ROADM Network Design Issues
Transcript of ROADM Network Design Issues
ROADM Network Design IssuesMarch 23, 2009,
NFOEC 2009, Tutorial
Sorin TibuleacSorin TibuleacADVA Optical Networking, Atlanta, GA
© 2009 OSA/OFC/NFOEC 2009 NMD1.pdf
Outline
Definition features benefitsDefinition, features, benefits
Node configurations
ROADM T h l iROADM Technologies
Transmission impairments
ROADM evolution
ROADM network control
2
Definition
ROADM = Reconfigurable Optical Add/Drop Multiplexer
An optical s bs stem capable of selecti e and a tomatic emo al An optical subsystem capable of selective and automatic removal or addition of individual wavelengths from an optical fiber
ROADM
ROADM can also denote a network node
1x9 WSS 9:1 coupler
Transponders
3
Transponders
Typical ROADM features
Typically associated with other features
Switching with no impact on other wavelengths
Wavelength monitoring (mostly power)a g o o g ( o y po )
Wavelength power equalization
Network management SW for end to end automated Network management SW for end-to-end automated provisioning
Support for all data rates, modulation formats, protocolspp , , p
Supports external wavelengths
4
Benefits
Reduction of OpExSimpler network planning Simpler installation and turn-up of initial systemSimpler installation and turn up of initial systemFaster provisioning and turn-up of new channelsIncreased network availability - avoid manual operations
R d ti f C EReduction of CapExLess OEO regeneration due to power equalizationOptical switching vs. OEO switching with MD-ROADMs
Dynamic provisioning of services
Mesh network protection options
ROADMDemux Mux ROADM
5
Transponders Transponders
ROADM Evolution
Mux / Switch / DemuxVOASwitches
Switched (iPLC) VOASwitches
λN
λ1
λN
... ...λ1
1 N1 N Add
1 x N iPLC
Add / DropNN 1 N
DropAdd
Broadcast and Select Switched (WSS)
1 N 1 N
1x1 WSS 1 x N WSS
1 N
. . .
6
1 NDrop
1 NAdd 1
AddN1 N
Drop
2-deg. ROADM Node – Fixed λ per port
Transponders iPLC implementation
l dd & O
2 1 WSS1 2 litt
Built-in add mux & OPM
100GHz/40λ
2x1 WSS1:2 splitter
Lowest pass-through loss
T d
Lowest pass through loss
100GHz/40λ and 50GHz/80λ
7
Transponders
2 deg. ROADM node - Colorless
1x9 WSS 9:1 coupler
TranspondersCurrently limited to 8 drop ports
Higher loss (mainly from coupler)Transponders Higher loss (mainly from coupler)
Higher cost compared to 2x1 WSS
1x9 WSS 9:1 coupler
h dd l SS’Expansion with additional Nx1 WSS’s
8
Transponders
ROADM scalability (deg-2)
Splitter
WSS
XPDR
XPDR
Add/Drop
XPDR
XPDR
Network Interface 1 (Degree 1)
Network Interface 2 (Degree 2)
WSS
9
ROADM scalability (deg-3)
Splitter
XPDR
XPDR
XPDR
XPDR
WSS
Add/DropNetwork Interface 1
(Degree 1)
Network Interface 2 (Degree 2)
WSS
Network Interface 3 Add/Drop
XPDR
XPDR
Network Interface 3 (Degree 3)
10
ROADM scalability (deg-4)
Splitter
XPDR
XPDR
XPDR
XPDR
WSS
Add/DropNetwork Interface 1
(Degree 1)
Network Interface 2 (Degree 2)
WSS
Network Interface 4 Network Interface 3 XPDR
XPDR
(Degree 4)XPDR
XPDR
Network Interface 3 (Degree 3)
11
Directionless multi-deg. ROADM node
Additional 9x1 WSS for directionless
Fixed wavelength per transponder Tx/Rx portsFixed wavelength per transponder Tx/Rx ports
Network Interface 1 Network Interface 2
1:N splitter
Nx1 WSS
12
Transponders
Colorless and directionless MD-ROADM
Network Interface 1 Network Interface 2
1:N splitter
Additional 1xN for colorless
Nx1 WSS
Wavelength blocking
Non-blocking options using
N M WSSNxM WSS
Optical cross-connect with filters, splitters, or 1xN WSS
T d
13
Transponders
ROADM Technologies
2-degree MEMS – one axis for switching other for attenuation2-degree MEMS – one axis for switching, other for attenuation
Liquid crystals – stacked for Nx1 WSS
Liquid crystal + 1-degree MEMS – MEMS attenuation LC switchingLiquid crystal + 1-degree MEMS – MEMS attenuation, LC switching
Liquid crystal on Silicon (LCOS) – multiple LC elements per λ
Digital MEMS (DLP array) multiple mirrors per λDigital MEMS (DLP array) – multiple mirrors per λ
Integrated planar lightwave circuits (iPLC) – silica or polymer
Tunable filters (free space optics fiber gratings PLC)Tunable filters (free-space optics, fiber gratings, PLC)
14
Transmission Impairments
Insertion loss
Bandpass width and shape
Laser wavelength vs. bandpass center offsetLaser wavelength vs. bandpass center offset
Crosstalk and isolation
Att ti d t bilitAttenuation accuracy and stability
PDL
PMD
Chromatic dispersion and phase ripple
15
Loss
ROADM loss on express path includes
WSS – across wavelengths, temperature, polarizationWSS across wavelengths, temperature, polarization
Splitter/Coupler
Power ripple from upstream fiber spans/network nodes
Monitoring taps, ageing margin, equalization tolerances…
1x9 WSS 9:1 coupler2 D C l l
8x1 WSS1:8 splitter
2 Deg. Colorless
2x1 WSS1:2 splitter
8 Deg. Colored
16
p
2 Deg. Colored
ROADM loss in long-Haul networks
ROADM
28
30ROADM 12dB
22
24
26
[dB
]
ROADM 20dB20dB Span
16
18
20
OSN
R [
25dB Span
10
12
14 25dB Span
17
0 2 4 6 8 10 12 14 16 18 20 22 24Number of Spans
ROADM loss in metro networks
ROADM
30
Lower Loss = Lower cost by eliminating post-amp
22
24
26
28
B]
ROADM 12dB - 1 amp
ROADM 20dB - 2 amps
16
18
20
22
OSN
R [d
B
10
12
14
18
0 2 4 6 8 10 12 14 16 18 20 22 24Number of Spans
Cascaded PLC ROADMs & Interleavers
ROADM
Passband narrowing and accumulated ripple in recirculating loop with 80λ ROADMs
Individual passbands of 50GHz i t l d 100GH PLC ROADM
Tx Rxin recirculating loop with 80λ ROADMs
Passband shape after 24 ROADMs
-4
-2
Individual passbands of all devices (even)interleavers and 100GHz PLC ROADMs
-4
-2
08x cascade of 6 interleavers (even) and 3 eROADMs(8 loops x3 ROADMs per loop
-12
-10
-8
-6
IL [d
B] PLC
ROADMinterleaver -12
-10
-8
-6
IL [d
B]
-20
-18
-16
-14
-20
-18
-16
-14
19
1530 1530.5 1531 1531.5[nm]
1530 1530.5 1531 1531.5[nm]
10G NRZ – 24 ROADMs
10G NRZ not impacted by passband narrowing and accumulated ripple in recirculating loop tests
16
17
)
With ROADMsWithout ROADMs
pp g p
15
16
mea
sure
d) Back-to-back
13
14
Q_e
ff [d
B] (
m
12
13
1525 1530 1535 1540 1545 1550 1555 1560 1565
Q
20
1525 1530 1535 1540 1545 1550 1555 1560 1565Wavelength [nm]
10G Metro-Access Lasers
-3
-2
-1
0
40
60
80
100
tance
sion
m]
100GHz PLC ROADM for metro applications
4.010
-9
-8
-7
-6
-5
-4
[dB
]
100
-80
-60
-40
-20
0
20
[ps/
nm]
ROADM 1ROADM 2ROADM 3ROADM 4
Tran
smitt
[dB]
Dis
per
s
[ps/
nm
Wavelength drift of unlocked lasers can generate higher penalties
2.5
3.0
3.5
lty [d
B]
16 ROADMs12 ROADMs8 ROADMs
-10-0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4
[nm]
-100
l i h d b
1.0
1.5
2.0
OSN
R P
enal 8 ROADMs
4 ROADMsPenalties enhanced by
propagation through same devices in recirculating loop
Wid hi h d
0.0
0.5
-0.10 -0.05 0.00 0.05 0.10
Wider, higher-order Gaussian shaped passband required for unlocked lasers
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Wavelength [nm]
S. Tibuleac et al. Asia Pacific Optical Communications Conference 2006
Tunable-filter ROADMs
<0.8dB OSNR penalty for 10G, +/-0.15nm drift after 32 devices
No penalty if adjacent λ’s passed throughNo penalty if adjacent λ s passed through
No penalty for 40G NRZ-DPSK after 8 devices (locked lasers)
UNLOCKEDAdd
Express CommonTF-ROADM
LO
CK
ED
TF-ROADM
x6
Tx Rx
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M. Filer et al. IEEE LEOS Conference 2008
40-Gb/s Modulation Format Comparison
ODB/
PSBT
NRZ-ADPSK RZ-ADPSK RZ-DQPSK PM-QPSK
OSNR @ 10-3 [dB] 17.5 13.0 12.5 13.5 12.5
Nominal reach [km] 700 1600 2200 1400 1700
Signal Bandwidth Narrow Medium Wide Narrow Very Narrow
PMD tolerance [ps] 2.5 3.5 3.5 6 3 … 6
Nonlinear sensitivity Medium Low Lowest High High
Complexity / Cost Low Low Low/ Medium High Highest
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Modulation formats with narrow optical spectrum are more sensitive to nonlinear impairments than formats with wide spectrum!
40G Modulation Formats
10
Modulation formats for commercial 40G transponders
-10
0
10
m]
-30
-20
10
Bm
/0.0
1n
-50
-40
Pow
er [d
NRZ-DPSKRZ-DPSKCS-RZ
-70
-60
-120 -80 -40 0 40 80 120
CS-RZRZ-DQPSKPSBT
24
-120 -80 -40 0 40 80 120Relative Frequency [GHz]
Comparison with ROADM Bandpass
Signal bandwidth clipped by passband of 50GHz WSS
0
nm]
20
-10
dBm
/0.0
1n
-30
-20
Pow
er [d
NRZ-DPSKRZ-DQPSK50 GHz
-40-80 -60 -40 -20 0 20 40 60 80
50 GHz100 GHz
25
Relative Frequency [GHz]
Bandwidth Narrowing
45
40
dth
[GH
z] Measured WSS-50 ROADM Cascade
30
35
dB B
andw
id
4½ Order Gaussian
4th Order Gaussian
25
Ove
rall
3-d
Calculated2nd Order Gaussian
3rd-Order Gaussian
4th-Order Gaussian
201 10 100
N b f C d d ROADM
2nd-Order GaussianTransmission Function
26
Number of Cascaded ROADMs
Impact of Bandpass Width & Shape
OSNR Penalty at BER 5E-5 after 12 ROADMs
40G DPSK FSR 66GHz
10
]40G DPSK FSR 66GHz
Gaussian Order
6
8
nalty
[dB
]
123
2
4
SNR
Pen
3468
03040506070
3 dB BW f i l ROADM (GH )
OS
27
3-dB BW of single ROADM (GHz)
43-Gb/s Transmission over Linear WSS Cascade
OSAOSNRPreset to λ0 = 1555.75 nm (Not Tunable )
43-Gb/s NRZ- / RZ-DPSK Transmitter
TapVar.Atten.
50-GHz WSS # 1
50-GHz WSS # 4
(N)RZ-DPSKAtten.WSS # 1 WSS # 4
50-GHz 50-GHzWSS # 5
1.1-nmFiltTODC
WSS # 8 WSS # 5 Filter
Optical Noise Inserted Midway in WSS Cascade(OSNR Corrected for Filtering in Following WSS’s)
TODC
Delay Δt (OSNR Corrected for Filtering in Following WSS s)
Conventional 43-Gb/s NRZ- / RZ-DPSK Transmitter Balanced Detector with Delay Interferometer for “St ” ADPSK
Delay Δt
Mintera MI 40000
28
“Strong” ADPSK,Evaluation Unit
F. Heismann and P. Mamyshev, OFC’09 Paper OThC1
OSNR Penalty vs. Optical Bandwidth
19
20
dB] 43-Gb/s Transmission Through Cascaded WSS's
17
18
19
−3 B
ER
[d
Optical
Steep Increase Below 32 GHz
16
17
NR
for
10
pDuobinary
14
15
uire
d O
SN
NRZ ADPSK
RZ-ADPSK
12
13
30323436384042444648505254565860
Req NRZ-ADPSK
29
3-dB Bandwidth of WSS CascadeF. Heismann and P. Mamyshev, OFC’09 Paper OThC1
Spectrally Dependent Interference
isolationJDSU MWS50
Interfering power is concentrated at edges of signalinterference
isolation
g p gchannel band
Constant Isolation at channel center, rising towards edges
f
signal
interference Interfering power is has components at center and at edges of channel
Spectrally Constant (Coherent)
isolation
signal
interference
Interfering power is concentrated at center of channel
Out-of-Band InterferenceInterfering power has no spectral overlap with
interference
Interfering power has no spectral overlap with signal
30
signal
Interference at Channel Center is ~10dB More Damaging
0.8
1
-3) [
dB]
FSO MEMS WSSFlat Isolation Profile WSSIn-Band InterferenceOut-of-Band Interference
0.8
1
0-3) [
dB]
FSO MEMS WSSFlat Isolation Profile WSSIn-Band InterferenceOut-of-Band Interference Ba
nd
t Iso
latio
n
0.4
0.6
nalty
(BER
10- Out-of-Band Interference
0 2
0.4
0.6
enal
ty (B
ER 1
0
Out
-of-B
n-Band
Flat
O MEMS~10dB
-0.2
0
0.2
OSN
R P
e
-0.2
0
0.2
OSN
R P
e In-BFSO M
-10
0
-10
0 FlatI l ti
Interference at Rx -10
0] -10
0]
Interference at Rx
-35 -30 -25 -20 -15 -10 -5Total Interference Power/Total Signal Power at Rx [dB]
-35 -30 -25 -20 -15 -10 -5Total Interference Power/Total Signal Power at Rx [dB]
-50
-40
-30
-20
10
Inte
nsity
[dB
]
-50
-40
-30
-20
10
Inte
nsity
[dB
] Isolationat Rx
-50
-40
-30
-20
10In
tens
ity [d
B]
-50
-40
-30
-20
10In
tens
ity [d
B]
FSO MEMS
at Rx
31
-60-40 -20 0 20 40
Normalized Optical Frequency [GHz]
-60-40 -20 0 20 40
Normalized Optical Frequency [GHz]
-60-40 -20 0 20 40
Normalized Optical Frequency [GHz]
-60-40 -20 0 20 40
Normalized Optical Frequency [GHz]
B. Collings, F. Heismann, C. Reimer, OFC ’09 Paper OThJ3
Developments in ROADM subsystems
Improvements in specifications: loss, passband shape, etc
Increased ports (1x20) for colorless ROADM
NxM for colorless and directionless multi-degree ROADM nodes
Integration of optical performance monitoring
Lower-cost WSS or tunable filters for access networks
Integration of new functions: bandpass shaping, dispersion compensation
Si d tiSize reduction
Lower power consumption
32
NxM WSS for multi-degree ROADM
12x40 MEMS array with integrated drive electronics
MEMS mirrorsMEMS mirrors
IC’s driving i tiltmirror tilt
33
M. Nagy and S. Tibuleac, Photonics Spectra Nov. 2006
DRAGON Network Washington DC
5x5 WSS ROADM used in dynamic private network
MIT Haystack ObservatoryU. S. Naval Observatory
University of Maryland Goddard Space Flight Center
CLPKDCGW
DCNE(Q t)
GIG-EF
ARLG
MCLN(Level3)
(Qwest)HOPI
NREN ABILNLR(Level3)
Univ of Southern California/Information Sciences Institute
National Center for Supercomputing Applications
34
S. Tibuleac et al. ECOC 2006, Xi Yang et al. OFC 2006
NxM Multicast WSS
4x8 WSS for Colorless and Directionless ROADM
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
N W E SDirectionless ROADM nodes
• Uses splitters, 4x1 l h d
1x8 TSp
1x8 TSp
1x8 TSp
1x8 TSp
N W E S
optical switches, and tunable filters
• Non-blocking
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
g
• Flexibility to change port and degree requirements
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
• Port expandable
I2C, RS232, DPRAM
λa λcλb λd λfλe λg λh
35
Customer’s Control Unit
DPRAM
www.enablence.com
Kx(NxM) Multicast WSS, Expandable Module
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
λ1 λ2..... λ43 λ44
• 1st stage, tunable splitter, split ratio can be adjusted freely from switch to splitter function. 44
1xK TSp
1xK TSp
44
1xK TSp
1xK TSp
switch to splitter function.
• setup one 4x8 first for 8 drop ports, then add more drop ports by adjusting split ratio when
1x8 1x8 1x8 1x8 1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
1x8 Sp
by adjust g sp t at o eneeded.
Sp SpSpSp
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
1x1 1x1 1x1 1x1 1x1 1x1 1x11x1
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
4x1 OSw
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
1x1 TF
36www.enablence.com
Passband shaping
LCOS 2D array with multiple mirrors per wavelength
Control of filter transmission profile
Linear amplitude slopeGaussian functions of different orders
37
Programmable dispersion
Dispersion control with LCOS WSS
+/ 80ps/nm for 0 5nm bandwidth+/-80ps/nm for 0.5nm bandwidth
6
-4
[dB
]
6
-4
[dB
]
-10
-8
-6
Inse
rtio
n lo
ss [
-90 ps/nm -10
-8
-6
Inse
rtio
n lo
ss [
90 ps/nm
0
20
p de
lay
[ps]
-70 ps/nm-40 ps/nm-20 ps/nm0 ps/nm
0
20
p de
lay
[ps]
70 ps/nm40 ps/nm20 ps/nm0 ps/nm
1552.8 1552.9 1553 1553.1 1553.2 1553.3 1553.4
-20
Wavelength [nm]
Gro
u
1552.8 1552.9 1553 1553.1 1553.2 1553.3 1553.4
-20
Wavelength [nm]
Gro
up
38
Ref: Roelens et al, JLT 2007
Programable Channel Plan on 2x1 WSS
Mixing of 50GHz, 100GHz and 200GHz frequency spacing
Future proof for any conceivable channel modulationp y
Relevant for infrastructure to support future 100 GbE
Programmable continuous spectral shaping
393939
T. Strasser, IEEE LEOS 2008
Continuous Programmable Passband
Continuous passband to define channels in software
No filtering impairment transmitting through full passbandg p g g p
High out-of-band attenuation
4040
Ultrafast Switching
Microsecond VOA and optical switching with digital MEMS
Improves power control of optical transients Improves power control of optical transients
Enables optical protection switching
VOA ChangeVOA Change
0-15 dB0-1 dB
4141
ROADM Challenges for Control Plane
New CapabilitiesD namic choice of add/d op s passth o gh (2 deg ee ROADM)Dynamic choice of add/drop vs. passthrough (2-degree ROADM)Transparent wavelength switching (multi-degree ROADM)Mesh topologies; multiple paths between endpointsOnboard power monitoring, equalization requirementsOnboard power monitoring, equalization requirements
New ConstraintsMany possible ROADM node architectures, with specific quirksROADM “switches” are not orthogonal (continuity requirements, etc)With many possible paths, path selection must be channel-awareUntil tunable filters channel selection still restricted at endpointsUntil tunable filters, channel selection still restricted at endpoints
Result: Management/Control Complexity
42
Mesh Topologies
B
A -> D, red
A
Blocked link
B -> C, red
C
Path selection must now consider many more factors
D
43
Control Plane Components
Automated Discovery Path Computation Signaling/Provisioning
Topology
How is this network connected?
Capabilities
Path Identification
Which paths are even available?
Path Selection
Element Level
What local equipment must be configured?
Network Level
Fundamental Control Plane technologies applied to reducing
What can this network accomplish?
Which paths meet my service criteria?
Which elements need configuring, in what order?
44
Fundamental Control Plane technologies applied to reducing complexity of managing ROADM networks
Power Equalization
End-to-End Service Power EqualizationROADMs include per-wavelength power monitoring, per nodeROADMs include per wavelength power monitoring, per nodeOptical service may traverse multiple ROADM nodes
End-to-end equalization requires adjustments at each node along pathNodes must equalize in sequence, to ensure convergence
Control plane has path, sequence knowledgeSignaling occurs in strict ingress-to-egress sequence
Path computation produces path, signaling follows path
Sequencing used during service provisioningEnables orderly setup, orderly rollback if error occurs
Same sequencing capability useful for power equalizationSame sequencing capability useful for power equalizationEnd-to-end equalization sequence same as initial setup sequenceControl Plane already knows how to follow a path, perform provisioning
45
Control Plane can automate initial end-to-end channel equalization
Equalization Process
Path
Path Setup phase (HW at max attenuation) …
[1533.47][1549.32][1549.32] [1533.47]
Resv
[DN EQ] [DN EQ][DN EQ][DN EQ]
… followed by Path Equalize phase (VOAs/ROADMs adjust)
[ Q]
[UP EQ][UP EQ][UP EQ] [UP EQ]
[ Q][ Q][ Q]
Data Flow
46
Summary
ROADMs have seen widespread deployments in long-haul and metro DWDM networksmetro DWDM networks
Multiple technology options and node configurations lower network cost and increase flexibility
DWDM network design must account for transmission impairments introduced by each ROADM type
40G transmission through large number of network nodesSignificant improvements in optical specifications of Nx1 WSSImproved understanding of system performance
ROADM technologies offer new features which benefit 40G/100G g /with full flexibility in wavelength routing
Control Plane technologies have adapted to incorporate capabilities of and constraints imposed by ROADM elements
47
p p y
Acknowledgments
Mark Filer, ADVA Optical Networking, p g
Wes Doonan, ADVA Optical Networking
Brandon Collings, JDSUg ,
Fred Heismann, JDSU
Tom Strasser, NisticaTom Strasser, Nistica
Simon Poole, Finisar
All colleagues at ADVA Optical NetworkingAll colleagues at ADVA Optical Networking
48