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Access Networks

Access Networks. lectures 200 8/09 - winter term Part 3: Classification of Access Networks 3.3 Optical Access Networks (OAN). OAN =

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Access Networks

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  1. Access Networks lectures 2008/09- winter term Part 3: Classification of Access Networks 3.3 Optical Access Networks (OAN)

  2. OAN = • access system with optical fibres and others optical and optoelectrical (optoelectronic) components + transmission of opt. signal through free space (opt. relay link) • - FITL (Fibre in the Loop) • advantages: frequency broadband,high bit rate, ability to operate in large access area • Phys. architecture: star 1xN coupler star coupler tree (multiple star) coupler ring bus OLT-optical line termination ONU – optical network unit Fig.3.3.1 - Logical arch.: Tree

  3. The main parts of OAN – OAN architecture: ODN = Optical Distribution Network NT = Network Terminal ONU = Optical Network Unit – in the user end – local loop connection (sometimes also NTU) OLT = Optical Line Termination – in the exchange end – connection to the exchange OAN upstream ONU NT network side ODN OLT user side ONU downstream Fig.3.3.2 Functional architecture of OAN

  4. Architectures (variants) of FITL: pure optical (FTTT) + hybrid (optics + metallic lines - the others apart from FTTT): FTTT (Fibre to the Terminal) FTTP (...Premise) FTTH (... Home) FTTB (... Building) FTTC (.... Curb – the edge of the footpath) FTTE (... Exchange) FTTO (...Office) FTTCab (...Cabinet) Exchange Fig.3.3.3 - on the metalic part (original POTS) there mostly operates VDSLsystem

  5. sometimes the most common solution – however, it is not OAN in fact • opt. cable ends in central office, where is DSLAM, and from it the the connections go out.

  6. FTTO and FTTH are signified as fair optical – because the opt. fibers are led as far as famale plug (user socket).

  7. shared source: http://access.feld.cvut.cz/view.php?nazevclanku=&cisloclanku=2006051702

  8. Management of access network Fig.3.3.4: Reference configuration of OAN Fig.3.3.5Reference model of AN in the building frequency splitters STB-SetTopBox CPN-Customer Premises Network B...Broadband NB...Narrow Band NTE-Network Termination Equipment

  9. Reference configuration of OAN – continue: functional blocks OLT and ONU: • system core • functions of access to services • common functions Optical distr.network Switching network Legend: DCCF… TMF… ODNIF… TUIF… SPF… OAMF… CaSMF… SIF… PSF… Fig.3.3.6.OLT Optical distr.network User ports Fig.3.3.7ONU

  10. DCCF – Digital CrossConnect Function • TMF – Transport & Multiplexing Function • ODNIF – Opt. Distrib.Network Interface Function • TUIF – Tributary UNIT Interface Function • SPF – Signalling Processing Function • common functions • OAMF – operation, administration and maintenance Function • PSF - power supply function • C&SMF – Customer and Service Multiplex Functions • SIF – Service Interface Function commutation and multiplex - EOC function - V5 interface - conversion from signalling of switching system to signalling in AN • control functions with access to overall network management TMN, and power supply - demultiplexing - services streams distribution

  11. passive DP active DP without EOC with EOC unique optical segment several optical segments ODN – Optical Distribution Network • active one (AON – active optical network) - equipment with power supply • passiveone (PON = passive optical network) – only passive equipments; in the building; short distances Fig.3.3.8ODN classification according to DP (Distribution Point) properties

  12. Optical hardware Multipoint (PMP) networks OAN Point-to-Point (P2P) relay links -FSO active - AON passive - PON fibers TDM FDM CWDM APON GPON EPON Fig.3.3.9 Optical access equipment classification PON technology APON – transport based on ATM cells (ITU-T G.983 standard ) BPON – Broadband PON – symetr.transportson higher bit rates (622,04 Mbps; either 2 vlákna, i.e.for each rout (direction) 1, orunique fiberwith WDM EPON – with Ethernet (Ethernet in the first Mile) GPON – gigabit version PON, 1,244 a 2,488 Gbps (ITU-T G.984) CWDM – Coarse WDM (coarsewave multiplexing) –interstage between WDM and DWDM (Dense WDM) – for the sake of cheaper increasing of information capacity, up to 8 channels, 1550nm window, uncooled lasers hybrid -

  13. Standards • ITU-TG.983 • APON (ATM Passive Optical Network)-the first Passive optical network standard - primarily for business applications, and was based on ATM. • BPON (Broadband PON) - standard based on APON. It adds support for WDM, dynamic and higher upstream bandwidth allocation, and survivability. It also created a standard management interface, called OMCI, between the OLT and ONU/ONT, enabling mixed-vendor networks. • ITU-TG.984 • GPON (Gigabit PON) - an evolution of the BPON standard - supports higher rates, enhanced security, and choice of Layer 2 protocol (ATM, GEM, Ethernet). In early 2008, Verizon began installing GPON equipment, having installed over 800 thousand lines by mid year. British Telecom, and AT&T are in advanced trials. • IEEE802.3ah • EPON or GEPON (Ethernet PON) is an IEEE/EFM standard for using Ethernet for packet data -is now part of the IEEE 802.3 standard. • IEEE802.3av • 10G-EPON (10 Gigabit Ethernet PON) is an IEEE Task Force for 10Gbit/s backwards compatible with 802.3ah EPON. 10GigEPON will use separate wavelengths for 10G and 1G downstream. 802.3av will continue to use a single wavelength for both 10G and 1G upstream with ATDMA separation. It will also be WDM-PON compatible (depending on the definition of WDM-PON). It is capable of using multiple wavelengths in both directions. • SCTEIPS910 • RFoG (RFoverGlass) is an SCTE Interface Practices Subcomittee standard in development for Point to Multipoint (P2MP) operations that MAY have a wavelength plan compatible with data PON solutions such as EPON,GEPON or 10GigEPON. RFoG offers an FTTH PON like architecture for MSOs without having to select or deploy a PON technology.

  14. Passive and active components of OAN

  15. Optical fibers and their properties -on the base of Si-glassor plastic - number of modes: 1-mode fibers and multimodes f. (largerΦ, the more number of modes), multimodes with step change of i, or with gradient change - velocity of light propagation~ 2/3 of c (in vacuum) cladding i – diffraction index core Fig.3.3.10: Opt.fiber with both higher and lower order mode - attenuation= {10log(P1/P2) } / length [dB/km] -dispersion - (different velocity depending onλ, also differenti  limiting of λ band of fiber) • max. modulation frequence band (bandwidth) Fig.3.3.11 [1]

  16. ...from optoelectronics: boundary 100% reflection Fig.3.3.13...total reflection on the boundary line of fibre-cladding (coating) [5]

  17. Fig. Optical fibers types source: http://en.wikipedia.org/wiki/Image:Optical_fiber_types.svg

  18. ...from optics / physics: n (or i) – diffraction index, v – velocity of propagation in solid material: • the most simple e-m waves – sinus: E(x,t) = E0cos(ωt-kx+Φ) – also: plane wavepropagatingin the direction x. k=2π/λ .... wave number, Φ .... phase constante (start phase) - remember also: - phase velocity -the group of waves with closedλ – they are moving by ‘group velocity’: - other terms: critical impact angle, totale reflection, law of reflection

  19. The other properties of optical fibers: 2nd window 3rd window width wave length Fig.3.3.15Attenuation dependance on wavelength and other factors optical fibers ... [1] reason of attenuation: presence and generation of OH ions, Raileigh scatter („total“ border, edge)

  20. Tab.3.3.1Standard properties of 1-mode fiber by G.652

  21. POFs = Plastic Optical Fibres • traditionally PMMA (acrylic) or new perfluorinated polymer core in fluorinated polymer cladding • equivalent to multimode glass fibers - plastic core (Φ about 1 mm)with step index profile • cheaper, suitable for LAN – for data and signals transport – in FTTH technology • manipulation with them is more simple • their specific attenuation is higher then this one of glass fibers; but they are in development (!) • good properties in unfriendly conditions (near the high voltage transformer stations) – that means they are resistant to disturbance, they are elastic (flexible) • EoPOF – Ethernet over POF info – e.g.: http://en.wikipedia.org/wiki/Plastic_optical_fiber

  22. Other passive components of OAN: Couplers – basic is so called “Y“ or“1 x 2“. • or splitters •  2 x 2 - devides signalfrom A to C andD but, there is possible also transmission of light into all 8 directions Creation of couplers – by fusionor by „tapering“ Fig.3.3.16 -a,b,c,d [1], [5]

  23. Transmission Star Coupler Reflection star coupler - the light arrives for instance at port A and is split equally through ports from G to L. -the light arrives for instance at port A and is reflected back to all ports Fig..3.3.17 - a,b,c - patch panel - demountable coupler [1]

  24. Passive DWDM module • 32, 16 passive channels DWDM Mux/Demux • 100GHz (0,8nm) ITU Grid, C Band • Transparent transmission (protocol independent) • secure physical isolating between channels • minimal insertion loss • fully passive component (without power supply) • High density of ports • (http://www.technicomms.sk/) • Wave multiplexors • Optical connectors • even there are switches - they operate as routers – they redirect opt. signal into choosed direction; their fundamental components are lens and optical prisms; there can be bypass switches and 2-state switches

  25. Active optical components • Optical sources (tunable lasers, diodes) • Optical detectors • Optical amplifiers • WADM – Wavelength add/drop multiplexor- programable optical switching array – between 2 optical links with WDM support

  26. Tab.3.3.2 Typical values of attenuation (insertion loss) of optical components in OAN (μ –mean value, σ-st. deviation) [3]

  27. Duplex in OAN: • 2 fibers Space Division Multiplex (SDM) – 1 fiber for each direction • 1 fiber with time alternating of directions (ping-pong system) – TCM (Time Compression Multiplex) • - 1 fiber with 2 wave length in the optical windows 1310 a 1550 nm – WDM Examples of professional optical access systems: Alcatel 1570 – narrowband optical access system in PON Alcatel 1575 (HYTAS – Hybrid Telecommunication Access System) – with AON, it allows incorporate metallic circuits Siemens Fast Link – hybrid

  28. OPTICAL RELAY LINKS • transmission through free space, analogous to RRL (Radio Relay Links) • advantages ....., disadvantages if compared to radio links..., • - the parts of opt. relay systems ... • - applications: ...

  29. Referencie: [1] http://www.oftc.usyd.edu.au/edweb/devices/networks/coupler8.html [2] V.Kapoun: Přístupové a transportní síte. VUT v Brně, 1999. [3] Vaculík: Prístupové siete. ŽU v Žiline, 2000. [4] J. Vodrážka: Přenosové systémy v přístupové síti. ČVUT, 2003. [5] J. Turán: Optoelektronika, Harlequin (s podporou FEI_TU-KE), 2002.

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