CS 268: Optical NetworksBig PictureOverviewOptical TransmissionFiber AttenuationDispersionSlide 7Slide 8DWDMDWDM System DesignSlide 11All-Optical Switching1-D MEMSOptical SwitchSlide 15Optical Add-Drop MultiplexerSlide 17SONETSynchronous Transport Signal (STS)EncodingSONET Overhead ProcessingSTS-1 Frame FormatSTS-1 HeadersSection Overhead (SOH)Line Overhead (LOH)Path Overhead (POH)STS-N Frame FormatSTS-N: Generic Frame FormatSTS-Nc Frame FormatPractical SONET ArchitectureProtection Technique Classification1+1 Protection1:1 Protection1:1 Ring ProtectionProtection in Ring NetworkProtection in Mesh NetworksPath Protection / Line ProtectionShared ProtectionSlide 39Generic Framing Procedure (GFP)Slide 41CS 268:Optical NetworksIon StoicaApril 21, 2004(Based in part on slides from Ed Bortolini (Network Photonics), Ling Huang (UC Berkeley), Shivkumar Kalyanaraman (RPI),Larry McAdams (Cisco))2Big PictureSONETDataCenterSONETSONETSONETDWDMDWDMAccessLong HaulAccessMetroMetro3OverviewOptical TransmissionDense Wavelength Division Multiplexing (DWDM) Synchronous Optical Network (SONET)Generic Framing Procedure (GFP)Optical TransmissionWaveform after 1000 kmTransmitted data waveform5Fiber AttenuationTelecommunications industry uses two windows: 1310 & 1550 nm1550 window is preferred for long-haul applications- Less attenuation- Wider window- Optical amplifiers1310window1550window6DispersionDispersion causes the pulse to spread as it travels along the fiber Chromatic dispersion-Light propagation in material varies with the wavelength-Degradation scales as (data-rate)2(Figure from http://lw.pennnet.com/)7DispersionModal dispersion-Only for fiber that carry multiple light rays (modes)-Different modes travel at different speeds-Multimodal fiber used only for short distances8OverviewOptical TransmissionDense Wavelength Division Multiplexing (DWDM)Synchronous Optical Network (SONET)Generic Framing Procedure (GFP)9DWDM1310/1510 nm1310/1510 nm16 uncorrelated vawelengths λ1 λ2 λ3 λ4 λ5 λ162.488 Gbps (1)2.488 Gbps (16)16*2.488 Gbps = 40 Gbps1530-1565 nm ramge16 stabilized, correlated vawelengtsDWDM System Design 40-80 kmTerminalRegenerator - 3R (Reamplify, Reshape and Retime)Terminal120 kmTerminalTerminalOptical Amplifiers (OA)TerminalOA amplifies all sTerminalTerminalTerminalTerminalTerminalDWDM System Design155015511552155315541555155615570123456701234567Amplify DWDM Filter Optical Combiner15xx nm 1310 nmReamplifyReshapeRetimeRxTx1310 nmRxExternal ModulatorLaser15xx nm12All-Optical SwitchingNatively switch s while they are still multiplexed Eliminate redundant optical-electronic-optical conversionsDWDMFibersinDWDMDemuxDWDMDemuxDWDMFibersoutDWDMMuxDWDMMuxAll-opticalOXC131-D MEMSMEMS: Micro-electromechanical systems1-Dimensional array of micro-mirrors-1 mirror per wavelength Digital control; no motors14Optical Switch1-input 2-outoput illustration with four wavelengths1-D MEMS with dispersive optics -Dispersive element separates the ’s from inputs-MEMS independently switches each -Dispersive element recombines the switched ’s into outputs1-D MEMSMicro-mirror ArrayDigital MirrorControl Electronics1011Wavelength Dispersive ElementInput FiberOutput Fiber 1Output Fiber 2Input & Output fiber array15Optical Switch2 in4 in5 in7 inN in1 out2 out4 out5 out7 outN out1drop2drop3drop4drop5drop6drop7dropMdrop1add2add3add4add5add6add7addMadd............Tunable lasers1 inWavelength-multiplexerN x M four-portoptical matrix switch3 in3 out6 out6 in16Optical Add-Drop MultiplexerAdd-drop one Each is associated with a fixed add/drop portUsed to implement ring topologies...............DEMUXMUX17OverviewOptical TransmissionDense Wavelength Division Multiplexing (DWDM)Synchronous Optical Network (SONET)Generic Framing Procedure (GFP)18SONETEncode bit streams into optical signals propagated over optical fiber Uses Time Division Multiplexing (TDM) for carrying many signals of different capacities-A bit-way implementation providing end-to-end transport of bit streams-All clocks in the network are locked to a common master clock -Multiplexing done by byte interleaving19Synchronous Transport Signal (STS)First two bytes of each frame contain a special bit pattern that allows to determine where the frame startsReceiver looks for the special bit pattern every 810 bytes-Size of frame = 9x90 = 810 bytes90 columns9 rowsData (payload)overheadSONET STS-1 FrameSynchronous Payload Envelope (SPE)20EncodingOverhead bytes are encoded using Non-Return to Zero-high signal 1; low signal 0 To avoid long sequences of 0’s or 1’s the payload is XOR-ed with a special 127-bit patter with many transitions from 1 to 0-Duration of a frame is 125 µsec (51.84 Mbps for STS-1)21SONET Overhead ProcessingThree layers of overhead-Path overhead (POH): end-to-end transport-Line overhead (LOH): mux-to-mux transport-Section overhead (SOH): adjacent network elementMUXIntermediateMultiplexer(ADM or DCS)Regenerator RegeneratorSection Section Section Section Line Line Path DEMUX22STS-1 Frame Format Two-dimensional: 9*80 = 810 bytesTime Frame: 125 µsecRate: 810*8 bit/125 µsec = 51.84 MbpsFor STS-3 only the number of columns changes (3*80 = 270)90 Bytes90 BytesOr “Columns”Or “Columns”99RowsRowsSmall Rectangle =1 Byte23STS-1 Headers90 Bytes90 BytesOr “Columns”Or “Columns”99RowsRowsSection Overhead (SOH)Line Overhead (LOH)Path Overhead (POH): Floating; can begin anywhere24Section Overhead (SOH)First 3 lines in the headerMain functions-Framing (A1, A2)-Monitor performance-Local orderwire (E1): select repeater/terminal within communication complex-Proprietary OAM (Operation, Administration, and Maintenance) (F1)SOH3 B87 BA1=0xF6A2A2=0x28=0x28J0/Z0J0/Z0STS-IDSTS-IDB1B1BIP-8BIP-8E1E1OrderwireOrderwireF1F1UserUserD1D1Data ComData ComD2D2Data ComData ComD3D3Data ComData Com25Line Overhead (LOH)Last 3 lines in the headerMain functions-Locating payload (SPE) in the frame (H1, H2)-Muxing and concatenating signals-Performance monitoring -Automatic protection switch (K1, K2)•Switchover in case of failure-Line maintenanceLOH3 B87 BH1H1PointerPointerH2H2PointerPointerH3H3Pointer ActPointer ActB2B2BIP-8BIP-8K1K1APSAPSK2K2APSAPSD4D4Data ComData ComD5D5Data ComData ComD6D6Data ComData ComD7D7Data ComData ComD8D8Data ComData ComD9D9Data ComData ComD10D10Data ComData ComD11D11Data
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