optical cross connect

8/3/2019 Optical Cross Connect

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OPTICAL CROSS CONNECT

MULTI-VARIANT SWITCHING

CAPABLE DEVICE


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Evolution of Optical Networks

SingleWavelength

Transmission

Greater Network Scale

Multi-Wavelength

Transmission

Multi-WavelengthNetworking


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.

.

.

.

.

.

Virtual Transport

Multi Wavelength Networking Network and operations

scaling v.S. Raw capacitySingle wavelength elements not

keeping paceOperations need to scale

Enabling technologiesScalable and ultra dense

arch

itectures of electronic+optical

Networking intelligence

N Wavelength Per Fiber

N Wavelength per Network Element


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Moving From Static to

Intelligent

Traditional

StaticTransport

Network

Point-to-Point WDM

Physical Transport OverlaysStatic Provisioning

Limited Line Rate

Linear or Ring Protection

Reduces total Cost of Ownership

Intelligent

Optical

Transport

Network

Intelligent Optical Networks

Virtual Transport Networks

Dynamic Provisioning

Flexible Capacity

Flexible Protection


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A Wavelength Routing

Network is ...

. . . a Mesh of Optical Transmission and Switching

Equipment

P-t-P DWDM System

Optical Cross Connect (OXC)


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. . . , which provides dynamic Point-to-Point ConnectionsSONET/SDH, Gigabit Ethernet, P


Network is ...


Network is ...

SONET/SDH

P

Gigabit Ethernet


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. . . to attached Internetworking Devices.IP Routers, SONET/SDH Muxes, ATM Switches, ...


Network is ...


Network is ...

SDH Mux

Black Box

IP Router

?

?

?


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Emergence Of Intelligent

Optical Core

Layer 3

IP

Layer 2

ATM

Layer 1Voice/P

.L.

Distributed

Intelligence

Provisioning &

Intelligent

Grooming

Full Suite of

Protection

Methods

Scalable and Granular CapacitySTM-1 to Wavelengths


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TopologyAn example of wavelength-routed network

1

2

3

46

5

7

P1

P2

P3

Wavelength Routers:

Lightpaths:


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OXC

A network device used by telecom carriers toswitch high-speed optical signals (STM level).

multiple high-speed signals that are switched in

their entirety and not multiplexed together.

To rearrange the wavelength from fibre to fibre

To provide wavelength switching.

To solve the output fabric port contention ,

interchangeris used. interchanger is expensive and required

only if necessary.


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Terminating

Equipment

|SONET, ATM, IP...

OpticalCross-

Connect

Optical SystemsOptical Cross-Connect

110101


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Optical Network Building

Blocks:Optical Cross-Connects (OXCs)

OXC switches signals on input {wavelengthi,fiberk} to output {wavelengthm, fibern}

Input fibers

with WDM

channels

Output fibers

with WDM

channels


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OXC

Fiber 2

Interchange

1

2

3

1

2

3

FIBRE IN FIBRE OUT

DeMUX

33

11

MUX

1

2

3

1

2

3


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OXC Multi-variant switching

capable device Fibre switching

Wavelength switching

Wavelength Band switching

Subwavelength switching

Space switching Time switching


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Figure 21. Optical Cross-Connects

Optical Switching


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Optical Cross-Connects (OXCs)

Opaque: o-e, e-o, electronic switch fabric

Transparent: o-o-o, optical switch fabric Hybrid, (o-e-o): optical switch fabric, o-e-o

Hybrid: both opaque and transparent fabrics

Input fibers

with WDM

channels

Output fibers

with WDM

channels


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Opaque/OEO/Electric

Pros ConsOEO - Known and maturetechnology

- 3R regeneration for free

- capable of bandwidth

grooming

bit error rate monitoring and

statistical multiplexing

Arbitrary concatenation andGrooming

- Optical Scalability limit

- Not bit-rate transparency

- Not protocol transparency

- Expensive


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DXC/DCS

SONET/SDHDigital Cross-connect (DXC)Also known as DigitalCross-connect Switch (DCS)

Opaque/Electric OXC


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DS-1 DS-3

STS-1

STS-N

ATM

DS-3

STS-NATM STS-1

DS-1

STS-N

ATM

DS-1

DS-1

DS-3

STS-N

Electrical

Switch

Matrix

SONET/SDHDigital Cross-connect (DXC)Also known as DigitalCross-connect Switch (DCS)

STS-N ATM DS-1 DS-3

Opaque/Electric OXC


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OEO vs OOO

OOO

- Optical Scalability

- Bit-rate transparency

- service/protocol

transparency

- Emerging Technology

- not capable of bandwidth

grooming, bit error rate

monitoring and statisticalmultiplexing


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All Optical Cross-connects

(OOO)

OXC/PXC

All Optical Cross-connect (OXC)Also known as PhotonicCross-connect (PXC)


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All Optical Cross-connects

(OOO)

Optical

Switch

Fabric

P3

P2

P2

P4

P4

P1

P1

P3

All Optical Cross-connect (OXC)Also known as PhotonicCross-connect (PXC)


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Optical CrossConnect with Full

Wavelength Conversion

M demultiplexers at incoming side M multiplexers at outgoing side Mn x mn optical switch has wavelength converters at

switch outputs

P1,P2, ... ,Pn

P1,P2, ... ,Pn

P1,P2, ... ,Pn

1

2

m

Optical CrossBarSwitch

WavelengthConverters

WavelengthMux

WavelengthDemux

P1,P2, ... ,Pn

P1,P2, ... ,Pn

P1,P2, ... ,Pn

.

.

.

.

.

.

P1

P2

Pn

P1

P2

Pn

P1

P2

Pn

P1

P2

Pn

P1

P2

Pn

Pn

P1

P2

1

2

m


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Wavelength Converters convert an incoming signal's wavelength to adifferent outgoing wavelength. A converter can improve thewavelength utilization, can server as a transponder at the boundariesbetween different networks managed by different entities.

Optical Port Contention-Optical Converter-benefits

P1

P2

P3

A B C(a)

P1

P2

P3

A B C

(b)

wavelength conversion

Fig. Illustrating the need for wavelength conversion(a) Node B does not convert wavelengths,and a new lightpathcan not be set up between node A and node C.(b) Node B can convert wavelengths, and a new lightpath can beset up between node A and node C now.


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Optical Converter-Categories

Converter categories:Fixed-input, Fixed-output:Always takes in afixed-inputP and converts it into a fixed-outputP;Variable-input, Fixed-output: takes in a variety ofPs but always converts it to a fixed-outputP;Fixed-input, Variable-output: takes in a fixed P

but can convert it into a variety of outputP

s;Variable-input, Variable-output: can convert anyinputP to any outputP


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OXC- Architecture and functionsAn OXC provides several key

functions in a larger network:

Wavelength Switching/Serviceprovisioning: It canprovision lightpaths in aautomated manner.

Protection: Protecting

lightpaths against failuresis one of the most importantfunctions of an OXC.

Bit rate transparency:An OXCcan switch signals witharbitrary bit rates and frame

formats. Performance monitoring,test

access, and faultlocalization.

Multiplexing and grooming.

Optical Add/drop functions


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Optical Crossconnects (OXCs)

OXC


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Optical Switching Fabric &

Requirement


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Switching fabric

Opaque fabric-

SDH DXC

Non-grooming fabric

Grooming fabric

Transparent fabric-

MEMS

Thermo-optical wave-

guide switch

Acoustic-optical

switch

Bubble switch Liquid crystal


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Several criteria for fabric Scalability

Switching speed

Power consumption

Reliability

Signal power loss Signal quality degradation


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Opaque vs TransparentFeatures Opaque Transparent

Wavelength conversion Intrinsic May or may not

Optical impairments Less or signal

regenerates

Need special mechanism

Interoperability Yes,multivendor Not yetTraffic grooming Can be supported Not

Ability to manipulate

data

Yes No

Scalability to high spped Less scalable Scalable

Scalability in ports Less scalable Scalable

Transmission cost perbit High Low

Flexibility High low


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Micro-electro-mechanical systems

(MEMS)

A micro-mirror is used to reflect a light beam. Thedirection in which the light beam is reflected can bechanged by rotating the mirror to different angles,

allowing the input light to be connected to any outputport.

Micro-machining techniques for fabricating themirror,

Optical design techniques for achieving low-lossoptical connections,

Control techniques for positioning the mirroraccurately.


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Reflector

MEMs tilting mirrors

Fibers

ImagingLenses

OXC/PXC Switching

Mechanisms Micro-electrical Mechanical Systems

MEMs

Used for many other applications

From Lucent, Corning, Xros (Nortel),

and others

Currently 8 x 8 OXC

256 mirrors, long-term goal 1,024

OXC

Electrical controls

Voltage applied to mirror; tilts on 2 axis +

or 6 degrees

Switch times typically 10 to 25 ms


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Figure 4-1: MEMs[2]


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Figure 6-5: 2-axis motion of MEMs OCX mirror[12]


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Figure 6-7: 256x256 OXC switching array[14]


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Nortel OPTera Connect PX

252/1008 port dual-core photonic cross connect

optical cross connect

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