Post on 25-Nov-2014
1© 2001, Cisco Systems, Inc. All rights reserved.© 2001, Cisco Systems, Inc. All rights reserved.© 2001, Cisco Systems, Inc. All rights reserved.
Optical Fundamentals
© 2001, Cisco Systems, Inc. All rights reserved. 2© 2001, Cisco Systems, Inc. All rights reserved. 2© 2001, Cisco Systems, Inc. All rights reserved. 2
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 3© 2001, Cisco Systems, Inc. All rights reserved. 3© 2001, Cisco Systems, Inc. All rights reserved. 3
Modern Lightwave Eras
0.1
1
10
100
1000
10000
1985 1990 1995 2000
Year
Cap
acit
y (G
b/s
)
FiberizationDigitization
SONET rings and DWDM linear systems
Optical networkingWavelength Switching
Research Systems
Commercial Systems
© 2001, Cisco Systems, Inc. All rights reserved. 4© 2001, Cisco Systems, Inc. All rights reserved. 4© 2001, Cisco Systems, Inc. All rights reserved. 4
• Decibels (dB): unit of level (relative measure) X dB is 10-X/10 in linear dimension e.g. 3 dB Attenuation = 10-.3 = 0.501
Standard logarithmic unit for the ratio of two quantities. In optical fibers, the ratio is power and represents loss or gain.
• Decibels-milliwatt (dBm) : Decibel referenced to a milliwatt X mW is 10log10(X) in dBm, Y dBm is 10Y/10 in mW. 0dBm=1mW, 17dBm = 50mW
• Wavelength (): length of a wave in a particular medium. Common unit: nanometers, 10-9m (nm)
300nm (blue) to 700nm (red) is visible. In fiber optics primarily use 850, 1310, & 1550nm
• Frequency (): the number of times that a wave is produced within a particular time period. Common unit: TeraHertz, 1012 cycles per second (Thz)
Wavelength x frequency = Speed of light x = C
Some terminology:
© 2001, Cisco Systems, Inc. All rights reserved. 5© 2001, Cisco Systems, Inc. All rights reserved. 5© 2001, Cisco Systems, Inc. All rights reserved. 5
• Attenuation = Loss of power in dB/km The extent to which lighting intensity from the source is diminished as it passes through a given length of fiber-optic (FO) cable, tubing or light pipe. This specification determines how well a product transmits light and how much cable can be properly illuminated by a given light source.
• Chromatic Dispersion = Spread of light pulse in ps/nm-km
The separation of light into its different coloured rays.
• ITU Grid = Standard set of wavelengths to be used in Fibre Optic communications. Unit Ghz, e.g. 400Ghz, 200Ghz, 100Ghz
• Optical Signal to Noise Ration (OSNR) = Ratio of optical signal power to noise power for the receiver
• Lambda = Name of Greek Letter used as Wavelength symbol ()
• Optical Supervisory Channel (OSC) = Management channel
Some more terminology
© 2001, Cisco Systems, Inc. All rights reserved. 6© 2001, Cisco Systems, Inc. All rights reserved. 6© 2001, Cisco Systems, Inc. All rights reserved. 6
dB versus dBm
• dBm used for output power and receive sensitivity (Absolute Value)
• dB used for power gain or loss (Relative Value)
© 2001, Cisco Systems, Inc. All rights reserved. 7© 2001, Cisco Systems, Inc. All rights reserved. 7© 2001, Cisco Systems, Inc. All rights reserved. 7
ITU Wavelength Grid
• ITU-T grid is based on 191.7 THz + 100 GHz
• It is a standard for the lasers in DWDM systems
1530.33 nm 1553.86 nm
0.80 nm
195.9 THz 193.0 THz100 GHz
Freq (THz) ITU Ch Wave (nm) 15201/252 15216 15800 15540 15454192.90 29 1554.13 x x x x x192.85 1554.54192.80 28 1554.94 x x x x x192.75 1555.34192.70 27 1555.75 x x x x x192.65 1556.15192.60 26 1556.55 x x x x x
© 2001, Cisco Systems, Inc. All rights reserved. 8© 2001, Cisco Systems, Inc. All rights reserved. 8© 2001, Cisco Systems, Inc. All rights reserved. 8
Bit Error Rate ( BER)
• BER is a key objective of the Optical System Design
• Goal is to get from Tx to Rx with a BER < BER threshold of the Rx
• BER thresholds are on Data sheets
• Typical minimum acceptable rate is 10 -12
© 2001, Cisco Systems, Inc. All rights reserved. 9© 2001, Cisco Systems, Inc. All rights reserved. 9© 2001, Cisco Systems, Inc. All rights reserved. 9
Optical Budget
Optical Budget is affected by: Fiber attenuation
Splices
Patch Panels/Connectors
Optical components (filters, amplifiers, etc)
Bends in fiber
Contamination (dirt/oil on connectors)
Basic Optical Budget = Output Power – Input Sensitivity
Pout = +6 dBm R = -30 dBm
Budget = 36 dB
© 2001, Cisco Systems, Inc. All rights reserved. 10© 2001, Cisco Systems, Inc. All rights reserved. 10© 2001, Cisco Systems, Inc. All rights reserved. 10
Power Budget with Power Penalties
Fiber Loss +
Splices +
Connectors +
Dispersion Penalties +
Fiber Nonlinearities Penalty +
Component Aging Penalties <
Power Budget = Launch Power – Receiver Sensitivity
Fiber Loss +
Splices +
Connectors +
Dispersion Penalties +
Fiber Nonlinearities Penalty +
Component Aging Penalties <
Power Budget = Launch Power – Receiver Sensitivity
© 2001, Cisco Systems, Inc. All rights reserved. 11© 2001, Cisco Systems, Inc. All rights reserved. 11© 2001, Cisco Systems, Inc. All rights reserved. 11
Glass Purity
Propagation Distance Need to Reduce theTransmitted Light Power by 50% (3 dB)
Window Glass 1 inch (~3 cm)
Optical Quality Glass 10 feet (~3 m)
Fiber Optics 9 miles (~14 km)
Fiber Optics Requires Very High Purity Glass
© 2001, Cisco Systems, Inc. All rights reserved. 12© 2001, Cisco Systems, Inc. All rights reserved. 12© 2001, Cisco Systems, Inc. All rights reserved. 12
AttenuationDispersion
Nonlinearity
Waveform After 1000 KmTransmitted Data Waveform
Distortion
It May Be a Digital Signal, but It’s Analog Transmission
Fiber Fundamentals
© 2001, Cisco Systems, Inc. All rights reserved. 13© 2001, Cisco Systems, Inc. All rights reserved. 13© 2001, Cisco Systems, Inc. All rights reserved. 13
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 14© 2001, Cisco Systems, Inc. All rights reserved. 14© 2001, Cisco Systems, Inc. All rights reserved. 14
Attenuation: Reduces power level with distance
Dispersion and Nonlinearities: Erodes clarity with distance and speed
Signal detection and recovery is an analog problem
Analog Transmission Effects
© 2001, Cisco Systems, Inc. All rights reserved. 15© 2001, Cisco Systems, Inc. All rights reserved. 15© 2001, Cisco Systems, Inc. All rights reserved. 15
CladdingCore
Coating
Fiber Geometry
• An optical fiber is made ofthree sections:
The core carries thelight signals
The cladding keeps the lightin the core
The coating protects the glass
© 2001, Cisco Systems, Inc. All rights reserved. 16© 2001, Cisco Systems, Inc. All rights reserved. 16© 2001, Cisco Systems, Inc. All rights reserved. 16
• Fiber dimensions are measured in µm1 µm = 0.000001 meters (10-6)
1 human hair ~ 50 µm
• Refractive Index (n)n = c/v
n ~ 1.46
n (core) > n (cladding)
Cladding(125 µm)
Coating(245 µm)
Core(8–62.5 µm)
Fiber Dimensions
© 2001, Cisco Systems, Inc. All rights reserved. 17© 2001, Cisco Systems, Inc. All rights reserved. 17© 2001, Cisco Systems, Inc. All rights reserved. 17
Snell’s Law1= 1r
n1Sin 1 = n2Sin 2
Geometrical Optics
• Light is reflected/refracted at an interface
1 = Angle of incidence
1r = Angle of reflection
2 = Angle of refraction
• Above critical=Sin-1(n2/n1), all light is totally internally reflected
r
n2
n1
© 2001, Cisco Systems, Inc. All rights reserved. 18© 2001, Cisco Systems, Inc. All rights reserved. 18© 2001, Cisco Systems, Inc. All rights reserved. 18
n2
n1
Cladding
Core
Intensity Profile
Propagation in Fiber
• Light propagates by total internal reflectionsat the core-cladding interface
• Total internal reflections are lossless
• Each allowed ray is a mode
© 2001, Cisco Systems, Inc. All rights reserved. 19© 2001, Cisco Systems, Inc. All rights reserved. 19© 2001, Cisco Systems, Inc. All rights reserved. 19
n2
n1
Cladding
Core
n2
n1
Cladding
Core
Different Types of Fiber
• Multimode fiberCore diameter varies
50 mm for step index
62.5 mm for graded index
Bit rate-distance product>500 MHz-km
• Single-mode fiberCore diameter is about 9 mm
Bit rate-distance product>100 THz-km
© 2001, Cisco Systems, Inc. All rights reserved. 20© 2001, Cisco Systems, Inc. All rights reserved. 20© 2001, Cisco Systems, Inc. All rights reserved. 20
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 21© 2001, Cisco Systems, Inc. All rights reserved. 21© 2001, Cisco Systems, Inc. All rights reserved. 21
• Light
Ultraviolet (UV)
Visible
Infrared (IR)
• Communication wavelengths
850, 1310, 1550 nm
Low-loss wavelengths
• Specialty wavelengths
980, 1480, 1510, 1625 nm
UV IR
Visible
850 nm
980 nm1310 nm
1480 nm
1550 nm1625 nm
Wavelength: (nanometers)
Frequency: (terahertz)
C =x
Optical Spectrum
© 2001, Cisco Systems, Inc. All rights reserved. 22© 2001, Cisco Systems, Inc. All rights reserved. 22© 2001, Cisco Systems, Inc. All rights reserved. 22
Optical Attenuation
• Specified in loss per kilometer (dB/km)
0.40 dB/km at 1310 nm
0.25 dB/km at 1550 nm
• Loss due to absorptionby impurities
1400 nm peak due to OH ions
• EDFA optical amplifiers available in 1550 window
1310Window
1550Window
© 2001, Cisco Systems, Inc. All rights reserved. 23© 2001, Cisco Systems, Inc. All rights reserved. 23© 2001, Cisco Systems, Inc. All rights reserved. 23
T T
P i P0
Optical Attenuation
• Pulse amplitude reduction limits “how far”
• Attenuation in dB=10xLog(Pi/Po)
• Power is measured in dBm: P(dBm)=10xlog(P mW/1 mW)
ExamplesExamples
10dBm10dBm 10 mW10 mW
0 dBM0 dBM 1 mW1 mW
-3 dBm-3 dBm 500 uW500 uW
-10 dBm-10 dBm 100 uW100 uW
-30 dBm-30 dBm 1 uW1 uW
)
© 2001, Cisco Systems, Inc. All rights reserved. 24© 2001, Cisco Systems, Inc. All rights reserved. 24© 2001, Cisco Systems, Inc. All rights reserved. 24
• Polarization Mode Dispersion (PMD) Single-mode fiber supports two polarization
states
Fast and slow axes have different group velocities
Causes spreading of the light pulse
• Chromatic Dispersion Different wavelengths travel at different speeds
Causes spreading of the light pulse
Types of Dispersion
© 2001, Cisco Systems, Inc. All rights reserved. 25© 2001, Cisco Systems, Inc. All rights reserved. 25© 2001, Cisco Systems, Inc. All rights reserved. 25
Fiber Chromatic Dispersion Characteristics
Wavelength
Dis
per
sio
n p
s/n
m-k
m 20
01310 nm 1550nm
Normal Fiber (SMF-28 or Equivalent)Nondispersion Shifted Fiber (NDSF) >95% of Deployed Plant
Normal(ITU-T G.652)Dispersion Shifted Fiber (DSF) (ITU-T G.653)Nonzero Dispersion Shifted Fibers (NZDSF) (ITU-T G.655)
© 2001, Cisco Systems, Inc. All rights reserved. 26© 2001, Cisco Systems, Inc. All rights reserved. 26© 2001, Cisco Systems, Inc. All rights reserved. 26
• Affects single channel and DWDM systems
• A pulse spreads as it travels down the fiber
• Inter-symbol Interference (ISI) leads to performance impairments
• Degradation depends on:
laser used (spectral width)
bit-rate (temporal pulse separation)
Different SM types
Interference
A Snapshot on Chromatic Dispersion
© 2001, Cisco Systems, Inc. All rights reserved. 27© 2001, Cisco Systems, Inc. All rights reserved. 27© 2001, Cisco Systems, Inc. All rights reserved. 27
• The refractive index is wavelength dependent
• Different frequency-components of the optical pulses travel at different speeds (the blue is faster than red for anomalous dispersion where D > 0)
• As a result, we see pulse broadening and ISI
z
z
z
zTransmission Fiber
Fiber Chromatic Dispersion (CD)
BlueRed
© 2001, Cisco Systems, Inc. All rights reserved. 28© 2001, Cisco Systems, Inc. All rights reserved. 28© 2001, Cisco Systems, Inc. All rights reserved. 28
60 Km SMF-28
4 Km SMF-28
10 Gbps
40 Gbps
Limitations From Chromatic Dispersion
t
t
• Dispersion causes pulse distortion, pulse "smearing" effects
• Higher bit-rates and shorter pulses are less robust to Chromatic Dispersion
• Limits "how fast“ and “how far”
© 2001, Cisco Systems, Inc. All rights reserved. 29© 2001, Cisco Systems, Inc. All rights reserved. 29© 2001, Cisco Systems, Inc. All rights reserved. 29
Combating Chromatic Dispersion
• Use DSF and NZDSF fibers
(G.653 & G.655)
• Dispersion Compensating Fiber
• Transmitters with narrow spectral width
© 2001, Cisco Systems, Inc. All rights reserved. 30© 2001, Cisco Systems, Inc. All rights reserved. 30© 2001, Cisco Systems, Inc. All rights reserved. 30
Dispersion Compensating Fiber
• Dispersion Compensating Fiber:
By joining fibers with CD of opposite signs (polarity) and suitable lengths an average dispersion close to zero can be obtained; the compensating fiber can be several kilometers and the reel can be inserted at any point in the link, at the receiver or at the transmitter
© 2001, Cisco Systems, Inc. All rights reserved. 31© 2001, Cisco Systems, Inc. All rights reserved. 31© 2001, Cisco Systems, Inc. All rights reserved. 31
Dispersion Compensation
Transmitter
Dispersion Compensators
Dispersion Shifted Fiber Cable
+1000
-100-200-300-400-500
Cu
mu
lati
ve D
isp
ersi
on
(p
s/n
m)
Total Dispersion Controlled
Distance fromTransmitter (km)
No CompensationWith Compensation
© 2001, Cisco Systems, Inc. All rights reserved. 32© 2001, Cisco Systems, Inc. All rights reserved. 32© 2001, Cisco Systems, Inc. All rights reserved. 32
How Far Can I Go Without Dispersion?
Distance (Km) =Specification of Transponder (ps/nm)
Coefficient of Dispersion of Fiber (ps/nm*km)
A laser signal with dispersion tolerance of 3400 ps/nm
is sent across a standard SMF fiber which has a Coefficient of Dispersion of 17 ps/nm*km.
It will reach 200 Km at maximum bandwidth.Note that lower speeds will travel farther.
© 2001, Cisco Systems, Inc. All rights reserved. 33© 2001, Cisco Systems, Inc. All rights reserved. 33© 2001, Cisco Systems, Inc. All rights reserved. 33
Polarization Mode Dispersion
• Caused by ovality of core due to:
Manufacturing process
Internal stress (cabling)
External stress (trucks)
• Only discovered inthe 90s
• Most older fiber not characterized for PMD
© 2001, Cisco Systems, Inc. All rights reserved. 34© 2001, Cisco Systems, Inc. All rights reserved. 34© 2001, Cisco Systems, Inc. All rights reserved. 34
Polarization Mode Dispersion (PMD)
• The optical pulse tends to broaden as it travels down the fiber; this is a much weaker phenomenon than chromatic dispersion and it is of some relevance at bit rates of 10Gb/s or more
nx
nyEx
Ey
Pulse As It Enters the Fiber Spreaded Pulse As It Leaves the Fiber
© 2001, Cisco Systems, Inc. All rights reserved. 35© 2001, Cisco Systems, Inc. All rights reserved. 35© 2001, Cisco Systems, Inc. All rights reserved. 35
Combating Polarization Mode Dispersion
• Factors contributing to PMDBit RateFiber core symmetryEnvironmental factorsBends/stress in fiberImperfections in fiber
• Solutions for PMDImproved fibers RegenerationFollow manufacturer’s recommended installation techniques for the fiber cable
© 2001, Cisco Systems, Inc. All rights reserved. 36© 2001, Cisco Systems, Inc. All rights reserved. 36© 2001, Cisco Systems, Inc. All rights reserved. 36
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 37© 2001, Cisco Systems, Inc. All rights reserved. 37© 2001, Cisco Systems, Inc. All rights reserved. 37
From Linear to Non Linear Propagation
• As long as optical power within an optical fiber is small, the fiber can be treated as a linear medium Loss and refractive index are independent of the
signal power
• When optical power levels gets fairly high, the fiber becomes a nonlinear mediumLoss and refractive index depend on the optical
power
© 2001, Cisco Systems, Inc. All rights reserved. 38© 2001, Cisco Systems, Inc. All rights reserved. 38© 2001, Cisco Systems, Inc. All rights reserved. 38
Inte
nsi
ty
Time
Slow Phase Velocity
Fast PhaseVelocity
Optical Pulsen = n0 + N2
Index of Refraction
NonlinearCoefficient
Light Intensity
Optical Fiber’s Nonlinear Index
• Intensity of an optical pulse modulates the index of refraction
• Nonlinearity scales as (channel power)2
© 2001, Cisco Systems, Inc. All rights reserved. 39© 2001, Cisco Systems, Inc. All rights reserved. 39© 2001, Cisco Systems, Inc. All rights reserved. 39
• A single channel’s pulses interact as they travel
Interference
Multiple channels interact as they travel
Interference
Effects of Nonlinearity
© 2001, Cisco Systems, Inc. All rights reserved. 40© 2001, Cisco Systems, Inc. All rights reserved. 40© 2001, Cisco Systems, Inc. All rights reserved. 40
FWM
Raman
Types of Nonlinearities
• Nonlinear index
Four-wave mixing
Self-phase modulation
Cross-phase modulation
• Stimulated scattering
Raman
Brillouin
© 2001, Cisco Systems, Inc. All rights reserved. 41© 2001, Cisco Systems, Inc. All rights reserved. 41© 2001, Cisco Systems, Inc. All rights reserved. 41
Out of Fiber
1 221-2 22-11 2
Into Fiber
Four-Wave Mixing
• Channels beat against each other to form intermodulation products
• Creates in-band crosstalk that can not be filtered (optically or electrically)
© 2001, Cisco Systems, Inc. All rights reserved. 42© 2001, Cisco Systems, Inc. All rights reserved. 42© 2001, Cisco Systems, Inc. All rights reserved. 42
Wavelength (nm)
-5
-10
-15
-20
-25
-30
-35
-40
1542 1543 1544 1545 1546 1547 1548
Input Power = 3 mw/ch
Po
wer
(d
Bm
)
Output Spectrum after 25 km of Dispersion Shifted Fiber
FWM Example
• FWM effects increase geometrically with:
Number of channels
Spacing of channels
Optical power level
© 2001, Cisco Systems, Inc. All rights reserved. 43© 2001, Cisco Systems, Inc. All rights reserved. 43© 2001, Cisco Systems, Inc. All rights reserved. 43
Channel Spacing (nm)
FW
M E
ffic
ien
cy (
dB
)
0.0 0.5 1.0 1.5 2.0 2.5
-50
-30
-10
0
-20
-40
D=0
D=17
D=2
D=0.2
Dispersion Washes Out FWM Effects
FWM and Dispersion
© 2001, Cisco Systems, Inc. All rights reserved. 44© 2001, Cisco Systems, Inc. All rights reserved. 44© 2001, Cisco Systems, Inc. All rights reserved. 44
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 45© 2001, Cisco Systems, Inc. All rights reserved. 45© 2001, Cisco Systems, Inc. All rights reserved. 45
• SMF (standard, 1310 nm optimized, G.652)
Most widely deployed so far, introduced in 1986, cheapest
• DSF (Dispersion Shifted, G.653)
Intended for single channel operation at 1550 nm
• NZDSF (Non-Zero Dispersion Shifted, G.655)– LS
For WDM operation in the 1550 nm region only
– TrueWave, FreeLight, LEAF, TeraLight…
Latest generation fibers developed in mid 90’s
For better performance with high capacity DWDM systems
– MetroCor, WideLight…
– Low PMD ULH fibers
Types of Single-Mode Fiber
© 2001, Cisco Systems, Inc. All rights reserved. 46© 2001, Cisco Systems, Inc. All rights reserved. 46© 2001, Cisco Systems, Inc. All rights reserved. 46
Fiber Dispersion Characteristics
Normal fiberNon-dispersion shifted fiber (NDSF) G.652 >90% of deployed plant
DSF G.653NZDSF G.655
-20
-15
-10
-5
0
5
10
15
20
25
1350 1370 1390 1410 1430 1450 1470 1490 1510 1530 1550 1570 1590 1610 1630 1650
DS NZDS+ NZDS- SMF
Dis
per
sio
n (
in p
s/n
m-
km)
Wavelength (in nm)
© 2001, Cisco Systems, Inc. All rights reserved. 47© 2001, Cisco Systems, Inc. All rights reserved. 47© 2001, Cisco Systems, Inc. All rights reserved. 47
1530 1540 1550 1560
+2
+4
- 2
- 4 Corning LS
DSF
Dis
pers
ion
(ps/
nm -
km) Lucent
TrueWave / Balanced +
LucentTrueWave / Balanced -
Dispersion Shifted Fibers
Pirelli FreeLight
Corning LEAF
Dis
per
sio
n
Wavelength (in nm)
Alcatel TeraLight
© 2001, Cisco Systems, Inc. All rights reserved. 48© 2001, Cisco Systems, Inc. All rights reserved. 48© 2001, Cisco Systems, Inc. All rights reserved. 48
Optimized for 1310 nm operation
Fiber ParameterFiber Parameter Expected ValueExpected Value
Attenuation at 1310/1550 nm (standard quality) 0.35 / 0.22 dB/km
Cut-Off Wavelength <1260 nm
Mode Field Diameter (@1310 nm) 9.2 m
Numerical Aperture 0.14
Zero Dispersion Wavelength 1313 nm
Zero Dispersion Slope <0.092 ps/(nm2-km)
PMD Link Value <0.1 ps/km.5
Core-to-Cladding Eccentricity <0.5 m
Designed for high bitrate TDMat 1310 nm
Standard Single-Mode Fiber (Corning SMF-28)
© 2001, Cisco Systems, Inc. All rights reserved. 49© 2001, Cisco Systems, Inc. All rights reserved. 49© 2001, Cisco Systems, Inc. All rights reserved. 49
Optimized for 1550 nm operation
Fiber ParameterFiber Parameter Expected ValueExpected Value
Attenuation at 1550 nm 0.25 dB/km
Cut-Off Wavelength <1260 nm
Mode Field Diameter (@ 1550 nm) 8.1 m
Numerical Aperture 0.17
Zero Dispersion Wavelength 1550 nm
Zero Dispersion Slope <0.085 ps/(nm2-km)
PMD Link Value <0.1 ps/km.5
Core-to-Cladding Eccentricity <1.0 m
Designed for high bitrate TDMat 1550 nm
60% less lossthan 1310 nm
Dispersion Shifted Fiber(Corning DSF)
© 2001, Cisco Systems, Inc. All rights reserved. 50© 2001, Cisco Systems, Inc. All rights reserved. 50© 2001, Cisco Systems, Inc. All rights reserved. 50
Optimized for WDM in 1550 nm window
Fiber ParameterFiber Parameter Expected ValueExpected Value
Attenuation at 1550 nm 0.25 dB/km
Cut-Off Wavelength <1260 nm
Mode Field Diameter (@1550 nm) 8.1 m
Numerical Aperture 0.16
Total Dispersion -3.5 to -0.1 ps/(nm2-km)
Dispersion Range 1530-1560 nm
PMD Link Value <0.08 ps/km.5
Core-to-Cladding Eccentricity <0.8 m
Designed for WDMin 1550 window
Non-Zero Dispersion Shifted Fiber(Corning SMF/LS)
© 2001, Cisco Systems, Inc. All rights reserved. 51© 2001, Cisco Systems, Inc. All rights reserved. 51© 2001, Cisco Systems, Inc. All rights reserved. 51
Optimized for DWDM in C-Band & L-Band
Fiber ParameterFiber Parameter Expected ValueExpected Value
Attenuation at 1550 nm 0.25 dB/km
Attenuation at 1625 nm 0.25 dB/km
Mode Field Diameter (@ 1550 nm) 9.6 m
Numerical Aperture 0.16
Total Dispersion (1530-1565 nm) 2.0 to 6.0 ps/(nm2-km)
Total Dispersion (1565-1625 nm) 4.5 to 11.2 ps/(nm2-km)
PMD Link Value <0.04 ps/km.5
Core-to-Cladding Eccentricity <0.5 mDesigned for DWDM
in C & L bands
Large Aeff for highpower operation
Next Generation Fiber(Corning LEAF)
© 2001, Cisco Systems, Inc. All rights reserved. 52© 2001, Cisco Systems, Inc. All rights reserved. 52© 2001, Cisco Systems, Inc. All rights reserved. 52
Attenuation @ 1310nm (dB/km) <=0.34-0.39
Attenuation @ 1385nm (dB/km) <=0.31
Attenuation @ 1550nm (dB/km) <=0.19-0.23
Attenuation @ water peak 1383 +/- 3nm <=0.31 dB/km
Attenuation vs Wavelength: 1285-1330nm Max difference 0.05 db/km (Ref. 1310nm)
Attenuation vs Wavelength: 1525-1575nm Max difference 0.05 db/km (Ref. 1550nm)
Mode Field Diameter @1310nm 9.2 +/- 0.4μm
Mode Field Diameter @1550nm 10.5 +/- 1.0μm
Zero Dispersion Wavelength 1300nm<= D >= 1322nm
Dispersion slope at 1550nm S0 <= 0.092 ps/km*nm2
PMD Link Value (concatenated fibers) <= 0.1 ps/√km
PMD Individual Fiber <= 0.05 ps/√km (typical)
Optimized for CWDM Transmission
Low attenuation in traditional
Water Peak area
Extended Band Fibers
Sample products:
OFS (Formerly Lucent) Allwave
Corning SMF-28e
Alcatel 6901
© 2001, Cisco Systems, Inc. All rights reserved. 53© 2001, Cisco Systems, Inc. All rights reserved. 53© 2001, Cisco Systems, Inc. All rights reserved. 53
The primary Difference is in the Chromatic Dispersion Characteristics
Different Solutions forDifferent Fiber Types
SMF
(G.652)
•Good for TDM at 1310 nm
•OK for TDM at 1550
•OK for DWDM (With Dispersion Mgmt)
DSF
(G.653)
•OK for TDM at 1310 nm
•Good for TDM at 1550 nm
•Bad for DWDM (C-Band)
NZDSF
(G.655)
•OK for TDM at 1310 nm
•Good for TDM at 1550 nm
•Good for DWDM (C + L Bands)
Extended Band
(G.652.C)
(suppressed attenuation in the traditional water peak region)
•Good for TDM at 1310 nm
•OK for TDM at 1550 nm
•OK for DWDM (With Dispersion Mgmt
•Good for CWDM (>8 wavelengths)
© 2001, Cisco Systems, Inc. All rights reserved. 54© 2001, Cisco Systems, Inc. All rights reserved. 54© 2001, Cisco Systems, Inc. All rights reserved. 54
Agenda
• Introduction
• Optical propagation in Fibers
• Attenuation & Dispersion
• Non Linearity
• SM Optical Fiber Types
• Summary
© 2001, Cisco Systems, Inc. All rights reserved. 55© 2001, Cisco Systems, Inc. All rights reserved. 55© 2001, Cisco Systems, Inc. All rights reserved. 55
The 3 “R”s of Optical Networking
A Light Pulse Propagating in a Fiber Experiences 3 Type of Degradations:
Loss of EnergyLoss of Energy
Loss of Timing (Jitter)(From Various Sources)Loss of Timing (Jitter)(From Various Sources) t
ts Optimum Sampling Time
tts Optimum Sampling Time
Phase Variation
Shape DistortionShape Distortion
Pulse as It Enters the Fiber Pulse as It Exits the Fiber
© 2001, Cisco Systems, Inc. All rights reserved. 56© 2001, Cisco Systems, Inc. All rights reserved. 56© 2001, Cisco Systems, Inc. All rights reserved. 56
Re-ShapeRe-Shape DCUDCU
The 3 “R”s of Optical Networking (Cont.)The Options to Recover the Signal from Attenuation/Dispersion/Jitter Degradation Are:
Pulse as It Enters the Fiber Pulse as It Exits the Fiber
Re-Gen to Boost the PowerRe-Gen to Boost the Power
tts Optimum Sampling Time
tts Optimum Sampling Time
Phase Variation
Re-TimeRe-TimeO-E-O
Re-gen, Re-shape andRemove Optical Noise
tts Optimum Sampling Time
Phase Re-Alignment*
*Simplification
57© 1999, Cisco Systems, Inc. F0_5585_c2