11/7/2000EE228A Lecture1 Problem We need more bandwidth –Data traffic doubles every 4 (up to 12) months –More users connect to the Internet … –And stay connected for longer times … –And have better connection speeds (56kbps modem  DSL & Cable modem) –New applications (e.g. NAPSTER, GNUTELLA) require more bandwidth –And we can expect numerous other bandwidth intensive applications –Data traffic >> Voice traffic

11/7/2000EE228A Lecture2 Solution Optical Networking –Enormous bandwidth made available WDM makes ~160 channels/wavelengths possible in a fiber Each wavelength carries about 10 Gbps Hence Tbps speeds become a reality –Low bit error rates as compared to for copper wires –High speed transmission –Transparent to bit rates and modulation schemes –Reconfigurability –Made possible due to developments in hardware

11/7/2000EE228A Lecture3 Hardware Fiber –reduced dispersion, non linearity and attenuation loss Lasers –reduced noise (both phase and intensity) –2.5 Gbps, 10 Gbps, tunability emerging –made from semiconductor or fiber Amplifiers (as opposed to regenerators) –make possible long distance transmissions –erbium-doped fiber amplifiers –transparent to bit rate and signal format –have large gain bandwidths (useful in WDM systems) –expensive (~$50K)

11/7/2000EE228A Lecture4 Hardware Filters –with narrower spacing, wider ranges and tunability Optical Add-Drop Multiplexor (OADM) OADM ’ 3 3 Optical cross-connects (OXC) –route a channel from any I/P port to any O/P port –can be fixed, rearrangeable, and also with converters

11/7/2000EE228A Lecture5 I/P port N I/P port 1O/P port 1 O/P port N … … …… … … 1 M 1 M Rigid OXC I/P port N I/P port 1 … … … O/P port 1 O/P port N … … … 1 M 1 M M M M Rearrangeable OXC Hardware

11/7/2000EE228A Lecture6 Hardware Wavelength ( ) converters (WC) –improve utilization of available wavelengths on links –needed at boundaries of different networks –all-optical WCs being developed –greatly reduce blocking probabilities No Wavelength converters New request 1  New request 1  3 With Wavelength converters WC

11/7/2000EE228A Lecture7 Earlier Optical Networks SONET/SDH, ATM, FDDI … –fiber as transmission medium –switching, processing and routing electronically require O/E/O conversions –use one wavelength only Primarily for voice traffic –lots of redundancy, overhead, protection New networks should optimize for data (IP traffic) –IP over WDM is emerging as the new architecture

11/7/2000EE228A Lecture8