1. Short repetition of two important facts (1)
Electronic/electrooptical
Now
Optical amplifier
WDM: channels pr fiber
1 channel pr fiber
Up to
Earlier

2. Optical switches Circuit switching Wavelength conversion
Switches signals between fibers and/or wavelengths.
Wavelength conversion
To avoid collision on wavelengths (in same fiber)
Wavelength
converter
Optical crossconnect

3. Optical Transport Network –OTN- G. 709 Optical protection switching
Repetition Outline:
Optical components
Transmission aspects
Optical Transport Network –OTN- G. 709
Optical protection switching
OPS/OBS

4. Optical fibre, characteristic
Large bandwidth (theoretical 50 THZ)
Low attenuation (0,2 dB/km at 1550nm).
Physical size beneficial, light and thin, simplifies installation
Splicing and mounting connectors more complex
Immune to electromagnetic interference
Environmentally friendly material (sand!).

5. Propagation through fibre
Lightpulses are reflected into the core when hitting the cladding => approximately zero loss
Andreas Kimsås, Optiske Nett

6. Coupling light into the fibre
Single modus
Coupling into the tiny 10 micrometer core is demanding
Lining up the light-source is a significant part of the production cost
Multimode
Larger core diameter simplifies coupling

7. Modulation OOK modulation (on-off-keying) Directly modulated laser
NRZ (No Return Zero) most often used
RZ (Return Zero), some use
Phase modulation currently not popular
More advanced modulation formats being launched for 40 Gb/s pr. Channel systems.
Directly modulated laser
For medium bitrates Gigabit
External modulation, e.g. Employing external modulator: MZ interferometer
For high bitrates 10 Gb/s and beyond
OOK kan gi ustabilitet mhp amplitude og frekvens brukes på frekvenser bitrater under 2G
- Ekster modulasjon kan man bruke Mach Zender interferrometer for å slå av og på lysstrålen.

8. What is a long distance? 100 m? 10 Km? 1000 Km? LAN Access network
Transport network

9. Long distance optical system
Attenuation must be compensated
Regeneration
Attenuation
Dispersion must be compensated
Dispersion compensation employing fibre
Electronic compensation

10. Regeneration 1R regeneration = Amplification (Reamplification)
Amplifies the signal without conversion to electrical
Typically transparent for signal (shape, format and modulation)
Usually an optical amplifier
2R Reamplification & Reshaping:
Reshapes the flanks of the pulse as well as the floor and roof of the pulse, removes noise.
Usually electronic
Optical solutions still subject to research
3R Reamplification & Reshaping & Retiming:
Synchronisation to original bit-timing. (regeneration of clock)
Usually involves electro-optic conversion
Optical techniques in the research lab.

11. Erbium Doped Fiber Amplifier (EDFA)
Widely deployed in optical networks

12. Available wavelength range depends on amplifier technology
PDFA
1300 nm
EDFA
C - band
EDFA
L - band
ALTERNATIVE AMPLIFIER TECHNLOGIES: RAMAN AND SOA
EDFA ( Erbium Doped Fiber Amplifier) er navnet på den vanligste forsterkeren. Den dekker bølgelengde spekteret som blir brukt i dagens systemer og sammen med L-bånd EDFA vil den også dekke framtidens behov. Raman forsterkere og Semiconductor Optical Amplifiers (SOA) er to konkurrenende forsterkertyper som kan dekke et bredere bølge-lengde spekter ( dvs. at vi kan bruke enda flere kanaler), disse er også komersiellt tilgjengelige men mindre vanlige. EDFAen er mest brukt siden den gir et godt kompromiss når det gjelder ytelser og pris, samt at det var den første forsterkertypen som kom på markedet.
Commercially available
Still subject to research

13. Dispersion Pulse spreading when propagating through the fibre.
To much spreading results in intersymbol- interference
Limits the maximum transmissionrate through the fibre.
Three types of dispersion:
Modi-dispersion: Light traveling in different modi undergoes different delays through the fibre. Not present in SM!
Material-dispersion (chromatic): Refractive index is function of wavelength
Waveguide-dispersion: Propagation of different wavelengths depends on the characteristic of the waveguide, e.g. Index, geometry of core and cladding.

14. Zero dispersion At 1300 nm in standard fibre
Material (chromatic) dispersion is close to zero at 1300 nm
Not minimum loss
~ 1500 nm in dispersion shifted fibre
Manufactured for zero dispersion in 1500 nm region
Design core and cladding to give negative waveguide dispersion
At a specific wavelength, material and waveguide dispersion will result in zero total dispersion.

15. Chromatic dispersion
Figure: S. Bigo, Alcatel: Talk at Norwegian electro-optics meeting
2004

16. Chromatic Dispersion in transmission fibre – key figures
Dispersion depends on fibretype
G652, “Standard fibre” nm
Dispersion shifted fibre: nm
Non – Zero (NZ) dispersion shifted fibre: -3 to -6 Ps/nm*km

17. Dispersion Compensating Fibre (DCF)
Negative dispersion compared to transmission fibre
Much higher dispersion/km => Shorter fibre than transmission fibre required for achieving zero dispersion

18. Compensation of amplitude and dispersion
Long distance fibre-optical transmission Basic optical components (For WDM systems: Additional mux/dmux required
Transmitter
(Laser+
modulator)
Receiver
(fotodiode +
amplifier)
EDFA
Long Fibre
DCF
Compensation of amplitude and dispersion

19. Optical couplers: splitter & combiner
One or more fibers in, several fibres out
Divides the optical signal on several fibres.
Signal power is divided on the output-fibres
Splitting ratio is varying
50/50, 50 % on each of two fibres
10/90, 10 % in one, 90 % in a second.
Attenuation from input to output depends on splitting ratio
50/50 splitter results in 3 dB attenuation (halving the power)
Combiner
Splitter

20. Arrayed waveguide Grating
1 X N or N X N coupler divides the light on N waveguides of different length
Waveguides is then coupled together, resulting in interference
On each of the N outputs, constructive interference is achieved for a specific wavelength and destructive interference for the other wavelengths

21. Multiplexing/Demultiplexing
Optical multiplexing: Couple several waveguides together into a fibre.
Optical demultiplexing: Separate wavelengths from an input fibre into several output fibres with a single wavelength in each.
Employed for mux/demux in optical network nodes

22. Optical add/drop Filter out a wavelength or a set of wavelengths.
Does not employ non-linear effects
Add a wavelength or set of wavelengths.
May be reconfigurable (ROADM)
Select which wavelength to drop and add on a fibre
Not as configurable as an optical cross connect (full cross-connection between several fibres)
l1,l2
l1,l2 l1 l1
Drop
Add

23. Most important components
Optical fibre
Principle
Key parameters: Chromatic Dispersion, attenuation
Optical coupler
Application
EDFA Optical Amplifier
AWG
Applications

24. Coarse WDM Cheaper technology with less scalability than DWDM
Typically maximum 16 channels
0,1
0,2
0,3
0,4
0,5
1200
1300
1400
1500
1600
Wavelength (nm)
Loss (dB/km)
2 dB/km
G.652
G.652C nm nm

25. 16 channel CWDM using two multiplexers for two different bands
EXT
C1 – (8+1)
C1– (8+1)
C1 – 8L
1471
1491
1511
1531
1551
1571
1591
1611
1271
1291
1311
1331
1351
1371
1431
1451

26. CWDM and DWDM hybrid C1-8 D1-52 C1–8 1471 1491 1511 1531 1551 1571
1591
1611
C1–8

27. Optical networks (Zouganeli)
Increased traffic demands (e.g. from broadband home users/businesses and new services) => Fat pipes needed.
”IP everywhere” and development in optical technology => Fokus on simplifications:

28. Reconfigurable (R-)OADM
Still use cross connect for some wavelength/wavebands, but introduce more flexible add-drop function:
Not single
wavelength!

29. Network element functionality: Bypass
Traffic bypassing intermediate IP routers => Less load on routers (can be smaller and cheaper)
In meshed networks: Used to directly connect node pairs with high traffic between them.
(UNINETT is in the process of doing this now).

30. Transparent (all-optical) switches (1)
Micro-electro-machining systems (MEMS)
Complicated, but has received a lot of attention.

31. Transparent (all-optical) switches (2)
Probably most promising alternative currently.
However: Tunable Wavelength Converters (TWCs) are very expensive.

32. Switching architectures with wavelength conversion (Borella)
Dedicated converters for each output
Many converters
Flexible, no blocking
Wavelength specific multiplexers minimizes attenuation.

33. Switches with shared wavelength conversion (Borella)
Shared between all input lines
Access from any input wavelength
Optimal wavelength converter resource utilization
WC may not be available if too few
Extra switch between WC and output MUX required.

34. Needed functionality for optical OXC based networks (1)
Opto-electronic or all-optical.
Scalability and flexibility
Handles much higher number of line ports and directions than R-OADM
Higher flexibility than R-OADM
Service provisioning: End-to-end lightpaths should be provisioned in an automated fashion (not necessarily all-optical or same wavelength end-to-end).
Protection and restoration: Must have mechanisms to protect against fiber cuts or equipment failure at nodes. I.e. redirect traffic from failed to backup paths.
Wavelength conversion: Lightpaths can change wavelength to increase flexibility in allocating network resources. Much easier to implement in opto-electronic OXC than in all-optical OXC; 3R versus 2R (Mach-Zhender interferometer).

35. Needed functionality for optical OXC based networks (2)
Multiplexing and grooming: Normally done in the opto-electronical add-drop part.
Today mainly opto-electronic solutions.
Many candidate all-optical solutions: - Generic switch architectures (Clos, Shuffle,..) where elements are simple optical switch elements, connected with fibers. - ”Broadcast and select” switching matrixes realized with splitters and Semiconductor Optical Amplifiers (SOAs) (0 – 1 : block or let-through light). - Two- or three dimensional array of micro mirrors (MEMS) - Tunable wavelength converters and Array Waveguide Gratings (AWG)

36. 4 different architectures
1a) Fixed patch panel between WDM systems with transponders.
1b) Electrical switch fabric between WDM systems with transponders.
1c) Transparent switch between WDM systems with transponders, complemented by a OEO switch for drop traffic.
1d) Transparent switch on a transparent network. The signal stays optical until it exits the network.

37. 1c) Transparent switch between WDM systems with transponders, complemented by a OEO switch for control and management functions
Figure 6 shows a transparent switch architecture that has transparent interface cards but no
opaque transceiver (TR) cards on its sides. The optical switch fabric is bit-rate independent
and it accommodates any data rates available (e.g., OC-48, OC-192, OC-768). The drop-side
ports are connected to an OEO switch that provides SONET/SDH line termination through
its opaque ports. Note that integrating the opaque interfaces at the drop-side interfaces of the
transparent switch can also provide the opaque function. O/E drop interfaces in an OOO
switch can be a cost-effective solution but cannot do grooming or multiplexing. Thus,
network level cost reduction may be achieved with two switches (an OOO and an OEO Figure 6 shows a transparent switch architecture that has transparent interface cards but no
network level cost reduction may be achieved with two switches (an OOO and an OEO
The optical switch fabric is bit-rate independent and accommodates any data rates available. Most lightpaths will bypass the OEO switch.
The drop side ports are connected to an OEO switch that provides SONET/SDH line termination through its opaque ports.

38. Optical Transport Network (OTN)
ITU-T standard G.709
Paper: Andreas Schubert: ”G.709 – The Optical Transport Network (OTN)”

39. Why OTN? Standard for optical networks required
Optical interconnection between equipment from different vendors
Optical interconnection between different operators
Once called “digital wrapper”
Framing of different protocols for transport over the physical optical layer
E.g. IP/Ethernet or IP/ATM or SDH
Takes SDH/SONET further, enabling optical functionality
Six level Tandem connection monitoring (TCM)
From a single to multiple wavelengths
Forward Error Correction (FEC)
What is FEC?

40. OTN hierarchy Client Client OPU OH Client OH OPUk ODU OH ODUk FEC OTU
OCh payload
OChannel
Associated
overhead
Non
OCCp
OCCp
OCCp
OCCp
OCCp
OCC
OMS payload
OTS payload

41. ODU OH PM - Path Monitoring, contains three sub-fields TCM1-TCM6
RES
TCM/ACT
TCM6
TCM5
TCM4
FTFL
TCM3
TCM2
TCM1 PM
EXP
GCC1
GCC2
APS/PCC
RES
PM - Path Monitoring, contains three sub-fields
TCM1-TCM6
OH for six independent TCM’s
Contains similar sub-fields as PM
TCM/ACT Activation/deactivation of TCM
GCC
Communication between network elements (management), two channels
APS/PCC
Automatic Protection Switching
Protection Communication Channel
RES Reserved for future use
EXP Experimental use
FTFL - Fault Type and fault location Channel
Fault status, type and location
Related to TCM span

42. FEC algorithms
Performance increase depends on algorithm and amount of overhead (redundancy information)
Standardized algorithms, G.709. Reed-Solomon based

43. Summary OTN Management to the high bandwidth WDM network
SDH/SONET single wavelength, OTN – multiple wavelengths
Builds on management functionality from SDH/SONET
Monitoring functionality
GCC channels for management communication
Transparency to other protocols, e.g. IP
Wrap whatever you like
FEC compensates physical impairments, increases cost-efficiency

44. Summary OTN Management to the high bandwidth WDM network
SDH/SONET single wavelength, OTN – multiple wavelengths
Builds on management functionality from SDH/SONET
Monitoring functionality
GCC channels for management communication
Transparency to other protocols, e.g. IP
Wrap whatever you like
FEC compensates physical impairments, increases cost-efficiency
OTN switching is being deployed
OTN transmission and switching market is increasing rapidly

45. Protection in mesh network (Also used in other networks)
Continuous signal on two alternative paths, choose the best.
Hitless protection switching possible (switching without loss)
1:N protection
Several parties share a single common protection path.
Enables the path to be employed by low priority traffic when not in use.
Implies information loss because of switching. Data in the fibre is lost. Not hitless.

46. Protection schemes Dedicating resources Shared protection
Dedicated protection (e.g. separate dedicated wavelength)
1+1 duplicating data, or 1:1, pre-empting low-pri. data
In context of rings these are called DPRings
Optical unidirectional path switched rings (OUPSRs), path
Optical unidirectional line-switched rings (OULSRs), line
Shared protection
Protection resources shared between several lightpaths
1:N, requires signalling
In context of rings these are called SPRrings
Optical bidirectional path switched rings (OBPSRs), path
Optical bidirectional line-switched rings (OBLSRs), line

47. Classification of resilience schemes WDM
Restoration
Dynamic lookup for backup paths, spare capacity in the network. Typical IP-layer.
Protection
Reserving dedicated backup paths in advance. Typical WDM layer.

48. Protection times SONET/SDH Optical layer IP-layer MPLS
60/50 milliseconds for establishing a connection.
May avoid interruptions in a phone call.
Optical layer
2 micro – 60 milli seconds.
SONET detects errors within 2.3 – 100 micro seconds. Protection at higher layers may be initiated.
IP-layer
Slow detection, calculation and signalling, typically seconds.
MPLS
Relatively fast detection with HELLO messages, the higher frequency of the messages, the higher the overhead.
Fast switching if pre-planned path, LSP.

49. Carrier-Grade Ethernet Technology
Based on the article:
“Ethernet as a Carrier Grade Technology: Developments and Innovations” by
R. Sanchez, L. Raptis, K. Vaxenavakis 49

50. Native Ethernet characteristics
Ethernet Frame: 1) 7octets Preamble for synchronization 2) SFD ( ) start of
MAC frames
3) 48 bit DestinationAdress,
48 bit SourceAddress
Simplicity (plug n’play) and cost effective
The switching logic (self-configuration)
Listening, Learning and Forwarding
Redundancy through xSTP
VLAN known as a broadcast domain
Connection-less (single hop)
CSMA/CD (do we still need it in switched Ethernet?) 50

51. Why Carrier Ethernet ? Standardized services Scalability Reliability
Ethernet is the technology of choice in the customer domain (85% of all networks and 95% of all LANs)
Internet is packet-switched, suitable to be transported over Ethernet
Eliminate potential internetworking problems between the core (carrier) network and Ethernet acess networks.
High bandwidth with simplicity and low cost?
The MEF1) has defined Carrier Ethernet as “an ubiquitous, standardized, carrier-class Service and Network defined by five attributes that distinguish Carrier Ethernet from familiar LAN based Ethernet”
Standardized services
Scalability
Reliability
QoS
Service Management 51

52. Carrier Ethernet Challenges
Moving Ethernet from the LAN to the carrier network brings out requirements/challenges:
Scalability
Support for 10exp6 customers of an SP
Evolving the VLAN-tagging standards
Protection (Reliability and Resiliency)
Achieve the required 50ms recovery time
Problems with xSTP recovery time, other protocols required
3. Hard QoS comparable with the guaranteed service from existing leased lines
Service Management
Service provisioning based to SLAs
Service Monitoring and Troubleshooting
TDM support (Inter-working with existing technologies) 52

53. Scalability - MAC-in-MAC header encapsulation -The MAC header is
added at the edge of the SP
- 24 bit I-SID
~16 service instances
- Dedicated set of
MAC addresses
-Total separation of the
customer and SP networks 53

54. PBB-Traffic Engineering
PBB-TE 802.1Qay introduce connection-oriented forwarding mode and Ethernet tunnels:
Deterministic service delivery, QoS
Resiliency
OAM requirements
Turning off xSTP
Forwarding is not based on the MAC learning mechanism but provided by the OAM plane 54

55. Operation, Administration and Maintenance (OAM)
Important building block toward carrier services Ethernet, multiple working/standardization bodies.
IEEE 802.1ag and ITU-T Y.1731:
Fault detection through Continuity Check Messages
Fault verification through Loopback and reply messages
Fault Isolation through Linktrace and reply messages
ITU-T Y.1731
Fault notification through Alarm Indication Signal
Performance monitoring
Frame Loss Ratio
Frame Delay
Frame Delay Variation 55 55

56. Conclusions
Its simplicity and cost-effectiveness makes Ethernet a desirable technology for the NGN carrier networks
Can Ethernet still be considered ”simple” after the discussed changes???
Native Ethernet is lacking capabilities for the MAN and WAN environment.
PBB, PBB-TE and OAM aim to enhance Ethernet and provide the required carrier-grade services as from SONET/SDH, ATM and MPLS.
Resiliency?
Work in progress! 56

57. Access technologies properties: xDSL
Typically asymmetric, downlink 1/4-1/8 of uplink
Twisted pair copper cable, fundamental physical limit is close, Shannon theorem
Bandwidth/distance tradeoff 52
VDSL
Shannon 25 15
Capacity
Mbit/s
ADSL 6
ADSL/RealADSL2 1
1.5 3 6
Distance (Km)
VDSL required for high capacity triple play

58. Fiber to the Home (FttH) variants
Many Fibers =>
no external power
is needed
Consentrator =>
less fibers,
needs power
Passive =>
Higher power loss
Do not need power

59. PON: SCMA, TDMA, WDMA Sub Carrier Multiple Access (SCMA)
Unique RF frekquency to each subscriber. Share wavelengths
Time Division Multiple Access (TDMA)
Collision avoidance with access protocols
ATM-PON (B-PON), Gigabit PON (G-PON), Ethernet-PON (E-PON), Gigabit Ethernet PON (GE-PON)
Wavelength Division Multiple Access (WDMA)
no collisions
higher capacity
more expensive

60. Passive Optical Network (TDMA)
Time-sharing of
fiber resources
ONU
OLT
downstream
passive splitter
Limitation on power budget
Burst mode transmission
Different power from each subscriber
Makes capacity upgrades difficult
up to 20km
OLT: Optical Line Terminal ONU: Optical Network Unit

61. Passive Optical Network (TDMA)
FttH architecture comparison
pros:
passive fibre plant
low OpEx
one connection at OLT
cons:
broadcast centric
less scalable
less upgradeable
complex customer differentiation
ONU
OLT
upstream
passive splitter
up to 20km
OLT: Optical Line Terminal ONU: Optical Network Unit

62. Downstream Ethernet-PON
ATM is expensive, Ethernet sells in high volume and is therefore cheap
QoS og VLAN
Fiber resources in E-PON is shared and Point-to-Point
Ethernet broadcast downstream (as in CSMA/CD)
All frames are received by all subcribers
Upstream the ONUs must share capacity and resources

63. Upstream and multiple access
Collisions must be avoided
Too long distances implies a too long collision domain
Time-sharing is therefore preferred, timeslots to each ONU
All ONUs are synchronized to a common time-reference
Buffer in ONU assembles packets and sends in time-slot
Allocation of resources is an issue

64. WDM PON for the future
GPON/EPON may not handle future requirements on bitrate
10GPON – 10 Gb/s
Power budget imposes severe limitations on distances and splitting ratio
WDM-PONs solves the limitations of TDMA-PON
Dedicated wavelength to each subscriber
May be combined with TDMA-PON in a hybrid, allowing 1:1000 splitting ratio.
Many variants of WDM-PON

65. WDM-PON (WDMA)
OLT
ONT
WDM, One wavelength to each subscriber

66. Basic WDM-PON architectures
B&S architecture
Passive splitter
Unique filter in ONU
Individual wavelength upstream
Broadcast security issues
AWG based
Low insertion loss, 5 dB
Universal Rx
Wavelength specific Tx
Periodic routing behavior
AWG + Identical ONU’s
Single shared wavelength upstream (TDMA)
Broadband LEDs and spectral slicing give poor power budget
Bidirectional OLT using a circulator

67. Most Cost effective: CWDM-PON
16 CWDM wavelengths on SFW supports 8 ONU’s
1270 nm to 1610, ITU-T standard
High power budget but potential problems with old fibers (OH peak)
Employs standard low-cost pluggable SFP modules
Capex is low, Opex moderate (higher than colourless)
DWDM much more expensive than CWDM, why?

68. Power budget CWDM What is a power budget? What is it useful for?
What causes the greatest loss?
Why is the power budget higher for DWDM compared to CWDM

69. CAPEX Cost on different PON-solutions
CWDM most cost-effective, but lowest splitting ratio
Amplified TDMA highest splitting ratio

70. Unified infrastructure: core to access
PON not only to residentials
Mobile back-haul
ADSL back-haul
Enterprise networks
Combine with WDM Metro rings
Combine with ROADM nodes
Cost optimization
Common management and control plane required
Common protocols required (Not SDH and Ethernet and…)

71. Layered Network Management
NMS
Core
EMS O3 O9
EMS 1 O2
EMS 2 O4 O1
O10 O8 O6 O7 M5 M1 M4 M2
Core Network M6 M3
Metro SubNetwork 2
Metro SubNetwork 1

72. GMPLS Introduction
IP -> MPLS => Datagram to Virtual Connection (VC) (point-to-point)
Explicitly routed label switched paths (LSPs) established before information transport – independent of actual routing paradigm
Label swapping used as forwarding paradigm
Forwarding equivalence classes (FECs)
Label hierarchy / Label stacking

73. Label-Switched Path (LSP)
MPLS Label Forwarding Example
LABEL SWITCHING
IP Forwarding IP
Packet
Label 1
Label 2
Label 3
Label-Switched Path (LSP)
LER
LSR

75. Introduction (2)
Constraint based routing - traffic engineering (QoS differentiation) - fast reroute (after failure) - diversity routing (disjoint alternative paths for protection)
Routing protocols (e.g. OSPF) must exchange sufficient information for ”constraint”
Resource reservation protocol with traffic engineering (RSVP-TE) is used to establish LSP/label forwarding states along path. (The alternative CR-LDP is not used any more)

76. Introduction (3) Generalized MPLS:
Extensions to handle e.g. optical network resources (OXC’s) (e.g. extensions of OSPF, RSVP-TE).
Common control plane for packet and optical network
New Link Management Protocol (LMP) for optical links.
Support for (label) switching in time, wavelength and space domains – and a label hierarchy.
Additional functionality to handle bidirectional links and protection/restoration.

77. ER-LSP setup example using RSVP-TE
RSVP Path message carried Explicit Route Object (ERO)
RSVP Resv message carries Label information (L)
LSR8
LSR2
LSR6
LSR3
LSR4
LSR7
LSR1
LSR5
LSR9
ERO=(2, 6, 7, 4, 5)
ERO=(6, 7, 4, 5)
ERO=(7, 4, 5)
ERO=(4, 5)
ERO=( 5)
L=21
L=10
L=14
L=5

78. Enhancements to signaling
Bidirectional LSP setup (New in GMPLS):
Bidirectional optical LSPs (lightpaths) are important for network operators
Fate sharing
Protection and restoration
Same QoS in both directions, same resource demands
Problems with two independent LSPs in MPLS:
Additional delay in set-up (problem in protection)
Race conditions for scarce resources => lower probability of success for both directions simultaneously
Twice the control overhead
In GMPLS: Single set of Path/Request and Resv/Mapping messages used to establish LSPs in both directions at once.

79. Enhancements to signaling
Notify messages:
Added to RSVP-TE for GMPLS
Provides a mechanism for informing nonadjacent nodes of LSP-related failures.
Inform nodes responsible for restoring connection
Avoid processing in intermediate nodes
Speed up
Failure detection and reaction
Re-establishment of normal operation

80. GMPLS Restoration When fault is handled after a failure has occurred
Dynamic resource allocation
Usually at least one order of magnitude higher delay than protection
Different levels of ”preparedness”
Pre-calculated routes or not;
Some resources reserved or not

81. GMPLS Protection and Restoration (3)
Protection mechanisms:
1+1 protection: simultaneous transmission of data on two different paths.
M:N protection: M pre-allocated back-up paths shared by N connections. (1:N is most usual; 1:1 also relevant).
Span protection – between adjacent nodes (NB! Avoid ”fate sharing”):

82. GMPLS Protection and Restoration (4)
1+1 Path protection (disjoint paths):
For M:N Path protection: back-up paths may be used for lower priority traffic in normal operation – preemption (Supported by GMPLS)

83. GMPLS Protection and Restoration (5)
Restoration mechanisms:
Alternative paths may be computed beforehand, but resources are seldom allocated before they are needed.

84. TTM1: ”Burst, packet and hybrid switching in the optical core network” Steinar Bjørnstad et al.

85. Introduction
Wanted: High capacity optical layer network with following requirements:
Support high utilization of resources
Support fine granularity
Support quality needed for strict real-time services
Support variable length packets

86. Some more OBS ”reservation” schemes

87. Packet/burst handling schemes

88. OpMiGua node design (Hybrid switch)
Buffer can be electronic (RAM) or
based on FDLs (or some future invention?)

89. TTM1: OPS and OBS “The Application of optical packet switching in Future Communication Networks” Mike J. O’Mahony et al.

90. Optical Packet Switching (OPS)
Bring packet switching into the optical domain
Switch packets at the optical layer
Fast optical switching matrixes required
Nanosecond switching time
Pure OPS still fare away
Packet header recognition, demonstrated for short headers
Header generation, demonstrated hardware encoded headers
Packet control (setup of switching matrix), far away …
Transparent payload switching: Feasible
Focus here is optical payload switching, but electronic header processing.

91. Adding OPS to an OCS/OXC network
A network that supports both SDH circuits and packet transport
Some wavelengths are reserved for SDH connections only
Other wavelengths are used for packet transport
Aggregation of packets in edge nodes (electronic RAM available for contention resolution in edges).
Packet switch in core added (if not all packets aggregated must be sent to same destination …).
=> OCS and OPS shares same infrastructure, but is in reality two different logical networks.
If large network
more core OPS
Switches added
for better utilization
of capacity.

92. Aggregation of packets in edge nodes
Topological and logical interface between service and transport layers.
Fast switching and packet traffic aggregation at edge of network; dynamic and fast wavelength allocation needed.
Only some wavelength channels allocated to packet traffic.
OPS and IP domains can have integrated control plane.
OPS needs additional information about the OTN (topology, configuration etc).
Wavelength channels used for packets may terminate in other edge nodes or in a core node. In latter case a new wavelength channel is used to next (edge or core) node.

93. Optical memory Large buffers are difficult to realize using FDLs only.
Suggested to use combination of electronic (RAM) and FDLs.
Electronic (RAM) to handle long delays.
Optical (FDL) to handle short delays.
Simulation: Probability that a randomly chosen byte stored within an output-buffered packet switch is experiencing a delay greater than a given value.
Possibilities of reducing use of FDLs:
Shared buffer (Multiple output channels use same FDL)
Multiple wavelengths in same fiber (used as FDL) => Wavelength converters.
Optical memory

94. TTM1: Approaches to Optical Internet Packet Switching
David K. Hunter and Ivan Andonovic

95. The design of Optical Packet Switches
Three principal sub-blocks (Note: This is a slotted network):
Input interface: Alignment of packets i time. Why?
Switching core: Transports packets to the correct output port
Buffering using Fiber Delay Lines (FDL’s) (connected to switching matrix)
Output interface: Header insertion

96. Wavelength in Contention Resolution
Broadcast and Select Switch (KEOPS)
Wavelength encoder. N wavelength converters, one for each input. Encoding each packet on a fixed wavelength with a unique wavelength for each input.
Buffer and broadcast section. Number of FDLs and a space switch stage. Electronically controlled selection (full signal?).
Wavelength selector block. N demultiplexers, followed by electronically controlled selection.
All packets available at all outputs => support multicast

97. Highlights you MUST know

98. Propagation through fibre
Lightpulses are reflected into the core when hitting the cladding => approximately zero loss
Andreas Kimsås, Optiske Nett

99. Erbium Doped Fiber Amplifier (EDFA)
Widely deployed in optical networks

100. Chromatic dispersion
Figure: S. Bigo, Alcatel: Talk at Norwegian electro-optics meeting
2004

101. Optical add/drop Filter out a wavelength or a set of wavelengths.
Does not employ non-linear effects
Add a wavelength or set of wavelengths.
May be reconfigurable (ROADM)
Select which wavelength to drop and add on a fibre
Not as configurable as an optical cross connect (full cross-connection between several fibres)
l1,l2
l1,l2 l1 l1
Drop
Add

102. 4 different architectures
1a) Fixed patch panel between WDM systems with transponders.
1b) Electrical switch fabric between WDM systems with transponders.
1c) Transparent switch between WDM systems with transponders, complemented by a OEO switch for drop traffic.
1d) Transparent switch on a transparent network. The signal stays optical until it exits the network.

103. Fiber to the Home (FttH) variants
Many Fibers =>
no external power
is needed
Consentrator =>
less fibers,
needs power
Passive =>
Higher power loss
Do not need power

104. Scalability through VLAN hierarchy(4)
104

106. The design of Optical Packet Switches
Three principal sub-blocks (Note: This is a slotted network):
Input interface: Alignment of packets i time. Why?
Switching core: Transports packets to the correct output port
Buffering using Fiber Delay Lines (FDL’s) (connected to switching matrix)
Output interface: Header insertion