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Spatially Multiplexed Transmission in Multicore Fibers
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S. Mumtaz and Govind P. Agrawal, Institute of Optics, University of Rochester
R. J. Essiambre, Alcatel-Lucent Bell Labs
Spatially Multiplexed Transmission in Multicore Fibers:
Role of Core Coupling on System Performance
1 | FIO12 | Oct 2012
Optical fiber communication systems
Data traffic has been growing exponentially every year.
2 | FIO12 | Oct 2012
[Essiambre and Tkach: Capacity Trends and Limits of Optical Communication Networks, IEEE proceedings, May 2012]
North American Internet traffic. Single channel systems (circles) WDM systems (squares).
System capacity must follow this growth to avoid a capacity crunch
Capacity increase through multiplexing
WDM: wavelength-division multiplexing
PDM: Polarization-division multiplexing
I/Q modulation (QPSK, 16-QAM)
?? SDM: Space-division multiplexing
3 | FIO12 | Oct 2012
[Essiambre and Tkach: Capacity Trends and Limits of Optical Communication Networks, IEEE proceedings, May 2012]
Single channel systems (circles) WDM systems (squares).
Space Division multiplexing
Multicore fiber
…LP01 LP11a LP11b LP02 LP21a LP21b
Multimode fiber
QPSK
QPSK
•Tx
•Tx
•DSP
Space division multiplexing
Performance of an SDM system limited by nonlinearities
Important to understand the nonlinear propagation
4 | FIO12 | Oct 2012
SDM increases capacity with reduced energy consumption
Digital signal processing
Nonlinear propagation in multicore fiber
Both linear and nonlinear couplings occur among the fields propagating in different fiber cores.
Electric field
Propagation equation
5 | FIO12 | Oct 2012
Linear core coupling
y
x
y
x
Coupling is a function of the distance among fiber cores.
Coupling length
Linear coupling coefficient
Core a Core b
Distance between cores
r
6 | FIO12 | Oct 2012
Nonlinear core coupling
Nonlinear coupling coefficients
: intra-core nonlinear effects (SPM)
: inter-core XPM effects
Inter-core nonlinear effects decrease exponentially with increasing distance between cores.
XPM nonlinear effects are several orders of magnitude smaller than intra-core SPM effects.
They can be neglected in most cases.
7 | FIO12 | Oct 2012
SPM: self-phase modulationXPM: cross-phase modulation
Nonlinear propagation equation for multicore fibers
We used this set of equations for numerical modeling.
We considered multicore fibers with up to 19 cores.
Two orthogonally polarized 112-Gb/s channel launched into each core using PDM.
Linear core coupling included through qmp parameters.
All intra-core nonlinear effects included through .
Birefringence and dispersion effects fully included.
8 | FIO12 | Oct 2012
Numerical simulations and Results
9 | FIO12 | Oct 2012
Simulation details
Two 28 Gbaud PDM-QPSK symbol streams launched into each core.
Propagation through fiber by the split-step Fourier method.
Least square equalizer (LSE): non-adaptive, based on training sequence.
Actual bit error rate (BER) calculated using 20,000 bits during simulation.
10 | FIO12 | Oct 2012
100km MCF
…
1000km
QPSK
QPSK RC filter
RC filter
MUX DEMUX
EDFA
•LSE
EqualizerDemod.
…0110101
BER0111010
Performance as a function of coupling length
Lc = 100m Lc = 1kmLc = 1m Lc = 10km
11 | FIO12 | Oct 2012
OSNR penalties Vs Injected power
1000km Trans. Lc=100m
Comparison between 1-core and 3-core fibers
Linear coupling reduces the impact of SPM effects better performance
12 | FIO12 | Oct 2012
Performance in function of the core number
1-Core 2-Core 3-Core 5-Core 6-Core4-Core 7-Core
13 | FIO12 | Oct 2012
Nonlinear noise
NL noise after 100 km for and input power of 12 dBm
1-core 3-core
14 | FIO12 | Oct 2012
Conclusions
SDM may be an important new technology in near future.SDM will make use of nulticore or multimode fibers.
We have derived a nonlinear propagation equation for multicore fibers.
We used it to study the impact of linear coupling on the performance PDM-QPSK systems.
Most experiments keep cores far apart to reduce linear coupling.
Our results show that strong coupling actually helps to improve system performance if DSP is used at the receiver.
More cores can be packed together when core spacing is reduced.
15 | FIO12 | Oct 2012
Questions ?
16 | FIO12 | Oct 2012