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Prof. Lian K Chen Part 6 - Optical Netwoks 1
IEG 4030 Optical Communications
Part VI. Optical Networks
Professor Lian K. ChenDepartment of Information EngineeringThe Chinese University of Hong Kong
Prof. Lian K Chen Part 6 - Optical Netwoks 2
Part VI. Optical Networks• Lightwave System Evolution• Undersea Transmission Systems• Optical Network Hierarchy and Topologies• Subscriber Loop• Passive Optical Networks• CATV systems• LAN/WAN/MAN
– FDDI– SONET/SDH
• All-optical Multiaccess Network• Network Management
– Protection and Restoration in Network Management
Prof. Lian K Chen Part 6 - Optical Netwoks 3
Lightwave Systems• Traditional Optical Fiber Transmission System
DET EQ DEC
TMGREC
LASERAMP AMP
Opto-Electronic Regenerative Repeater
E|
MUX
E|
DMUX
XMTR RCVRREGRPTR
REGRPTR
Low-RateData Out
Low-RateData In
Traditional Regenerated Transmission Line
E-Mux: electronic multiplexerE-DMUX: elecrtonic demultiplexerXMTR: transmitterREG: regeneratorRPTR: repeaterRCVR: receiverDET: detectorAMP: amplifierEQ: equalizerTMG REC: timing recoveryDEC: decision circuit
Prof. Lian K Chen Part 6 - Optical Netwoks 4
• Single-channel operation• Opto-Electronic TDM of synchronous data• electronic regenerative repeaters• 30-50km repeater spacing• Distortion and noise do not accumulate• Capacity upgrade requires higher-speed operation
Traditional Optical Fiber Transmission System
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Optically amplified Fiber Transmission System
• Multi-channel WDM operation• Data-rate and modulation-format transparent• One optical amplifier (per fiber) supports many wavelength channels• 80-140 km amplifier spacing• Distortion and noise accumulate• Graceful growth (upgrade) of channels• Capacity upgrade by adding wavelength-multiplexed channels
OA OAOA
O|
MUX
Data In
XMTRλ1
λN
λ2O
|
DMUX
Data Out
RCVRλ1
λN
λ2XMTR
XMTR
RCVR
RCVR
Prof. Lian K Chen Part 6 - Optical Netwoks 6
System Limitations• Attenuation → system power budget
– Solutions: optical amplifiers; coherent detection
• Dispersion → pulse broadening → intersymbol interference– Solutions: dispersion compensation - use dispersion-
compensating fibers, dispersion-shifted fibers, pre-chirping; soliton (dispersion and nonlinear effect compensate each other)
• Polarization → polarization dependent gain/loss, polarization mode dispersion (PMD), polarization sensitive → power penalty – Solutions: polarization tracking+polarization controller to fix the
polarization into components, polarization scrambling, polarization diversity, use polarization-maintaining fibers
Prof. Lian K Chen Part 6 - Optical Netwoks 7
System Limitations• Nonlinear effects → four-wave-mixing (FWM), stimulated Raman
scattering (SRS), stimulated Brilluoin scattering (SBS), self-phase modulation (SPM), cross-phase modulation (XPM) → system degradation– Solutions: advanced modulation format, power control, phase
modulation; frequency assignment
• Noises → reflection noise, phase noise, back-scattering, modal noise, mode partition noise, thermal noise, shot noise, amplifier beat noise, RIN, etc. → power penalty– Solutions: isolator can reduce some types of noises
• All impairments can be remedied by using forward error correction; electronic equalizer can also resolve dispersion problems
Prof. Lian K Chen Part 6 - Optical Netwoks 8
System Transmission Capacity
Bit
Rat
e -D
ista
nce
( Gb/
skm
)
1970 1975 1980 1985 1990 1995 2000 2005 Year
1101
102
103
104
105
106
107 WHAT’S NEXT ??WDM + Optical AmplifiersOptical AmplifiersCoherent Detection
1.5μm Single-Frequency Laser1.3μm SM Fiber0.8μm MM Fiber
First Generation
Second Generation
Fourth Generation
Third Generation
Prof. Lian K Chen Part 6 - Optical Netwoks 9
Capacity Toward 25 Tbit/s
• Chromatic Dispersion
• Fiber Nonlinearity
• Polarization Mode Dispersion
• Channel Xtalk
• L-band EDFAs
• Raman Amplifiers
• Novel Modulation Format
• Polarization or bidirectional interleaving
Higher Data Rate Closer ChannelSpacing
Wider Optical Bandwidth
Higher Spectral Efficiency
0.05 Bits/Hz >1 Bits/Hz
• Fiber Nonlinearity
OC-48 OC-768 100 GHz 12.5 GHz
10 nm 300 nm
• Available Components
System Transmission Capacity
Prof. Lian K Chen Part 6 - Optical Netwoks 10
Undersea Transmission Systems• Design Considerations
– span distance– data rate– repeater/amplifier spacing– fault tolerance, system monitoring/supervision, restoration, repair– reliability in components: aging– cost
• Leading supplier– Tycom (formerly Tyco Submarine System)– KDD Submarine Cable Systems– Alcatel Submarine Networks
http://www.telegeography.com/products/map_cable/index.php
Prof. Lian K Chen Part 6 - Optical Netwoks 11
Undersea Transmission Systems
Prof. Lian K Chen Part 6 - Optical Netwoks 12
Undersea Transmission Systems
Prof. Lian K Chen Part 6 - Optical Netwoks 13
Undersea Transmission Systems
Prof. Lian K Chen Part 6 - Optical Netwoks 14
Undersea Transmission Systems
Prof. Lian K Chen Part 6 - Optical Netwoks 15
Undersea Transmission Systems
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Undersea Transmission Systems
Prof. Lian K Chen Part 6 - Optical Netwoks 17
Submarine cable systems
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Transmission Aspects
Optical Networks
Multi-Access
Network Management
Services/Applications
• Dispersion• Power Budget• Non-linearity• Polarization, etc.
• Network Topology• Node Architecture• Multiplexing Scheme• Media Access Protocol
• Data/Voice• Video/Image• Interactive Multimedia• Internet/Web Access
• Fault Management• Configuration Management• Performance Management
Optical Networks
Prof. Lian K Chen Part 6 - Optical Netwoks 19
Optical Network Hierarchy
Prof. Lian K Chen
About 50,00 Route Miles Of Fiber Cable
Carrier Optical Networks in US
Prof. Lian K Chen Part 6 - Optical Netwoks 21
Yanji
The Existing Over-Head Fiber Optic Cables
Beijing
XiAn
Shanghai
Hongkong
Wuhan
To Europe
To Japan
Lanzhou
Hohhot
FLAG
To Southeast Asia
To South Korea
To North Korea
To Russia
YiningUrumqi
Korla
Ruoqiang
Lhasa
Golmud
Yinchuan
XiningYulin
Taiyuan
ZhangjiakouChengde
ShijiazhuangTianjin
Hengshui
Qingdao
Dalian
Dandong
Qiqihaer
MudanjiangHarbin
Baicheng
ChangchunFuxin
Shenyang
Qinhuangdao
JinanLianyungangKaifeng
ZhengzhouLuoyang
Chengdu
Kunming
Gejiu
Pingxiang
HaikouZhanjiang
Xingyi
Guiyang
Chongqing
Nanning
Beihai
FuzhouTaipei
HuzhouHangzhou
NanjingHefeiXinyang
Wuhu
Jiujiang
NanchangJianyang
Xiangfan
Shashi
Huaihua Changsha
Guilin
Hengyang
HuizhouGuangzhou
Shenzhen
The Existing Buried Fiber Optic Cables
Backbone Fiber Routes in China
Prof. Lian K Chen Part 6 - Optical Netwoks 22
Optical Networks • Network Topologies
RingBus
Tree
Star Mesh Multi-hop
Prof. Lian K Chen Part 6 - Optical Netwoks 23
Network Types• Network Types
Broadcast and Select Network
Static Wavelength Routing Network
λ1,λ2,λ3
λ1’,λ2',λ3’
λ1’’,λ2'’,λ3’’
λ1’,λ2,λ3’’
λ1’’,λ2’,λ3
λ1,λ2'’,λ3’
Dynamic Wavelength Routing Network
Space Switches
λ1
λ2
λ3
Prof. Lian K Chen Part 6 - Optical Netwoks 24
Broadcast and Select WDM Networks
Tunable receiver/fixed transmitter
Prof. Lian K Chen Part 6 - Optical Netwoks 25
DLCRT
O E
Traditional Fiber Feeder (Digital Loop Carrier)
EU
Subscriber Loop• Fiber-In-The-Loop (FITL) /Passive Optical Networks (PON)
ONU
O ERT
O E MUX
E OCO
Fiber To The Curb (Active Star)
EU
Prof. Lian K Chen Part 6 - Optical Netwoks 26
Subscriber Loop (contd.)
POS: Passive Optical Splitter ONU: Optical Network UnitRT: Remote Terminal CO: Central OfficeEU: End-User
ONU
O ECO
POS
1
N
Fiber To The Curb (Passive Optical Network)
EU
Prof. Lian K Chen Part 6 - Optical Netwoks 27
Fiber-In-The-Loop (FITL)
Okada, FSAN, 1988.
Prof. Lian K Chen Part 6 - Optical Netwoks 28
Passive Optical Networks (PON)
Optical Line Terminal
Optical Network Terminal
Optical Network Unit
Network Terminals
Prof. Lian K Chen Part 6 - Optical Netwoks 29
PON Architecture• At CO:
– Optical Line Terminal (OLT) generates downstream traffic on its own or takes the Sonet signal from a co-located Sonet XC.
– OLT aggregates traffic from multiple customers sites using TDM to ensure no interference.
• At Outside plant, – passive optical splitters are used to split signal 2 to 32 branches using
various topologies• At Customer premises
– PON terminates in Optical network unit (ONU), or a.k.a. Optical network terminations (ONT)
– The ONU converts optical signal to specific types of bandwidth (e.g. 10/100 Mb/s Ethernet, ATM, or T1 voice and data) and passes it on to routers, PBX, switches. ONU also uses laser to send upstream traffic to CO.
Prof. Lian K Chen Part 6 - Optical Netwoks 30
Evolution of Passive Optical Networks
APON(155Mb/s-622Mb/s)
GPON(1.25Gb/s-2.5Gb/s)
BPON(155Mb/s-1.25Gb/s)
EPON(1.25Gb/s)
Downstream:
1550nm for video, 1490nm for data
Upstream:
1310nm
WDM PON(1.25Gb/s-10Gb/s)
Downstream:
1550nm
Upstream:
1310nm
TDM-PON
Prof. Lian K Chen Part 6 - Optical Netwoks 31
TDM-PON
Prof. Lian K Chen Part 6 - Optical Netwoks 32
Upstream: Burst-Mode Transmission
ONU
ONU
ONUOLT
• Each ONU has different propagation distance from the OLT
• At the OLT, the receiver will see packets from ONUs with varying amplitudes and phases, also varying inter-packet time-gaps
• For each packet: • Require fast clock recovery to get the clock
• Require fast peak detector to get the best threshold level
Burst-Mode Receivers
Prof. Lian K Chen Part 6 - Optical Netwoks 33
Ethernet PON
Prof. Lian K Chen Part 6 - Optical Netwoks 34
Prof. Lian K Chen Part 6 - Optical Netwoks 35
Major TDM-PON Technologies Summary
6416 nominal, 32 allowed32Number of split
20km10km20kmSpan
D/S: 1244/2488 U/S: 155/2488
D/S: 1244 U/S: 1244
D/S: 622/1244 U/S: 155/622
Speed (Mbps)
ATM and EthernetEthernetATMProtocol
ITU-T G.984IEEE 802.3ahITU-T G.983Standard
GPONEPONBPONCharacteristics
Ref: G Keiser, FTTX concept and application
Prof. Lian K Chen Part 6 - Optical Netwoks 36
WDM-PON
Q: what are the pros and cons for WDM-PON, compared to TDM-PON?
Prof. Lian K Chen Part 6 - Optical Netwoks 37
WDM-PON
• WDM-PON: Wavelength Division Multiplexed Passive Optical Network
• use multiple wavelengths, each serves a certain group of users
• higher capacity, future-proof
Prof. Lian K Chen Part 6 - Optical Netwoks 38
Hybrid Fiber-Coax (HFC)• To provide new interactive service, cable TV systems are gradually
upgraded to HFC architecture.• Cable modem is used to provide internet access (IEE802.14).• Telephone service can be provided through VoIP.
Fiber NodeCentral
Office Fiber Coax Amplifier
200-1000Homes
Down-link: 50-750MHz, @1.55μmUp-link: 5-40MHz, @1.3μm
Prof. Lian K Chen Part 6 - Optical Netwoks 39
CATV (Community Antenna TeleVision)
• Headend : distribution source; include programs received from satellite, local TV station, together with in-house production programs.
• Super-trunk : no fan-out, connection from headend to the hub.• HUB : distribution node; requires high carrier-to-noise ratio (CNR)
~52-56 dB.• Subscriber : home users, required CNR ~ 35 dB
Headend Hub Hub
Drop line
subscriber
subscriber
Trunk amplifier
Prof. Lian K Chen Part 6 - Optical Netwoks 40
Modulation format of CATV system(1) AM-VSB (vestigial side-band) :
• simple modulation scheme• compatible to existing modulation format• requires high CNR limited power budget, unless high-power diode-
pump solid state laser (>20 dBm) with external modulation is used. • NTSC : 6MHz spacing, 4.2MHz VSB bandwidth
(2) FM : • easier to achieve since the required CNR ~16.5 dB.• requires more bandwidth (40MHz spacing, 30MHz bandwidth)• typically used in satellite broadcasting and by some CATV operators.
Prof. Lian K Chen Part 6 - Optical Netwoks 41
Modulation format of CATV system (contd.)
(3) Digital : – baseband– FSK and PSK - spectral efficiency not as good as baseband (0.5-1.0
bit/s/Hz), but easier channel tuning– QPSK - spectral efficiency (2.0 bit/s/Hz)– required large bit-rate (>100Mbit/s) if uncompressed– compression schemes - JPEG(ISO), MPEG(ISO), H.261(CCITT), …
• Channel multiplexing scheme : SCM (subcarrier multiplexing)
Prof. Lian K Chen Part 6 - Optical Netwoks 42
Distortion in CATV• Sources of noise or distortion :
– transmitter - relative intensity noise (RIN), clipping noise, intermodulation. (RIN is very sensitive to reflection)
– receiver noise - shot noise, thermal noise, circuit noise, APD noise.
• Performance index :
CNR (carrier-to-noise ratio) per channel ~ 52 dBCSO (composite-second-order distortion) ~ -65 dBcCTB (composite-triple-beat distortion) ~ -65 dBc
dBc: dB respect to carrier
Prof. Lian K Chen Part 6 - Optical Netwoks 43
CNR calculation
where m : modulation index per channel I dc : d.c. photo currentBW : receiver bandwidth Ft: electronic preamp noise figureR eq: receiver equivalent resistance RIN: laser relative intensity noise
The last term (laser intensity contribution) in the denominator is introduced since the noise becomes non-negligible when I dc is large.
Note that the above CNR is per channel.
2
2
1 ( )2
2 4 /
dc
dc t eq dc
m ICNR
e I BW k T BW F R RIN I BW
⋅=
⋅ ⋅ ⋅ + ⋅ ⋅ ⋅ ⋅ + ⋅ ⋅
Prof. Lian K Chen Part 6 - Optical Netwoks 44
CNR for analog modulation Ex: Assume a laser with
Pdc= 2mW, m= 0.01, RIN = -150 dB/Hz, BW = 4MHz, Ft= 3, R eq= 75Ω, Ro= 1.0 mA/mW
Baseline (without distribution loss, fan-out, ….) CNR is
Q : How to determine the modulation index?Q : When will shot noise/thermal noise/RIN noise dominate?Q : What are the effects when we change the value of m, loss, BW, RL, or
RIN?
3 2
1503 6 6 3 2 610
1 (0.01 1.0 2 10 )2
2 (1.0 2 10 ) 4 10 4 4 10 3/ 75 10 (1.0 2 10 ) 4 10CNR
e k T
−
−− −
⋅ ⋅ ×=
⋅ ⋅ ⋅ × ⋅ × + ⋅ ⋅ ⋅ × ⋅ + ⋅ ⋅ × ⋅ ×
Prof. Lian K Chen Part 6 - Optical Netwoks 45
Broadband Local AccessSeveral approaches• xDSL (digital subscriber line) by Telco (telephone company).
(http://www.adsl.com)dedicated bandwidth (<10Mb/s)
• Cable modem by CATV industry (http://www.cablemodem.com)40Mb/s share bandwidth; low cost; reliability and security issues; need
• FTTx (Fiber-to-the-x)bring fiber close to residential building
• Wirelss - LMDS (local multipoint distribution service) (+ WiFi, WiMax)At 28 GHz with 1.3GHz bandwidth by FCC; fast deployment; inexpensive;
limits by rain-fade; • Powerline (http://en.wikipedia.org/wiki/Power_line_communication)
• Satellitewide-coverage; down link traffic only
Ref: Scientific America Oct. 1999.
Prof. Lian K Chen Part 6 - Optical Netwoks 46
Internet Users Projection
Optical Fiber Telecommunications V.B
Prof. Lian K Chen Part 6 - Optical Netwoks 47
LAN/MAN• Various network protocols by IEEE
and others
• 802.11: wireless LAN (WLAN)• 802.12: 100 VG-Any LAN• 802.15: Wireless PAN (WPAN)
• 802.15.1 bluetooth• 802.15.2 UWB• 802.15.4 ZigBee
• 802.16: WiMax• 802.17: Resilient Packet Ring
Prof. Lian K Chen Part 6 - Optical Netwoks 48
Fiber Distributed Data Interface (FDDI), ANSI X3T9.5
• dual counter-rotating token passing ring, one ring is the protection ring
• data rate: 100Mb/s, clock rate: 125Mb/s• support 1000 physical connections (500
terminals) • support a total fiber path length of 200km
(100km dual ring)• line coding: 4B5B• frame format (packet)• protocol: Timed -Token Rotation Protocol
– Ref: R. Jain, “Performance Analysis of FDDI Token Ring Networks: Effect of Parameters and Guidelines for Setting TTRT”, Computer Communications Review, vol. 20, no. 4, pp. 264-275, 1990.
MAC
B A
MAC
B A
MAC
B A
MAC
BA
MAC
BA
MAC
BA
Outer ring used for data
Inner ring for protection
Prof. Lian K Chen Part 6 - Optical Netwoks 49
Fault-tolerance in FDDI
In case of a link failure, the dual rings will be automatically configured into a single ring as shown below:
MAC
B A
MAC
B A
MAC
BA
MAC
BA
MAC
BA
MAC
B A
Station Station
To Ring 1 To Ring 2 To Ring 1 To Ring 2
Bypass Switch
Node FailureNo Node Failure
station adjacent to failure loops backfailed station
Prof. Lian K Chen Part 6 - Optical Netwoks 50
SONET and SDH• Synchronous Optical Network (SONET) ANSI T1.105.06• Synchronous Digital Hierarchy (SDH) ITU-T G.957
• SONET: North America standards, SDH: standards in Europe and Japan
• robust for transporting all types of voice, video and data services
SONET/SDH Signal Rates Rate (in MHz) SONET Frame SDH Frame Physical Signal Capacity
51.84 STS-1 - OC-1 28 DS1 155.52 STS-3 STM-1 OC-3 84 DS1 622.08 STS-12 STM-4 OC-12 336 DS1
2488.32 STS-48 STM-16 OC-48 1344 DS1 9953.28 STS-192 STM-64 OC-192 5376 DS1
STS: Synchronous Transport Signal Level (for SONET)STM: Synchronous Transport Module Level (for SDH)
“SONET: now it's the standard optical network”, IEEE Communication Mag. Vo.40, no.5, 2002.
Prof. Lian K Chen Part 6 - Optical Netwoks 51
SONET and SDH (contd.)• direct synchronous multiplexing: individual tributary signals may be
multiplexed, using Add-Drop Multiplexer (ADM) and Digital Cross-Connect, directly into a higher rate SONET signal without intermediate stages of multiplexing
→ cost-effective, flexible telecommunications networking
• provides flexible signal transportation capabilities, capable oftransporting all existing and future signals
→ can overlay to existing networks
Prof. Lian K Chen Part 6 - Optical Netwoks 52
SONET network spansPath: end-to-end; (path)Line: between transport nodes; (multiplex section)Section: between line regenerators (regenerator section)
SONET TERMINAL
MULTIPLEXER
SONET TERMINAL
MULTIPLEXER
SONET DIGTIAL CROSS_CONNECT
SONET REGENERATOR
SONET REGENERATOR
LINE LINE
SECTION SECTIONSECTION
PATH
TRIBUTARY SIGNALS
TRIBUTARY SIGNALS
Prof. Lian K Chen Part 6 - Optical Netwoks 53
• Frame rate: 8000 frames per second; 125μs per frame• Line rate of STS-1
SONET STS-1 Frame Format
3 rows
6rows
3 columns Path Overhead (1 column)
Sectionoverhead
Lineoverhead
STS-1 Synchronous Payload Envelope (SPE)(87 columns)
STS-1=(90 bytes/row)(9 rows/frame)(8 bits/byte)/(125 s/frame) =51.84 Mb/s
μ
Prof. Lian K Chen Part 6 - Optical Netwoks 54
SONET ring architecture• SONET ring architecture
ADM
ADM
ADM
Digital Cross Connect
Terminal Multiplexer
Dual Ring
Integrated Timing System Clock
Protection Ring
CentralExchange
DS1, E1, etc.
Prof. Lian K Chen Part 6 - Optical Netwoks 55
Key features of WDM Network• Simple Capacity upgrade
System capacity can be increased easily by adding more channels operating on different wavelength sufficient apart from the existing ones.
• Transparency Different modulation formats (analog AM, FM, PCM, … or digital ASK, FSK,
PSK, QAM, …) on different channels. • Wavelength routing
Wavelength is used as the intermediate or final address for routing datagram. Wavelength selective devices such as WGR (wavelength grating router) or AWG (array waveguide grating) can be used as the router.
• Wavelength switchingWavelength-switched networks provide re-configurable network architecture
on optical layer. Key components for implementing these networksinclude optical cross-connect, wavelength converter, wavelength router, and optical add-drop.
Prof. Lian K Chen Part 6 - Optical Netwoks 56
Wavelength Routing Networks• Broadcast-and-select networks are difficult to scale to wide-area
networks – no. of wavelength channel required – passive star couplers exhibit high insertion loss as the no. of ports
increases.• Wavelength routing networks overcome the problems by wavelength
reuse, wavelength conversion, and optical switching.
Station 1
λ1
Station 2
Station 5Station 4Station 3
λ1
λ2
Wavelength reuse
Prof. Lian K Chen Part 6 - Optical Netwoks 57
All-Optical Multiaccess Networks• “All-Optical” Networks
– transparent to multiple signal format and bit rate → facilitates upgrade and compatible with most existing electronics
– reduce number of costly electrical interface (?)– manage the enormous capacity on the information highway– provide direct photonic access, add-drop and routing of broadband full
wavelength chunk of information
• “Multiaccess” Networks (don’t confuse with access network) – efficient network resource sharing among network nodes– need multiplexing, routing and switching– techniques: SCMA, WDMA, TDMA, CDMA and their hybrids
Prof. Lian K Chen Part 6 - Optical Netwoks 58
Design Considerations of Multiaccess Networks
• Design Considerations– architectures/topologies → network capacity and connectivity– multi-access schemes and protocols→ network throughput and delay– node complexity → cost– all-optical processing vs. opto-electronic processing – switching speed → multi-/demultiplexing, switching– channel accessibility → device tunability (Tunable Transmitters-Tunable
Receivers, Fixed Transmitters-Tunable Receivers or Tunable Transmitters-Fixed Receivers)
– timing and synchronization– control signaling → network management– optical technology → dispersion, nonlinear effects, crosstalk, noise, …
Prof. Lian K Chen Part 6 - Optical Netwoks 59
Network Management• Network management is essential to operate and maintain any
networks.• However attractive a technology might be, it can be deployed only if it
can be managed.• The cost of managing a large network typically dominates the cost of
the equipment deployed in the network.• For optical networks, certain factors such as transparency limit the
number of parameters that can be monitored.
Prof. Lian K Chen Part 6 - Optical Netwoks 60
Network Management Function• Configuration Management • Performance Management• Fault Management• Security Management• Accounting Management• + Safety Management (optical power)
Network Management
Performance management
Security management
Configuration management
Accounting management
Fault management
Prof. Lian K Chen Part 6 - Optical Netwoks 61
Network ManagementPerformance Management:• measure and monitor the network performance such as network throughput,
user response times, line utilization, signal quality, etc.• ensure network can perform at acceptable level.• gather data analyse data check for thresholds alarms if below
threshold
Configuration Management:• monitor network and system configuration such as equipment inventory,
topology, connection setup, etc.• effects on network operation of hardware and software can be tackled and
managed.
Accounting Management:• measure network utilization to regulate network usage of users, maximize
fairness of network access• usage validation, billing
Prof. Lian K Chen Part 6 - Optical Netwoks 62
NM database
NM agent
Network Element
NM database
NM agent
Network Element
Management System
Network Management Protocols
Network ManagementFault Management:• fault detection generate alarms, fault isolation• automatically fix/recover network problems (restoration)• keep log of faults
Security Management:• control and monitor access to network resources • prohibits information and resource access without
appropriate authorization
Prof. Lian K Chen Part 6 - Optical Netwoks 63
Network Protection• In a network, each link carry data from different sources to different
destination.• Two ways to protect the traffic
(1) path switching - restoration is handled by the source and destination nodes of each individual stream
(2) line switch - restoration is handled by the nodes at both ends of the failed linkLine switching can be implemented by span protection and line protection
connection x
reroute path
x
(a) normal (b) path switching
(c) line switching-span protection
(c) line switching -line protectionx
Prof. Lian K Chen Part 6 - Optical Netwoks 64
• 1+1• 1:1 (only one fiber is on)• 1:N
splitter switch
(a) 1+1
switch switch
(b) 1:1
Working fiber
Protection fiber(c) 1:N
Protection fiber
switch
switch
switchswitch
switch
switch
•••
Working fiber
Working fiber
Working fiber
Low priority data
switc
h
Different Protection Techniques for Point-to-point Links
switc
h