ProblemSolutionHardwareSlide 4Slide 5Slide 6Earlier Optical NetworksPowerPoint Presentation11/7/2000 EE228A Lecture 1Problem•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 traffic11/7/2000 EE228A Lecture 2Solution•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 •10-9 as compared to 10-5 for copper wires–High speed transmission–Transparent to bit rates and modulation schemes–Reconfigurability–Made possible due to developments in hardware11/7/2000 EE228A Lecture 3Hardware•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)11/7/2000 EE228A Lecture 4Hardware•Filters–with narrower spacing, wider ranges and tunability•Optical Add-Drop Multiplexor (OADM)OADM12312’3’33•Optical cross-connects (OXC)–route a channel from any I/P port to any O/P port–can be fixed, rearrangeable, and also with converters11/7/2000 EE228A Lecture 5I/P port NI/P port 1 O/P port 1O/P port N………………1M1MRigid OXCI/P port NI/P port 1………O/P port 1O/P port N………1M1M111MMMRearrangeable OXCHardware11/7/2000 EE228A Lecture 6Hardware•Wavelength () converters (WC)–improve utilization of available wavelengths on links–needed at boundaries of different networks–all-optical WCs being developed–greatly reduce blocking probabilitiesNo Wavelength converters123New request 1 3123New request 1 3With Wavelength convertersWC11/7/2000 EE228A Lecture 7Earlier 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 architecture11/7/2000 EE228A Lecture
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