Optical Multiplexing and Optical Multiplexing and DemultiplexingDemultiplexing

Brian SchulteBrian SchulteAhmed AlsinanAhmed Alsinan

AbstractAbstract

Optical multiplexing (and demultiplexing) Optical multiplexing (and demultiplexing) allows for sending multiple signals through allows for sending multiple signals through a single medium as well as for a single medium as well as for bidirectional use of that medium.bidirectional use of that medium.

Optical Time Domain Multiplexing (OTDM)Optical Time Domain Multiplexing (OTDM) Wavelength-Division Multiplexing (WDM)Wavelength-Division Multiplexing (WDM)

HistoryHistory Multiplexing and DemultiplexingMultiplexing and Demultiplexing

When did it start? When did it start?

HistoryHistory

• TelegraphyTelegraphy• 1800s1800s

HistoryHistory

• 18941894• Baudot’s multiplex Baudot’s multiplex

telegraphtelegraph

HistoryHistory Western Union problemWestern Union problem

Thomas Edison:Thomas Edison: Wavelength strengthWavelength strength PolarityPolarity

Western Union Western Union electrical-mechanical multiplexing device electrical-mechanical multiplexing device

8 messages in 19138 messages in 1913 72 messages in 193672 messages in 1936

HistoryHistory Data Transmission Speeds Data Transmission Speeds

Characters Per Minute (CPM) Characters Per Minute (CPM)

Words Per Minute (WPM) Words Per Minute (WPM) 5 characters and space5 characters and space

Bits Per Second (bps) Bits Per Second (bps) 1950s 1950s 1200 bps 1200 bps Currently Currently 10 Gbps10 Gbps

HistoryHistory

Multiplexing Devices Development:Multiplexing Devices Development: Telegraph lines utilized DCTelegraph lines utilized DC Vacuum Tubes allowed AC in 1930s Vacuum Tubes allowed AC in 1930s Transistors replaced Vacuum Tubes in1960sTransistors replaced Vacuum Tubes in1960s Integrated CircuitsIntegrated Circuits

ApplicationsApplications

Optical Multiplexing Fiber Optic CableOptical Multiplexing Fiber Optic Cable

long distance communication at high bandwidthslong distance communication at high bandwidths

Useful for Fiber Optic Sensors Useful for Fiber Optic Sensors Sensors Sensors multiplexed into a single fibermultiplexed into a single fiber

Optical MultiplexingOptical Multiplexing

Optical Time-Division MultiplexingOptical Time-Division Multiplexing Based on Time-Division MultiplexingBased on Time-Division Multiplexing

Wavelength-Division Multiplexing Wavelength-Division Multiplexing Based on Frequency-Division Multiplexing of Based on Frequency-Division Multiplexing of

radio wavesradio waves

Time-Division MultiplexingTime-Division Multiplexing Transmitting digitized data over one mediumTransmitting digitized data over one medium

Wires or optical fibers Wires or optical fibers Pulses representing bits from different time slots Pulses representing bits from different time slots

Two Types:Two Types: Synchronous TDMSynchronous TDM Asynchronous TDMAsynchronous TDM

Synchronous TDMSynchronous TDM Accepts input in a round-robin fashion

Transmits data in a never ending pattern

Popular – Line & Sources as much bandwidth Popular – Line & Sources as much bandwidth Examples: T-1 and ISDN telephone lines SONET (Synchronous Optical NETwork)

Asynchronous TDMAsynchronous 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

Examples: used for LANs

Optical Time Division Multiplexing Optical Time Division Multiplexing (OTDM)(OTDM)

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

Frequency-Division Multiplexing Frequency-Division Multiplexing (FDM)(FDM)

All signals are sent All signals are sent simultaneously, simultaneously, each assigned its each assigned its own frequencyown frequency

Using filters all Using filters all signals can be signals can be retrievedretrieved

Wavelength-Division Multiplexing Wavelength-Division Multiplexing (WDM)(WDM)

WDM is the combining of light by using WDM is the combining of light by using different wavelengthsdifferent wavelengths

Grating MultiplexerGrating Multiplexer

Lens focuses all Lens focuses all signals to the same signals to the same pointpoint

Grating reflects all Grating reflects all signals into one signalsignals into one signal

Grating MultiplexerGrating Multiplexer

Reflection off of Reflection off of grating is dependent grating is dependent on incident angle, on incident angle, order, and wavelengthorder, and wavelength

d(sinθi + sinθo) = mλ

Grating MultiplexerGrating Multiplexer Multiplexer is Multiplexer is

designed such that designed such that each each λλ and and θθii are are related related

Results in one signal Results in one signal that can then be that can then be coupled into a fiber coupled into a fiber optic cableoptic cable

Fabry-Perot FilterFabry-Perot FilterL R

ng

RIin

Iout

Fabry-Perot MultiplexerFabry-Perot Multiplexer

Separates based on Separates based on wavelength = demuxwavelength = demux

Can be reversed for Can be reversed for multiplexermultiplexer

ConclusionConclusion

History History Applications Applications Optical Time Division MultiplexingOptical Time Division Multiplexing Wavelength-Division MultiplexingWavelength-Division Multiplexing

Grating MultiplexerGrating Multiplexer Fabry-Perot MultiplexerFabry-Perot Multiplexer