View
217
Download
2
Category
Preview:
Citation preview
UMBC
New Approaches to Modeling Optical Fiber Transmission Systems
Presented by
C. R. MenyukWith
R.M. Mu, D. Wang, T. Yu, and V. S. Grigoryan
University of Maryland Baltimore CountyComputer Science and Electrical Engineering Department
Baltimore, MD 21250
UMBC
New Approaches to Modeling Optical Fiber Transmission Systems
Presented by
V. S. GrigoryanWith
R.M. Mu, D. Wang, T. Yu, and C. R. Menyuk
University of Maryland Baltimore CountyComputer Science and Electrical Engineering Department
Baltimore, MD 21250
UMBC
Professors
Gary Garter Curtis Menyuk
Associates
Vladimir Grigoryan Edem Ibragimov Pranay Sinha
Students
Ronald Holzlöhner Ivan Lima, Jr. Ruomei Mu Yu Sun Ding Wang Tao Yu
Current research group
UMBC
A Decade Ago
System with Electronic Repeaters
• 500 Mb/s looked achievable; 100 Mb/s was achieved
• Only attenuation mattered in fibers
– fibers were a transparent pipe
• Repeaters had limited bandwidth (WDM and upgrading impossible)
– Cost and complexity rose dramatically with data rate
– spacings of 20 km were required
R R R
20 km
UMBC
Today
System with Erbium-doped amplifiers
• 1 Tbit/s looks achievable; 200 Gbits/s achieved
• Wavelength division multiplexing (WDM) is possible
and becoming widely used (200 Gb/s = 80 channels 2.5 Gb/s)
• Fiber dispersion, nonlinearity, and polarization effects all accumulate!
• Fiber impairments set the limits on what is achievable
– nonlinearity is strong and hard to model properly.
50 km or more
UMBC
What formats should be used?
1 1 0 1 0 0 1
Non-return to zero (NRZ)
(close to zero dispersion)
Solitons
(anomalous dispersion)
vs.
11 0 1 00 1
UMBC
Approaches are converging!
Solitons and NRZ resemble each other
– solitons dispersion-managed solitons
– NRZ phase- and amplitude-modulated pulses
01110 01110 01110 01110
UMBC
What formats should be used?Time-division multiplexed (TDM)
1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8
I
t
channels
Wavelength-division multiplexed (WDM)
channels
1 2 3 4 5 6 7 8
I
UMBC
Fiber impairments
Chromatic Dispersion Polarization Effects Nonlinearity ASE noise
Four Horsemen of the Apocalypse
Albrecht Dürer
Four Horsemen of Optical Fiber Transmission
UMBC
Modeling approaches
Multiple scale length methods— for establishing equations
Split-step modeling— often too slow (especially with WDM)
Reduced methods— dealing with many channels, long-term effects, networks
UMBC
Modeling approaches
Monte Carlo— often too slow
Ito’s method— often does not work
Linearization
Randomly varying effects
UMBC
Multiple Scale Lengths methods
Light wavelength1 m
10 m
100 m
1 mm
10 mm
100 mm
1 m
100 m
10 m
1 km
100 km
10 km
1 Mm
10 Mm
100 Mm
Core diameter
Pulsedurations
Polarizationbeat length
Attenuation length
Nonlinearlength
Fiber correlationlength
Dispersionlength
FLAG
trans-Atlantic
Manakov-PMDapproximation
Slowly varyingenvelopeapproximation
Maxwell’s equations
land link
Optical systems have a wide spread in length scales!
Scale lengths in fiber transmission
UMBC
Coupled Nonlinear Schrödinger Equation
Maxwell’s Equations
Coupled Nonlinear Schrödinger Equation
Manakov-PMD Equation
Averaging over the Poincaré sphere
Using the slowly varying envelope approximation
UMBC
Linearization approach
Monte Carlo:
Linearization (with small noise):
signal noise complicated mix
signal noise Gaussian statistics
(nonlinear) (linear)
UMBC
Comparison of theory & experiment
0
1
2
0 10000 20000
Tim
ing
jitte
r (p
s)
Distance (km)
experimentMonte Carlo simulationour approach
UMBC
Average Power Approximation
With N channels, scaling reduces from N 2 to better than N!
Useful for point-to-point systems(Yu, Reimer, and Menyuk; Wang and Menyuk)
Critical for network simulations(Bellcore: R. Wagner, I. Roudas, & colleagues)
target channelcomplete channelaveraged channel
UMBC
With polarizationS
toke
s ve
ctor
distance (km)
simulation simulationtheory
Evolution of the Stokes vector
–0.5
0
0.2
0 10000–0.5
0
0.2
0 10000–0.5
0
0.2
0 10000
S 1 S3
S2
(a)
S 1 S3
S2
(b)
S 1 S3
S2
(c)
realistic dispersion large dispersion
UMBC
Reduced Polarization Model
PDL effects calculated — one year ago
Verification of model effectiveness with chromatic dispersion and
nonlinearity — now
Inclusion of PMD, PDL, and PDG — in one year
UMBC
Experimental Applications
D
LNormal
AnomalousAverage
1.2 nmFilter
AO
Switch60/40 Coupler
Input To Receiver
PC
EDFANormalAnomalous
Dispersion-managed soliton experiments
UMBC
Theory and experimentDynamic Evolution in One Round Trip
Amplitude Margin
0 bit
1 bit
⎫⎬⎭experimental
theoretical
experimental
theoretical
0 30000Amplidute Margin (mV)
Distance (km)0200
–200
0510152025
FWHM (ps) Normal Anomalous2550751003.57.0Distance
UMBC
Normal dispersion solitons:
A
B
0
10
20
0 0.2
D=110D=100D=90D=80D=70D=60
Pul
se e
nerg
y
Average dispersion
— Solitons exist in the normal dispersion regime— These solutions are stable
Inte
nsity
0
Time– 5
5
10000
0
5000
1
0.001
At point B:
Distance
UMBC
World record experiment
20 Gbit/s: BER < 1×10−9@ 20 Mm
20 Gbit/s input 10 Gbit/s Demux output (20 Mm)
experimental
theoretical}
1 Bit 0 Bit
}
0
0.2
0 250T (ps) 0 250
0.8
0
– 0.4
T (ps)
0
300
0 25000
Amplitude Margin (mV)
Z (km)
sliding no sliding
– 100
UMBC
Conclusions
Optical fiber transmission systems are rapidly changing
Good modeling has become critical
Enormous strides have been made
Recommended