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Optical CDMAOverviewHistory Overview (CDMA)History Overvirew (Optical CDMA)Introduction…introduction (comparison)Drawbacks DWDM (revisited)…comparisonSlide 9…comparison (Advantages)How does o-CDMA workTwo optical orthogonal Code with length L = 32 and λα = λc =1.…how does o-CDMA worksSlide 14Slide 15Internet Traffic – The need -Internet Traffic some statisticsReferencesSlide 19Optical CDMA Electrical  EE566: Optical CommunicationOptical CDMAPresented by: George Partasideshttp://partasides.da.ru Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsOverview Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsHistory Overview (CDMA)1938, in the field of radar systems, examples of frequency hopping signal patterns were patentedDuring and after WWII the fact of BW expansion without pulse narrowing could also provide finer time resolution.1950s Sol Golomb first Books on CDMAEarly system are ARC-50 by Magnavox and satellite radios as well as few GPS systems Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsHistory Overvirew (Optical CDMA)Relatively new technique in Optical Fiber communications and seems to outperform traditional TDM and WDMFirst applied in mid 1980’s by A.Salehi Prucnal and some others.Aim for Terabit performance on Broadband Networks by reducing the cost of every aspect in optical network. Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsIntroductionCDMA used extensively in radio frequency communication systems, especially in 2G and 3G cellular telephone networks.Basic Advantage is the way it handles a finite BW among a large number of users (more users can transmit the same data over the same Bandwidth) Optical CDMA Electrical by George PartasidesEE 566: Optical Communications…introduction (comparison)TDMA and WDMA schemes present significant drawbacks in Local Area Systems when large number of users must be considered.TDMA: one user tx at a time  System capacity = users * tx rateWDMA: Four wave mixing as discussed (next slide) Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsDrawbacks DWDM (revisited)DispersionAttenuationFour wave mixingNon-linear nature of refractive index of optical fiberLimits channel capacity of the DWDM System Difficult to construct for dynamic set of multiple users because of the significant amount of coordination among the nodes required for successful operation. Optical CDMA Electrical by George PartasidesEE 566: Optical Communications…comparisonOptical CDMA does not need time and frequency management because all the users transmit using the whole BW at the same time!It can also operate asynchronously (as in wireless applications) without packet collisions.Slot allocation requirements are not needed here in contradiction to TDMA and WDMA Optical CDMA Electrical by George PartasidesEE 566: Optical Communications Optical CDMA Electrical by George PartasidesEE 566: Optical Communications…comparison (Advantages)Simple implementation, using existing fiber networksReduce the cost in every aspect:Equipment , outside plantFacilities , Operational Support systemsSECURITYEliminate many of intermediate time-division multiplexing steps required by SONET Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsHow does o-CDMA workThe principle is the same as in wireless application. Each user is assigned a unique code (spreading length -L-) which is multiplied by each bit. This code is only known to the receiver in order to demodulate the data.The most important part for correct detection is the code. This code must be uncorrelated from other user’s codes and be orthogonal. Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsTwo optical orthogonal Code with length L = 32 and λα = λc =1.(a) First code is represented by placing a pulse at the 1st, 10th 13th and 28th chip positions. (b) Second code is represented by placing a pulse at the 1st, 5th 12th and 31st chip positions.Orthogonal Code example Optical CDMA Electrical by George PartasidesEE 566: Optical Communications…how does o-CDMA worksO-CDMA divides the fiber spectrum into individual codes, all derived from a single broadband optical source (WDM divides the spectrum into narrow optical wavelengths)It is a simple 3 – step process:Source – Filter – ModulatorFilter: Spatial Filter can be thought an optical Bar code (fixed or programmable) Optical CDMA Electrical by George PartasidesEE 566: Optical Communications Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsOptical CDMA is a broadcast technology, with all information going to all parts of the network. When a receiver is placed anywhere on the network with a bar code that matches a transmitter, that signal alone is decoded and extracted from the network. The second requirement for an all-optical network, the ability to economically add users. A simple tap and insert coupler is installed in the lateral fiber run to multiple users, and a receiver is installed at each terminating location Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsInternet Traffic – The need -The increase of data through network and specifically LANS Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsInternet Traffic some statistics250% increase in internet traffic in our University in one year time! Optical CDMA Electrical by George PartasidesEE 566: Optical CommunicationsReferencesTextbooksSpread Spectrum CDMA Systems for wireless Communications (savo Glisic , Branka Vucetic)Spread Spectrum Communications Handbook(Marvin K. Simon, Jim K. Omura, Robert A. Scholtz, Barry K.Levitt)Wireless Network Evolution 2G to 3G (Vijay K. Garg)LinksOptical CDMA with Optical Orthogonal CodeEffects of Optical Layer Impairments on 2.5 Gb/s Optical CDMA Transmissionhttp://www.tks.buffalo.edu/usg/Public/Mail/Imap-s/Stats/lookup.htmlhttp://www.technologie.pl/fiber/zalacznik/artykuly/http://www.technologie.pl/fiber/zalacznik/artykuly/report09981.htmhttp://telephonyonline.com/ar/telecom_seamless_mobility_real/index.htm Optical CDMA


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UB EE 566 - Optical CDMA

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