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September 24, 2014
Modular and Expandable
CDC ROADMs
2
OUTLINE
• Why CDC ROADMs?
-- Together with coherent detection systems, set the foundation for SDN
• Evolution of ROADM architectures
• Port-expandable modular multicast switch cards
- Pay-as-you-grow add/drop ports
• Degree-expandable modular multicast switch cards
- Pay-as-you-grow degree expansion
• Summary
3
Carriers’ Need for Agile ROADMs
● Wavelength Provisioning
– Opex Reduction
• Service time reduced to seconds/minutes
• Once installed, no more re-wiring!
– Network rebalancing or routing re-optimization
– Maintenance switching
● Network Restoration
– Tune l around fiber cuts or equipment outages
(e.g., 1:n protection)96 l’s
96 l’s96 l’s
96 l’s
96 l’s 96 l’s
96 l’s
96 l’s
DWDM/ROADMCore Router
(4-deg)
Core Router
4
Physical Layer Enablers for Software Defined Networks
SDN
Coherent
Transmission
CDC ROADM
Switching
5
SDN requires Predictable Transmission Performance in Meshed Networks
Unpredictable Performance
(10G, 40G)
Predictable Performance
(100G Coherent Systems)
Data rates, modulation formats 28~32Gbaud, DP-QPSK
(112~128 Gb/s)
Standardized by ITU-T and OIF
Chromatic dispersion penalty due to
different paths and fibers
±40,000 ps/nm
( > 2,300km SSMF)
Polarization mode dispersion penalty
due to different paths and fibers
100 ps
(good for ULH, and metro with new or
old fibers)
OSNR requirement < 16 dB
≥100Gb/s coherent systems are predictable,
enabling software-defined networks
6
Coherent Detection Enables Low-Cost Colorless Drop
● No optical pre-filtering (e.g., demux, tunable filter)
● 100G/400G data rates enable lower $$/Gbps/Port
Coherent Receiver is an integrated part of a CDC-ROADM
No
channel-filter
LO
ICR
OSNR< 0.5 dB
for up to 80 co-incident channels
(Nelson, et al, IPC 2012)
7
ROADM Architecture
Evolution
8
PS
PS
WSS
WSS
WSS
WSS
ROADM Architecture – Express Directions (I)
PS
PS
Broadcast and Select - CD
9
PS
PS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
ROADM Architecture – Express Directions (II)
Route and Select - CD
10
Express Direction (Colorless and Directionless) Contention always happens
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
11
PS
PS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
Colored Add/Drop
AWG
AWG
40-88 drop ports
40-88 add ports
Route and Select with colored add/drop
12
PS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
PC
PS
PS
PC
Colorless & Directionless Add/Drop with Contention
13
CDC ROADM
14
PS
WSS
WSS
WSS
WSS
WSS
WSS
WSS
4-Degree CDC ROADM Architecture
WSS
3% drop ratio1
1x16 1x16
16 (4x1)
Switches2 15 16
1x16 1x16
Number of Degrees
Number of Drop Ports
15
Port Expansion: 16 32 48 ….
EDFAs
3% drop ratio1
1x16 1x16
16 (4x1)
Switches2 25 16
1x16 1x16
Express
1xN WSS
Express
Messy connection,
but integrated on
PLC (no shock &
vibration concerns)
16
Predictable Agile Transport Network (add/drop) CDC ROADM in a meshed network
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM
ROADM • ROADM degrees: 8~12
• Wavelength per degree: ≤ 96
• Add/drop to/from multi-degrees implies a
few hundred wavelengths add/drop per node
17
Metro CDC ROADM
● Metro optical network requires much smaller number of add/drop ports of 100Gb/s coherent data
● Metro network node may have traffic in ≤16~20 directions
18
Degree-Expandable
CDC ROADMs
19
Degree Expansion: 4x16 8x16 12x16
Expansion
ports
4x16 MCS
1x16PS
1x16PS
1x16PS
1x16PS
4x16 MCS
1x16PS
1x16PS
1x16PS
1x16PS
Expansion
ports
4x16 MCS
1x16PS
1x16PS
1x16PS
1x16PS
Expansion
ports
#1 #2 #15 #16
20
Degree Scalability Example: from 4 to 12
4x16 MCS
MPO (1-4)
4x16 MCS
MPO (5-8)
4x16 MCS
MPO (9-12)
MPOMPO
MPOMPO
MPO
MPO
21
4x16 Degree-Expandable Multicast Switch (Add + Drop)
Degree ports
(4+4)
16 ADD ports
16 ADD Upgrade ports
16 DROP Upgrade ports
16 DROP ports
22
Summary
● Future SDN relies on optical transport networks with predictablephysical layer performance
– Transmission: ≥100Gb/s Coherent Systems
– Switching (express): CD ROADMs- WSS based
– Switching (add/drop): CDC ROADMs – multicast switch based
● Metro CDC ROADM requires a small number of add/drop ports, but may need a large number of degrees
● Based on a small granular 4x16 MCS with both port- and degree-expandability, an excellent pay-as-you-grow economics can be achieved