EE 566 Optical Communication Optical CDMA Presented by

EE 566: Optical Communication Optical CDMA Presented by: George Partasides http: //partasides. da. ru Optical CDMA Electrical

EE 566: Optical Communications Overview Optical CDMA Electrical by George Partasides

EE 566: Optical Communications History Overview (CDMA) n n 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. 1950 s 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 Partasides

EE 566: Optical Communications History Overvirew (Optical CDMA) n n n 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 Partasides

EE 566: Optical Communications Introduction n n CDMA used extensively in radio frequency communication systems, especially in 2 G and 3 G 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 Partasides

EE 566: Optical Communications …introduction (comparison) n n 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 n n System capacity = users * tx rate WDMA: Four wave mixing as discussed (next slide) Optical CDMA Electrical by George Partasides

EE 566: Optical Communications Drawbacks DWDM (revisited) n n n Dispersion Attenuation Four wave mixing n n 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 Partasides

EE 566: Optical Communications …comparison n 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 Partasides

EE 566: Optical Communications Optical CDMA Electrical by George Partasides

EE 566: Optical Communications …comparison (Advantages) n n Simplementation, using existing fiber networks Reduce the cost in every aspect: n n Equipment , outside plant Facilities , Operational Support systems SECURITY Eliminate many of intermediate time-division multiplexing steps required by SONET Optical CDMA Electrical by George Partasides

EE 566: Optical Communications How does o-CDMA work n n 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 Partasides

EE 566: Optical Communications Orthogonal Code example Two optical orthogonal Code with length L = 32 and λα = λc =1. (a) First code is represented by placing a pulse at the 1 st, 10 th 13 th and 28 th chip positions. (b) Second code is represented by placing a pulse at the 1 st, 5 th 12 th and 31 st chip positions. Optical CDMA Electrical by George Partasides

EE 566: Optical Communications …how does o-CDMA works n n 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: n Source – Filter – Modulator Filter: Spatial Filter can be thought an optical Bar code (fixed or programmable) Optical CDMA Electrical by George Partasides

EE 566: Optical Communications Optical CDMA Electrical by George Partasides

EE 566: Optical Communications n n n 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. n 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 Partasides

EE 566: Optical Communications Internet Traffic – The need n The increase of data through network and specifically LANS Optical CDMA Electrical by George Partasides

EE 566: Optical Communications Internet Traffic some statistics 250% increase in internet traffic in our University in one year time! Optical CDMA Electrical by George Partasides

EE 566: Optical Communications References n n 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 2 G to 3 G (Vijay K. Garg) n n n n Textbooks 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/report 09981. htm http: //telephonyonline. com/ar/telecom_seamless_mobility_real/index. htm Optical CDMA Electrical by George Partasides

EE 566: Optical Communications Optical CDMA Electrical by George Partasides