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)

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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

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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)

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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

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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

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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

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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

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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

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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