S Optical Networks Course Lecture 12: The Course Recap

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1 S Optical Networks Course Lecture 12: The Course Recap Edward Mutafungwa Communications Laboratory, Helsinki University of Technology, P. O. Box 2300, FIN TKK, Finland Tel: , edward.mutafungwa@tkk.fi

2 1. Introduction Electrical communications Data Source Electrical signal source Light or optical communications Data Source Electrical signal Electrical signal Electrical signal source Light source Optical signal Slide 2 of 54

3 1. Introduction Electrical repeater Metallic cable Copper Links Orbiting satellite Terrestrial radio links Satellite links Radio relay stations Fiber Fiber links Optical to electrical converter Electrical repeater O E Electrical to Optical converter E O Slide 3 of 54

4 1. Introduction Advantages of the fiber transmission media Low transmission loss (typically db/km) Large information carrying capacity (multi Gbit/s) Immunity to electromagnetic interference More secure to eavesdropping or wiretapping Smaller size and weight Slide 4 of 54

5 1. Introduction Link performance is limited by: Loss Receiver Spreading Receiver Slide 5 of 54

6 1. Introduction Bit Rate Graphical representation of fiber limitations Disp e rsion Dispersion & Loss Limited Limi t it im Costly! L ss Lo Feasible Regime Distance Slide 6 of 54

7 2. Wavelength-Division Multiplexing Fiber Optical to electrical converter Electrical repeater O E Electrical to Optical converter E O O E O E E O E O O E E O Space-division multiplexing fiber link with electrical regeneration O E E O O E O E O E E O E O E O WDM fiber link with electrical regeneration Optical amplifier WDM fiber link with optical amplification Slide 7 of 54

8 2. Wavelength-Division Multiplexing Attenuation (db/km) Amplified optical communications systems Optical amplification enables WDM in 1550 nm window Less attenuation than 850 nm and 1300 nm windows 10 First window 850-nm Second window 1300-nm Third window 1550-nm Standard fiber 0.2 Low water-peak Fiber Optical signal sources available Less loss and zero λ dispersion Optical amplification, even lower loss (nm) Slide 8 of 54

9 2. Wavelength-Division Multiplexing Coarse WDM (CWDM) ITU-T G.694.2/695 grid with 2500 GHz or 20 nm channel spacing 18 channels spanning O-, E-, S-, C- and L-bands ( nm) Source: F. Audet, Understanding CWDM, EXFO application note. Slide 9 of 54

10 2. Wavelength-Division Multiplexing DWDM enables many channels with amplification,...but requires stable transmitters and good filtering (sharp skirts and precise center frequency) CWDM simplifies filter and transmitter design (cheaper)...but no amplification and few channels Source: F. Audet, Understanding CWDM, EXFO application note. Slide 10 of 54

11 2. Wavelength-Division Multiplexing A typical amplified WDM link includes: Optical transmitters and receivers (1 each per wavelength) Wavelength multiplexer and demultiplexers Optical amplifiers Boost amplifier: to increase the output power Line amplifier: to compensate for fiber losses Preamplifier: to improve receiver sensitivity Slide 11 of 54

12 2. Modulation/Demodulation Two popular optical modulation schemes On-off keying (OOK) modulation Subcarrier modulation (SCM) Slide 12 of 54

13 2.1 On-Off Keying (OOK) Modulation It is possible to directly or externally modulate (i.e. turn off and on) a light source (laser or LED) Direct modulation simple, chirp External modulation more complex, less chirp Slide 13 of 54

14 2.1 On-Off Keying (OOK) Modulation Non-Return-to-Zero (NRZ) format NRZ Power Binary Data TT Time RZ Power Return-to-Zero (RZ) format TFWHM T Time Duty Cycle = TFWHM/T where TFWHM is full width at half maximum of power Slide 14 of 54

2.2 Subcarrier Modulation Subcarrier modulated (SCM) systems Multiplex multiple data streams onto one optical signal Each data stream assigned a unique

15 2.2 Subcarrier Modulation Subcarrier modulated (SCM) systems Multiplex multiple data streams onto one optical signal Each data stream assigned a unique subcarrier frequency subcarrier multiplexing Data stream 1 ~ Data stream 2 ~ Data stream 3 f2 Laser fc ~ f1 f3 5 signal subcarrier multiplexing Slide 15 of 54

16 2.3 Demodulation Data signal recovery is a two step process (1) Recovering the clock (2) Determining whether a 0 or 1 bit was sent in a bit interval direct detection Slide 16 of 54

17 2.3 Demodulation P isignal + ishot + ithermal + idark Photodetector Shot noise, Dark current, Thermal noise Incident optical pulses Regenerated output pulses Photocurrent + photodetector noise Amplifier & filter Photodetector Current to voltage conversion Sampler & Decision circuit Clock/timing recovery Figure: Block diagram showing various functions and noise components in a receiver Slide 17 of 54

18 2.3 Demodulation * For optically preamplified receiver, a noise figure of 6dB assumed * Optical bandwidth Bo =50 GHz Slide 18 of 54

19 2.3 Demodulation Also performance improvements with electrical DSP BER techniques Equalizers Error detection and correction (forward error correction) Receiver Sensitivity (dbm) Source: G. Barlow, A G.709 Optical Transport Network Tutorial, Innocor white paper. Slide 19 of 54

20 3. Transmission System Engineering Link power budget Receiver Transmitter Fiber Item Value Transmitter: 1a) Average output power 1.0 mw Channel: 2a) Propagation losses (10 km) 0.2 db/km Receiver: 3a) Signal power at receiver 3b) Receiver sensitivity Link Margin (Power Margin) db value 0.0 dbm db dbm dbm = (3a 3b) db Slide 20 of 54

21 3. Transmission System Engineering Power penalty analysis -3-4 Signal without impairment Log(BER) Signal with impairment -7 Power Penalty Received optical power (dbm) Slide 21 of 54

22 3. Transmission System Engineering Power penalty analysis Impairment Ideal Q-factor Allocation (db) 17 Transmitter Crosstalk Dispersion Nonlinearities Polarization dependent losses Component ageing System margin Required Q-factor Slide 22 of 54

23 4. SDH/SONET Dominant standard for optical transmission and multiplexing for high-speed signals Single master clock synchronous multiplexing Easier and cheaper multiplexers and demultiplexers Extensive management information Standard optical interfaces enable interoperability Network topologies and protection switching for high availability service Basic transmission rates SDH 155 Mb/s STM-1 (synchronous transport module-1) SONET Mb/s (STS-1) Slide 23 of 54

24 4. SDH/SONET Layer (except physical layer) has associated overhead bytes POH for path layer, MSOH for multiplexer section layer and RSOH for regenerator section layer RSOH 270 N Bytes 261xN Bytes AU MSOH Pointer SOH 9 Rows STM-1 Payload Capacity (VC-4) POH STM-N frame structure Slide 24 of 54

25 4. SDH/SONET Bit Interleaved Parity AU Pointer Regenator Section Overhead Framing Framing Framing Framing Framing Framing Ident A1 A1 A1 A2 A2 A2 J0 BIP 8 Orderwire User B1 E1 F1 Datacom Datacom Datacom D1 D2 D3 Pointer Pointer Pointer Pointer Pointer Pointer Pointer Pointer Pointer H1 H1 H1 H2 H2 H2 H3 H3 H3 BIP 24 APS APS K1 K2 Datacom Datacom Datacom D4 D5 D6 Datacom Datacom Datacom D7 D8 D9 Datacom Datacom Datacom D10 D11 D12 B2 Multiplexer Section Overhead B2 Sync stat. Growth S1 Z1 B2 Growth Growth Z1 Z2 Growth Trans err. Orderwire Z2 M1 Automatic Protection Switching E2 Figure: SDH section overhead bytes. Crossed bytes are auxiliary bytes Slide 25 of 54

26 4. SDH/SONET Path Terminating Equipment used in the SDH networks DS1 VC-11 E1 VC-12 E3 STM-1 VC-3 STM-N STM-1 VC-N STM-N STM-N STM-N TU-12 TU-3 AU-4 VC-12 VC-3 VC-4 E1 E3 STM-N STM-N STM-N STM-N STM-N STM-1 VC-N interface STM-N bus Timeslot High Speed Multiplexer Interface STM-N Add/Drop Multiplexer Terminal Multiplexer STM-N STM-N Switch Matrix STM-N STM-N E4 VC-12 VC-3 E1 E3 VC-4 E4 STM-N STM-N STM-N STM-N Digital Cross-Connect System Slide 26 of 54

27 4. SDH/SONET Resilient SDH network topologies Point-to-point configuration TM Working fiber Protection fiber TM TM: Terminal Multiplexer ADM: Add/Drop Multiplexer Linear add/drop configuration TM ADM Drop ADM Add Drop TM Add Slide 27 of 54

28 4. SDH/SONET Resilient SDH network topologies Drop Add 2-fiber MS-SPRing Add ADM Drop Add 4-fiber MS-SPRing Slide 28 of 54 Add Add Drop Add Drop ADM ADM ADM Drop ADM Add Add SNCP ring ADM Drop Add Drop ADM Drop Add Add ADM Drop Add ADM Drop Drop ADM Drop ADM TM: Terminal Multiplexer ADM: Add/Drop Multiplexer ADM Working fiber Protection fiber

29 5. Multiservice Optical Networks Multiservice networks provide more than one distinct communications service type Voice, data, Internet etc. Over a common physical infrastructure e.g. fiber Increased prominence of data-centric protocols ATM, IP/MPLS, Ethernet, SAN protocols etc. SDH originally defined to carry voice traffic Unsuitable for asynchronous packet-switched bursty data traffic Four-fold capacity increase increments (e.g. from STM-1 to STM-4) Inflexible provision of capacity to users Slide 29 of 54

30 5. Multiservice Optical Networks Upgrade current systems with next-generation SDH/SONET (NG-SDH) solutions Virtual Concatenation (ITU-T G.7043) Link Capacity Adjustment Scheme (ITU-T G.7042) Generic Framing Procedure (ITU-T G.7041) These upgrades only needed at source and destination terminal equipment of required service Intermediate equipment do not need to be aware and can interoperate with upgraded equipment Enables operater to make only partial network upgrades on as-needed basis Slide 30 of 54

31 5. Multiservice Optical Networks Example ways of transporting IP packets over optical DWDM (WDM) networks via SDH/NG-SDH Fiber Link SDH Services λ1 STM-N λ2 STM-N λ3 STM-N FC, FICON, ESCON PDH, ATM Ethernet, IP/MPLS IP 10GbE, AAL5(ATM), PDH PPP/HDLC, PoS 10GbE, GbE, Ethernet Frame-Mapped GFP DVB, Fiber Channel, ESCON Transparent-Mapped GFP SDH/NG-SDH Optical (WDM) Slide 31 of 54

32 5. Multiservice Optical Networks Optical WDM network with open interfaces simplifies direct access to fiber capacity sharing by different clients Services DWDM λ1 Fiber Link STM-N λ2 IP/MPLS λ3 Ethernet PDH, ATM Slide 32 of 54

33 5. Multiservice Optical Networks Optical Transport Network (OTN) ITU-T G.709, G.872 Truly global standard unlike SDH/SONET Enables SDH-like Operations, Administration, Maintenance and Provisioning for WDM networks Reduces the requirement to run every service through SDH/SONET to benefit from the management features More efficient multiplexing, provisioning, and switching of high-bandwidth ( 2.5 Gbit/s) services Improved multivendor and inter-carrier interoperability Forward error correction (FEC) from the beggining Less complex than NG-SDH easier to manage Slide 33 of 54

34 Optical Digital (electrical) 5. Multiservice Optical Networks Slide 34 of 54

5. Multiservice Optical Networks Multiservice provisioning platforms e.g. Cisco s ONS 15454 Supported interfaces Cisco ONS 15454 Electrical (DS1, E1, E3, STM-1E etc.

35 5. Multiservice Optical Networks Multiservice provisioning platforms e.g. Cisco s ONS Supported interfaces Cisco ONS Electrical (DS1, E1, E3, STM-1E etc.) SDH (up to STM-64) CWDM and DWDM (OTN) Ethernet (up to GbE) SAN (Fiber Channel and FICON) Video (D1 video, HDTV) Cross-connection levels DS1/E1 up to STM-64 Slide 35 of 54

36 5. Multiservice Optical Networks MSC/ BSC NIU NIU PDH/ Ethernet/ ATM 10/100/1000 Mbit/s Ethernet 2G/3G/WiMAX PBX Public WiFi IP/MPLS MSPP IP/MPLS Metro Access / Edge MSPP IP/MPLS MSPP ATM/Ethernet MSPP FC, FICON, isci Figure: Example service mix supported by deployment of MSPPs Wireless local loop 10/100/1000 Mbit/s Ethernet ATM Storage Center MSPP: Multiservice Provisioning Platform PBX: Private Branch Exchange MPLS: Multiprotocol Label Switching ATM: Asynchronous Transfer Protocol MSC: Mobile Switching Center BSC: Base Station Controller Slide 36 of 54

37 7. Optical Network Design B SDH Digital Cross-Connect Voice Switch ATM Switch PSTN Optical Node Optical connections Optical Network Open Optical Interface Fiber Link A Client Equipment/ IP Router Networks IP/ATM Network Slide 37 of 54

38 7. Optical Network Design Example fixed OADM WDM MUX λ2 λ1 WDM DEMUX λ1 λ4 λ1λ2λ3λ4 λ3 λ2 λ1λ2λ3λ4 Output Fibers λ2 λ1λ2λ3λ4 λ1 WDM MUX Optical switch λ3 WDM MUX Example reconfigurable OADM λ1λ2λ3λ4 WDM DEMUX Add WDM DEMUX λ4 (a) Parallel λ 1 λ 2 λ W Example fixed OXC WDM MUX Drop λ 1 λ 2 λ W Input Fibers λ 1 λ 2 λ W WDM DEMUX λw λ 1 λ 2 λ W The example OXC scaled to handle 4 wavelength channels on each fiber port Any λ Any λ Any λ Any λ (b) Fully tunable OADM using a large multiport optical switch Slide 38 of 54

39 7. Optical Network Design A WDM network may be realized by solving: Physical topology design (PTD) problem Lightpath topology design (LTD) problem Routing and wavelength assignment (RWA) problem B B A 2 1 Solve LTD Problem C 3 4 A C D D B B A 2 A 2 1 C 3 4 D Solve RWA Problem 1 λ3 λ2 λ1 C 3 4 D Slide 39 of 54

Q-factor meter Digital Test Modules SDH (up to STM-64) PDH Ethernet (up to 10GbE) Source: Talk set

40 8. Test and Measurement Example: Acterna MTS-8000 Tester Fiber characterization OTDR/Power meter CD/PMD Testing Connection checklist tester CWDM/DWDM Testing OSA (OSNR, LED/laser/EDFA test) Q-factor meter Digital Test Modules SDH (up to STM-64) PDH Ethernet (up to 10GbE) Source: Talk set (communication & file transfer) Software tools (result postprocessing, report generation) Slide 40 of 54

41 8. Test and Measurement Figure: Example OTDR measurement for a fiber link to customers optical termination unit (ONU) Source: Introduction to Optical Communications, by L. Hart, Althos Publishing Slide 41 of 54

42 9. Network Management and Survivability Subnetwork connection protection (SNCP) rings Working fiber Protection fiber ADM Drop Duplicate traffic ADM Add After Failure Before Failure Drop SNCP ring Drop Add Add ADM Add Drop ADM Add SNCP ring Drop ADM Add Working traffic Drop Add ADM Drop Drop Add ADM ADM Traffic on protection fiber selected Slide 42 of 54

43 9. Network Management and Survivability IP/MPLS network protection schemes When failure detected packets could be rerouted on new setup LSP New LSP LSR Ingress LER Customer Site A LSR Penultimate Egress LSR LSR LSR LSP IP/MPLS Network Customer Site B LER: Label Edge Router LSR: Label Switched-Router LSP Label Switched Path Slide 43 of 54

44 9. Network Management and Survivability Example of SDH protection involving optical layer Fiber Lightpath SDH connection OXC SDH ADM 3 SDH ADM 3 (a) Normal operation before failure. SDH connection realized using lightpaths provided by optical layer between ADMs SDH ADM 2 OXC OXC SDH ADM 2 OXC OXC OXC SDH ADM 4 OXC SDH ADM 4 SDH ADM 1 OXC SDH ADM 1 (c) Fiber fails and OXCs perform optical layer restoration and reroute lightpath. SDH carries on with normal operation awaiting another failure Slide 44 of 54

45 9. Network Management and Survivability Classical network management constitutes FCAPS functions Fault management: detecting failures and isolating failed component Configuration management: managing orderly network changes e.g. equipment addition/removal Accounting management: billing and developing component lifetime histories Performance management: monitoring and managing various network performance metrics Security management: user authentication, control access to network elements, user data protection etc. Safety management: (specifically for optical networks) ensure that optical radiation conforms to eye safety requirements. Slide 45 of 54

46 9. Network Management and Survivability Interaction between optical and client layers (IP, SDH etc.) is important aspect of connection management protocols Different control plane models proposed for interconnecting optical layer control plane and client layer control plane Overlay model Overlay+ model Augmented (dynamic overlay) model Peer model Optical Node 2 Optical Node 1 IP router A Fiber IP router B IP connection provided via lightpath in optical layer Figure: Example of client layer connection provision via the optical layer Slide 46 of 54

of rights-of-way Time constraints Operator s business strategy Figure:

47 10. Deployment Considerations Selected fiber cable deployment method depends on various factors Geographical topography of an area Availability of rights-of-way Time constraints Operator s business strategy Figure: Fiber cables deployed on power transmission lines (source: Alcatel) Slide 47 of 54

48 10. Deployment Considerations Slide 48 of 54

10. Deployment Considerations Fiber-optic

(Copper or Fiber), GbE (future) Planned for

49 10. Deployment Considerations Fiber-optic communications now used in diverse areas Example: Avionics Full-Duplex Ethernet/ARINC 664 standard 10 Mb/s (Copper), 100 Mb/s (Copper or Fiber), GbE (future) Planned for A380s, 787s 2006 BMW X5 Flexray Airbus A380 Slide 49 of 54

50 10. Deployment Considerations Wireless or free space optics communications now also available Satellite Satellite Optical/infrared link RF link RF link Figure: Rooftop FSO installation Sources: Waseda University, Hamamatsu Photonics, IEEE/ConTEL conference Earth station Earth Earth station Slide 50 of 54

51 (Capacity x Distance)/Cost 11. Future Directions of Optical Net. Current Optical Comm. Systems Optical Technologies Coded Modulation Adaptive Equalization Non-Binary Modulation Optical Dispersion Compensation WDM Optical Amplifiers FDM/ SCM ErrorCorrection Coding Adaptive Threshold, Transversal Filters Non-Optical Technologies OEO Transponders Time *Ref: J. Kahn & K. Ho, Proceedings of SPIE, Vol. 4872, July 2005 Slide 51 of 54

52 11. Future Directions of Optical Net. Still need for optical digital signal processing (> 40 Gb/s) with photonic integrated circuits Figure: A typical photonic crystal PIC envisioned for the future (source: Nature Photonics, pp. 11, Jan 2007). Slide 52 of 54

53 About the Exam Please note that YOU CAN ONLY DO ONE(1) EXAM. That is if you do Exam A, you will not do Exam B, OR if you do Exam B you will not do Exam A. Exam A: Day: Ma/Mon , Time: 13-16, Place: S1,S4 Exam B: Day: Ke/Wed , Time: 16-19, Place: S4 Each exam will have five questions, whereby Question 1 is compulsory, and you can choose to do any three out of Questions 2 to 5. Slide 53 of 54

54 Thank You and Good luck!? Slide 54 of 54

S Optical Networks Course Lecture 7: Optical Network Design

S Optical Networks Course Lecture 7: Optical Network Design S-72.3340 Optical Networks Course Lecture 7: Optical Network Design Edward Mutafungwa Communications Laboratory, Helsinki University of Technology, P. O. Box 2300, FIN-02015 TKK, Finland Tel: +358 9 451