lecture: 10 new trends in optical networks
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Lecture: 10 New Trends in Optical Networks. Ajmal Muhammad, Robert Forchheimer Information Coding Group ISY Department. Outline. Challenges Multiplexing Techniques Routes to Longer Reach Distributed amplification Hollow core f ibers Routes to Higher Transmission Capacity - PowerPoint PPT PresentationTRANSCRIPT
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Lecture: 10 New Trends in Optical Networks
Ajmal Muhammad, Robert ForchheimerInformation Coding Group
ISY Department
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Outline
Challenges Multiplexing Techniques Routes to Longer Reach
Distributed amplification
Hollow core fibers
Routes to Higher Transmission Capacity
Space division multiplexing (SDM)
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The Challenge
Traffic grows exponentially at approximately 40% per year Optical system capacity growth has been approximately 20%
per year In less than 10 years, current approaches to keep up will not
be sufficient
Main physical barriers:
Channel capacity (Shannon) + available optical bandwidthTransmission fiber nonlinearities (Kerr)
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Capacity Limits
Signal launch power [dBm]
Ref:IEEE, vol.100, No.5May 2012
Noise
Fiber nonlinearity
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… Moore’s Law for Ever… ?
Courtesy ofPer O. Andersson
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Multiplexing Techniques
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100G Fiber Optic Transmission :: DP-QPSK
DP-QPSK: Dual Polarization Quadrature Phase Shift Keying
DP-QPSK is a digital modulation technique which uses two orthogonal polarization of a laser beam, with QPSK digital modulation on each polarization
QPSK can transmit 2 bits of data per symbol rate, DP-QPSK doubles that capacity
For 100Gbps, DP-QPSK needs 25G to 28G symbols per second. Electronics have to work at 25 to 28 GHz
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BPSK- Binary Phase Shift Keying
BPSK transmits 1 bit of data per symbol rate, either 1 or 0
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QPSK- Quadrature Phase Shift Keying
Use quadrature concept, i.e., both sine and cosine waves to represent digital data
Two BPSK used in parallel
Cosine wave
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DP-QPSK in Fiber Optic Transmission
DP-QPSK transmits 4-bits of data per symbol rate
Laser source is linearly polarized
Cosine wave
Sine wave
Vertical polarized
Horizontal polarized
Assume horizontal polarized laser source
Data stream
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Outline
Challenges Multiplexing Techniques Routes to Longer Reach
Distributed Amplification
Hollow Core Fibers
Routes to Higher Transmission Capacity
Space Division Multiplexing (SDM)
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Routes to Longer Reach
Deal with low SNR Advance FEC More power efficient modulations format
Maintain a high SNR Ultralow noise amplifiers Distributed amplification
Deal with more nonlinearities Digital back-propagation
Reduce the nonlinearity Install new large-area or hollow-core fibers
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Distributed Amplification
Raman pump power= 700 mWEDFA gain=20 dB, NF=3 dB
High SNR but will excite nonlinearities
SNR degrades due to shot noiseno issues of nonlinearity
Ideal distributed amplification (constant average signal power in the entire span)
PSA: Phase sensitive amplifierwith noise free gain medium
Courtesy:Peter Andrekson, Chalmers Uni.
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New Telecom Window at 2000 nmHollow-Core Fibers
Guiding by Photonic Bandgap Effect
Key potential attributes:Ultra-low loss predicted near 2000nm (not single mode operation) (~ 0.05 dB/km predicted opt. Express, Vol.13, page 236, 2005)Very wide operating wavelength range (700 nm)Very small non-linearity: 0.001 x standard SMFLowest possible latencyDistributed Raman amplification may be challenging, however.
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Hollow-Core Fiber :: SNR
Comparison of ultralow loss (0.05 dB/km) hollow-core fiber and EDFAIn conventional fiber (0.2 dB/km)
Courtesy:Peter Andrekson, Chalmers Uni.
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Hollow-Core Fiber :: SNR
Comparison of ultralow loss (0.05 dB/km) hollow-core fiber, EDFA and distributed Raman amplification in conventional fiber (0.2 dB/km)
Span loss: 20 dB Backward Raman (100 km)Bidirectional Raman (100 km) (10 + 10 dB)
A low-loss hollow core fiber with EDFA spacing of 400 km performs similar to backward pumped Raman system with 100 km pump spacing
Courtesy:Peter Andrekson, Chalmers Uni.
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Spectral Efficiency Impact of Nonlinear Coefficient
+ 2.2 b/s/HZ for each X 10Gamma reduction
Ref: R-J. Essiambre proc. IEEEvol. 100, p. 1035, 2012
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Thulium-Doped Silica Fiber Amplifiers (TDFA)at 1800-2050 nm
• Suitable with low-loss hollow core transmission fiber• Very wide operation range (> 200nm)• Noise figure ~ 5 dB• Laser diode pumping at 1550 nm• 100 mW saturated output signal power
ECOC 2013 Paper Tu.1.A.2
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Outline
Challenges Multiplexing Techniques Routes to Longer Reach
Distributed Amplification
Hollow Core Fibers
Routes to Higher Transmission Capacity
Space Division Multiplexing (SDM)
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Routes to Higher Transmission Capacity
CLB= N * B * log2(1+SNR)
Overall transmission capacity:
Available optical bandwidth (B) New amplifiers Extend low-loss window
X
Spectral efficiency (bit/sec/Hertz) Electronics signal processing Low nonlinearity
X
Number of channels (N) Install new multi-core/multi- mode fibers
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Typical Attenuation Spectrum for Silica Fiber
Only 8-10 % is utilized in C bandWith SE of 10 per polarization a fiber can support well over a Pb/s
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Space Division Multiplexing (SDM)
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Inter-Core Crosstalk (XT)
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Inter-Core Crosstalk (XT)
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From WDM Systems to SDM & WDM Systems
Flexible upgrade:Add transponder in lambda and M
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State of the Art Systems
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