Flexible optical networking with spectral or spatial super-channels

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“Networks and Optical Communications” research group – NOC
Flexible optical networking with
spectral or spatial super-channels
Presented by: Dr. Ioannis Tomkos (itom@ait.gr)
Co-Authors: P. S. Khodashenas, J.M. Rivas-Moscoso, D. Klonidis,
D. M. Marom, G. Thouénon, A. Ellis, D. Hillerkuss, J. Zhao, D. Siracusa, F. Jiménez, N. Psaila
IV International Workshop on trends in optical technologies
Campinas, Sao Paulo, Brazil – May 27th & 28th 2015

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AIT’s role in the optical network evolution
Scope:
Research on architectures,
protocols, algorithms, transmission
systems and technologies for high-
speed telecommunication systems
applicable in backbone networks,
access networks and
interconnection of servers (DCNs)
and processors (HPC)
Scientific Results (2003-2015):
 Over 150 publications in archival
scientific journals and magazines
(including best paper awards and
highly cited papers)
 Over 400 publications in major
international conferences and
workshops
 Participated in over 25 research
projects: 5 projects within FP6 and 12
projects within FP7 and 1 H2020
 Led 8 EU research projects as
Technical Manager of the entire
consortium: 2 FP6 and 6 FP7

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FOX-C & INSPACE goals & status

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Presentation overview
 Evolution of Optical Communication Systems & Networks
 Spectrally flexible optical networking
• The activities of EU project FOX-C
Spectrally flexible super-channel transceivers
Nodes for all-optical add/drop of sub-channels
Networking studies to demonstrate the benefits of FOX-C solution
 Spatially flexible optical networking
• The activities of EU project INSPACE
Nodes for independent or joint switching of SDM super-channels
Networking studies to demonstrate the benefits of INSPACE solution
Development of an SDN-based control plane for SDM-based networks
 Summary & Conclusions

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Historical evolution of optical communications system
capacity and bit-rate  distance product
0.00001
0.0001
0.001
0.01
0.1
1
10
100
1000
0
1
10
100
1,000
10,000
100,000
1,000,000
10,000,000
1983 1987 1991 1995 1999 2003 2007 2011 2015
TotalFibreCapacity(Tbit/s)
BitRateDistanceProduct
(Gbit/s.Mm)
Year Published
WDM
TDM
OFDM/CoWDM
Coherent Detection
Spatial Multiplexing
Total capacity
• Traffic increases at a rate of 20-40%
per year, while capacity of deployed
SMF-based networks approaches
fundamental limits…
• New traffic characteristics lead to
new network requirements:
• Rapidly changing traffic patterns
• High peak-to-average traffic ratio
• Ultra-large data-chunks transfers
• Asymmetric traffic between nodes
• Increasing high-QoS traffic
• Fiber bandwidth was consider for many years as an abundant resource, but we have
almost utilized to the maximum extend the EDFA amplifiers bandwidth (i.e. while
approaching the fundamental SE limits)
• A short-term solution is to utilize the available fiber spectrum more efficiently/wisely as is
the case in wireless networks where bandwidth was always a limited/scarce resource -
(Spectrally flexible systems/networks)
• A forward-looking option is to deploy new fibers (or use strands of available SMF fibers)
that can support multi-cores or/and multi-modes per core (SDM/Spatially-flexible systems/
networks)
Data from Prof. Andrew Ellis

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Spectrally flexible optical networking
The activities of EU project FOX-C

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Main building blocks to enable spectrally
flexible optical networking
Flexible Optical Networking
Flexible
transponders
Strong research
field over last 5
years
Network planning
and control plane
issues
Networking
studies have proved
the benefits of flexible
networking
Flexible switching
nodes
Limited number of
demos showing
mostly “drop”
function
Ioannis Tomkos et. al., “A Tutorial on the Flexible Optical Networking Paradigm: State-of-the-Art, Trends, and
Research Challenges”, Invited paper at the “Proceedings of the IEEE” (Impact Factor: 6.91) 05/2014

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Super-channels when
combined with
mini/flexi-grid offer
spectrum savings!
Super-channels can enable a path to higher bit-rates
and support flexible optical networking

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How to add/drop sub-channels out of super-channels
in a three-level spectrally flexible optical node?
 Level 3  Express through or add/drop of Tb super-channels (via conventional WSSs)
 Level 2  Processing (add/drop/erase) of super-channel contents
• Offers grooming capabilities in the optical domain! – How to do it?
 Level 1  Generation/Detection and regeneration of sub-channel contents
• Electronic processing

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The FOX-C project consortium
 Optronics Technologies S.A
• Mr. George Papastergiou (Coordinator)
• Dr. Marianna Angelou
• Dr. Thanasis Theocharidis
 Finisar Israel LTD • Dr. Shalva Ben-Ezra
 W-Onesys S.L. • Dr. Jordi Ferré Ferran (WP6 Leader)
 Orange Labs – FT
• Dr. Erwan Pincemin (WP5 Leader)
• Dr. Christophe Betoule
• Dr. Gilles Thouenon
 Athens Information Technology
 The Hebrew University of
Jerusalem
 Eidgenössische Technische
Hochschule Zürich
 University College Cork
 Aston University
• Dr. Ioannis Tomkos (Technical Mngr)
• Dr. Dimitrios Klonidis (WP2 Leader)
• Dr. Pouria S. Khodashenas
• Dr. José M. Rivas-Moscoso
• Prof. Dan Marom (WP4 Leader)
• Prof. Juerg Leuthold
• Dr. David Hillerkuss (WP3 Leader)
• Mr. Benedikt Bäuerle
• Dr. Jian Zhao
• Prof. Andrew Ellis
• Dr. Stylianos Sygletos
• Dr. Simon Fabbri
• Dr. Andreas Perentos

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Spectral super-channel multiplexing schemes in FOX-C
QAM  qN-WDM
super-channels
Conventional WDM
e(f)OFDM  MB-e(f)OFDM
AO-OFDM
NFDM  qN-WDM
super-channels
(q)N-WDM

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FOX-C system test-bed
 Testbed assembled at FT/Orange Labs premises:

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Experimental characterisation of flexible transceivers
 BER vs SNR
ROF: Roll-off factor
NWDM e-fOFDM
Nyquist FDM MB-eOFDM

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The FOX-C node architecture for N-WDM super-channels
Enables all-optical add/drop of sub-channels out of
non-spectrally-overlapping (q)N-WDM super-channels

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FOX-C’s novel ultra-fine spectral resolution filters
 Based on a state-of-the-art phased array
implemented with a high resolution AWG
 Achieved record resolution and addressability
values
• Record resolution: <1GHz
• Record addressability (spectral granularity): 200MHz
* Roy Rudnick, et. al., “One GHz Resolution Arrayed Waveguide Grating Filter with LCoS Phase Compensation”,
in proc. OFC/NFOEC 2014, paper Th3F.7

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The EU project FOX-C node architecture
for AO-OFDM super-channels
Enables all-optical add/drop of sub-channels out of
spectrally-overlapping OFDM super-channels

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Novel all optical ROADM for OFDM signals
* S. Sygletos et al., “A Novel Architecture for All-Optical Add-Drop Multiplexing of
OFDM Signals”, in proc. ECOC 2014, Sept. 2014.

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 Results demonstrate that, in the case of qN-WDM, there is negligible reach
penalty when the FOX-C nodes are considered along the signal path
Transmission studies with cascaded FOADMs
N-WDM qN-WDM
f = 25 GHz f = 25.9 GHz f = 26.8 GHz

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Nyquist WDM super-channel composed of Nyquist-
shaped sub-channels: Do we need “Gridless”?
12.5GHz
187.5 GHz
200 GHz
134 GHz
150 GHz
(*) P. Sayyad Khodashenas et al., “Evaluating the Optimum Filter Resolution and Sub-Channel Spectrum Granularity
for Flexible Super-Channels”, OFC 2015, paper W1I.5.
 Sub-band allocation options according to frequency slot width
• ITU-T 12.5 GHz grid
• Gridless
The super-channel bandwidth depends on the chosen sub-channel granularity.
Two examples are shown above:
 Super-channels allocated on ITU-T 12.5 GHz grid (including GB = 12.5GHz).
 “Gridless” operation – Does it offers significant advantages?
* P. S. Khodashenas, J. M. Rivas-Moscoso, D. Klonidis, D. M. Marom and I. Tomkos, “Evaluating the Optimum Filter
Resolution and Sub-Channel Spectrum Granularity for Flexible Super-Channels”, in proc. OFC/NFOEC 2015, paper W1I.5.

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Networking studies to derive specifications
 Optimized sub-channel slot size from a network-level perspective:
• Flex-grid qN-WDM systems with frequency-slot size of 12.5 GHz and coarse
switching in GÉANT2 pan-EU network topology.
• Optimum sub-channel grid was investigated:
Best
compromise
* P. S. Khodashenas, J. M. Rivas-Moscoso, D. Klonidis, D. M. Marom and I. Tomkos, “Evaluating the Optimum Filter
Resolution and Sub-Channel Spectrum Granularity for Flexible Super-Channels”, in proc. OFC/NFOEC 2015, paper W1I.5.

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Techno-economic studies – FOX-C vs legacy solutions
 Is the FOX-C solution worth considering for real deployments?
• Are the resulting network-wide capital expenditure savings significant
enough to justify a FOX-C-like solution?
• Inputs for the analysis:
Network topology, traffic matrix (FT/Orange national network)
Cost model *
It requires also a novel routing, modulation level and spectrum allocation algorithm that
matches the FOX-C networks solution characteristics (AOTG-RMLSA) **
• Outputs from the analysis:
Utilized resources (such as transceivers, nodes and spectrum) to guarantee blocking-free
connection establishment, while minimizing the spectral occupancy.
– Benchmarks:
» SLR over fixed-grid (widely deployed network solution)
» MLR over flexi-grid (common understanding of flexible optical networks)
* Ref: J. Rivas-Moscoso, S. Ben-Ezra, P. Khodashenas, D. Marom, D. Klonidis, P. Zakynthinos & I. Tomkos “Cost & Power
Consumption Model for Super-channel Transmission with All-Optical Sub-channel Add/Drop Capability” ,(Invited) ICTON 2015.
** Ref: P. S. Khodashenas, J. M. Rivas-Moscoso, D. Klonidis, G. Thouénon, C. Betoule and I. Tomkos, “Impairment-aware
Resource Allocation over Flexi-grid Network with All-Optical Add/Drop Capability”, submitted to ECOC 2015.

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FOX-C cost & power consumption model
 Cost and power consumption model:
• Benchmark: Single carrier 100G transceiver
• Tb/s super-channel transceiver based on:
 Electrical multiplexing schemes:
– NFDM, NWDM with electrical filtering, MB-e(f)OFDM
 Optical multiplexing schemes:
– (q)NWDM with optical filtering
– Conventional AO-OFDM with DSP
• ROADM implementations:
Supporting non-overlapping sub-channel A/D
Supporting overlapping and non-overlapping sub-channel A/D
• Sensitivity analysis
J. Rivas-Moscoso, S. Ben-Ezra, P. Khodashenas, D. Marom, D. Klonidis, P. Zakynthinos & I. Tomkos “Cost & Power
Consumption Model for Super-channel Transmission with All-Optical Sub-channel Add/Drop Capability” ,(Invited) ICTON 2015.

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Benchmark: 100G transceiver
 SLR/MLR 100G transceiver:
DSPchip
Datain/out
/2
Q I
/2
DP IQ Mod
Q I
DAC
DAC
DAC
DAC
ADC
ADC
ADC
ADC
ECL
LO
Drivers
RF LP filters
RF LP filters (optional)
PBS
PBS
Sx
Sy
LOy
LOx
Ix
Qx
Iy
Qy
Balanced
photodetector
DFB
Intensity
modulatorsplitter
50/50
211
-1PRBS
(3.5or7)
Gb/s
BPG
4:1
MUX
QPSK↔16QAM
to
Balanced
photodetector
DFB
Intensity
modulatorsplitter
50/50
211
-1PRBS
(3.5or7)
Gb/s
BPG
4:1
MUX
QPSK↔16QAM
to
Balanced
photodetector
DFB
Intensity
modulatorsplitter
50/50
211
-1PRBS
(3.5or7)
Gb/s
BPG
4:1
MUX
QPSK↔16QAM
to
Balanced
photodetector
DFB
Intensity
modulatorsplitter
50/50
211
-1PRBS
(3.5or7)
Gb/s
BPG
4:1
MUX
QPSK↔16QAM
to
90º Hybrid
TIA
DP coherent receiver

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Benchmark: 100G transceiver
 SLR/MLR transceiver:
(*) Relative to cost of 100G transceiver.
(**) Relative to cost of 10G transceiver
SLR/MLR TRx
Component
Relative Unit
cost (*)
Power (W)
[max]
#
Relative
cost (*)
Relative
cost (**)
Total
power (W)
DSP Chip 0.36 38.5 1 0.36 1.9 38.5
PM IQ Mod 0.22 0.0 1 0.22 1.1 0.0
Laser (Tx & Rx LO) 0.05 1.5 2 0.11 0.3 3.0
4-Port Modulator Driver 0.07 6.0 1 0.07 0.4 6.0
RF LP filter 0.004 0.0 8 0.03 0.0 0.0
DP Coherent Receiver 0.22 1.5 1 0.22 1.1 1.5
1.00 5.2 49.0
Actual cost (not
price!) in the range
of 25-30K!!!

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Cost/power comparison of spectrally
flexible super-channel transceivers
 Cost/power per sub-channel for super-channel transceivers
capable of generating different numbers of sub-channels:
(*) Relative to cost of 100G transceiver.
Electrical
multiplexing
schemes
NWDM with
optical filters
AO-OFDM
Number of
sub-
channels
Cost (*) P (W) Cost (*) P (W) Cost (*) P (W)
4 0.80 50.8 0.98 52.8 0.79 50.8
6 0.76 49.2 0.84 50.5 0.75 49.2
8 0.74 48.4 0.77 49.4 0.73 48.4
10 0.73 47.9 0.73 48.7 0.72 47.9
12 0.72 47.6 0.71 48.3 0.71 47.6

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Non-overlapping sub-channel A/D capable OXC node
 Node with D=3 degrees:
W Sch Tx
NRxSRx
N Sch Tx
S Sch TxW Rx
Switches with
D-1 switching
states
Sbch Tx
Sbch Tx
Drop Add
Sbch
Tx
W
S
N
A/D
+22
+10
+22+10
+22+10
-5
-5
-5 -5
-5 -5
+8 +14 -0.5 -0.5-15
-22 dBm/50 GHz
-2 dBm/C-band
0
20
-5 / 15
-5
-10 / 10
0 / 20
0
-15
-10
0
-5
Numbers in
black: dB
Numbers in
green: dBm
A/D
A/D
Number of sub-channel
add/drop cards M = 3
A/D card
based on
HSR filter in
R. Rudnick,
ECOC 2014,
PD.4.1

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Non-overlapping sub-channel A/D capable OXC node
 Node with D=3 degrees and M = 3 A/D cards:
(*) Cost relative to 100G transceiver cost
(**) Cost relative to 10G transceiver cost
(***) Cost relative to cost of an OXC node of degree D without sub-channel A/D capability
(^) Due to sharing of management between amplification modules. Factor is applied to number of amplifiers minus 1
F-OXC with degree D and M HSR filters
Component
Relative
unit cost (*)
Power
(W)
#
Relative
cost (*)
Relative
cost (**)
Relative
cost (***)
Power
reduction
factor (^)
Total Power
(W)
1×20 WSS 0.54 4.00 6 3.24 16.92 0.86 24.0
1x1 HSR filter 0.54 4.00 3 1.62 8.46 0.43 12.0
Variable gain dual-stage
amplifier
0.18 12.00 6 1.08 5.64 0.29 0.10 66.0
1x(D-1) switch 0.01 0.00 6 0.09 0.45 0.02 0.0
6.02 31.47 1.59 102.0
Note: A similar investigation was performed for nodes suitable for overlapping sub-channels

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Overlapping sub-channel A/D capable OXC node
 Node with D=3 and M=3 for an A/D card implementation based on N gates
F-OXC with degree D and M TIDE filters
TIDE with N gates
Component
Unit
cost (*)
Power
(W)
#
Cost
(*)
Cost
(**)
Cost
(***)
Power
reduct.
factor
(^)
Total
Power
(W)
1×20 WSS 0.54 4.00 6 3.24 16.9 0.9 24.0
1x1 HSR filter 0.54 4.00 0 0.00 0.0 0.0 0.0
1xN HSR filter 0.72 4.00 4 2.88 15.0 0.8 16.0
Integrated TIDE 0.11 4.00 2 0.22 1.1 0.1 8.0
Variable gain
amplifier
0.11 9.00 2 0.22 1.1 0.1 0.10 16.2
Variable gain dual-
stage amplifier
0.18 12.00 5 0.90 4.7 0.2 0.10 55.2
1x(D-1) switch 0.01 0.00 4 0.06 0.3 0.0 0.0
7.50 39.2 2.0 119.4
(*) Cost relative to 100G transceiver cost
(**) Cost relative to 10G transceiver cost
(***) Cost relative to cost of an OXC node of degree D without sub-channel A/D capability
(^) Due to sharing of management between amplification modules.

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Results of techno-economic studies comparing
FOX-C vs SLR/MLR legacy solutions
* P. S. Khodashenas, J. M. Rivas-Moscoso, D. Klonidis, G. Thouénon, C. Betoule, E. Pincemin and I. Tomkos, “Techno-
Economic Analysis of Flexi-Grid Networks with All-Optical Add/Drop Capability”, submitted to PS2015.
~15%
~30%
~30%
FOX-C based solutions can
offer up to 30% cost savings
compared to non-grooming
capable end-to-end solutions
using either SLR or MLR

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Techno-economic studies – FOX-C (all-optical grooming)
vs. OTN (electronic grooming ) based solutions - I
* G. Thouénon, C. Betoule, E. Pincemin, P.S. Khodashenas, J.M. Rivas-Moscoso, I. Tomkos, submitted to ECOC 2015.
S0: SLR over fixed-grid
S1: Nyquist WDM
S2: MB-OFDM
… but can FOX-C based solutions offer significant cost savings
compared to conventional OTN based grooming-capable solutions?
(study performed in collaboration with France Telecom/Orange)

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Techno-economic studies – FOX-C (all-optical grooming)
vs. OTN (electronic grooming ) based solutions - II
+37% +36%
+60%
-29%
(a) For Traffic Volume V1
+23%
+10%
-21%-18%
(b) For Traffic Volume V2
V1: 7 Tbps of ingress traffic
V2: traffic increase projection spanning roughly eight years with a constant per-year traffic
growth of 35%
Global multi-layer transport network cost comparison

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Spatially (and spectrally) flexible optical networking
The activities of EU project INSPACE

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What’s next in capacity expansion… In Space
 Space is the obvious yet unexplored (until 2009) dimension
• …BUT by simply increasing the number of systems, the cost and power consumption also
increase linearly!
 Efficient use of the space-domain requires “spatial integration of elements”*
• Significant efforts in the development of FMF and MCF (fibre integration)
• Multi-link amplification systems have also be proposed and developed
• Tx/Rx integration is a hot and very active topic
• Optical switches are largely unexplored so far (INSPACE focus!)
MC/FM EDFA/
EDFA array
MCF/FMF/
Bundle of SMF
Tx PIC Rx PIC
* Peter J. Winzer, “Spatial Multiplexing: The next frontier in network capacity scaling”, Tutorial paper at ECOC 2013

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Degrees of freedom in SDM transmission/switching are defined by
the type of transmission medium and how crosstalk is handled
 Core count
 Mode count
 Cladding diameter
 Core layout
• Geometry
• Homo-/heterogeneous core
structure
 Refractive-index profile
• Graded-index
• Step-index
• Trench-assisted
Becarefulwith:
dBUFFER=250m
dCLADDING=125m
dCORE=8m
SMF
 Inter-core crosstalk
 Inter-mode crosstalk
 Differential mode group
delay (DMGD)
 Bend loss
 Nonlinearity
 Process variability

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Degrees of freedom in SDM transmission
 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
dBUFFER=250m
dCLADDING=125m
dCORE=8m
SMF

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 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
Bundle of SMF
(A) Uncoupled spatial modes

37
 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
Bundle of SMFMCF
(A) Uncoupled spatial modes

38
 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
MCF
(A) Uncoupled spatial modes(B) Coupled spatial modes

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 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
MCF

40
 Core count
 Mode count
 Core layout
• Geometry
structure
• Graded-index
• Step-index
• Trench-assisted
delay (DMGD)
 Bend loss
 Nonlinearity
Becarefulwith:
FM-MCF
LP01
LP11
LP21
LP02
(C) Coupled spatial
subgroups

41
Hero transmission experiments based on SDM
… BUT all these are very good for the spatial capacity increase in Point-to-Point
systems…
…WHAT ABOUT using the spatial dimension for optical networking

42
Evolution from spectrum flexible to spatially (& spectrum)
flexible optical networking
Spectrum based
BW allocation
Spatial & Spectrum based
BW allocation
Spectrum Flexible Optical Networking
- Combined selection of channel
bandwidth (format/ data rate) and
spectral allocation according to:
demand, distance and required
performance
- λ + format/rate tunable TxRx
- Flexible switching of variable
spectral slots at different wavelengths
- Optimized spectral usage
Spatially and Spectrally Flexible Optical
Networking
- Extend flexibility to the space switching
domain
- Multi-dimensional switching granularity
- Channel allocation over
a. multiple Modes/Cores/fibres
b. multiple spectral slots
- Optimized system bandwidth usage
- Combined spectral – spatial optimization.
- Multi-dimensional flexible switching

43
The INSPACE project consortium
 Optronics Technologies S.A
• Mr. George Papastergiou (Coordinator)
• Dr. Nina Christodoulia
• Dr. Thanasis Theocharidis
 Telefónica Investigación y
Desarrollo SA
• Mr. Felipe Jiménez-Arribas (WP2 Leader)
• Dr. Víctor López
• Dr. Óscar González de Dios
 The Hebrew University of Jerusalem • Prof. Dan Marom (WP4 Leader)
• Dr. Miri Blau
 Athens Information Technology
• Dr. Ioannis Tomkos (Technical Mngr)
• Dr. Dimitrios Klonidis (WP6 Leader)
• Dr. Pouria S. Khodashenas
• Dr. José M. Rivas-Moscoso
 Optoscribe Ltd.
 CREATE-NET (Center for Research and
Telecommunication Experimentation for
Networked Communities)
 Aston University
 Finisar Israel Ltd.
 W-ONE SYS SL
• Dr. Nicholas Psaila
• Dr. John MacDonald
• Dr. Paul Mitchell
• Dr. Domenico Siracusa (WP5 Leader)
• Dr. Federico Pederzolli
• Dr. Elio Salvadori
• Prof. Andrew Ellis (WP3 Leader)
• Dr. Stylianos Sygletos
• Dr. Naoise Mac Suibhne
• Dr. Filipe Ferreira
• Dr. Christian Sánchez-Costa
• Dr. Shalva Ben-Ezra
• Dr. Jordi Ferré Ferran (WP7 Leader)
• Dr. Jaume Mariné

44
INSPACE project channel allocation concept
Modes/Cores
Wavelengths
Data rate
(Modulation level)
Degrees of Flexibility
Modes
or
Cores
f
f
f
f
f
• Channels with flexible capacity can be allocated over:
– one or few modes/multi cores
– occupying a single or multiple spectral slots
: end-to-end allocated channel
“Spatial expansion of
the spectrum over
multiple modes/cores
and therefore definition
of a superchannel over
two dimensions
(instead of the
spectrum only
dimension)”
SMF-
Bundle
or
FMF
or
MCF
Frequency Frequency
ConventionalopticalOFDM OpticalfastOFDM
(N-1)/T
(N-1)/2T
Nisthechannelnumber(=7inthisexample)
(a) (b)
Frequency Frequency
ConventionalopticalOFDM OpticalfastOFDM
(N-1)/T
(N-1)/2T
Nisthechannelnumber(=7inthisexample)
(a) (b)
N-WDM
or
OFDM
or
SC-M-QAM
Fibre,
Mode
,Core

45
SDM switching classification
Independent spatial/spectral channel switching Spectral channel switching
Spatial channel switching Spectral channel switching of spatial subgroups
* D. M. Marom et al.,''Switching Solutions for WDM-SDM Optical Networks'', IEEE Comm. Mag. 53, 60-68 (2015)

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(A)
R&S node
design for
independent
spatial/spectral
channel
switching

47
R&S node design for spectral channel switching across all spatial modes
(A)
R&S node
design for
independent
spatial/spectral
channel
switching

48
R&S node design for spectral channel switching across all spatial modes
(C)
OXC design for spatial channel switching across all spectral channels

49
(C)
OXC design for spatial channel switching across all spectral channels
(D)
R&S node design for hybrid fractional space-full spectrum switching granularity

50
Comparison of SDM switching options
Space-wavelength granularity Space granularity Wavelength granularity
Fractional space-full
wavelength granularity
Minimum
switching
granularity
Bandwidth of a single WDM channel
present at a single spatial mode.
Bandwidth of entire optical
communication band carried on a
single spatial mode.
Bandwidth of a single WDM
channel spanning over all spatial
modes.
Bandwidth of a single
WDM channel over a
subset of spatial modes.
Realization
With OXC: High-port count OXC and at
least 2M conventional WSS per I/O fiber
link.
Without OXC: 2M conventional WSS per
I/O fiber link. 4M if WSS placed on
add/drop.
Moderate port count OXC, and 2 WSS
per mode selected for WDM channel
add/drop.
4 joint switching WSS per I/O
fiber link in route-and-select
topology applied to all spatial
modes in parallel.
4×M/P joint switching
WSS modules per I/O fiber
link.
Flexibility
With OXC: Each mode/WDM channel
independent provisioned and routed.
Supports SDM lane change. Single point of
failure.
Without OXC: Each mode/WDM channel
independently provisioned and routed.
Spatial mode maintained. Prone to
wavelength contention.
The complete optical communication
band is routed across network. Coarse
granularity. If WDM channels need to
be extracted from many modes then
WSS count quickly escalates.
Each spatial super-channel
provisioned across all modes.
Susceptible to wavelength
contention. Add/drop bound to
direction.
Compromise solution using
small SDM groups. More
efficient when provisioning
low capacity demands.
Scaling
With OXC: Can quickly escalate to very
large port counts.
Switching node cost linearly scales with
capacity, no price benefit to SDM.
Conventional OXC can support
foreseeable mode and fiber counts.
OXC is single point of failure. Pricing
favorable but with greater add/drop
require more WSS modules.
Cost roughly independent of SDM
count. Inefficient for low capacity
connections due to minimum BW
provisioned across SDM. Large
SDM Rx/Tx are integration and
DSP challenge.
Cost scales as group count.
Groups can be turned on as
capacity grows, offering
pay-as-you-go alternative.
Maintaining small group
sizes facilitates MIMO
processing at Rx.
Estimated
loss
With OXC: 13 dB per I/O fiber link.
Without OXC: 10 dB per I/O fiber link
For MCF or FMF transmission fiber, extra 4
dB loss is induced by the spatial
MUX/DEMUX
3 dB per I/O fiber link being switched.
If add/drop from SDM fiber is
extracted, 10 dB excess loss for
through.
For MCF or FMF transmission fiber,
extra 4 dB loss is induced by the
spatial MUX/DEMUX
10 dB per I/O fiber link.
For MCF or FMF transmission
fiber, extra 4 dB loss is induced by
the spatial MUX/DEMUX
10 dB per I/O fiber link.
For MCF or FMF
transmission fiber, extra 4
dB loss is induced by the
spatial MUX/DEMUX

51
SDM technology elements
 INSPACE SDM Wavelength Selective Switch
• High port count WSS for joint switching of spatial modes
A conventional 120 WSS can turn into a 7-mode(12) spatial-spectral WSS.
First demonstration in OFC 2012
New port definition: S(MN)
S = nº of spatial modes
In1
Out1
Out2 M = nº of input fibre subgroups
N = nº of output fibre subgroups

52
A conventional 120 WSS turns into a 7-mode(12) spatial-spectral WSS. First
demonstration in OFC 2012
New port definition: S(MN)
 INSPACE SDM Wavelength Selective Switch
• High port count WSS for joint switching of spatial modes
By adding a 2-D SMF array, a higher port count can be achieved
With a fibre array of 316 (functional) fibres, a 3-mode(115)
spatial spectral high port count WSS has been designed/fabricated
S modes per input/output
M = 1 input
N outputs
2-D Fibre array

53
 INSPACE Mode MUX/DEMUX
• MCF breakout designed and fabricated for MCF
• FMF photonic lantern designed and fabricated
Fabrication optimisation yielded
low IL (2 dB) with a loss uniformity
of 0.8 dB

54
 INSPACE Mode MUX/DEMUX
• MCF breakout designed and fabricated for MCF
• FMF photonic lantern designed and fabricated
Fabrication optimisation yielded
low IL (2 dB) with a loss uniformity
of 0.8 dB
The performance of the photonic lantern is
better than competing commercial devices
and fully packaged devices are ready to be
deployed. These will be launched as an
improved product at ECOC in Sept. 2015.

55
 Comparison of spectral and spatial super-channel allocation
policies for SDM network operation, taking into account the
spectral efficiency/reach trade-off
 First study carried out for SDM networks based on SMF
bundles
 For such an SDM system, the focus is
on the comparison between two
extreme allocation strategies:
• Parallel systems with spectral super-channels (SpeF)
• Parallel systems with spatial super-channels (SpaF)
SDM resource allocation issues
• MCFs and FMFs with coupled transmission
cores/modes present special challenges in
terms of their physical layer performance and
implementation complexity

56
 SDM allocation options:
• A: SpeF – Spectral super-channels with flexi-grid
• B: SpaF – Spatial super-channels with fixed spectral width
SDM allocation options considered

57
 Super-channel allocation options:
• A: Over spectrum (SpeF)
• B: Over space (SpaF)
Resource allocation options and trade-offs
Big enough spacing to neglect
the crosstalk between adjacent
super-channels
* The GB size is the same for both cases
No
crosstalk
among
cores
Crosstalk between adjacent
sub-channels leads to optical
reach reduction

58
Blocking results (under independent switching)
1.E-4
1.E-3
1.E-2
1.E-1
300 600 900 1200 1500
BP
Input Load [Erlang]
SpeF-Var
SpeF-34.375
SpeF-37.5
SpeF-WDM
SpaF-WDM
 BP vs input load to the network for several SpeF and SpaF allocation options
(simulations performed for Telefónica’s Spain national network):
(a) SpeF-Var: SpeF using
variable spacing adapted to
the path length
(b) SpeF-34.375, SpeF-37.5,
SpeF-50: SpeF using fixed
spacing (34.375, 37.5 GHz
and 50 GHz) with 12.5-GHz
GB on both sides of each Sp-
Ch
(c) SpeF-WDM and SpaF-
WDM: SpeF and SpaF on
fixed-grid WDM conditions
with 50-GHz channel
spacing including GB.
* D. Siracusa, F. Pederzolli, P. S. Khodashenas, J. M. Rivas-Moscoso, D. Klonidis, E. Salvadori, I. Tomkos, “Spectral vs.
Spatial Super-Channel Allocation in SDM Networks under Independent and Joint Switching Paradigms”, ECOC 2015.

59
Blocking results (under independent, joint and
fractional joint switching)
 BP vs. input load to the network for several SpaF allocation
options and switching paradigms:
• Joint switching imposes a BP penalty compared to independent
switching, which can be minimised through proper traffic engineering
(better match between traffic profile and Tx maximum capacity)
1.E-4
1.E-3
1.E-2
1.E-1
200 400 600 800 1000 1200 1400
BP
Input Load [Erlang]
SpaF-InS
SpaF-FJoS
SpaF-JoS

60
Number of WSSs required (under joint and fractional
joint switching)
 Joint switching can alleviate the cost problem associated with independent
switching (resulting from the requirement of one WSS per fiber and degree) by
allowing WSS-sharing between fibers.
 Total number of WSSs required, under different switching paradigms, for a
colorless, directionless R&S ROADM architecture in the Telefonica Spain
national network:
Switching Number of WSS (general)
Number of WSS
(Telefónica topology)
InS 2·Nd·D·S+4·NdA/D·S 2502
JoS 2·Nd·D+4·NdA/D 278
FJoS 2·Nd·D·S/G+4·NdA/D·S/G 834
·: ceiling
S: number of fibers
Nd: total number of nodes
NdA/D: number of nodes with
A/D
D: avg. nodal degree
G: number of groups of
spatial modes (G = 3)
(For Nd = 30, NdA/D = 14, D = 3.7, S = 9, G = 3)

61
Characteristic Distributed GMPLS Hybrid PCE/GMPLS Centralized SDN
Implementation
complexity
Translate network model changes to
OSPF/RSVP representation, handle
concurrent reservations in RSVP
signaling
Same as GMPLS, plus extensions
to PCEP to represent spatial
services
Develop the SDM network model
from scratch, develop or extend
controller and north-bound
interface
Computational
Capability
Typically limited in scope (source
routing based on limited
information) on multiple low power
CPUs
Conceptually encompassing
complex algorithms based on
extensive information and run on
powerful, dedicated hardware
Conceptually encompassing
complex algorithms based on
extensive information and run on
powerful, dedicated hardware
Scalability / Overhead
Slower reactivity due to large
increase in information to
disseminate
Similar to GMPLS: more
computational resource but small
pool of points of failure
Centralized controller gives high
computational resources, south-
bound protocol can limit flooding
Resiliency
High (distributed system), but
partition-crossing services fail
eventually
Only partitions which can reach the
PCEs continue to operate, partition-
crossing services fail eventually
Data plane can use hard
reservations, but CP partitioning
would prevent controlling part of
the network
Programmability
Not supported, and very difficult to
retrofit
PCEP limiting as north-bound
protocol, but could be adapted with
extra software
Supported
Multi-domain/carrier
Supported using e.g. BGP-LS to
flood information, but
confidentiality issues
Supported, if nothing else through
horizontal PCE chains
Open issue
Multi-vendor
Theoretically supported (IETF
standard), but advanced features are
mostly vendor-specific
Theoretically supported, relies on
the underlying GMPLS control
plane
Depends on south-bound protocol,
theoretically supported
INSPACE control plane framework: comparison of
architectural archetypes
IN
Hybrid PCE/GMPLS was the choice for EU projects DICONET & CHRON – INSPACE now shifts to SDN

62
INSPACE SDN controller architecture
Network AbstractionModule(NAM)
North-boundCommunicationsManager(NCM)
Topology
Service (TS)
TDB
South-boundProtocol
Manager(SPM) #1
Optical Node
CPAgent
Optical Node
CPAgent
Optical Node
CPAgent
Client
Application
…Client
Application
Client
Application
TED Manager
(TM)
PCE / RSSA
Engine(PRE)
Virtualization
Engine(VE)
Connection
Manager(CM)
CDB
VDB
South-boundProtocol
Manager(SPM) #2
1
5
12 13
4 6 2
8
3
97
15
14
10 16
17
11

63
Summary
 The activities of EU project FOX-C were presented
All possible spectrally flexible super-channel transceivers were implemented and tested
Nodes for all-optical add/drop of sub-channels (for both NWDM and AO-OFDM multiplexing)
were developed and tested
Networking studies were performed to demonstrate the benefits of FOX-C solution
 The activities of EU project INSPACE were presented
Nodes for independent or joint switching of SDM super-channels were developed and tested
Networking studies were performed to demonstrate the benefits of INSPACE solution
Development of an SDN-based control plane for SDM-based networks is underway
 The EU-funded projects FOX-C and INSPACE are developing the
optical networking solutions that will dominate the market after
2020!
• Stay tuned!!!

64
Obrigado!
Acknowledgement
Dr. Ioannis Tomkos
itom@ait.gr
to all partners of FOX-C and INSPACE EU projects

Flexible optical networking with spectral or spatial super-channels

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