Data IK2211 Links and LANs Optical Networks module
Lena Wosinska
[e-mail]
The Royal Institute of Technology (KTH), School of Information and Communication Technology (ICT) Next Generation Optical NETworks (NEGONET) http://www.ict.kth.se/MAP/FMI/Negonet/
Outline
Introduction
Development of optical networks Telecom market evolution
Overview of broadband access technologies Evolution of fiber access networks Passive Optical Network (PON)
Current generation PON Next generation PON: short term and long term development PON protection schemes
Reliability performance vs. cost tradeoff in PON.
Conclusions
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Development of optical networks
What Is An Optical Network?
It is NOT NECESSARILY all optical packet switched Characteristics of an optical network
Transmission: optical Switching: could be optical, could be electronic, could be hybrid could be circuit, could be packet, could be burst
First-generation optical networks
Transmission in the optical domain (to provide capacity) Example: SONET network (Synchronous Optical Network) More functionality in the optical domain (optical networking)
Second-generation optical networks
Circuit Switched Optical Networks (wavelength routed networks) Some of routing, switching and intelligence is moving into the optical layer
Third-generation optical networks (?)
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Internet Model
Most widely used WAN technology
IP: the network protocol that is designed to operate above a variety of data link layer (network access) protocols
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Multiple protocol stacks
ATM network
SONET network
IP router
ATM switch SONET cross-connect
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IP router
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Photonics in switching
Optical circuit switching (OCS)
Wavelength-routed networks Relatively mature technology today Providing lightpaths A lightpath corresponds to a circuit
Set-up a lightpath The whole lightpath is available during the connection Disconnect
WDM network elements: OLT, OADM, OXC Not available today due to some technological problems
Optical packet switching (OPS)
Controllable optical memory for optical buffering, control functions in the optical domain, synchronization, etc
Optical burst switching (OBS)
Hybrid packet switching: a feasible solution?
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Optical Networking (OCS)
Circuit switched optical networks Lightpath
Optical connection
Transparent Routed One wavelength channel on each link Wavelength conversion
Spans multiple links
Transparency
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The optical layer
The optical layer provides lightpath service to its client layers. Lightpath: optical connection
An optical channel trail between two nodes that carries the entire traffic within a wavelength
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Functions of the optical layer
Multiplexing wavelengths Switching and routing wavelengths Monitoring network performance at various locations in the network
Client layers of the optical layer:
SONET/SDH ATM (Asynchronous Transfer Mode) IP
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WDM Core Network
OLT OXC
Lightpath OADM
IP
IP
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Traffic demand drivers
User behavior
Always on (reachability, upgrades and downloads) File sharing
Services
High-Speed Internet VoIP IPTV Gaming Telemedicine E-Goverment etc
Triple play
Traffic increases very rapidly
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Triple play capacity requirements
3P Telephony Basic 3P and extended 3P Number of channels Capacity 1 80 kb/s symmetric Basic 3P 2 TV Extended 3P Internet access Basic 3P 1 10 Mb/s symmetric 30 Mb/s symmetric Extended 3P
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2 x 9 Mb/s 4 x 15 Mb/s asymmetric asymmetric
Basic: design for basic triple play today Extended: design for five years from now
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Development in Sweden
COMPUTER AT HOME
Population
INTERNET AT HOME
BROADBAND AT HOME
Year
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Broadband access technologies
Telecom Network Hierarchy
Long haul - 100s-1000s km - Mesh Metro (interoffice) - 10s of km - Rings Access - a few km - Hubbed rings, PONs Users
The Last Mile First
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Broadband access technologies
Digital subscriber loop DSL (from telcos)
High-speed digital access to the Internet Based on existing twisted pair Cable (from cable TV companies)
Wireless access: WIMAX, WIFI, 3G Fiber access
Fiber to the cabinet (FTTCab) Fiber to the curb (FTTC) or Fiber to the Building (FTTB) Fiber to the home(FTTH)
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Broadband access technologies: limitations
Access based on: Capacity/user ADSL VDSL Coax Wi-Fi WiMax EPON GPON
2 Mb/s (typical) 20 Mb/s (typical) 2 Mb/s * 54 Mb/s (max) 28 Mb/s (max) 60 Mb/s * 40 Mb/s *
Max Reach
5.5 km 1 km 0.5 km 0.1 km 15 km 20 km 20 km
FTTx
* Bandwidth depends on the number of users
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OECD broadband statistics
Source: OECD
Other
are mostly fixed wireless access (3G or WIMAX) In Japan and Korea the DSL penetration decreases because of swap to FTTH FTTx completely dominated by a few national operators in Japan and Korea China not an OECD member and therefore not included here
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www.oecd.org/sti/ict/broadband
FTTH growth prediction
Forecasts for Europe (subscribers in thousands)
IDATE predicts a drop in active ADSL in Europe from 2010 (in Japan happened in 2006) In 2016 FTTX users are estimated to grow to 30% of the total broadband lines.
(Ref: IDATE February 2007)
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Evolution of fiber access networks
Fiber To The X (FTTx)
Why fiber access?
Internet ONT Leased Line Frame/Cell relay ONU OLT NT Telephone Interactive Video ONU
ODN Copper ODN Copper ODN
Fiber is a future proof infrastructure
FTTH/O
Low attenuation long distances High capacity many broadband users
FTTB/C
But
Too expensive to roll out overnight
Other access technologies will complement FTTCab (especially wireless) In some areas FTTH is not economically viable
CO
Electronics
OLT ONT ONU NT
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Optical line terminal Optical network termination Optical network unit Network termination
NT
Home network NIU
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Point-to-Point links
Simple, standardized and mature technology
N Users
CO
L km
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Active Optical Network
Simple, standardized and mature technology
N subscribers Curb Switch
CO
L km
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Passive Optical Network (PON)
Simple, under standardization technology Passive devices (splitters). No active elements in the signals path from source to destination
Passive Optical Splitter L km N subscribers
CO
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Comparison
P2P links
N fiber lines 2N transceivers
Concentration switch in the neighborhood
1 fiber line Power in the field 2N + 2 transceivers
PON
1 fiber line N + 1 transceivers Path transparency
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Wireless fiber and common platform
Core network Wimax, FWA
C/DWDM links
Radio over Fibre with C/DWDM links
Hot spot, WLAN
FTTC+VDSL FTTH
Mobile 3G/4G
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Passive Optical Networks PONs
and reliability models
Basic PON topologies
Ring topology Tree topology
Bus topology
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Passive architectures
Advantages
Simple Easy to operate Do not have any active devices in the outside plant Do not need to be powered Time Division Multiplex PON (TDM PON)
PON architectures
Ethernet PON (EPON) Gigabit PON (GPON)
A broadcast-and-selected WDM PON (WPON) A wavelength-routing PON (WRPON)
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Time vs. Spectrum Sharing
TDM-PONs: Current generation PON
Standardized Use few wavelengths (typically 2 or 3) Low cost and mature devices (splitters, lasers, etc.) Limited power budget Maximum distances 20km, Split ratios 64 Traffic distribution Broadcast scheme downstream TDMA techniques upstream Examples: APON/BPON, EPON & GPON
WDM-PONs: Next generation PON (long term)
Proposed in literature and/or demonstrated Introduce WDM technology and devices (AWG) Long-reach and high bandwidth Examples: CPON, LARNET, RITENET, Success-DWA
Hybrid WDM/TDM-PONs: Next generation PON (short term)
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TDM PON
Downstream traffic is broadcasted to all ONUs Low security ONUs filter data (frames) by destination address Upstream traffic is time division multiplexed at the RN Upstream and downstream traffic is sent at different wavelengths to share one fiber between OLT and RN
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PON with analogue video overlay
Data and voice in both directions Video in only one direction Video on dedicated wavelength all the way to ONU Analogue video overlay commonly used in the US in FTTx installations (temporary solution)
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Ethernet PON (EPON)
EPON preserves 802.3 frame format EPON uses existing MAC EPON uses existing 8B/10B encoding EPON uses standard 802.3 line rate (1 Gbps) 320 million Ethernet ports deployed worldwide (~95% of all switch ports)
Focus: simplicity and integrity of Ethernet Work is done by IEEE802.3ah task force
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Downstream Transmission
passive optical splitter
Downstream channel is broadcast. 802.3 Frames extracted by ONUs.
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Upstream Transmission
Upstream time slicing No packet fragmentation No collisions
How to schedule ONUs?: static vs. dynamic bandwidth allocation
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WDM PON
WRPON: Wavelength Routed PONs (incl. AWG)
WPON: WDM broadcast and select PONs
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Hybrid WDM/TDM-PON
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PON protection schemes
and reliability models
Motivation
Evolution of broadband access networks towards FTTH. Passive optical networks (PONs): an attractive option. Growing importance of reliable access to (broadband) network services. Access network is very cost sensitive
minimizing the cost for network protection
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Main issue: low cost solutions
Requirements on technology
Core
Low installation and operational cost i.e. low CAPEX and OPEX
Metro
Access
Requirements on cost effectiveness
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Protection schemes
Standard protection schemes (ITU-T G.983.5 )
Type A: feeder fiber (FF) is duplicated Type B: FF and optical interface at OLT are duplicated Type C: 1+1 path protection all resources duplicated Type D: full/partial protection
Novel (cost efficient) protection schemes for hybrid WDM/ TDM PON
Investment cost for burying redundant DFs to each optical network unit can be saved CAPEX reduction Efficient utilization of wavelength reduction of number of wavelengths needed for protection
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Standard schemes (ITU-T G.983.5 )
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Novel Protection Scheme 1
Hybrid WDM/TDM PON
J. Chen and L. Wosinska, Analysis of protection schemes in PON compatible with smooth migration from TDM-PON to hybrid WDM/ TDM-PON, OSA Journal of Optical Networking, Vol. 6, No 5 (May 2007)
Built-in redundancy where two neighbouring ONUs protect each other Main advantages: (i) no extra DFs are needed for protection CAPEX saving (ii) protection for both FF and DF failures is provided. (iii)1:1 link protection provides good reliability performance Our approach minimizes the investment cost for protection while keeping connection availability at the acceptable level
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Novel Protection Scheme 1
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Novel Protection Scheme 2
Hybrid WDM/TDM PON
Jiajia Chen, L. Wosinska, and S. He, High Utilization of Wavelengths and Simple Interconnection Between Users in a Protection Scheme for Passive Optical Networks, IEEE Photonics Technology Letters, Vol. 20, No 6, pp: 389 391 (March15, 2008)
Utilizing the cyclic property of the AWG our protection scheme has three main advantages (compared to the existing schemes): (i) 50% fewer wavelengths are needed; (ii) in the case of DF break there is no influence on the remaining ONUs; (iii) protection for FF failure is provided. Our approach maximizes the wavelength utilization for protection while maintains an acceptable level of connection availability
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Novel Protection Scheme 2 Normal operation
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Novel Protection Scheme 2 Protection
In the case of distributed fiber-cut between AWG and ONU1,1 In the case of feeder fiber-cut between OLT and AWG
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Ring Protection (1)
Normal operation Protected operation
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Ring Protection (2)
SUCCESS-HPON
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Conclusions
Broadband access (at least 10 Mb/s in short run) to every household Next-generation access network will be based on fiber PON is considered to become the choice
TDM PON (EPON and GPON): today 10GPON and Hybrid WDM/TDM PON: short term (D)WDM PON: long term
Next-generation access network must be reliable and robust
Protection
CAPEX and OPEX need to be very low Scalability
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Topics for this module
and reliability models
Fiber access network architectures
Point-to-point
(P2P) Active optical network (AON) Passive optical network (PON)
Definitions Scalability Cost Performance
(power budget, security, etc)
Passive Optical Networks
PON
topologies Resource sharing in PON (TDM vs. WDM)
TDM
PON, WDM PON, hybrid WDM/TDM PON
Current
and next generation PON Performance parameters Long Reach PON
TDM Passive Optical Networks
Review standards Compare physical layers and MAC layers Compare performance Define conditions where GPON is better than EPON and vice versa. Motivate. Bandwidth allocation
Static bandwidth allocation (SBA) Semi-static Bandwidth allocation (S-SBA) Dynamic bandwidth allocation (DBA)
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