Presentation on theme: "DWDM Transmission Technology and Photonic Layer Network"— Presentation transcript:
1 DWDM Transmission Technology and Photonic Layer Network Chao-Xiang ShiSprintTransmission Network Development GroupAdvanced Technology Laboratories1 Adrian , BurlingameCA 940101
2 Outline DWDM Technology in terrestrial network - DWDM capacity and transmission distance: technology review- DWDM transmission system- Span design in DWDM transmission- Optical transmitter in DWDM system: DFB laser withexternal modulator- Wavelength multiplex/de-multiplex technology in DWDM:AWG, Dielectric filter, and Fiber grating type- Two-stage optical fiber amplifier- Optical amplification, bandwidth , and capacity- Optical fiber nonlinearity: SPM, XPM, SBS, and FWM- Polarization mode dispersion (PMD) limitation for 10 Gbit/sand beyond
3 Continue DWDM technology in Submarine network - PMD compensation technologyDWDM technology in Submarine network- capacity and transmission distance : technology review- uniquely designed LCF fiber and non-zero dispersion shift fiber- chromatic dispersion compensation in Submarine transmission- PMD concern in submarine transmission- one stage Er. Doped fiber amplifier- comparison of WDM transmission between terrestrial andsubmarine networkPhotonic layer network- Optical network architecture- Protection and restoration mechanism for IP/ATM directly overWDM optical network
4 Continue for all-optical networks - Key issue in Metro WDM network and - Issues of protocols and interfaces requirementsfor all-optical networks- Key issue in Metro WDM network andpossible solutions- Application of Metro WDM equipment in transparenttransport network: Experimental VerificationEmerging Technology of Optical Network- Optical CDM (CDMA)- Optical Packet Switching Network
5 Today Technology Tomorrow Technology After… DWDM Capacity and transmission:Technology reviewToday Technologynm window (used to call C-band)80 ~ 100 channels of 2.5 Gb/s (50 GHz spacing)32 ~ 40 channels of 10 Gb/s (100 GHz spacing)70 ~ 90 km span length4 in-line optical amplifiers and 5 spanstotal 400 km transmission for 10 Gbit/stotal 600 km transmission for 2.5 Gbit/sTomorrow Technologynm window (used to call L-band)100 ~ 200 channels of 2.5 Gb/s64 ~ 100 channels of 10 Gb/sAfter…nm window by Raman amplification
6 DWDM transmission system OC-48/OC-19270-90kmTxOC-48/OC-192Uni-directionaltransmissionOSC1510 nm or 1480 nmOC-48/OC-192OC-48/OC-19270-90kmBi-directionaltransmission1510 nmor 1480 nm
7 3 span: span distance 90 km, total 270 km Span design in DWDM transmissionOC192 (10 Git/s) +6~8 dBm/ch3 span: span distance 90 km, total 270 km4 span: span distance 80 km, total 320 km5 span: span distance 70 km, total 350 kmOC 48 (2.5 Gbit/s)3 span: span distance 120 km, total 360 km5 span: span distance 100 km, total 500 km8 span: span distance 80 km, total 640 km
8 DFB laser with External modulation (for backbone long distance) Optical transmitter in DWDM system:DFB laser with external modulatorDFB laser with External modulation (for backbone long distance)Wavelength stable, narrow band DFB laser- DFB laser spectrum width : ~ 20 mHz- wavelength stability: +/ nmDFB laser integrated with EA modulator- Low chirping effect- polarization stability- low driving power requiredDFB laser with external LN modulator- polarization problem- high driving power required- chirping problemDFB laser with Direct modulation (for local area short distance)- spectrum broaden- wavelength stability
9 AWG (array waveguide grating) Wavelength multiplex/demultiplex technologyin DWDM: AWG, Dielectric filter, Fiber gratinglWDM Mux/DemuxAWG (array waveguide grating)- Insertion loss : 6 ~ 8 dB (insertion loss is almost- channel crosstalk ~ 25 db- application for higher channel numberDielectric filter WDM Mux/Demux-insertion loss: increases when channel number increases-channel crosstalk: 25 ~ 30 dB-application for lower channel number WDM Mux/DemuxFiber Bragg grating- need optical circulator- cascade multipile grating to form a WDM Mux/Demux
10 Two-stage Optical fiber amplifier DCFopticalfilterOSC980 nmpumpEDFA11480 nmEDFA2WDM980 nm low noise pump laser for first stage EDFA1480 nm high power pump laser for second EDFADCF (dispersion compensation fiber) is required for 10 Gbit/sAttenuater is needed for 2.5 Gbit/sOptical isolator is used to reduce back ASE noise impactOptical filter is used for gain equalizationTotal gain of fiber amplifier is from 25 dB to 30 dBN.F. (noise figure): 5 ~ 7dBOutput power : +17 ~ +23 dBmFlatten gain : +/- 1 dB with 30 nm ~ 40 nm over Er. gain rangeDynamic input range: 15 dB
11 Optical amplification, bandwidth , and capacity Fiber loss0.4 db0.25 db1310 nm1550 nmWavelength (l)C band: ~ 1560 nm (100 Ghz channel space for 10 Gbit/s, total 40 channels,50 Ghz channel space for 2.5 Gbit/s, total 96 channels )L band: ~ 1600 nm (40 channel available for 10 Gbit/s, i.e. 40 gbit/s, , and100 channels available for 2.5 gbit/s)S band: ~ 1520 nm (40 channel available for 10 Gbit/s, i.e. 40 gbit/s, , and100 channels available for 2.5 gbit/s)Total 1.2 Tbit/s capacityS Band: Raman amplificationL Band: EDFFA, Ti-EDFAC Band: EDFA
12 Fiber nonlinearity: SPM, XPM, SBS, and FWM SPM: Self-phase modulation- Create positive chirping, which cause pulse distortion due to fiber dispersion- Result in the optical spectrum broaden which limits the channel spaceXPM: Cross phase modulation- Phase modulation between two channels due to fiber Kerr effect- Convert phase noise (due to ASE) to intensity noise via fiber dispersion- Limit channel space (for 10 Gbit/s channel space is 100 Ghz , 0.8nm)SBS: Stimulated Brillouin Scattering- Creating a new wave in backward direction through interaction between lightwave and acoustic wave- SBS threshold can be reduced by decreasing the power level and increasingoptical spectrum.- For 10 Gbit/s, FM modulation (~100 Mhz) of DFB laser can reduce the SBSthreshold from +5 dBm to +10 dBm.FWM: Four wave mixing- Optical parametric process through 3 or 4 light wave.- Cause nonlinear channel crosstalk when transmission near zero dispersionwavelength (a critical problem for dispersion-shift fiber)- Standard SMF-28 is good to suppress FWM, but has too much chromatic dispersion- True wave fiber has larger enough dispersion to suppress FWM, and smallenough chromatic dispersion, but still has dispersion slope problem.
13 Polarization mode dispersion limitation for beyond 10 Gbit/s Y-polarizationY-polarizationX-polarizationtX-polarizationXt ~ c, (nx-ny) and LPMD is caused by differential group delay (DGD) between two- polarization modesPMD is a statistic process satisfying Maxwellian distributionPMD becomes serious issue for 10 Gbit/s and beyondPMD design- Instantaneous PMD should be smaller than 25% pulse width- Assuming fiber PMD is 0.3 ps/km^1/2, 400 km fiber gives mean PMD 6 ps.If we use safety number 4 for Maxwellian distribution, the instantaneousPMD is 24 ps. Which means 0.3 ps/km^1/2 PMD gives 400 km distancelimitation for 10 Gbit/s.
14 PMD compensation technology Y-polarizationX-polarizationLong distanceSM fiberPolarizationcontroller (PC)XPM fiberReceiverTransmitterfeedbackcontrol signalElectronicprocessPM fiber: with high PMD due to strong fiber birefringencePMD induced by long distance single mode fiber can be canceled byusing a short PM fiber with a greater PMDFeedback control signal to adjust input polarization of PMfiber, so that the fast polarization axis of single mode fiber matchesto the slow axis of PM fiber and vice versa.
15 Capacity and transmission distance Current Transmission Technology1530 ~1560 nm window of EDFA- 10 Gbit/s X 16 ch transmission (channel space 0.6 nm)- 45 ~ 50 km span length- ~ 150 in-line optical amplifiers- total 7500 km transmission without electronic regenerterfor 10 Gbit/sFuture Transmission Technology- 10 Gbit/s x N (N=32~50) transmissionGbit/s WDM technologiesGbit/s WDM technologies
16 …. …. Uniquely designed LCF fiber and non-zero dispersion shift fiber (NZ-DSF)EDFALCF fiberNZ-DSF fiberEDFA….….25 km25 kmLCF (Large core fiber)- chromatic fiber dispersion -2 ps/km.nm- large effective area 75 ~ 80 um^2- bigger dispersion slope- suppression of nonlinear effect- used in first half span distance for higher channel powerNZ-DSF fiber- chromatic fiber dispersion -2 ps/km.nm- smaller dispersion slope- used in second half span for smaller power- to reduce accumulation of chromatic dispersion
17 ..…. …. Chromatic dispersion compensation in Submarine transmission EDFALCF fiberNZ-DSF fiberEDFAEDFAStandard SMF fiberEDFA..….….25 km25 km50 km10 span 500 kmStandard single mode fiber (SMF) is used for chromatic dispersioncompensationDispersion compensation is performed at every 10 span (500 km)In order to resolve dispersion slope problem, pre-dispersion andpost-dispersion compensation are needed at transmitter andreceiver ends
18 how is PMD impact for ultra- long distance such as PMD concern in submarinetransmissionhow is PMD impact for ultra- long distance such asSubmarine transmission (7500 km)?- PMD is accumulated through the long distancetransmission by both fiber cable and every opticalcomponent.- define a low PMD fiber (PMD as low as0.008 ps/km^1/2). Over 7500 km, mean fiberPMD =6.9 ps .- define each optical component with a smallPMD, e.g, EDFA with 0.1 ps, WDM with 0.1ps.
19 One stage Er. Doped fiber amplifier Opt.isolatorASEfilterGain equalizationfilterEr. fiber980 nm pumplaser module980 nm low noise pump laser module for first stage EDFAOptical isolator is used to reduce back ASE impactOptical filter is used for gain equalizationASE filter (FBG) is used to get off ASE and its accumulationTotal gain of fiber amplifier is from 10 dB to 12 dBsmall N.F. (noise figure): ~4 dBOutput power : ~ +11 dBm
20 more than 100 span and fiber amplifiers at 10 Gbit/s, but Comparison of WDM transmission betweenterrestrial and submarine networkWhy submarine network can transmit over 7500 km withmore than 100 span and fiber amplifiers at 10 Gbit/s, butterrestrial network can only handle 5 span over 400 km?7500 km vs/ 400 km is a big difference!- Submarine transmission network is a pre-definedsystem, which is more like a well controlledexperimental system in Lab.- In terrestrial network, the characteristic of fiber inunderground is unknown. The system designer shouldbuild equipment to cover a lot of statistic cases.
21 Next Generation Network lRIP/WDMRRRllRRRRouterNon-IP Data SourceATM SwitchRIP/SONETSONET DCS or ADMROptical XC or ADMIP/ATMlOptical line System
22 All Optical Network: WDM Long Haul, Metro Backbone, and Local Collecting Ring CentralNode126WDM MetroBackbone ringHub3Hub5WDM localcollecting ring4WDM localcollecting ring
23 The ring size of metro backbone WDM network is Description of Metro WDM RingThe ring size of metro backbone WDM network isdefined to be from 100 km to 200 km, and WDM localcollecting ring is defined from 20 km to 50 km.In order to have a transparent (protocol independent)transport optical network also for the low cost reason, noelectronic regenerators should be allowed in Metro WDMrings.Optical amplifiers might be needed in WDM metro backbonering network, but not in WDM local collecting ring.Metro WDM ring should be self-healing optical ring.network protection and restoration should be atphotonic layer .
24 Optical Protection Efficiency 1+1 OSNCP (Path Switch) vs. OSPRING (Optical Line)l51+1 OSNCPl5OSPRINGInterconnections between routers requires 4protection wavelengths with path switchSame interconnections between routers requires1 protection wavelength with OSPRING
27 Optical Network Evolution Issues How to transport large pipes (OC-48c & above) reliably? Should OC-192 be deployed in an existing OC-48 based network?Should SONET be bypassed for ATM, FR, and IP transport over wavelengths?No standards on optical data interface, multi-vendor interoperabilityWhat survivability architecture best balances performance, cost, and flexibility?Is synchronization required for optical network?Mechanisms for providing OCH trail trace, mechanisms to discover fiber topology, performance monitor and management across administrative boundaries.Meeting latency requirements in detecting, reporting, localizing, and reacting to faults (e.g. protection switching).
28 Survivability Alternative Tradeoffs Service Layer MeshEvery survivability mechanism makes tradeoffs:Speed vs. Facility Cost (Overbuild) is most fundamentalPhysical Layer (SONET & Optical) SchemesCentralizedMeshMaximum OutageDistributedMeshGoodMS/SPRINGSNCPMSPGoodFacility Cost [Restoration Overbuild]
29 Metro WDM Network’s Key Issue: Limited Number of OADM Nodes and Small Ring Size CentralNodeOADMOADMOADM
30 l3 l4 l1 l2 l1 Central Node : l8 l8 l6 l5 l7 Metro WDM Network’s solution: Boost and Pre-Amplifiersl3l4l1l2Att.OADMOADMOADMOADMBoost-Ampl1CentralNode:l8Pre-AmpOADMOADMOADMOADMl8l6l5l7
31 Metro WDM Network’s solution: One Line-amplifier ATT.ATTOADMOADMOADMOADMEDFA Input(after ATT control)EDFA Input (beforeTx ATT)l1l2l4l3CentralOfficel3l2l1l4l5l7l8l3l1l5l7l8l4.EDFAl8l1l2l8...OADMOADMOADMOADMEDFA Outputl8l7l6l5
32 Metro WDM Network’s solution: Line-Amplifier with Gain Slope OADMOADMOADMOADMEDFA Inputl1l4l3l2l2l1l5l7l8l3CentralOfficel4.Gain curveEDFAl8ll4l3l8...OADMOADMOADMOADMEDFA Outputl8l7l6l5
33 Metro WDM Network: Experimental Set-up BCDTXRXLRSplitterlAlB7dBSRClientCombinerSwitchOADMfilter
34 Transparent WDM Network: SONET-Less , Photonic Layer Restoration By Metro WDM Equipment HubOADMOADMAWDM Long HaulNetworkDHubHubBOADMOADMMetro WDMMetro WDMNetwork 1Network 2
35 Hybrid WDM Metro and Long Haul: Experimental Set Up 16 ch. Long Haul WDM Transmission 500 kmFiberTransponderFiber cutl16l16...::Metro WDMNetwork 1HP DigitalScopel1l1B40 ch. Long Haul WDM Transmission 500kmFlClFGAlAlADElElELA2LA3lClFErroroutputCHl1’l1’LA1LA4::Tektronix ST2400 SONET testsetTARAl40’l40’
36 Protection time when 16 channel long haul WDM fails Error periodError freeError free
37 Protection time when 40 channel long haul WDM fails Error freeError period