM)

Typically one channel utilizes 1320 nm and the other 1550 nm. (if signal is more then 2 then DWDM)

Broad channel spacing, several hundred nm .2

Recently WDM has become known as Coarse WDM or CWDM to distinguish it from DWDM

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A

2B

1

X

2

Y1 2

Fiber

Wavelength Division

Multiplexer

Wavelength Division

Demultiplexer

Multiple channels of information carried over the same fiber , each using an individual wavelength

Attractive multiplexing technique High aggregate bit rate without high speed electronics or modulation Low dispersion penalty for aggregate bit rate Very useful for upgrades to installed fibers Realizable using commercial components, unlike OTDM

Loss, crosstalk and non-linear effects are potential problems

Dense Wavelength Division Multiplexing

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Dense wavelength division multiplexing multiplexes multiple data streams onto a single fiber optic line.

Different wavelength lasers (called lambdas) transmit the multiple signals.

Each signal carried on the fiber can be transmitted at a different rate from the other signals.

Dense wavelength division multiplexing combines many (30, 40, 50, 60, more?) onto one fiber.

Multiple channels of information carried over the same fiber, each using an individual wavelength.

Transmitter T1 communicates with Receiver R1 as if connected by a dedicated fiber as does T2 and R2 and so on

Dense WDM is WDM utilizing closely spaced channels

Channel spacing reduced to 1.6 nm and less

Cost effective way of increasing capacity without replacing fiber

Commercial systems available with capacities of 32 channels and upwards; > 80 Gb/s per fiber

Wavelength Division

Multiplexer

Wavelength Division

Demultiplexer1

Fiber1T

1 2

N

T2

TN

R1

2

N

R2

RN

1 2 ... N

Transmitters

DWDM Multiplexer

Power Amp

Line Amp

Line Amp

Receive Preamp

200 km

DWDM DeMultiplexe

r

Each wavelength behaves as if it has it own "virtual fiber"

Optical amplifiers needed to overcome losses in mux/demux and long fiber spans

Receivers

Optical fiber

Greater fiber capacity

Easier network expansion

No new fiber needed

Just add a new wavelength

Incremental cost for a new channel is low

No need to replace many components such as optical amplifiers

DWDM systems capable of longer span lengths

TDM approach using STM-64 is more costly and more susceptible to chromatic and polarization mode dispersion

Can move to STM-64 when economics improve

Not cost-effective for low channel numbers

Fixed cost of mux/demux, transponder, other system components

Introduces another element, the frequency domain, to network design and management

SONET/SDH network management systems not well equipped to handle DWDM topologies

DWDM performance monitoring and protection methodologies developing

Applications of WDM

Several light carriers (different λs) in the same fiber

ScalabitityUsually in C band (1530-1565 nm) → EDFAsTransparent: no conversions, no formattingInexpensiveWDM uses optical devicesFiber capacity is dramatically increased WDM is used in SONET(Synchronous Optical

Network).It makes use of multiple optical fiber lines which are multiplexed & demultiplexed.

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Code Division Multiplexing (CDM)Old but now new method

Also known as code division multiple access (CDMA)

An advanced technique that allows multiple devices to transmit on the same frequencies at the same time using different codes

Used for mobile communications

Code Division Multiplexing

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oAn advanced technique that allows multiple devices to transmit on the same frequencies at the same time.

oEach mobile device is assigned a unique 64-bit code (chip spreading code)

oTo send a binary 1, mobile device transmits the unique code

oTo send a binary 0, mobile device transmits the inverse of code

Receiver gets summed signal, multiplies it by receiver code, adds up the resulting values

Interprets as a binary 1 if sum is near +64

Interprets as a binary 0 if sum is near –64

Advantages & Disadvantages of Multiplexing techniques

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WDM /OTDM (Optical Time DomainMultiplexing) OTDM: Technology limits speed → limits capacity WDM: More λs → more capacity

Longer distances between repeaters Easier add and drop Cheaper

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Thank you very much..!!