Optical SwitchingSwitch Fabrics, Techniques and Architectures (INC lab) Oct 30, 2006

OutlineIntroduction

Optical Switch

Optical Packet Switch

Optical Burst Switch

GMPLS

Conclusion

IntroductionInternet traffic has doubled per yearNew services like VOD, IPTVDWDM (Dense Wavelength Division Multiplexing) is developedCan transport tens to hundreds of wavelengths per fiber

Then, What is problem?Slow O/E/O conversion.Electronic equipment is dependent on the data rate & protocol. (non-transparent)Goal?All optical!

Optical switch - OXCWhat is Optical Cross-Connect (OXC)?Set up light pathsElectrical XC, All-optical XC, Opaque XC

Major difficulties of All-optical XCThe lack of processing at bit level in optical domainThe lack of efficient buffering in optical domain

Optical switch - Optical Switch FabricsOptical Switch FabricsAllow switching directly in the optical domain (All-optical)

Important parametersSwitching time ()Insertion loss ( and loss uniformity at all input-output connections)Crosstalk ()Extinction ratio (ratio of ON-OFF power) ()Polarization-dependent loss ()Reliability, energy usage, scalability, temperature resistance

Optical switch - Optical Switch FabricsMain optical switching technologiesOpto-mechanical SwitchUse prisms, mirrors, directional couplers.Lack of scalabilityMicro-electro-mechanical System Device (MEMS)Use tiny reflective surfaces to redirect the light2D-MEMS(on-off mirror)3D-MEMS(movable mirror)Scalabilitylow lossshort switching timeLow power consumptionLow crosstalk Low polarization effect

Optical switch - Optical Switch FabricsElectro-optic SwitchUse a directional couplerIts coupling ratio is changed by varying the refractive index

Thermo-optic SwitchLiquid-Crystal SwitchBubble SwitchAcousto-optic Switch

Optical switch - Optical Switch Fabrics

Optical switch large switchesMain considerations in building Large switchNumber of small switches requiredLoss uniformityNumber of crossovers cause power loss, crosstalkBlocking CharacteristicsBlocking vs. non-blocking

Optical Packet SwitchingOptical Circuit SwitchingLimited circuitLow efficiency (due to fixed bandwidth)

Optical Packet SwitchingUsing Packet ( = Header (for routing) + Data )

If Optical Packet Switching is realized, it canallocate WDM channels on demand (microsecond)share network resource efficientlysupport burst traffic efficientlyoffer high-speed data rate/format transparency & configurability

Optical Packet SwitchingWhat is the problem in implementing OPS?Long Switching timeBuffer is neededLong switching time is due toExtracting the routing information from the headerControlling switching matrix electronicallyPerforming the switching and buffering functionsBuffer at Optical domain is neededData should be buffered while header is processedWhen a contention is occurredWhen the bandwidth is not sufficientWe dont have perfect solutions yet.

Optical Packet SwitchingContention ResolutionBufferingUsing FDL (Fiber Delay Line) bulky, expensive, indefinite, Quality degradationSolutions to reduce the number of FDLs, synchronous mannerUse TOWC (Tunable optical wavelength converter)

Deflection routingOnly one packet desired link, others longer linksThere can be the looping of packets

Optical Packet SwitchingArchitectureOutputInputO/E interface: extract the header info.FDL

Optical Packet SwitchingShared Wavelength ConvertersReduce Tunable Wavelength converter

Optical Burst SwitchingSwitch the channels entirely in the optical domain using electronic tech.

ProcessAssemble the packets (have same destination) -> make bursts at the edgeBursts are assigned to wavelength channelsSwitched through transparently without any conversionDisassemble into the original packets

No need for Optical buffer.

Optical Burst SwitchingHow is it possible?reservation request (control packet)Using offset-timereservation

Optical Burst SwitchingQoS SupportBigger offset, lower probability of discardOptical Composite Burst SwitchingMinimize packet lossLow priority burstNot discarded

The future of Optical switching

GMPLS - Generalized Multiprotocol Label SwitchingExtends common control plane to support various interfaces.GMPLS can supportPacket switching Time-division (SONET/SDH) + MPS (wavelength switching) + Spatial-switching (OXC)It can support integrated control and management

ConclusionOptical fiber is not fully exploitedSwitching functions must be executed opticallyTwo obstaclesThe lack of optical memory processing capabilities in optical domainIn the future, breakthroughs may counteract the fundamental limitations of optics Then, current network is completely changed

introduction optical switch Optical packet switch , . optical burst switch GMPLS . ? . data rate protocol . data rate protocol .

Electrical XC, All-optical XC, Opaque XC all optical optical switch fabric .MEMS Si GMPLS PSC inf, TDM inf. LSC, FSC . LSP . PSC TDM inf. . GMPLS MPLS signaling routing protocol