Outline
• Part 1: Fiber Basics• Part 2: Fiber Optic Networks for Traffic and
Transportation Systems• Part 3: Troubleshooting
(Problems, Test & Measurement)
Part 1: Fiber Basics
Basic Communications Link
ChannelSource Transmitter Receiver Destination
Noise Interference
Basic Fiber Transmission Link
DriveCircuit
SignalRestorer
LightSource
AmpPhoto-detector
Transmitter Channel Receiver
Electrical OutputSignal
Electrical InputSignal
Attenuation Distortion
Rays of Light Photons
Light is Oscillating Electromagnetic Energy
Smallest Particle of light is called a Photon
A Photon is a quantum or bundle of energy
Only exists if the particle is in motion
Electromagnetic EnergyElectromagnetic Energy
Electromagnetic EnergyElectromagnetic EnergyMagnetic
Field
Electric Field
Direction of Propagation
Travels through free space @ 300,000 Km/sec or 186,000 Miles/sec
Consists of Oscillating Electric and Magnetic Waves at right angles to each other
In free space the Velocity of an Electromagnetic Wave is the Speed of Light 300,000 Km/sec
Wavelength
Sine-Wave
Cycle
Frequency (Hertz’s) = The number of Cycles/sec
WavelengthWavelength (Meters) = (Meters) = The distance between the same points on consecutive waves
Positive AmplitudeNegative Amplitude
Electromagnetic Waves are Sinusoidal in shape
Electromagnetic EnergyElectromagnetic EnergyMagnetic
Field
Electric Field
Direction of Propagation
Travels through free space @ 300,000 Km/sec or 186,000 Miles/sec
Consists of Oscillating Electric and Magnetic Waves at right angles to each other
In free space the velocity of an Electromagnetic Wave is the Speed of Light 300,000 Km/sec
Wavelength
Sine-Wave
Cycle
Frequency (Hertz’s) = The number of Cycles/sec
WavelengthWavelength (Meters) = (Meters) = The distance between the same points on consecutive waves
Positive AmplitudeNegative Amplitude
Electromagnetic Waves are Sinusoidal in shape
Wavelength =Velocity
FrequencyWavelength = Meters
Velocity = 300,000Km/Sec.
Frequency = Hertz
What is the wavelength of 60 Hz ?
Wavelength = 300,000 Km 60 Hz
= 5000Km
Los Angeles Boston5000 Km
60 Hz
QuestionQuestion
Electromagnetic EnergyElectromagnetic EnergyMagnetic
Field
Electric Field
Direction of Propagation
Travels through free space @ 300,000 Km/sec or 186,000 Miles/sec
Consists of Oscillating Electric and Magnetic Waves at right angles to each other
In free space the velocity of an Electromagnetic Wave is the Speed of Light 300,000 Km/sec
Wavelength
Sine-Wave
Cycle
Frequency (Hertz’s) = The number of Cycles/sec
WavelengthWavelength (Meters) = (Meters) = The distance between the same points on consecutive waves
Positive AmplitudeNegative Amplitude
Electromagnetic Waves are Sinusoidal in shape
Wavelength =Velocity
FrequencyWavelength = Meters
Velocity = 300,000Km/Sec.
Frequency = Hertz
QuestionQuestionWhat is the wavelength of 2.4 GHz ?
Wavelength = 300,000 Km 2.4 GHz
= 125 microns
Approximately the same diameter as a strand of human hair!
100 Sub-sonic
(1 MHz) 10 6 AM Radio
10 410 5
(1 KHz) 10 3 Sound10 2
(1 THz) 10 12
10 8
10 7
(1 GHz) 10 9Radar
Television
Short-wave RadioFM Radio
10 1010 11
10 14
10 16Ultraviolet Rays
Visible LightInfrared Light10 13
10 15
10 22
10 18
10 20
Cosmic Rays
Gamma Rays
X-Rays
10 17
10 19
10 21
Electromagnetic SpectrumElectromagnetic SpectrumHigh Frequency
Ultra- Short Wavelengths
Low Frequency
Long Wavelengths
Sound
18K Hertz
20 Hertz
Ultra Violet
Violet
Blue
Green
Yellow
Orange
Red
Infrared
400
455
490
550
580
620
750
800
850Far Infrared
Wavelength (nm)
Short
Long
Sight
Electromagnetic SpectrumElectromagnetic Spectrum
Violet Blue Green Yellow Orange RedUltra-Violet Infrared
Invisible Light
400 455 490 550 580 620 750 800
Wavelength (nm)
10 – 9 m
1m
1,000,000,000
1nm =
850 1300 1550
Visible Light
Fiber Optics Transmission
The Speed Of LightThe Speed Of Light
1 1.0003
1.331.46 1.48
0.000.200.400.600.801.001.201.401.601.802.00
Vacuum Air Water FusedGlass
FusedGlass
Material
The ratio of the speed of light in a vacuum to the speed of light in a specific medium
CoreCladding
IOR
Index of Refraction
Velocity
300,000 Km/s
205,000 Km/s
225,000 Km/s
Journey of LightJourney of Light
InterfaceInterface
GlassGlassI.O.RI.O.R1.481.48
I.O.RI.O.R1.461.46
Angle ofAngle ofIncidence Incidence
RayRay
Refracted Refracted RayRay
NormalNormal
Angle ofAngle ofIncidence Incidence
RayRay
Angle ofAngle ofRefractionRefraction
CriticalCriticalAngleAngle
Angle ofAngle ofIncidenceIncidence == Angle ofAngle of
ReflectionReflection
Advantages of Optical FiberAdvantages of Optical Fiber••Wide Bandwidth Wide Bandwidth
••Low Loss Low Loss
••Electromagnetic Immunity Electromagnetic Immunity
••Light Weight Light Weight
••Small Size Small Size
••Safety Safety
••Security Security
Flat OC192 129,024 Voice ChannelsFlat OC192 129,024 Voice Channels
Fiber is Dielectric, does not carry electricityFiber is Dielectric, does not carry electricity
0.25dB/Km @ 1550nm0.25dB/Km @ 1550nm
Optical FiberOptical FiberTwo Types Of Fiber -
MultimodeMultimode
SinglemodeSinglemode
• Used for Low Bandwidth (less than 650MHz), Short Haul Communications with distances of up to 3Km (850nm) & 10Km (1300nm)
• Two operating wavelengths, 850nm and 1300nm
• Used for High Bandwidth, Long Haul Communications with distances of up to 40Km (1310nm) and 100Km (1550nm) or more
• Two operating wavelengths at 1310nm and 1550nm
MMultimode & Singlemodeultimode & Singlemode
125 / 62.5 125 / 62.5 micronsmicrons
125 / 62.5 125 / 62.5 micronsmicrons
MultimodeMultimode
CoreCore
FiberFiberBufferBuffer
CladdingCladding
Core / Cladding sizes 50/125, 62.5/125 and 100/140 microns
FDDIFiber Distributed Data Interface
WavelengthWavelength
850 & 1300nm850 & 1300nm
SinglemodeSinglemode
FiberFiberBufferBuffer
125 / 125 / 9/ 9micronsmicrons
CladdingCladdingCoreCore125 / 125 / 99/
9micronsmicrons
Core less than 10 microns Cladding 125 micronsWavelengthWavelength
1310 & 1550nm1310 & 1550nm
Attenuation vs. λ
MultimodeMultimode
Refractive Index Profiles
• Multimode Stepped Index Fiber
• Multimode Graded Index Fiber
• Singlemode Stepped Index Fiber
Mode Time Scale
Multimode Stepped Index Fiber
ModalModal
Input Input Output Output Bandwidth Limited to about Bandwidth Limited to about
150Mhz/Km 150Mhz/Km Refractive Refractive
Index Profile Index Profile
Core 100 microns
Cladding 140 microns
Mode Time Scale
Multimode Graded Index Fiber
ModalModalRefractive Refractive
Index Profile Index Profile
Input Input Output Output Bandwidth Limited to Bandwidth Limited to
about 650Mhz/Km about 650Mhz/Km
Signal DistortionImportant in determining the information capacity (bandwidth) of an optical fiber as a function of transmission distance.
Intermodal DispersionIntermodal dispersion - pulse spreading (in time) in multimode fibers, due to varying arrival times at the RX because each mode travels with a slightly different velocity.
core
cladding
cladding
mode 1
mode 2
Axial Cross-Sectio
Refractive Refractive Index Profile Index Profile
Stepped Index, Terahertz Bandwidth Stepped Index, Terahertz Bandwidth
Singlemode Step Index Fiber
Dynamic Range Dynamic Range
Wavelength / Attenuation Wavelength / Attenuation
850nm 850nm
1300nm 1300nm
1310nm 1310nm
1550nm 1550nm
Multimode Multimode
SinglemodeSinglemode
3.5dB/Km3.5dB/Km
1.75dB/Km1.75dB/Km
0.5dB/Km0.5dB/Km30 Km30 Km
60 Km60 Km
8.75 Km8.75 Km
0.25dB/Km0.25dB/Km
/ Distance / Distance
=15dB=15dB
P0 P0 --15dBm15dBm
TxTx
4.28 Km4.28 Km
RxRx
LDL LDL --30dBm 30dBm
BER 1x10BER 1x10 66--
Wavelength / Attenuation / Bandwidth Wavelength / Attenuation / Bandwidth
1310nm 1310nm
1550nm 1550nm
SinglemodeSinglemode0.5dB/Km0.5dB/Km
0.25dB/Km0.25dB/Km
UnlimitedUnlimited
UnlimitedUnlimited
850nm 850nm
1300nm 1300nm
Multimode Multimode 3.5dB/Km3.5dB/Km
1.75dB/Km1.75dB/Km650 MHz/Km650 MHz/Km
100 MHz/Km100 MHz/Km
Four Operating Wavelengths Four Operating Wavelengths Four Operating Wavelengths
1310nm1310nmSinglemodeSinglemode
850nm850nm1300nm1300nm
1550nm1550nm
MultimodeMultimode LED’sLED’s
ELED’s
LASER’s
ELED’s
LASER’s
Fiber Cables
Point-to-Point Digital Transmission Links
• Link Requirements:– Transmission Distance– Data Rate or Bandwidth
A designer has the choice of the following:
1) Fiber -Multimode or single-modeCore size and refractive index profileAttenuationNumerical aperture
2) Source -Laser diode or LEDEmission Spectral widthOutput powerSpeed (bandwidth)Effective emitting areaEmission pattern
3) Detector –Sensitivity (or responsivity)Speed (bandwidth)Operating λ
Link Power Budget Analysis
PS - PR ≥ [ αf L + m(lc) + n(lsp) + system margin ]
where αf = fiber attenuation (dB/km)L = fiber length (km)m = number of connectorslc = loss per connector (dB)n = number of spliceslsp = loss per splice (dB)PS = source output power (dBm)PR = receiver sensitivity (dBm)
System Margin
• System margin is typically specified at 6 to 8 dB to allow for new components, component aging, and temperature fluctuations.
Link Rise Time Budget
• One accepted method for determining the dispersion limitiation of a fiber optic transmission system is to calculate the system rise time, tsys, and ensure that it does not exceed 70% of the NRZ bit period.
tsys = [ ( ttx)2 + ( tGVD)2 + ( tmod)2 + ( trx)2 ]1/2
Signal Coding
where ttx = transmitter rise time (spec'd by manufacturer)
tmat = material dispersion rise time = DσλLor
tGVD = group-velocity dispersion ≈ |D|Lσλwhere D = material dispersion
σλ = source spectral widthL = fiber length
tmod = modal rise time 0 for single-mode fibertrx = receiver rise time (spec'd by
manufacturer)
Exercise
A 1550 nm single-mode digital fiber optic link needs to operate at 622 Mb/s over 80 km without amplifiers. A single-mode InGaAsP laser launches an average optical power of 0 dBm into the fiber. The fiber has a loss of 0.25 dB/km, and there is a splice with a loss of 0.1 dB every km. The coupling loss at the receiver is 0.5 dB, and the receiver uses an InGaAs APD with a sensitivity of –39 dBm.
a) Find the system margin.b) Find the system margin at 2.5 Gb/s with an APD
sensitivity of –31 dBm.
SolutionPS - PR ≥ [ αf L + m(lc) + n(lsp) + system margin ]
so we can calculate the system margin fromsystem margin ≤ PS - PR - αf L - m(lc) - n(lsp)
where PS = 0 dBmαf = 0.25 dB/kmL = 80 kmm = 1lc = 0.5 dBn = 79lsp = 0.1 dB
Solution (continued)a) PR = –39 dBm for a data rate of 622 Mb/ssystem margin ≤ 0 dBm – (-39 dBm) – (0.25 dB/km)(80 km)
– (1)(0.5 dB) – (79)(0.1 dB)system margin ≤ 10.6 dB, which is very respectable
b) PR = –31 dBm for a data rate of 2.5 Gb/ssystem margin ≤ 0 dBm – (-31 dBm) – (0.25 dB/km)(80 km)
– (1)(0.5 dB) – (79)(0.1 dB)system margin ≤ 2.6 dB, which is really not good enough to
ensure long-term, problem-free operation of the link
ExerciseYou are assisting with the design of an OC-192 fiber
optic transmission link. Given a 1550 nm laser diode with a rise time of 25 ps and a spectral width of 0.1 nm, and a receiver with a rise time of 25 ps:
a) Determine the maximum dispersion-limited transmission distance through a fiber optimized for a 1310 nm source (assume a material dispersion of 15 ps/nm-km).
b) Determine the maximum dispersion-limited transmission distance through a dispersion-shifted fiber optimized for a 1550 nm source (assume a material dispersion of 2 ps/nm-km).
Solution
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )
( ) ( ) ( ) ( )
12 2 2 2 2
mod
12 22 2 2
mod
12 22 2 2
mod
substituting for
and solving for
sys tx GVD rx
GVD
sys tx rx
sys tx rx
t t t t t
t D L
t t D L t t
L
t t t tL
D
λ
λ
λ
σ
σ
σ
= + + + =
= + + +
− − − =
Solution (continued)From the problem statement,
ttx = 25 pstmod ≈ 0trx = 25 psσλ = 0.1 nm
For an OC-192, the data rate is approximately 10 Gb/s, so the NRZ bit period isTb= 1x10-10 s = 100 ps. Thus, tsys should not exceed 70% of Tb, so set tsys=70 ps.
Solution (continued)
( ) ( ) ( )( )( )
12 2 2 2
max
max
a) transmission through a fiber optimized for a 1310 nm source with 15 / .
70 25 25
15 / 0.1
40.28
b) transmission through a dispersion-shifted fiberoptimized for
D ps nm km
ps ps psL
ps nm km nm
L km
= ⋅
− − =⋅
=
( ) ( ) ( )( )( )
12 2 2 2
max
max
a 1550 nm source with 2 / - .
70 25 25
2 / 0.1
302.08
D ps nm km
ps ps psL
ps nm km nm
L km
=
− − =⋅
=
End of Part 1
Fiber Optic Networks for Traffic and Transportation Systems
Part 2
CommonCommunication Network
InfrastructureMediums (Wire, Wireless, Fiber)
Field MastersBridges, Routers, Multiplexers, Cross-Connects
Infrastructure Interfaces
SignalSystem
CMS
HAR
RampMetering
VideoControl
Sensors
Environ-mental
RuralSuburbanUrbanFreeway/Metropolitan
CountyStateNationalPrivateServices
Other StateAgencies
ITS Communication Interface Concept
NTCIP-CompatibleField Interfaces
& Protocols
TMCInterfaces
ExternalInterfaces
Advantages:Share DataTMC BackupShared External InterfacesReduced Comms Costs
Agency Options
• Install-Operate-Maintain• Lease• Public/Private Partnerships
Network Requirements
• Data - Signal systems, VMS, video PTZ, vehicle detectors, sensors, etc.
• Voice - Craft interfaces, HAR, emergency call boxes.
• Video - Incident monitoring, surveillance, video detection.
Analog vs. Digital Video? The answer drives required network bandwidth.
MultiplexingMultiplexing
Multiplexing De-Multiplexing
DATADATADATA
LANLANLAN
PLCPLCPLC
VOICEVOICEVOICE
M
U
X
MM
UU
XX
DATADATADATA
LANLANLAN
PLCPLCPLC
VOICEVOICEVOICE
M
U
X
MM
UU
XX
Separates out the Input Signals from the Composite to form Corresponding Outputs
Combines Two or More Signals into a Composite Signal for Transmission
MultiplexingMultiplexing
Network TopologiesStar Ring
Linear
Fault-Tolerant Ring Topologies
PrimaryData Path
SecondaryData Path
Fiber Cut
Typical Fiber Network Application
SONETNODE
SONETNODE
SONETNODE
SONETNODE
TCC
RS-232
Modem Controller
Modem Controller
Modem Controller
Modem Controller
Modem Controller
Modem Controller
Modem Controller
Modem Controller
Modem Controller
ModemConnections
Sensors
Sensors
Sensors
Sensors
Interconnect DiagramInterconnect Diagram
Hybrid Fiber/Wireless Network
SONETNODE
SONETNODE
SONETNODE
SONETNODE
ProtocolInterface
Controller ProtocolInterface
Controller
Radio Controller
ProtocolInterface
ProtocolInterface
Radio
Antenna
Antenna
TCC
RS-232
Radio Controller
Antenna
Sensors
SONETSynchronous Optical Network
SONETLevel
(optical)
SONETLevel
(electrical)
Line Rate(Mb/s)
SDHLevel
OC-1 STS-1 51.84 STM-0OC-3 STS-3 155.52 STM-1OC-12 STS-12 622.08 STM-4OC-24 STS-24 1,244.16 STM-8OC-36 STS-36 1,866.24 STM-12OC-48 STS-48 2,488.32 STM-16
OC-192 STS-192 9,953.28 STM-64
OC - Optical Carrier STS - Synchronous Transport Signal STM - Synchronous Transport Module
OC - 1
OC - 1
OC - 1
OC - 1OC - 1
OC - 1
OC - 1
OC - 1
OC - 1
OC - 1
OC - 1
OC - 1
OC - 3
OC - 3
OC - 3
OC - 3 OC - 12
OC - 12
OC - 12
OC - 12
OC - 48
OC - 48
OC - 48
OC - 48
OC - 192
SONET Multiplexing
SONET NetworkingSuper Capacity
(WDM)OC-192 OC-192
High Capacity(WDM)
SuperCapacity
LowCapacity
LowCapacity
LowCapacity
HighCapacity
OC-192OC-192OC-48
OC-48
OC-48
OC- 48 OC- 48
OC- 48
OC-12
OC-12OC-12OC - 3
OC - 3OC - 3OC - 3
OC - 3OC - 3
Super - ExpressLayer
ExpressLayer
AccessLayer
OC-192OC-192
OC-192OC-192
Transmission Over SONET
• PCM Digital Hierarchy• ATM Over SONET• Packet Over SONET (POS) or IP over
SONET
Wavelength Division Multiplexing (WDM)
WDM
1300 nm
1550 nm
WDM1550 nm
1300 nm
WDM 1550 nm
1300 nm
WDM 1550 nm
1300 nm
Dense WDM (DWDM)
TX
TX
TX
RX
RX
RX
λ1
λ2
λN
λ1
λ2
λN
.
.
.
.
.
.
WDM
(mux)
WDM
(demux)
Optical Transport Network (OTN) G.709
• For data rates of 10 Gb/s and above, optical transmission lengths decreaseOTN uses Forward Error Correction (FEC) to increase optical link distance
• Need to transport a wide range of servicesOTN offers flexible payload management with minimum additional overhead
Optical Transport Network (OTN) G.709
• Minimize O/E/O conversionsEnd-to-end transport of optical channels without O/E/O conversions
• Ability to manage emerging DWDM networksOTN offers management capabilities in the optical domain
Optical Transport Network
PhotonicTransport
Router
BackboneIP Router
BackboneIP Router
PhotonicTransport
Router
SONET
ATM
SONET
ATM
DWDM Link
Photonic Transport Node
Virtual Photonic CoreTransport Network
(no electrical terminations)
End of Part 2
Part 3Part 3
Troubleshooting ProblemsTroubleshooting Problems
Test & MeasurementTest & Measurement
ProblemsProblems
Typical Problems
Low Levels
RXTXFiber Optic Cable
Dirty Connectors
Connectors not seated properly
Pinched Fibers
Tight bending radius’s
Bad Patchcords
Patchcord Patchcord
Low Transmit Levels
Ferrule Must be Clean
Key/Keyway must be engaged in mating
hardware
Avoid Tight Bending Radius’s
Avoid Stress Points Tie wrap Cinched Tight,
Must be Loose
ProblemsProblems
Typical Problems
High Levels
RXTXFiber Optic Cable
Not enough Loss in Fiber Plant
Patchcord Patchcord
High Transmit Levels (LASER) Fixed Attenuator
Barrel Type Variable Attenuator
Screw adjustable Attenuator
5db increments
3 to 30db
3 to 30db
A
Attenuators
ProblemsProblems
Typical Problems
No Receive Level
RXTXFiber Optic Cable
Dirty Connectors
Connectors not seated properly
Bad Patchcord (Open)
No Transmit Output
Wrong Fiber
Patchcord Patchcord
Ferrule Must be Clean
Key/Keyway must be engaged in mating
hardware
Avoid Tight Bending Radius’s
Avoid Stress Points Tie wrap Cinched Tight,
Must be Loose
Optical Loss Measurements
Patchcord PatchcordBulkhead
Connection
Power MeterLight Source
Reference Measurement
Relative Reference Measurement
-15.0dBmRef-0.00dBm850nm
850nmReceived Level
Test & MeasurementTest & Measurement
Test & MeasurementTest & Measurement
Patchcord Patchcord
Bulkhead Connection
Power MeterLight Source
Attenuation Measurement ---Forward Direction
Loss
-5.00dBm
Bulkhead Connection
Fiber under test
850nm
850nm
Fiber Loss
Optical Loss Measurements
Test & MeasurementTest & Measurement
Optical Loss Measurements
Patchcord Patchcord
Bulkhead Connection
Power Meter Light Source
Attenuation Measurement ---Reverse Direction
Loss
-4.80dBm
Bulkhead Connection
Fiber under test
850nm
Fiber Loss850nm
Test & MeasurementTest & Measurement
Recording the Results
BA LossAB LossFiber Cable #
Test & MeasurementTest & Measurement
OTDR Measurements
OTDR DEAD ZONES
Near End or
Attenuation DZ Splice DZ
Connector DZ
End of Cable
Test & MeasurementTest & Measurement
OTDR Measurements
Splice Loss
LSA Two Point
1
2
3
Distance between Markers Km
dB Loss
1 32
Distance between Markers Km
Test & MeasurementTest & Measurement
OTDR Measurements----
Optical Return Loss
Large Reflection
Large Reflection
Small Reflection
Cleave Fiber -14.5db
Flat Finish -14.5db
PC Finish - 45db
Dirty Connectors also cause Reflections
Increases Bit Error Rates
Increases Noise in Analog Systems
Optical Return Loss ---- Problems with Reflections
Test & MeasurementTest & Measurement
Set up an Electronic Data Base
Fiber Characterization
• Record losses for all useable wavelengths
• Bi- Directional Loss Measurements
• OTDR traces for 850 / 1300nm Multimode and 1310 / 1550nm Singlemode
• Bi- Directional traces for each fiber
End of Part 3
