Under the guidance:Prof. Dr. Shun Ping Chen Presented by:

Sumana Vinay [739436]Vijaykumar Kulkarni [739437]

NEXT GENERATION

ROADMs

CONTENTS:IntroductionOverview on ROADMFlexible Optical Network• Functionality requirements of NG ROADMs

Technology building blocks of NG ROADMs• Route and Select architecture• Wavelength Switched Optical Network • Benefits of NG ROADMsConclusion AcknowledgementReferences

Introduction

ROADMs are evolving to support market demands for increasing bandwidth and enhanced flexible wavelength routing.

The trend towards dynamic capacity allocation demands ROADMs to be-

Colorless, Directionless, Contentionless and Gridless.ROADM evolution from 2-degree fixed wavelength

add-drop to present >= 8 degree CDC add-drop architecture.

Next-generation solution that offers true network agility has put ROADM at the forefront of the race to stay ahead of the traffic explosion.

Overview on ROADMFujitsu was the first vendor to develop and deploy ROADM technology

in 2003 and the first to incorporate a WSS-based optical switch fabric. ROADM (Reconfigurable Optical Add Drop Multiplexer) is an optical

network element which is able to Add/Drop or Pass through any wavelength.

ROADM along with optical amplifiers, multiplexer-demultiplexer, transponder or/and muxponder cards constitutes a complete, flexible, optical transport node.

All optical subsystem which enables remote configuration of wavelengths at any time.

Technologies used- Wavelength blocking, Planar Lightwave Circuit (PLC), Wavelength Selective Switch (WSS).

FIXED RECONFIGURABLE

MANUALINTERVENTIO

NAUTOMATED

Operational Benefits: Operational Simplicity

Remotely configurable. Per wavelength SW provisioning and

management. Simple cabling.

Faster Deployment No re-engineering when capacity is

exceeded as in fixed OADM. Increased Reliability

Network requires fewer manual touches.

Software configuration reduces erroneous cabling errors.

De-Mux Mux

MuxOpticalSpaceSwitch

De-mux

ADM

ROADM is a

TECHNOLOGY

ENABLER

Flexible Optical NetworksWSS based ROADMs have been deployed widely in

networks through out the world –they are functionally efficient but not flexible.

Flexibility is required to move towards next phase of optical switching.

First generation ROADMs architectures are limited by:-Fixed wavelength assignments to specific ports.-Fixed direction assignments for multiplexers (i.e. North only, South only…)-Partitioned add/drop structures due to wavelength contention conflicts.

Need for NEXT GENERATION ROADMs …

Functionality requirements of NG ROADMs

COLORLESS or COLOR INDEPENDENT functionality

DIRECTIONLESS or DIRECTION INDEPENDENT functionality

CONTENTIONLESS or WAVELENGTH CONTENTION FREE functionality

GRIDLESS or FLEXIBLE ITU GRID functionality

High-Level NG ROADM Requirements

1 Multi-degree ROADMN = 8-16 for MetroN = 6-8 for Long Haul9.6 Tb capacity per fiberFlexible bandwidth allocation Future proof express pathHigh level of integrationAdvanced AutomationSupervision and Monitoring

Degree

Degree

Degree

Degree

Degree

Degree

CDCTransponder

Pools

3

N N

4

2

Current Transponder Pools support 40G/100G (coherent)

ColorlessDirectionless Contentionless

Directed V/s Directionless ROADM

•Fixed add/drop portsfor particular direction

•Change in direction requires physicalrewiring by technician

Figure : 3rd degree ROADM with directed architecture

If Nod

e fails

?

ROADMWest

ROADMEast

Directional ROADMLineWest

LineEast

Add/DropWest

Add/DropEast

ROADMWest

ROADMEast

Directionless ROADM

NxN Switch FabricNxN Switch FabricNxN Switch Fabric

In directional ROADM recabling of transponders needed.

In directionless ROADM , no recabling is needed

Colored V/s Colourless ROADM

Colored access ports imply that physical access ports (add or drop) are assigned to a specific wavelength.

Physically change the fiber connectivity between the transceiver and access ports to change wavelength.

No dynamic wavelength change.

In colorless architecture, without changing port the color of the wavelength can be reconfigured.

No recabling needed.

ROADMWest

ROADMEast

Colourless ROADM

Contentionless ROADMs

Even with colorless and directionless functionality, the ROADM network is still limited by the total number of flexible CD add/drop ports available.

If two wavelengths of same color converge at same add/drop port of WSS -

Leads to Wavelength blocking /wavelength contention!Solution- Replace CD mux/demux units with new

set of add/drop units called Contentionless add/drop units (n X m unit instead of 1 X n /n X 1)

What is Contentionless Add/Drop ?

ROADM

RX

TX

RX

TX

Contention-less – In the same Add/Drop device you can add and drop the same frequency to multiple ports.

ROADM

RX

TX

RX

TX

Directionless – Wavelength can be routed from any Add/Drop port to any direction in software.

ROADM

RX

TX

RX

TX

Colorless – ROADM ports are not frequency specific (re-tuned laser does not require fiber move)

Increasing traffic

Increased usage of video and online applications through new devices such as smart phones and tablets- demands more BANDWIDTHNeed for faster network and higher optical performance.

Pressure on optical networks!Insufficient bandwidth!

SOLUTION ?

1) Increase number of channels :80 96 100 150

More channels= more spectrum space.

But problem of physics!

2) Allocate bandwidth flexibly instead of 50GHz

Not a standard!

3) Signal shaping- DSP in transmitters of transponder

- OFDM

- Nyquist filtering

Gridless or Flexible GRID

Capacity Enhancements in DWDM Networks

…

Legacy networks as deployed today:

50 GHz, fixed grid

40G

40G

40G

40G

10G

10G

10G10

0G

50GHz

Spec

tral

occ

upan

cy

1T

…

50GHz

200GHz

, nm

100

G

400

G

1T

200

G

100GHz

Spec

tral

occ

upan

cy 50GHz

Future networks:50-200 GHz, flexible grid

, nm

Flex Spectrum DWDM Architecture

Ch1 Ch2 Ch3 Ch4

DSP-Enabled

Transmitters

Flex SpectrumROADM

Signal Shaping

50GHz 50GHz 50GHz

TX1

TX2

TX3

TX4

Ch1 Ch2 Ch3 Ch4

Today‘s 50GHz Grid SystemFlexSpectrum DWDM system

Optical multiplexer

Denser ChannelSpacing

SUPER CHANNEL

OFDM/

Flexible Grid/Gridless implies a more granular version of the spectrum usage, down to 12.5GHz (ITUT G.694.1)

Hence, ROADM nodes supporting a flexible grid could operate at any speed that is based on increments of 12.5GHz spacing.

This ensures optimum and wise usage of spectrum.Moreover, it opens a gate for dynamic allocation and usage of

the ITU Grid.

Isn’t it AMAZING!

Technology building blocks of NG ROADMs

•Wavelength selective switch (WSS) is the heart of current generation ROADM networks also for the NG networks.

•CDC ROADM is nothing but N X M WSS capable of switching wavelength from multiple input port to several output port.

2003

WSS Year of deployment2 x 1 20039 x 1 200716 x 1 201220x1 2013

Traditional----------Current

BroadcastMesh

Patch Panel

Legacy ROADM – Broadcast & Select

• Ingress channels from each degree are passively split (broadcast) to all other degrees (plus the per-degree add/drop)

• Mux WSS blocks all channels not intended for that degree (selects those that are)

• Channel isolation becomes difficult as the number of degrees increases (creates large penalty for 16 QAM channels)

• directionless add/drop consumes an available degree; Colorless requires add/drop WSS ( using a larger split ratio on the ingress not practical from a network OSNR requirement)

WSS ‘Select’

WSS

‘Sel

ect’

WSS

‘Select’

Per DegreeAdd/Drop

Per DegreeAdd/Drop

Per DegreeAdd/Drop

Deg

ree

A

Degree B

Degree C

“Broadcast and Select” Architecture

RoutedFull Mesh

Patch Panel

ROADM – Route & Select

• Demux WSS ‘routes’ any combination of waves from COM-RX to any output port (drop and other degrees)

• Mux WSS ‘selects’ any combination of waves from its input ports (add and other degrees) to COM-TX

• Channels are isolated by both the ingress and egress WSS, improving performance

• By eliminating the splitter, insertion loss is reduced, preserving channel OSNR

• Enables directionless and colorless at large scale

Add Structure

Drop Structure

WSS‘Select’

WSS‘Route’

WSS

‘Sel

ect’

WSS

‘Rou

te’ W

SS‘Select’

WSS

‘Route’

Deg

ree

A

Degree B

Degree C

“Route and Select” Architecture

WSONWSON (wavelength swithed optical network) is a standards based GMPLS control plane which imparts intelligence to the optical layer.

Two types of control plane are prominent : Peer type and overlay type.WSON is an overlay based control plane.Control plane can be centralised or distributed.

Looking ahead for – Agile Optical Layer!

NCS 2000

Embedded Optical

Intelligence

Tunable Laser

Colorless

Tunable Receiver

Directionless

Contention-less

Gridless

WSONWavelength Switched Optical Network

Complete Control in Software, No Physical Intervention Required

TOUCHLESS OPTICAL LAYER + EMBEDDED

WSON INTELLIGENCE = COMPLETELY AGILE

OPTICAL LAYER

Benefits of NG ROADMs

Wavelength and Route flexibility (with CDC architecture)

Automatic wavelength restorationLoad balancing as network and traffic evolvesSupport for datarates beyond 100Gb/sFully automated link provisioning

ROADM market

Ref: Dupont Photonics Technologies

CONCLUSIONNext-generation ROADM devices prepares service

providers to meet today’s traffic needs and the needs of tomorrow.

“Gridless” or flex spectrum enables mixed channel plans adjustable in software to accommodate a mix of today’s modulation as well as future modulations.

ACKNOWLEDGEMENT:

Firstly, we would like to thank Prof. Dr. Chen for giving us an opportunity to share a gist of our knowledge in next generation optical networks.

Also , we thank our friends and colleagues for their immense support and co-operation for making this presentation successful.

REFERENCES:M.A.F. Roelens, D. Williams, J. Bolger and B.J. Eggleton “Advanced

applications of flexible ROADM technology PhotonicsGlobal@Singapore, (2008). IPGC 2008. IEEE 10.1109/IPGC.2008.4781453.

“ New Devices Enabling Software Defined Optical Networks”, Brandon Collings from JDSU.IEEE Communications Magazine • March 2013.

“The ROADM to smarter Optical Networking”, George Lawton, Computing Now Exclusive Content — July 2010 .

“Benefits and Requirements of Flexible Grid ROADM’s and networks” by Sheryl L Woodward and Mark.D. Feuer.VOL. 5, NO. 10/OCTOBER 2013/J. OPT. COMMUN. NETW.

S. Gringeri, B. Basch, V. Shukla, R. Egorov, and T. J. Xia,“Flexible architectures for optical transport nodes and networks,” IEEE Commun. Mag., vol. 48, no. 7, pp. 40–50, July 2010.

 

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