Pune, India, 13 – 15 December 2010
ITU-T Kaleidoscope 2010Beyond the Internet? - Innovations for future networks and services
M. Jinno, T. Ohara, Y. Sone, A. HiranoO. Ishida, and M. Tomizawa
NTT Network Innovation Labs.([email protected])
Introducing Elasticity and Adaptation into the Optical Domain
Toward More Efficient and Scalable Optical Transport Networks
2
Outline
Background: Growing anticipationSE-conscious optical networkingEarly 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
3
Background (1): Successful Deployment of Optical Networks
Worldwide intensive R&D activitiesContinuous initiative by ITU-T toward OTNs and ASONsG.709 OTN augmentation to transport 100 GE traffic
100 M
1 G
10 G
100 G
1 T
10 T
100 T
1980 1990 2000 2010 2020
0.01
0.1
1
10
Year of commercialization in Japan
Per fi
ber c
apac
ity (b
/s)
Spec
tral
effi
cien
cy (b
/s/H
z)100 Gb/s x 80 (projected)
40 Gb/s x 4010 Gb/s x 80
WDM
TDM
4
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)
Bit loading higher than that for QPSK causes rapid increase in SNR penalty, and results in shorter optical reachSE improvement for P2P is slowing down, meaning higher rate data need more spectrum
0.01
0.1
1
0 100 200 300 400 5000.01
0.1
10
Bit rate per channel (Gb/s)
Rela
tive
optic
al re
ach
with
co
nsta
nt e
nerg
y pe
r bit
(a.u
.)
Spec
tral
effi
cien
cy (b
/s/H
z)
DP-QPSK
DP-16QAM
DP-64QAM
DP-256QAM
DP-1024QAM
QPSKBPSK
600
@25 Gbaud
Optical amplifier bandwidth (~ 5 THz)
TDM
WDM
Multiplexing technology evolutionPDM
Multi-level mod.
5
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
OFC2011WS“Spectrally/bit-rate flexible optical network”
ECOC2010Symposium“Towards 1000 Gb/s”
OFC2010 WS“How can we groom and multiplex data for ultra-high-speed transmission”
ECOC2009 Symposium“Dynamic multi-layer mesh network”
OECC2010 Symposium“Future optical transport network”
2008.9 2010.92009.92009.3 2010.3 2011.3
ECOC2008
“Demonstration of novel spectrum-efficient elastic
optical path network ….” (NTT)
“Demonstration of novel spectrum-efficient elastic
optical path network ….” (NTT)
6
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
7
Elastic Optical Path Network
Spectrum-efficient transport of 100 Gb/s services and beyond through introduction of elasticity and adaptation into optical domainAdaptive spectrum resource allocation according to
Physical conditions on route (path length, node hops)Actual user traffic volume
1. SE-conscious adaptive signal modulation2. SE-conscious elastic channel spacing
Elastic channelspacing
250 km 250 km
400 Gb/s 400 Gb/s 400 Gb/s100 Gb/s 100 Gb/s
1,000 km 1,000 km 1,000 km
Fixed format, grid
Adaptive modulation
QPSKQPSK200 Gb/s QPSK 16QAM 16QAM
Path length
Bit rate
Conventionaldesign
Elastic optical path network
8
Enabling Hardware Technologies (1)Rate and Reach Flexible Transponder
Introduce coherent detection followed by DSPOptimizing 3 parameters provides required data rate and optical reach while minimizing spectral width
(Symbol rate) x (Number of modulation levels) x （ Number of sub-carriers ）Flexible reach
Change the number of bits per symbol with high-speed digital-to-analogue converter and IQ-modulator
Flexible rateOptical OFDM is spectrally-overlapped orthogonal sub-carrier modulation schemeCustomize number of sub-carriers of OFDM
Flexible reach transmitter
100 G
400 G
Flexible rate/reach transmitter
100 G~400 G
9
BVWXCBV
WXC
BV WSSBV WSS
BV WSSBV WSS
BV WSSBV WSS
BVWSSBV
WSSBV
WSSBV
WSS
BV WSSBV WSS
BVtransponder
BVtransponder
Outputfiber
Inputfiber
Bandwidth agnostic WXC
Spatial light modulator
Bandwidth variable wavelength selective switch (WSS)
GratingGrating
Optical freq.
Tran
s-m
ittan
ce
Enabling Hardware Technologies (2)Bandwidth Agnostic WXC
Introduce bandwidth-variable WSS based on, e.g., LCoSRequired minimum spectrum window (optical corridor) is open at every node along optical path
Required width of optical corridor is determined by factoring in signal spectral width and filter clipping effect accumulated along nodes.
400 Gb/s
40 Gb/s
100 Gb/s
100 Gb/s
400 Gb/s
40 Gb/s
10
Possible Adoption Scenarios
Step-by-stepTriggered by future
higher rate client signals (e.g., 400 Gbps)
Earlier adoptionTo facilitate
100 GbpsROADM design
11
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
Elastic channel spacing
High-SE multi-rate traffic accommodation
Dynamic spectral allocation
Optical BoD, highly survivable restoration
1 G
10 G
100 G
1 T
1995 2000 2005 2010 2015 2020Year of standardization
Bit r
ate
(b/s
)
GE
10 GE
40 GE
100 GE
OTU1
OTU3
OTU2
OTU4
OTU5(projected)
STM256
400 GE(projected)
STM64
Equally-spaced Non-ITU-T grid
High-SE 400 G accommodation
P2P
Distance adaptive spectral
allocation
High-SE multi-reach traffic accommodation
P2P
Network
12
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.
Distance adaptive spectrum allocation will facilitate 100 Gb/s ROADM design for longer paths
Significant spectral-saving when compared with the worst-case design on a 100 GHz grid.
112 Gb/s DP-QPSK
112Gb/s DP-16QAM
112 Gb/s DP-QPSK
0
25
50
75
100
1 2 3 4 5 6 7 8 9 1011 12 1314Number of node hopsAl
loca
ted
spec
tral
wid
th [G
Hz] 112 Gb/s DP-QPSK
100 GHz grid
Distance adaptive
Spectrum allocation mapsDistance–adaptive
spectrum allocation
121
11
2
3
5
4
67
8
9
10
Network utilization efficiency 0
1
2
3
4
5
6
7
-45%
100
GH
z gr
id
Dis
tanc
ead
aptiv
e
Requ
ired
tota
l spe
ctru
m a
t m
ost o
ccup
ied
link
(TH
z)
13
Possible SG15 Study Items
OTN•NW Architecture•IF & Mapping•NW Architecture•IF & Mapping
Physical Layer•Frequency Grid•Line-IF Application•Frequency Grid•Line-IF Application
ASON•Protocol Neutral Spec.•Routing & Signaling •Protocol Neutral Spec.•Routing & Signaling
14
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
OMS
OTSOTS
OMS
OTSOTS
OMS
OTSOTS
Mux
Dem
ux
Mux
Dem
uxTx
Mux
Dem
uxTx Rx3R
ODUflex, ODUk
OTUflex, OTUk-xv
OCh OCh
Bandwidth agnostic WXC
Bandwidth agnostic WXC
OTUflex, OTUk-xv
15
ODU
OTN Interfaces and Mapping:Current OTN
G.709 “Interfaces for the optical transport network (OTN)” specifies Interfaces and mappings of OTNConflicting 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.
1 Gb/s
10 Gb/s
100 Gb/s
OD
Ufle
x (L
)
Clientsignal
ODU (L) ODU (H) OTU
ODU 0ODU 1
ODU 2
ODU 3
OTU 1
OTU 2
OTU 3
Map Mux Map OChE/O
OCh
ODU 4 OTU 4
16
OTN Interfaces and Mapping:Possible Flexible OTU Extension
Rate-flexible OCh enables cost-effective transport of various client signals in fully optical domain w/o electrical multiplexing and groomingIntroduction of rate-flexible OTUs (OTUflex) and rate-flexible HO ODUs (HO ODUflex).
1 Gb/s
10 Gb/s
100 Gb/s
1 Tb/s
OD
Ufle
x (H
)
OTU
flex
Clientsignal
ODU (L) ODU (H) OTU
ODU 0ODU 1
ODU 2
ODU 3
ODU 4
OTU 1
OTU 2
OTU 3
OTU 4
OTUflexODUflex
Map Mux Map
Rate-flexibletransponder
Conventionaltransponder
OChE/O
OCh
OD
Ufle
x (L
)
17
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
Explicitly allocate spectral resources to optical path
To quantize continuous spectrum into contiguous frequency slots with appropriate slot width.
1 3 4 5 6 7 82-4 -3 -2-8 -7 -6 -5 -1 0
Frequency slot (12.5 GHz width)
H L HL H L
50 GHz 125 GHz37.5 GHz
Frequency slot allocation
n=0 n=1n=-1
f=193.1 THz f=193.2 THzf=193.0 THz
100 GHz
50 GHz
25 GHz
12.5 GHz1 2 3 4 5 6 7 8-8 -7 -6 -5 -4 -3 -2 -1 0
Frequency grid (G.694.1)
18
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
(TD1, TC1)
DistanceCa
paci
ty
i
iBR
(TD2, TC2)(TD3, TC3)
Elastic optical path network
(TD, TC)
Distance
Capa
city
lambdaBR
Conventional optical network
TD: Target distanceTC: Target capacityBR: Bit rate
40.10G-20L652A(C)
Target Capacity=40 x 10 Gb/s
Target distance=20-span, long-haul G.652.A-fiber (C-band)
Recommendation G.696.1 Longitudinally compatible intra-domain DWDM applications
Ex.
19
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
20
Possible Technology-Specific Extension of Routing and Signaling
Need discussion on extension of GMPLS protocols in IETF and OIF with ITU-T SG15Define new parameters in signaling messages
Label request object
Upstream label object
…
Explicit route object
Sender TSpec object…
Label object
Record route object
…
Flow spec object
…
PATH message RESV message
Switching type: spectrum
switching capable
Parameters in objects
Label: (start slot, end
slot)
Modulation format: (symbol rate, no. of sub-carriers,
modulation level)
21
Conclusions
Elastic optical path networkRequired 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
