Optical Networks

1. Optical Networks 2008

2. Topics • Optical Links • Light Sources, Detectors and Receivers • Optical Fiber Channel • Optical Amplifiers • Digital Optical Communications • Time and Wavelength Multiplexing • Optical Cross-Connects (OXC) • Optical Networks • First Generation Optical Networks and SONET • Second Generation Optical Networks • Multi Protocol Lambda Switching • DWDM optoelectrical metro network

3. Review of Optics • What is a monochromatic wave • Polarization of light • Interaction between Light and Matter Total Internal Reflection and Absorption • Diffraction • Interference

4. Light Sources • LED -- Light emitter diodes • Laser diodes • Single mode laser diodes

5. Detectors and Receivers • Solid state detectors • PIN diode • Circuit noise and signal to noise ratio in a receiver • Direct detection and bit error rate • Avalanche photodiodes (APD)

6. Detectors and Receivers (cont.)

8. Optical Fiber Channel (1) • Total internal reflection in a optical fiber • Telecommunications industry uses two windows: 1310 & 1550 nm • 1550 window is preferred for long-haul applications (Less attenuation, Wider window, Optical amplifiers)

9. Optical Fiber Channel (2) • Multimode fibers and their limitations

10. Optical Fiber Channel (3) • Single mode fibers and limitations • Non-linearities in fibers • Coupling light in a fiber and connecting two fibers

11. Fiber Amplifiers erbium doped fiber amplifiers (EDFA)

12. Semiconductor Optical Amplifiers (SOA)

13. Topics • Optical Links • Light Sources, Detectors and Receivers • Optical Fiber Channel • Optical Amplifiers • Digital Optical Communications • Time and Wavelength Multiplexing • Optical Cross-Connects (OXC) • Optical Networks • First Generation Optical Networks and SONET • Second Generation Optical Networks • Multi Protocol Lambda Switching • DWDM optoelectrical metro network

14. Digital Optical Communications • Signal Quantization / Coding: from analog to digital signal and vice versa • Digital Modulation: Amplitude, Phase, and Frequency Modulation • Multiplexing to increase the bandwidth of an optical channel • Time Division Multiplexing • Wave Division Multiplexing (WDM) • WDM vs. DWDM

15. Digital Optical Communications (cont)

16. DWDM 2.488 Gbps (1) 1310/1510 nm 2.488 Gbps (16) λ1 λ2 λ3 λ4 λ5 λ16 1530-1565 nm ramge 1310/1510 nm 16*2.488 Gbps = 40 Gbps 16 uncorrelated wavelengths 16 stabilized, correlated wavelengts

17. Fiber Optics Transmission

18. Input & Output fiber array Wavelength Dispersive Element 1-D MEMS Micro-mirror Array Input Fiber Output Fiber 1 Output Fiber 2 Digital MirrorControl Electronics 1011 Optical Switch • 1-input 2-outoput illustration with four wavelengths • 1-D MEMS (micro-electromechanical system) with dispersive optics • Dispersive element separates the ’s from inputs • MEMS independently switches each  • Dispersive element recombines the switched ’s into outputs

19. All-opticalOXC DWDM Fibersin DWDM Fibersout DWDM Demux DWDM Demux DWDM Mux DWDM Mux All-Optical Switching • Optical Cross-Connects (OXC) • Wavelength Routing Switches (WRS) • route a channel from any I/P port to any O/P port • Natively switch s while they are still multiplexed • Eliminate redundant optical-electronic-optical conversions

20. Optical Add-Drop Multiplexor (OADM) 1 1 2 OADM 2 3 ’3 3 ’3

21. 3 3 2 2 WC 1 1 New request 1 3 New request 1 3 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 With Wavelength converters

22. Topics • Optical Links • Light Sources, Detectors and Receivers • Optical Fiber Channel • Optical Amplifiers • Digital Optical Communications • Time and Wavelength Multiplexing • Optical Cross-Connects (OXC) • Optical Networks • First Generation Optical Networks and SONET • Second Generation Optical Networks • Multi Protocol Lambda Switching • DWDM optoelectrical metro network

23. Optical Networks • 1 st Generation: optical fibers substitute copper as physical layer • Submarine Systems • SONET (synchronous optical) in TDM • FDDI for LAN, Gbit Ethernet etc. • 2 nd Generation: optical switching and multiplexing/ WDM • broadcast-and-select networks • WDM rings • wavelength routing networks • 3 th Generation: optical packet switching???

24. SONET SONET SONET SONET Data Center DWDM DWDM Metro Long Haul Metro Access Access Big Picture

25. SONET • Encode 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 interleaving

28. Practical SONET Architecture ADM – Add-Drop Multiplexer DCS – Digital Crossconnect

29. Protection Technique Classification • Restoration techniques can protect network against: • Link failures • Fiber-cables cuts and line devices failures • Equipment failures • OXCs, ADMs, electro-optical interface. • Protection can be implemented • In the optical channel sublayer (path protection) • In the optical multiplex sublayer (line protection) • Different protection techniques are used for • Ring networks • Mesh networks

30. Path Switching: restoration is handled by the source and the destination. Line Switching: restoration is handled by the nodes adjacent to the failure. Span Protection: if additional fiber is available. Line Switching: restoration is handled by the nodes adjacent to the failure. Line Protection. Path Protection / Line Protection Normal Operation

31. Shared Protection • Backup fibers are used for protection of multiple links • Assume independent failure and handle single failure. • The capacity reserved for protection is greatly reduced. Normal Operation 1:N Protection In Case of Failure

32. Protection in Ring Network (Unidirectional Path Switched Ring) (Bidirectional Line Switched Ring) 1:1 Line Protection Used for interoffice rings 1+1 Path Protection Used in access rings for traffic aggregation into central office 1:1 Span and Line Protection Used in metropolitan or long- haul rings

33. Working Path Backup Path Protection in Mesh Networks • Network planning and survivability design • Disjoint path idea: service working route and its backup route are topologically diverse. • Lightpaths of a logical topology can withstand physical link failures.

34. Trend: IP over DWDM • IP is good for routing, traffic aggregation, resiliency • ATM for multi-service integration, QoS/signaling • SONET for traffic grooming, monitoring, protection • DWDM for capacity

35. IP over DWDM: Why? • IP and DWDM => Winning combination • IP for route calculation, traffic aggregation, protection • DWDM => Cheap bandwidth • Avoid the cost of SONET/ATM equipmnt • IP routers at OC-192 (10 Gbps) => Don't need SONET multiplexing • Optical layer for route provisioning, protection, restoration • Coordinated restoration at optical/IP level • Coordinated path determination at optical/IP level

36. MPS • MPS = Multi-Protocol Lambda Switching • MPLS + OXC • Combining MPLS traffic eng control with OXC • All packets with one label are sent on one wavelength • Next Hop Forwarding Label Entry (NHFLE) • <Input port,  > to <output port,  > mapping

38. DWDM Summary • DWDM => Switching Bottleneck => O/O/O switches • High speed routers => IP directly over DWDM • Data and control plane separation => IP Control Plane • Data will be circuit switched in the core • IP needs to be extended to provide addressing, signaling, routing, and protection for lightpaths • High-speed point-to-point Ethernet => LAN-WAN convergence

40. Why Optical Networks?DWDM optoelectricl metro network