ITU-T Kaleidoscope 2010
Beyond the Internet? - Innovations for future networks and services
Introducing Elasticity and Adaptation into
the Optical Domain
Toward More Efficient and Scalable Optical
Transport Networks
M. Jinno, T. Ohara, Y. Sone, A. Hirano
O. Ishida, and M. Tomizawa
NTT Network Innovation Labs.
(Jinno.masahiko@lab.ntt.co.jp)
Pune, India, 13 – 15 December 2010
Outline
Background: Growing anticipation
SE-conscious optical networking
Early initiatives by ITU-T
Elastic optical path network as a candidate to
support future Internet and services
Adoption scenarios from rigid optical networks to
elastic optical path network
Possible standardization study items and some
solutions relevant to future ITU-T activities
2
Background (1):
Successful Deployment of Optical Networks
Worldwide intensive R&D activities
Continuous initiative by ITU-T toward OTNs and ASONs
G.709 OTN augmentation to transport 100 GE traffic
10 T
WDM
1T
100 Gb/s x 80
(projected)
40 Gb/s x 40
10 Gb/s x 80
10
100 G
1
TDM
10 G
1G
0.1
100 M
0.01
1980
1990
2000
2010
Spectral efficiency (b/s/Hz)
Per fiber capacity (b/s)
100 T
2020
Year of commercialization in Japan
3
Background (2):
Slowing Down of SE Improvement
Fixed optical amplifier bandwidth (~ 5 THz)
Per fiber capacity increase has been accomplished through
boosting SE (bit rate, wavelength, symbol per bit, state of
polarization)
TDM
WDM
BPSK
QPSK
Relative optical reach with
constant energy per bit
(a.u.)
Optical amplifier bandwidth (~ 5 THz)
1
10
DP-QPSK
DP-16QAM
DP-64QAM
0.1
Multi-level mod.
PDM
Multiplexing technology evolution
0.01
0.1
DP-256QAM
@25 Gbaud
0
100
200
300
DP-1024QAM
400
Spectral efficiency (b/s/Hz)
Bit loading higher than that for QPSK causes rapid increase in
SNR penalty, and results in shorter optical reach
SE improvement for P2P is slowing down, meaning higher rate
data need more spectrum
0.01
500 600
Bit rate per channel (Gb/s)
4
Background (3): Growing Concern of SE in
Networking
Fiber capacity crunch concerns are driving optical
networking toward a spectral-efficiency-conscious
design philosophy
Right-sized optical bandwidth is adaptively allocated to an
end-to-end optical path
Spectral-efficiency-conscious, adaptive networking
approach has attracted growing interest
Ex. Elastic optical path network
2008.9
2009.3
ECOC2008
“Demonstration of
novel spectrumefficient elastic
optical path
network ….” (NTT)
2009.9
ECOC2009
Symposium
“Dynamic
multi-layer
mesh
network”
2010.3
OFC2010 WS
“How can we
groom and
multiplex data
for ultra-highspeed
transmission”
OECC2010
Symposium
“Future
optical
transport
network”
2010.9
ECOC2010
Symposium
“Towards
1000 Gb/s”
2011.3
OFC2011
WS
“Spectrall
y/bit-rate
flexible
optical
network”
5
Expected Early ITU-T Initiatives
Early ITU-T initiatives on studying possible extension
of OTN and ASON standards are indispensable.
Greatly support rapid advance and adoption of
spectrally-efficient and adaptive optical networks
Starting point regarding studying possible extension
of OTN and ASON standards in terms of network
efficiency
Clarify what should be inherited, what should be
extended, and what should be created
6
Elastic Optical Path Network
Spectrum-efficient transport of 100 Gb/s services and beyond
through introduction of elasticity and adaptation into optical
domain
Adaptive spectrum resource allocation according to
Physical conditions on route (path length, node hops)
Actual user traffic volume
1.
2.
SE-conscious adaptive signal modulation
SE-conscious elastic channel spacing
Path length
Bit rate
Conventional
design
1,000 km
400 Gb/s
Fixed
format, grid
QPSK
Elastic
optical path
network
1,000 km
400 Gb/s
QPSK
200 Gb/s
1,000 km
100 Gb/s
QPSK
250 km
250 km
400 Gb/s
100 Gb/s
16QAM
16QAM
Adaptive
modulation
Elastic channel
spacing
7
Enabling Hardware Technologies (1)
Rate and Reach Flexible Transponder
Introduce coherent detection followed by DSP
Optimizing 3 parameters provides required data rate and optical
reach while minimizing spectral width
(Symbol rate) x (Number of modulation levels) x （Number of subcarriers）
Flexible reach
Change the number of bits per symbol with high-speed digital-toanalogue converter and IQ-modulator
Flexible rate
Optical OFDM is spectrally-overlapped orthogonal sub-carrier
modulation scheme
Customize number of sub-carriers of OFDM
100 G
400 G
Flexible reach
transmitter
100 G~
400 G
Flexible rate/reach
transmitter
8
Enabling Hardware Technologies (2)
Bandwidth Agnostic WXC
Introduce bandwidth-variable WSS based on, e.g., LCoS
Required minimum spectrum window (optical corridor) is open
at every node along optical path
BV
WXC
BV
WSS
BV
WSS
40 Gb/s
400 Gb/s
100 Gb/s
40 Gb/s
BV
WSS
BV BV
transponder
transponder
Transmittance
400 Gb/s
Output
fiber
BV
WSS
Input
fiber
BV
WSS
BV
WSS
Required width of optical corridor is determined by factoring in
signal spectral width and filter clipping effect accumulated along
nodes.
Optical freq.
Spatial light modulator
100 Gb/s
Bandwidth
agnostic WXC
Grating
Bandwidth variable
wavelength selective switch (WSS)
9
Possible Adoption Scenarios
Step-by-step
Triggered by future
higher rate client signals
(e.g., 400 Gbps)
Earlier adoption
To facilitate
100 Gbps
ROADM design
10
Step-by Step Adoption Scenario:
Higher Rate Client Triggered (e.g., 400 Gb/s)
Possible next Ethernet rate, 400 G, could appear around 2015.
Optical reach and SE are not independent parameters in 400 G
era.
Balancing optical reach and SE in 400 G systems will most
likely require elastic spectral allocation
Bit rate (b/s)
1T
OTU5
(projected)
OTU4
100 G
100 GE
OTU3
STM256
STM64
400 GE
(projected)
OTU2
1995
Elastic
channel spacing
High-SE multi-rate
traffic
accommodation
Distance
adaptive spectral
allocation
High-SE multireach traffic
accommodation
Dynamic spectral
allocation
Optical BoD,
highly survivable
restoration
10 GE
OTU1
1G
High-SE 400 G
accommodation
P2P
40 GE
10 G
Equally-spaced
Non-ITU-T grid
GE
2000
2005
2010
2015
Year of standardization
2020
Network
11
Earlier Adoption Scenario:
Large-Scale 100 Gb/s ROADM Design Facilitation
Even employing DP QPSK modulation, transmitting 100 Gbps
signals over multiple hops of ROADMs on a 50 GHz grid is still
tough task.
3
10
4
9
5
8
7
6
Distance–adaptive
spectrum allocation
50
25
100 GHz grid
112 Gb/s DP-QPSK
112 Gb/s DP-QPSK
112Gb/s DP-16QAM
Distance
adaptive
0 1 2 3 4 5 6 7 8 9 1011 12 1314
Number of node hops
Spectrum allocation maps
7
6
5
4
3
2
1
-45%
Distance
adaptive
11
75
112 Gb/s DP-QPSK
100 GHz grid
2
100
Required total spectrum at
most occupied link (THz)
12
1
Allocated spectral width [GHz]
Distance adaptive spectrum allocation will facilitate 100 Gb/s
ROADM design for longer paths
Significant spectral-saving when compared with the worstcase design on a 100 GHz grid.
0
Network utilization efficiency
12
Possible SG15 Study Items
OTN
•NW Architecture
•IF & Mapping
Physical Layer
•Frequency Grid
•Line-IF Application
ASON
•Protocol Neutral Spec.
•Routing & Signaling
13
OTN Network Architecture
G.872 “Architecture of optical transport networks”
specifies functional architecture of OTN from network
level viewpoint
Layered structure of Optical Channel (OCh), Optical
Multiplex Section (OMS), and Optical Transmission Section
(OTS)
Although data rate, modulation format, and spectral
width of optical path in elastic optical path network may
change, elastic optical path is naturally mapped into OCh
See no significant impact on current G.872
Bandwidth
agnostic WXC
OTS
3R
OTS
OTS
OMS
OTS
OMS
Demux
Tx
Mux
Demux
Mux
Mux
Tx
Demux
Bandwidth
agnostic WXC
OTS
OTS
OMS
OCh
OCh
OTUflex, OTUk-xv
OTUflex, OTUk-xv
ODUflex, ODUk
Rx
14
OTN Interfaces and Mapping:
Current OTN
G.709 “Interfaces for the optical transport network (OTN)”
specifies Interfaces and mappings of OTN
Conflicting operator requirements
Transport a wide variety of client signals while minimizing types of
line-interfaces in order to reduce capital expenditures, which are
dominated by line-interface costs.
LO/HO ODUs and ODUflex can address these conflicting
requirements.
LO ODU offers versatility to accommodate various client signals
and HO ODU offers simplicity in terms of physical interface.
ODU 4
OTU 4
ODU 3
OTU 3
10 Gb/s
ODU 2
1 Gb/s
ODU 1
ODU 0
Client
signal
Map
ODUflex (L)
100 Gb/s
OTU 2
OCh
OTU 1
ODU(L) Mux ODU (H) Map
ODU
OTU E/O
OCh
15
OTN Interfaces and Mapping:
Possible Flexible OTU Extension
ODU 4
100 Gb/s
Rate-flexible
transponder
OTUflex
OTU 4
ODU 3
OTU 3
10 Gb/s
ODU 2
OTU 2
OTU 1
1 Gb/s
ODU 1
ODU 0
Client
signal
Map
ODU (L) Mux ODU (H) Map
OTUflex
ODUflex
ODUflex (H)
1 Tb/s
ODUflex (L)
Rate-flexible OCh enables cost-effective transport of
various client signals in fully optical domain w/o
electrical multiplexing and grooming
Introduction of rate-flexible OTUs (OTUflex) and
rate-flexible HO ODUs (HO ODUflex).
OCh
Conventional
transponder
OTU E/O
OCh
16
Physical Layer Specification (1):
Possible Frequency Grid Extension
G.694.1 “Spectral grids
for WDM applications:
DWDM frequency grid”
Anchored to 193.1 THz,
and supports various
channel spacings of 12.5
GHz, 25 GHz, 50 GHz,
and 100 GHz
f=193.1 THz
f=193.0 THz
n=-1
n=0
To quantize continuous
spectrum into contiguous
frequency slots with
appropriate slot width.
n=1
100 GHz
50 GHz
25 GHz
-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8
12.5 GHz
Frequency grid
Explicitly allocate spectral
resources to optical path
f=193.2 THz
(G.694.1)
-8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8
Frequency slot (12.5 GHz width)
L
50 GHz
H
L
H
37.5 GHz
L
H
125 GHz
Frequency slot allocation
17
Physical Layer Specification (2):
Possible Intra-Domain Application Extension
Conventional systems:
Target distance and capacity are a fixed set of values
Elastic optical path network:
Line interfaces will have multi-reach functionality
Trade-off between optical reach and SE
Variable sets of parameters for target distance and
capacity
 BR
Recommendation G.696.1
Longitudinally compatible intradomain DWDM applications
Ex.
40.10G-20L652A(C)
(TD, TC)
Distance
Conventional optical network
Target Capacity Target distance
=40 x 10 Gb/s =20-span,
long-haul G.652.Afiber (C-band)
i
i
Capacity
TD: Target distance
TC: Target capacity
BR: Bit rate
Capacity
BR  lambda
(TD1, TC1)
(TD2, TC2)
(TD3, TC3)
Distance
Elastic optical path network
18
ASON Control Plane
G. 805, G.7713, G.7714, and G.7715 provide
network resource model, requirements, architecture,
and protocol neutral specifications for automatically
switched optical networks (ASONs),
Based on functional models for SDH (G.803) and OTN
(G.872)
No significant impact on current ASON standards
when introducing distributed control plane into
elastic optical path networks
19
Possible Technology-Specific
Extension of Routing and Signaling
Need discussion on extension of GMPLS protocols in
IETF and OIF with ITU-T SG15
Define new parameters in signaling messages
PATH message
Parameters in objects
Switching type:
spectrum switching
capable
Label:
(start slot, end slot)
Modulation format:
(symbol rate, no. of
sub-carriers,
modulation level)
…
…
Label request
object
Upstream label
object
Explicit route
object
Sender TSpec
object
RESV message
Label object
Record route
object
Flow spec object
…
…
20
Conclusions
Elastic optical path network
Required minimum spectral resources are adaptively
allocated
Possible adoption scenarios
Study items relevant to future standardization
activities of ITU-T SG15
Possible extension of OTN, physical layer, and ASON
standards in terms of network efficiency
21