This document discusses technologies for improving the capacity of optical transport networks. It outlines how networks have evolved from 10G to 100G+ capacities through increased channel counts and complex modulation formats. Key technologies discussed for further improving capacity include space division multiplexing using multi-core or multi-mode fibers, superchannels that pack optical carriers more densely, and elastic optical networks that flexibly allocate spectrum. The document also discusses optimizing network efficiency through port virtualization and reducing transit traffic loads on routers.

1. High Capacity Optical
Transport Networks
Nisha Menon K
Roll No:16
FISAT
28 July 2014 1

2. Outline
Introduction
Optical network evolution
Technologies that improve
capacity
Technologies to improve
network efficiency
Conclusion
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3. Introduction
• Optical fiber was believed to offer effectively infinite
capacity to support the rapid traffic growth.
• As demand has grown and technology has developed, we
have begun to realize that there is a fundamental limit to
fiber capacity.
• The rapid growth in interactive bandwidth-hungry services
demands ever higher capacity at various stages of the
optical network, lead to a potential capacity exhaust,
termed the capacity crunch.
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4. 28 July 2014 4

5. Optical Network Evolution
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2006
2008
2011
2012
2015-
10G
40 Channels
 SDH / Sonet
/services support
 Ring topology
 Reconfigurable
OADM
 WDM over OTN
40G
80 Channels
 IP over WDM
 Mesh topology
40G/100G
Coherent
 Colorless /
directionless /
contentionless
400G/1T
Superchannel
 Bandwidth on
Demand
 Fully automated
network
 SDH / Sonet
Networks
 Increase capacity
 Point-to-point
 Up to 40 channels
2.5G
CWDM, DWDM

6. Increasing network capacity
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7. Modulation
Previous method
• increasing the speed of simple on-off-keying
(OOK) up to the limitations of available
electronics technology.
Disadvantage
• such electronics equipments are difficult to
manufacture, they are expensive and
thermally sensitive.
• spectrally broadened channels overlap with
neighboring channel
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8. Complex Modulation
spectrally broadened signals are shaped by the
wavelength filters but the crosstalk cannot be
eliminated and it results in degradation of the
modulated information.
complex modulation schemes such as polarization
multiplexed modulation schemes can be used for
high speed transmission.
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9. Modulation Techniques
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9
PM-
16QAM
PM-
8QAM
PM-
QPSK
PM-BPSK
Reach Capacity

10. Multiplexing
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11. Space domain Multiplexing
• Single-mode fiber (SMF) has been the medium for
high capacity data transmission for over three
decades.
• The exponential growth of internet traffic at about 2
dB per annum could exhaust the available capacity of
SMF in the near future.
• Space division multiplexing (SDM) based on
multicore fiber (MCF)or multimode fiber (MMF) can
overcome the barrier - capacity limit of SMF
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12. Space domain Multiplexing
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13. Space domain Multiplexing
Multi-core fibers have several cores embedded in
the fiber cladding.
multi-mode fibers allow the propagation of several
independent modes within a single core.
Multi-mode fibers offer more efficient performance
than multi-core fibers
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14. Superchannels
• A superchannel is an evolution in Dense Wavelength
Division Multiplexing (DWDM)
• Provides higher data rate
• The major difference between superchannel and
conventional WDM is the channel gap.
• channel gap is reduced close to the Nyquist
bandwidth.
• These techniques include uses no guard interval
(NoGI)-OFDM 28 July 2014 14

15. Superchannels
• The frequency gap is removed to have a more tightly
packed channel arrangement.
• Many optical carriers can be packed closely together to
form a superchannel.
• The challenge for superchannel implementations is to
tightly pack the optical sub-carriers while minimizing the
interactions between the carriers.
• By lifting the limit of channel spacing, an optical band
can hold more 100 Gb/s channels.
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16. Superchannels
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17. Elastic Optical Network
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The optical
spectrum
can be
divided up
flexibly.
The
transceiver
s can
generate
elastic
optical
paths
(EOPs)
EON

18. Elastic Optical Network
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Spectral widths of different bit rates relative to the ITU grid

19. Elastic Optical Network
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20. Elastic Optical Network
The development of EON will require
innovations in both hardware and
software.
New components will need to be
developed, and they are often more
complex than their fixed grid
counterparts.
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21. Improve network efficiency
Optimize the interactions between
transport networks and clients such as
routers to maximize bandwidth
utilization in the transport network.
port
virtualization
transit traffic
reduction
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22. Port Virtualization
Traffic flow rate between end-points of
router and network are generally less than
the port rate.
Port virtualization allows multiple flows to be
tagged and sent to the same port.
The flows are then switched in the transport
network to their destinations.
This maximizes the port fill since traffic
bound can be packed into the same port.
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23. Transit Traffic Reduction
In many networks, a significant amount of
traffic enters a router and is simply switched
back into the transport network.
This transit traffic wastes processing and
port resources on the router since the
transport network could deliver the traffic
directly to the proper endpoint thus
reducing traffic load in the router.
This switching function can be handled
directly in the transport network using
MPLS switching.
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24. Conclusion
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Various optical technologies, such as higher
order
modulation, multiplexing schemes,
superchannels and EONs will help transport
networks provide the needed capacity for the
near future.

25. REFERENCES
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1. Tiejun Xia, Steven Gringeri, Masahito Tomizawa,” High-capacity
optical transport networks.” IEEE Communications Magazine, 2012
2. M. Jinno et al., “Spectrum-Efficient and Scalable Elastic Optical Path
Network: Architecture, Benefits, and Enabling Technologies,” IEEE
Commun. Mag., vol. 47, no. 11, 2009, pp. 66–73.
3.S. Gringeri et al., “Technical Considerations for Supporting Data
Rates Beyond 100 Gb/s,” IEEE Commun. Mag.,vol. 50, no. 2, 2012, pp.
S21–S30.