Next-Generation ROADMs October 1, 2012 Sheldon Walklin CTO, Optelian.
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Transcript of Next-Generation ROADMs October 1, 2012 Sheldon Walklin CTO, Optelian.
© 2011 Optelian. All rights reserved. 2
Contents
• Introduction• Wavelength Selective Switch• Colorless, Directionless and Contentionless• Flexible Bandwidth ROADMs and Transmission
Beyond 100 Gb/s• ROADM Control, OpenFlow and SDN• Conclusion
© 2011 Optelian. All rights reserved. 3
Wavelength Selective Switch Functionality
Nx1 WSS
. . .
SW 1 VOA 1
VOA M
CommonPort 1 . . .
. . .
. . .. . .
. . .
Port N
SW M
© 2011 Optelian. All rights reserved.
Colorless, Directionless and Contentionless (CDC)
4
Colorless
Any wavelength can be dynamically added/dropped without having to re-fiber a transceiver.
Directionless
A wavelength can be dynamically added/dropped from any direction without having to re-fiber a transceiver.
Contentionless
A wavelength can be re-used on all directions without any restrictions.
© 2011 Optelian. All rights reserved. 5
4-Degree ROADM (Colored)
Tx
RxTransceiver
Colored add ports Colored drop ports
ComOut
ComIn
WS
S
ComOut
ComIn
WS
S
ComOut
ComIn
WSS
ComOut
ComIn
WSS
A
B
C
D
A
. . .. . .. . .. . . . . .. . .. . .. . .
B C D A B C D
• In general, can build an N-degree ROADM using Nx1 WSSs and 1xN splitters.
• The color and direction are fixed by fiber connections.
© 2011 Optelian. All rights reserved. 6
4-Degree ROADM (Colorless)
ComOut
ComIn
WS
S
ComOut
ComIn
WS
S
ComOut
ComIn
WSS
ComOut
ComIn
WSS
A
B
C
D
A
. . .
B C D A B C DWSS WSS WSS WSS
. . . . . . . . .. . . . . . . . . . . .
Colorless add ports Colorless drop ports
Tx
RxTransceiver
• Any transceiver wavelength (color) can be remotely configured
• The direction is fixed by fiber connections.
• Reduced number of access ports compared to colored.
© 2011 Optelian. All rights reserved. 7
Colorless and Directionless
4x1 WSS
1xN WSS. . .
A
Drop directions
B C D
Colorless drop ports
. . .
A
Add directions
B C D
Colorless add ports
Passivecombiner
WavelengthContention
• Structure for cross connecting between degrees remains the same as shown for the 4-degree ROADM on earlier slide.
© 2011 Optelian. All rights reserved. 8
Colorless, Directionless and Contentionless(using NxM WSSs)
4xN WSS. . .
A
drop directions
B C D
Nx4 WSS. . .
A
add directions
B C D
CDC add portsCDC drop ports
© 2011 Optelian. All rights reserved. 9
Colorless, Directionless and Contentionless (using Broadcast-and-Select with Tunable Filters)
4x1SW
A
Drop directions
B C D
4x1SW
4x1SW
TF TF TF
4x1SW
4x1SW
4x1SW
A
Add directions
B C D
CDC add ports
CDC drop ports
© 2011 Optelian. All rights reserved. 10
Colorless, Directionless and Contentionless (using Adjunct NxM Photonic Switches)
• Use NxM photonic switches to upgrade existing colored ROADMs to full CDC functionality
NxM Switch NxM Switch. . . . . .
Colorless add ports Colorless drop ports
Tx
RxTransceiver
ComOut
ComIn
WS
S
ComOut
ComIn
WS
S
ComOut
ComIn
WSS
ComOut
ComIn
WSS
A
B
C
D
A
. . .. . .. . .. . . . . .. . .. . .. . .
B C D A B C D
© 2011 Optelian. All rights reserved. 11
Ideal CDC WSS
CDC ROADM(module)
Directions
A B C
D
CDC add portsCDC drop ports
• Concept module
• Non-blocking wavelength switching between any set of ports.
• Per wavelength attenuation control at line egress ports.
• Low insertion loss (up to a few dB)
• Very high reliability.
© 2011 Optelian. All rights reserved. 12
The Benefit of CDC Functionality
• Without CDC, cannot automatically restore optical circuit for failure on Span S1 or S6, or power failure at Node R2 or R4.
• CDC allows more flexibility to remotely reroute optical circuit when optimizing network utilization.
• Consideration: OTN and/or Layer 2+ protection and switching capabilities may reduce need for optical circuit dynamic routing.
R2
R3
R7
R4
R1
R8
R5
R6
s1s3
s2
s10
s5s4
s7s11
s12
s6
s8
s9
© 2011 Optelian. All rights reserved. 13
Flexible Bandwidth ROADMs
• Flexible bandwidth (FB) ROADMs (aka gridless ROADMs) allow the passband center and/or width to be dynamically adjusted.
• Many people advocate that FB ROADMs will be required to support bit rates beyond 100G.
1 2 3 4
Ch1 Ch2 Ch3 Ch4 Ch5
5 6
© 2011 Optelian. All rights reserved. 14
Considerations for Transmission Beyond 100 Gb/s
• For 40G and 100G transmission, the client interface has transitioned to parallel optics, while the line interface has retained single-carrier optics for improved transmission capacity. Parallel optics will likely be required on the line interface for bit rates approaching 1 Tb/s and beyond.
• Multi-carrier channels or superchannels are likely to be used for long-haul transmission beyond 100 Gb/s, with PDM-QPSK used for each constituent carrier. PDM-xQAM may be used in Metro (shorter distance) applications.
• Although FB ROADMs may provide improved spectral efficiency, they are not required for transmission beyond 100 Gb/s.
© 2011 Optelian. All rights reserved.
ROADM Control
15
Automated Optical Layer• Controls the power level of each wavelength at ROADM
ports to a set target (Automatic Power Balancing)• Span or link gain control
Automated Wavelength Circuit Provisioning• Impairment-aware path computation (wavelength routing)• ROADM switch configuration
© 2011 Optelian. All rights reserved.
Automated Wavelength Circuit Provisioning
16
Connection Controller
Path Computation
Element
A-to-Z circuit request with
routing constraints
viable route(s) and required regen
location(s)
impairment-aware
OpticalNetwork
OpticalNetwork
wavelength circuit request
signaling
12
3
4
done5
© 2011 Optelian. All rights reserved.
OpenFlow and SDN
17
R2
R3
R7
R4
R1
R8
R5
R6
s1s3
s2
s10
s5s4
s7s11
s12
s6
s8
s9
OpenFlowController
App
App
App • Centralized dynamic control
• Simple flow table entry at each ROADM for wavelength connection
• Smart Apps – must be aware of topology, resource availability and state, fiber properties, impairment modeling, etc.
• Opportunity for OpenFlow applications to have multi-layer control and visibility
• Apps can evolve independently of physical network
© 2011 Optelian. All rights reserved. 18
Conclusion
• Current generation ROADMs use WSS modules and have colored or colorless access ports.
• CDC functionality generally has a higher capital cost and lower access port density, but may provide lower operational costs.
• FB ROADMs may provide improved spectral efficiency, but are not required to achieve transmission beyond 100 Gb/s
• Multi-carrier channels or superchannels will likely be used for long-haul transmission beyond 100 Gb/s, with PDM-QPSK used for each constituent carrier. PDM-xQAM may see application in the Metro
• Automated ROADM networks are well-suited to centralized control, making OpenFlow a good match. This could also facilitate multi-layer control.