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

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access networks

Access Networks

lectures 2008/09- winter term

Part 3: Classification of Access Networks

3.3 Optical Access Networks (OAN)

slide2

OAN = Optical Access Network

  • access system with optical fibres and others optical and optoelectrical (optoelectronic) components + transmission of opt. signal through free space (opt. relay link or FSO – Free Space Optics)
  • - 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

slide3

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 Function architecture of OAN

slide4

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)

FTTO (...Office)

FTTCab (...Cabinet)

*************************************************

FTTE (... Exchange)

Exchange

Fig.3.3.3

- on the metalic part (original POTS) there mostly operates VDSLsystem

slide7

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

slide9

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

slide10

shared

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

slide11

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

slide12

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

slide13

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

slide14

passive DP

active DP

without EOC

with EOC

unique optical segment

several optical segments

ODN – Optical Distribution Network

  • active one (AON) - equipments with power supply
  • passiveone (PON) – only passive equipments, in the building, short distances

Fig.3.3.8ODN classification according to DP (Distribution Point) properties

slide15

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 fibers, 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 -

slide16

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.
slide19

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

Fig.3.3.11

[1]

slide20

...from optoelectronics:

boundary

100% reflection

Obr.3.3.13 ...total reflection on the boundary line of fibre-cladding (coating)

[5]

slide21

Fig. Optical fibers types

source: http://en.wikipedia.org/wiki/Image:Optical_fiber_types.svg

slide22

...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

slide23

The other properties of optical fibers:

2nd window

3rd window width

wave length

Fig.3.3.15Attenuation dependance on wavelength ane others factors

optical fibers ...

[1]

reason of attenuation: presence and generation of OH ions, Raileigh scatter („total“ border, edge)

slide25

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

slide26

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]

slide27

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]

slide28

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
slide29

Wavelength multiplexors

Couplers - simple, or demountable

Optical connectors

29

slide30

- patch panel -for connecting opticalfibers and for their cover and screening

sources: http://www.b2bfiberoptic.com/04-01002.htm

http://www.alibaba.com/product-gs/212149133/Patch_Panel_Fiber_Optic_Patch_Panel.html

- ODF – Optical Distribution Frame –for controled connecting of fibers

30

source: http://www.huihongfiber.com/fiber-test-equipment.html

slide31

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

slide33

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
slide34

Duplex in OAN:

  • 2 fibers Spice 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

slide35

OPTICAL RELAY LINKS

  • FOS - Free Space Optics
  • transmission through free space, analogous to RRL (Radio Relay Links)
  • advantages ....., disadvantages if compared to radio links...,
  • - the parts of opt. relay systems ...
  • - applications: ...
slide36

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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