Transcript ROADM Network Elements

ROADM Network Elements
Brandon Collings
Optical Networks Research, JDSU
[email protected]
OFC 2007 OThR1
Overview
 Market Drivers for ROADM Networks
 Primary ROADM Network Features
 ROADM Node Building Blocks and Node
Architectures
 Physical Layer Operational Features and
Automation
 ROADM Component Characteristics and System
Performance
 Network Management
 Current and Future Trends
2
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Market Drivers for ROADM
Networks
Bandwidth is increasing…
 Capacity increase is significant
 But the real story is how that capacity is evolving…
source: G.K. Cambron, AT&T, OFC/NFOEC ‘06
4
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Drivers of the Today’s All Optical Networks
Triple Play
Services
Rich Media
Services
US HQ
Business
Services
Tokyo
5
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Consumer Driven Applications
Content and bandwidth is evolving in a peer-to-peer topology
Bandwidth is increasing and predictability decreasing
 Downloading TV programs from the Web is becoming more popular with
consumers. There was a 39% increase in subscription rentals of TV
content and a 255% increase in TV-title digital video downloads
between August 2005 and August 2006. (NPD Group)
 In December 2006, Xbox Live surpassed 4 million members worldwide.
Microsoft expects it to surpass 6 million members by the summer of
2007.
 According to YouTube, it is currently serving 100 million videos per day,
with more than 65,000 videos being uploaded daily.
 In January of 2007 Apple announced that more than two billion songs,
50 million television episodes and over 1.3 million feature-length films
have been purchased and downloaded from the iTunes Store
6
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Rich Media Services Have Changed the Network Model
The “Telephony Network”




7
Sonet-SDH network
Bandwidth predictable
Traditional usage voice, dial-up
Low bandwidth, low use and short duration
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The Agile Optical Network




DWDM Network
High bandwidth applications
Always-on
Unpredictable traffic and growth patterns
Market Overview : Technology Trends
$900
Agile + Fixed CAGR = 19%
$800
$700
39%
$600
$(M)
$500
$400
$300
Rapid Transition from Fixed to Agile
79%
$200
$100
61%
Agile CAGR = 55%
21%
$2004
2005
2006
Agile
2007
2008
Fixed
Source: Ovum-RHK, Transition to agile optical network drives
ROADM and related modules growth, 2/2006
CAGR data is 2004-2010
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The Agile Optical Network is Happening Today
“While not everyone has
announced their
deployment of Agile
Optical Networks, most
are using them in some
form or fashion”
Brett Azuma
Exec VP, Ovum-RHK
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Primary ROADM Network Features
Let’s just get this out of the way…
Unsuccessful Business
Case
COST!
Successful Business
case in some market
segments
A Technology and
Manufacturing
Challenge
11
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Static Networks Based on Fixed-Wavelength Filters
 Topology and capacity/node determined
at time of network design
– Traffic projections based upon best
estimates at the time
– Frequently changes even during
design/bid/deployment
– Not always cost effective to “overbuild”
the system
Hub
 Can lead to premature system exhaust
– Expected system lifetime: 5-10 yrs
– Traffic projections not accurate leading
to premature system exhaust
Ch 1-8
Ch 1-32
• Insufficient l’s available to hot spots
• Unlit l’s to cold spots cannot be utilized
– Topology is inconsistent for emerging
applications
• Telephony, SAN, Enterprise, VoD, TBD
topologies look different
Ch 9-16
Physical WDM Ring
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Ch 17-24
Ch 25-32
ROADMs Enable Any-Node-to-Any-Node Topologies
– Relieves need for accurate traffic
growth forecasting
(2x1 Switch+VOA) Array
MUX
TAPs &
PD Arrays
ROAM
ROADM
DEMUX
 Provision wavelengths
independently between nodes
 No blocking extends system
life to capacity limitation
ADD
CHANNELS
VOA
Tap
PD
DEMUX
TAP
& PD
Array
ROADM
DROP
CHANNELS
Demux-T
ROADM
ROADM
ROADM
Physical WDM Ring
13
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All Optical Ring Interconnect Reduce OEO Costs
ROADM
ROADM
ROADM
ROADM

OEO transition requires additional equipment with each wavelength
Electrical switching fabrics generally not as scalable
Traffic can be routed without craft visit to node
ROADMs are bit-rate independent
–
14
Removes cost of OEO and electrical fabric
ROADM Nodes capable of remotely routing full capacity of channels without additional
equipment
–
–


Required O/E transponders on both rings
Requires electrical switch and grooming fabric
Multi-Degree ROADM Nodes enable inter-ring traffic to remain in the optical domain
–

ROADM
Ring-to-Ring traffic previously electrically cross-connected
–
–

ROADM
OEO
ROADM
Implement higher line rates when, where and if the economics prove in
© 2007 JDSU. All rights reserved.
All Optical Ring Interconnect Reduce OEO Costs
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM

Ring-to-Ring traffic previously electrically cross-connected
–
–

OEO transition requires additional equipment with each wavelength
Electrical switching fabrics generally not as scalable
Traffic can be routed without craft visit to node
ROADMs are bit-rate independent
–
15
Removes cost of OEO and electrical fabric
ROADM Nodes capable of remotely routing full capacity of channels without additional
equipment
–
–


Required O/E transponders on both rings
Requires electrical switch and grooming fabric
Multi-Degree ROADM Nodes enable inter-ring traffic to remain in the optical domain
–

ROADM
Implement higher line rates when, where and if the economics prove in
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Accelerated Service Roll-out
 Remote provisioning and automated control plane
enable more rapid service commissioning
–
–
–
–
16
Shorter Time-to-Revenue and Return on Investment
Increased customer capture
Shorter and predictable deployment intervals
Network topology flexibility reduces network
configuration churn
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ROADM Node Building Blocks and
Node Architectures
Four Basic Types of ROADM Components
Tunable
Channel
Filter
Tunable
Band
Filter
PLC
ROADM
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Wave
Blocker
(WB)
Wavelength
Selectable
Switch
(WSS)
Typical Tunable Channel Filter Node Architecture
From
West
Coupler
To
East
Coupler
OA
OA
Wave
Blocker

Tx
Tx
Tx
Tx
Receivers
Rx
Rx
Rx
Rx
Tunable
Filters
DROP
ADD
Transmitters
Independent access to all wavelength channels
– Number of Add/Drop ports less than maximum wavelength count


Tx/Rx ports are wavelength provisionable (colorless)
Supports drop and continue
– Waveblocker required for wavelength reuse

Add channels power equalized
– Express channels equalized if WaveBlocker included

19
Supports 2-degree nodes
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Typical Tunable Band Filter Node Architecture
From
West
OA
Band
Filter

DROP
ADD
Channels added/dropped in bands
– Width of bands may be fixed or adjustable
– Band is tunable in wavelength





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Tx/Rx ports are wavelength specific (colored)
Wavelengths may be reused
Add channels power equalized
Does not support drop and continue
Supports 2-degree nodes
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OA
AWG
Tx
Tx
Tx
Tx
Receivers
Band
Filter
Rx
Rx
Rx
Rx
AWG
To
East
Transmitters
Typical WaveBlocker Node Architecture
From
West
Coupler
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AWG
Tx
Tx
Tx
Tx
Wave
Blocker
OA
Rx
Rx
Rx
Rx
AWG





Coupler
Block
OA
Receivers
To
East
DROP
ADD
Transmitters
Independent access to all wavelength channels
Tx/Rx ports are wavelength specific (colored)
Express and Add channels are power equalized
Supports drop and continue
Supports 2-degree nodes
© 2007 JDSU. All rights reserved.
Typical PLC ROADM Node Architecture
From
West
Coupler
OA
To
East
PLC
ROADM
OA



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DROP
ADD
Independent access to all wavelength channels
Tx/Rx ports are wavelength specific (colored)
High level of integration
–
–
–
–

Tx
Tx
Tx
Tx
Receivers
Rx
Rx
Rx
Rx
AWG
Add direction wavelength multiplexing
Per channel power monitoring (Add and Express)
Add and Express channel power equalization
Express or Add channel selection
Supports 2-degree nodes
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Transmitters
PLC ROADM Block Diagram
220 mm X 135 mm X 36 mm : DOUBLE SLOT MS A
PD 1
VPD 1
COMMON
INPUT
DROP
OUTP UT
SPLITTER
COMMON
OUTP UT
DEMUX AWG
MUX AWG
VPD 2
PD 4
PD 5
EXPRESS
OUTP UT
EXPRESS
INPUT
PD 2
PD 3
LEGEND
VOA
ADD INPUTS
SWITCH
TAP
DETECTOR
PD: Physical
VPD: Virtual
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Mux and Demux WSS Node Architecture
To
East
Receivers
WSS
WSS
Tx
Tx
Tx
Tx
OA
Rx
Rx
Rx
Rx
From
West
DROP
ADD
OA
Transmitters
 Independent access to all wavelength channels
– Number of Add/Drop ports less than maximum wavelength count
– Cascade secondary WSS components off primary WSS for additional ports




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Tx/Rx ports are wavelength provisionable (colorless)
Express, Add and Drop channels power equalized
Does not support drop and continue
Supports 2-degree nodes
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Demux WSS Node Architecture
From
West
To
East
Coupler
OA
OA
WSS
Tx
Tx
Tx
Tx
Receivers
Rx
Rx
Rx
Rx
Coupler
DROP
ADD
Transmitters
 Independent access to all wavelength channels
– Number of Add/Drop ports less than maximum wavelength count
– Cascade secondary WSS component off primary WSS for additional ports




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Tx/Rx ports are wavelength provisionable (colorless)
Express, Add and Drop channels power equalized
Does not support drop and continue
Supports 2-degree nodes
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Multi-Degree WSS Node Architectures
Demux 1xN WSS
North In
South In
Mux Nx1WSS
North Out
South Out
East In
East Out
West In
West Out
 Demux
WSS
selectively
routes
wavelengths
to destination
Replace
Mux
Demux
WSS
WSS
with
with
power
power
combiner
splitter
output degrees
 Mux
Demux
WSS
WSS
selectively
selectively
accepts
routeswavelengths
wavelengths
 Mux WSS selectively accepts wavelengths intended for its
intended for its
each
respective
respective
degree
degree
respective degree
–
isolation
for those wavelengths not intended for
– Provides
Blocks undesired
wavelengths
a given
its
respective
degreedegree
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Multi-Degree Demux WSS Node Architecture
Coupler
Tx
Tx
Tx
Tx
ADD
Coupler
WSS
DROP
Rx
Rx
Rx
Rx
OA
OA
North
East
West
Coupler
OA
OA
WSS
Coupler
Tx
Tx
Tx
Tx
Coupler
Rx
Rx
Rx
Rx
OA
WSS
ADD
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OA
OA
27
South
DROP
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Coupler
Coupler
ADD
Tx
Tx
Tx
Tx
ADD
Tx
Tx
Tx
Tx
WSS
Coupler
DROP
DROP
OA
Characteristics of Multi-Degree Demux WSS Architecture
 Supports any wavelength from any degree to any degree
 Drop port count limitations due to port sharing with interdegree connections
 Add/drop ports are colorless
– No add port filtering rejects rogue wavelengths or noise
 Does not support drop and continue
 Drop and express channel equalization provided by WSS
OA
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OA
Rx
Rx
Rx
Rx
South
DROP
Coupler
Coupler
ADD
Tx
Tx
Tx
Tx
WSS
– Add port VOAs provide add channel equalization
Multi-Degree Mux WSS Node Architecture
Tx
Tx
Tx
Tx
ADD
WSS
AWG
OA
Coupler
AWG
DROP
Rx
Rx
Rx
Rx
OA
North
East
West
WSS
Coupler
OA
OA
AWG
Coupler
Tx
Tx
Tx
Tx
OA
Rx
Rx
WSS
Rx
Rx
AWG
ADD
DROP
AWG
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South
DROP
AWG
OA
OA
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Coupler
WSS
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Rx
Tx
Tx
Tx
Tx
AWG
ADD
Tx
Tx
Tx
Tx
ADD
AWG
DROP
OA
Characteristics of Multi-Degree Mux WSS Architecture
 Supports any wavelength from any degree to any degree
 Add/drop ports present for all supported channels
 Add/drop ports are colored
– Add port filtering rejects rogue wavelengths
 Supports drop and continue
 Add and express channel equalization provided by WSS
OA
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Rx
Rx
Rx
Rx
South
DROP
Coupler
WSS
OA
AWG
ADD
Tx
Tx
Tx
Tx
AWG
– No per channel power control on drop ports (unless VOAs included)
Multi-Degree Mux and Demux WSS Node Architecture
ADD
Tx
Tx
Tx
Tx
WSS
Coupler
WSS
DROP
Rx
Rx
Rx
Rx
OA
OA
North
East
West
Coupler
WSS
OA
OA
Coupler
Rx
Rx
Rx
Rx
OA
Tx
Tx
Tx
Tx
WSS
WSS
ADD
WSS
© 2007 JDSU. All rights reserved.
South
DROP
Coupler
OA
OA
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Rx
Rx
Rx
Rx
Rx
Rx
Rx
Rx
WSS
ADD
Tx
Tx
Tx
Tx
ADD
Tx
Tx
Tx
Tx
WSS
DROP
DROP
OA
Characteristics of Multi-Degree Mux and Demux WSS
Architecture
 Supports any wavelength from any degree to any degree
 Drop port count limitations due to port sharing with interdegree connections
 Add/drop ports are colorless
– Add port filtering rejects rogue wavelengths and noise
 Supports drop and continue
 Add and express channel equalization provided by Mux
WSS
© 2007 JDSU. All rights reserved.
OA
OA
32
Rx
Rx
Rx
Rx
South
DROP
Coupler
WSS
ADD
Tx
Tx
Tx
Tx
WSS
– Demux WSS provides drop channel power control
Optical Layer Architectural Feature Comparison
Tunable
Filter
Wave
Blocker
PLC
WSS
(Mux)
WSS
(DMx)
East/West Node Equipment Separability





Add/Drop with Channel Granularity
O




Access to Any Combination of Channels
O




Add/Drop Port Count Equal to Channel Count
-



O
Non-service Affecting Upgrades
O




Drop and Continue


-

-
Equalization of Expressed Channels
-




Add Channel Rogue Wavelength Protection




-
Add Channel Power Control
O



O
Drop Channel Power Control
-
-
-
-

Colorless ports
O
-
-
O

Mesh Topology/Higher Degree Node Support
-
-
-


Feature
 Intrinsically Supported
O Support depends upon particular configuration or inclusion of specific elements (i.e. VOA’s)
- Not Supported
33
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Physical Layer Operational
Features and Automation
ROADM Network Operational Features and Automation
 Reconfigurability requires visibility into the optical layer and automated
control
– Monitor wavelength routing
– Monitor optical layer performance
– Provide feedback for channel power adaptation
 Automated optical layer eases installation and operational activities
–
–
–
–
–
–
Quicker, cheaper, more predictable installation intervals
Reduces required craft training and in the field measurements
Minimizes complex activities such as power measurement and balancing
Neighbor node and configuration discovery
Minimizes errors
Provides fault correlation
 Automated control enables increased performance and reliability
– Longer system reach due to channel power equalization
– Increased adjustment accuracy than possible manually
– Performance monitoring and early warning alarms
 Simplifies support for alien wavelengths
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Optical Layer Monitoring Components
 Possible Monitored Parameters
–
–
–
–
Optical channel power
OSNR
Wavelength alignment
Wavelength ID or tag
 Characteristics
–
–
–
–
–
Measurement refresh rate
Single or multi-input (shared)
Single channel dynamic range
Adjacent channel dynamic range
Accuracy
Two Basic Types
Parallel
Scanning
AWG
Scanning
Tunable Filter
36
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Automatic Optical Power Management
 ROADM networks have a rich complement of
power control actuators
– Per channel power control at ROADMs
– Total average gain control at EDFAs
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Automated Channel Power Equalization
 Channel power levels become unequal
–
–
–
–
Accumulated optical amplifier gain shape
Non-uniform fiber loss
Inter-channel Raman pumping
Optical elements
 Added channels require leveling when introduced into
system
– Many transponders do not produce tightly controlled output power
– Power level may not be appropriate
– Insertion loss of add path can vary
 Feedback algorithms control both optical amplifier and per
channel attenuation
– Optical amplifiers operate on all channels
– Goal is to minimize amplifier gain
– Minimizes OSNR degradation
38
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Channel Power Level Transient Timescales
min/hour/day/year
~2ms
~100ms
Long Term Effects
Spectral Hole
15
Burning EDFA Transient
sat
sat
Hole Depth (dB)
GAIN (dB)
•Fibertime
loss aging
l for
Blue Curve•PDL
•Upstream fiber break or power
•Laser aging
•Gain spectrum
Difference of gain spectra
failure
changes due to
10
l for
Redinput
Curve
•Rapid
decrease
in
power
change in channel
Holes
at l
and/or
channel
count
loading
•EDFA reacts to maintain 1540 1560
5
1540
1560
stable
gain
for surviving
•Change can be
WAVELENGTH (nm)
positive or negative channels
sat
Srivastava et al, OFC 1995
39
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Reaction Rate of Power Control
 Power Measurement (Optical Channel Monitor)
– Parallel techniques: capable of sub-millisecond
– Scanning techniques: 10’s of ms to seconds
• Technology dependent
– Multi-Input OCMs
• Utilizes high isolation Nx1 selection switch
• Decreases refresh rate by >N times
 Attenuation Change Actuation
– VOAs: typically on the order of milliseconds
– ROADMs: several milliseconds to seconds
• Technology and magnitude of attenuation change dependent
40
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Power Level Transient Mitigation
 Transient suppression in the EDFA
– ROADM and VOA reaction rates currently insufficient
 Gain change due to SHB requires ROADM attenuation
correction
– Gain change is typically small per amplifier (<0.5dB)
– Change to channel power can accumulate with EDFA cascade
– Depending upon ROADM attenuation speeds, some channels may
be “unequalized” for several milliseconds
 During this period, system performance may be impacted
– Duration is sufficient to trigger protection switch if impact is
sufficiently severe
– System design concern on extent to which system reach can be
extended by capitalizing on channel power equalization
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Commissioning/Decommisioning
 Intentionally slow introduction and removal of
optical power during network activities
– Channel installation or removal
– EDFA installation or removal
– Fiber connection or disconnection
 Power control algorithms can react and keep
system in equilibrium
42
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ROADM Component
Characteristics and System
Performance
Cascading ROADM Nodes
 Details of the channel filtering become significant
as number in cascade increases
– Amplitude Response
• Wide, flat top shape required
– Phase response
• a.k.a group delay which causes dispersion
• Group delay ripple and structure must be minimized
– PMD
 Channel spacing and Bit Rate
– 10Gb/s typically not significantly impacted
– 40Gb/s over 50GHz ROADMs has been deployed
• Using advanced modulation techniques
44
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Typical WSS-based Node and Port Isolation
…what happens to li in WSS?
li,port_1 from deg 1
AWG
AWG
splitter
Degree 2
splitter
Degree 1
li,port_2
from deg 2
li,port_3
from deg 3
li,port_4
from deg 4
from deg m-1
li,port_m-1
li,add
1xm WSS
AWG
splitter
Degree m-1
AWG
45
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from add
port isolation (PIso)
port selected to pass
Output (at li) is
coherent combination
of li,port_2 along with m1 li signals, each
suppressed by PIso
OSNR Penalty versus Port Isolation
 Assumes nominal attenuation of 4 dB for channel power
equalization
 N is the number of interfering signals present
OSNR Penalty [dB, BER=1e-4]
3
2.5
N=8
N=16
2
N=24
N=48
1.5
N=64
1
0.5
0
35
37.5
40
42.5
45
WSS Port Isolation, PIso [dB]
46
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47.5
50
Network Management
Network Management
 Physical Layer Configuration Discovery
– Inventory
– Adjacent nodes
– Intra-node element interconnection verification
 Wavelength Routing Verification
 Performance Monitoring
– Full visibility into active wavelength performance
– Threshold crossing warnings and alarms
 Alarm Correlation
– Prioritize alarm closest to root cause
– Suppress other alarms resulting from fault condition
48
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Current and Future Trends
Current and Future General Trends
 Increased Component Integration
– Reduce cost through circuit pack consolidation
 Increased Use of Open Photonic Layers
– Improving physical layer automation increases acceptance criteria
for non-native (alien) wavelengths
– IP migration and proliferation of pluggable DWDM interfaces
 ROADMs Penetrating Edge/Access
– Highly cost sensitive
– Perhaps most rapidly evolving network space
 Enhanced In-situ Diagnostics
– Link performance and engineering rules validation
– Fiber plant characterization (dispersion, PMD, etc.)
 Increased utilization of topology flexibility and wavelength
tunability
– Restoration and disaster recovery
– Load balancing
– Protection switching
50
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Thank You