aon vs. pon

White Paper

2008-05-26 © KEYMILE 2008

AON vs. PON –A comparison of two optical access network technolo-gies and the different impact on operations

White PaperAON vs. PON

2008-05-26 © KEYMILE 2008

Table of content

1. Basic facts 3

1.1. Passive Optical Networks (PONs) 3

1.2. Active Optical Networks (AONs) 4

1.3. Network topologies with PON and AON 5

2. Comparison of the technologies AON vs. PON 6

2.1. Bandwidth 6

2.2. Security and quality of services 7

2.3. Business case aspects 9

2.3.1 Investment costs (CAPEX) comparison 9

2.3.2 A comparison of operating expenses (OPEX) 10

2.4. Flexibility and scope for usage 11

3. Summary 12

4. Glossary 13


2008-05-26 © KEYMILE 2008

AON vs. PON

The key technical difference between active and passive access technology is that a passive splitter is used for passive optical networks. The splitter is basically a kind of multi-mirror that distributes the optical signal for the subscriber line to fi bre optic routes without any electrical current (which is why it is called passive).

The fi rst active optical access networks used TDM technology. The fi rst passive optical networks on the other hand used ATM for voice and data traffi c (APON, BPON, ITU-T Standard G.983). Because early PON systems could already transmit a TV broadcast signal on a separate wavelength in the optical spectrum, simultaneously to the voice-data signal, they were popular in cable TV networks. The topologies of PON and CATV networks are also very similar to one another, so existing cable lines, or ducts can be used and costs saved in the network rollout. The objective of both PON and AON is to get the fi bre optics as

close as possible, ideally right into the sub-scribers’ houses and apartments. This FTTH-solution is technically the best option with respect to the transmission quality and the bandwidth.

Passive Optical Networks (PONs)1.1. As regards the core network, the fi rst network element of a PON network is the OLT (Optical Line Termination Unit), that provides n x 1 Gbps and n x 10 Gbps Ethernet interfaces to the core network and the PON interfaces to the sub-scriber. The PON types used here today are usually Ethernet-PON (EPON), Gigabit-PON (GPON) or Gigabit-Ethernet-PON (GEPON). Ethernet technology is the common denomina-tor in all these technologies. Nowadays, EPON installations tend to occur more in the Far East and GPON more in the USA and Europe. Consequently, we will be looking at the GPON-type (ITU-Standard G.984) below.

The telecommunications industry has had more than ten years of experience with active and passive optical networks and debates about their advantages and disadvantages have been running for that long at the very least. Fibre optic networks can be laid directly to house-holds (Fibre-to-the-Home [FTTH]) by using Passive Optical Networks (PONs) and Active Optical Networks (AONs). In the mid 1990s, the fi rst large-scale PON installations were commissioned in Japan. In many other parts of the world, FTTH concepts were a long way off. The Internet was still in its infancy, attractive online offerings for private customers were practically non-existent and the technology was much too expensive in any case. As a result, most end customers did not require more bandwidth (i.e. more than ISDN was capable of at the time) till the beginning of the new millennium.

The subsequent escalation of bandwidth, fuelled by the availability of broadband DSL connections via copper wire, has turned the Internet and associated services into an unpar-

alleled success story. Today, considering all the new services like high defi nition IPTV, online gaming and remote surveillance, ICT service providers are well advised to seek access network solutions with even more bandwidth for the post-DSL era. However, due to the physical properties of copper wire in the last mile, VDSL2 has reached its limits, even if technology called DSM (Dynamic Spectrum Management) is being developed to boost the transmission capacity on copper. Communica-tion solutions like WiMAX, or LTE in mobile telephony, reach the limits of their capabilities even more quickly because of poorer physical transmission properties (in comparison with copper). To date, the only solution for seem-ingly infi nite bandwidths has been the optical wave guide, also called fi bre optics.

Basic facts1.


2008-05-26 © KEYMILE 2008

Packet

Network

Optical Line

Termination (OLT)

Passive optical

Splitter

Optical Network

Termination

(ONT)

Subscriber line in a PONFigure 1:

GPON’s current standard can provide a maxi-mum of 2.5 Gbps towards the subscriber (downlink) and 1.25 Gbps towards the core network (uplink) per PON interface on the OLT. To the subscriber, a passive splitter, that is either fi tted to an outdoor cabinet in a colloca-tion room, or in the end subscriber’s premises, multiplies the signal on the fi bre optics into n optical subscriber branches. In other words, the network structure is a point-to-multipoint structure (PMP). The structure is similar to a tree, colloquially called a PON tree, or a twig or branch is referred to in the subscriber access line (see fi gure 1).

In an FTTH network architecture, subscriber access is implemented using optical network termination (ONT) that terminates the optical signal and converts it into one or more electri-cal interfaces, such as for example 100BaseTx, POTS, ISDN or Coax. If copper wire is used for the last mile, an optical network unit (ONU) can be used instead of the optical network termina-tion in the PON, which then provides interfaces such as POTS, ISDN or DSL. In this case, the network architecture is a Fibre-to-the-Curb (FTTC) connection.

All PON subscribers receive the same optical signal at the end of the fi bre optics. The personal allocation of data is carried out via a time multiplex procedure, i.e. each subscriber receives their own time slot to transmit and receive. Synchronisation of the right user time slot is carried out in the ONT.

Active Optical Networks (AONs)1.2. AON is a point-to-point network structure (PTP), i.e. each subscriber has their own fi bre optic line that is terminated on an optical concentrator (Access Node [AN]).

Packet

Network

Access Node

Optical Ethernet

Optical Network

Termination

(ONT)

Subscriber line in an AONFigure 2:

This type of AN can be designed differently, depending on specifi cations. Usually Metro-Ethernet-Switches, IP-Edge routers or Multi-Service Access Nodes (MSANs) with optical Ethernet interfaces are used in this case. The fi bre optics can be terminated by an ONT here too, but also by any Ethernet switch or IP router with an optical uplink interface. If the last mile to the subscriber is to be bridged using copper wire, DSLAMs or other MSANs are used. When MSANs are used, both copper and optical lines can be used for the last mile from the same access node.


2008-05-26 © KEYMILE 2008

OLT

ONT

ONU

OLT

NT

OLT

ONU

OLT

ONT

OLT

ONU

NT

NTNT

NT

Splitter

Downlink 2,5 Gbps

Uplink 1,25 Gbps

Splitter

FTTH

FTTE

FTTB

FTTH

FTTC

POTS/ISDN

ADSL2plus

VDSL2

POTS/ISDN

ADSL2plus

ADSL2plus

VDSL2

Splitter

Splitter

FTTE

CO

MDF

MDU

Copper double pairOptical fibre

Curb

Households

Network type

Packet

network

Packet

net

Packet

network

Packet

net

Packet

net

n x 1000BaseFX

AN

NT

AN

ONT

ONT

AN

AN

NT

AN

DSLAM

NTNT

NT

Uplink/Downlink

≥100 Mbps

FTTH

FTTE

FTTB

FTTH

FTTC

POTS/ISDN

ADSL2plus

VDSL2

POTS/ISDN

ADSL2plus

ADSL2plus

VDSL2

Packet

network

Copper double pairOptical fibre

n x 1000BaseFX

Ethernet

Switch

Ethernet

Switch

Ethernet

Switch

Packet

network

Packet

network

Packet

network

Packet

network CO

MDF

Curb

MDU

Households

Network type

As fi gure 3 and 4 show, PON and AON can be used to implement all network topologies, starting with Fibre-to-the-Exchange (FTTE), to Fibre-to-the-Curb (FTTC), Fibre-to-the-Building (FTTB) and Fibre-to-the-Home (FTTH).

Both technologies have to take the fi bre optics to the end subscriber, but can also bridge the

last mile with copper wire. For PON this can be implemented directly from the OLT, or in AON from the access node. Optical Network Units (ONUs), or DSL Access Multiplexers (DSLAMs) can be integrated to provide the POTS or ISDN interfaces for telephony and various DSL types for High-Speed Internet (HSI).

Network topologies with PON and AON1.3.

Overview of network topologies in PON networksFigure 3:

Despite the obvious aspects both technologies have in common, there are variations inherent in the systems that affect operations, costs and the value they provide differently. Because

PON and AON technology is so widespread and changing from one to the other is costly, operators should be aware of all the facts. The main differences are shown below.

Overview of network topologies in AON networksFigure 4:


2008-05-26 © KEYMILE 2008

Comparison of the technologies AON vs. PON2.

AON PON Assessment

Bandwidth allocation

GoodThe amount allocated to the subscriber is governed by the interface type, or traffi c shaping on the access node and is therefore adjustable in kilobit incre-ments.

AverageThe GPON interface on the OLT nowadays is 2.5/1.25 Gbps (downlink/uplink). The bandwidth per subscriber is determined by the splitting factor (usu-ally 1:32 or 1:64). Modern PON systems however permit bundling of several time slots and therefore an increase in bandwidth per PON terminal point.

AON’s advantageAON clearly has the edge because of its fl exibility. Due to the static splitting factor and the interfaces on the OLT, PON is at a disadvantage.

Maximum bandwidth per subscriber

GoodAs each subscriber is connected with their own fi bre optics, bandwidth can today be implemented at between 100 Mbps and 1 Gbps per household or company.

SatisfactoryWith regard to the PON standards available today, the maximum feasible capacity of fi bre optics is the same as the total capacity of an OLT port, i.e. 2.5 Gbps (PTP connection without a splitter). Therefore, realistically the bandwidth with splitter and a separa-tion of usually 1:32 is 78 Mbps, or at 1:64 39 Mbps (all fi gures relate to downstream).

AON’s advantageAON technology is clearly better as regards the bandwidth per subscriber. The maximum bandwidth per sub-scriber is a lot higher. The fl exibility to allocate different bandwidths to indi-vidual subscribers is also greater (e.g. for corporate customers) than when PON systems are used. Depending on the splitting factor, a PON connection via fi bre optics supplies less bandwidth than a VDSL2 connection via copper wire.

Increasing bandwidth

SimpleAs the active access node has a modular structure, subscriber interfaces can be upgraded to include more bandwidth. It is often suffi cient to just switch the fi bre optic lead to be able to operate it again.

Diffi cultDepending on the systems technology, it would be feasible in the future to bundle several time slots and therefore, at the cost of the maximum number of subscribers per PON branch, to increase individual bandwidth by a fac-tor of n + 1. The bandwidth of the PON port on the OLT is the absolute limit, i.e.. 2.5/1.25 Gbps (down/up).

AON’s advantageIn this case, the PTP architecture is superior to the PON’s PMP architecture. Just by converting boards, subscribers can obtain an upgrade, without the net-work architecture or the service of other subscribers having to be changed.

The trend towards increasing bandwidth continues unabated. Due to the launch of TV-over-IP (IPTV) there is no sign of the increase in bandwidth tailing off, in fact quite the opposite. Because of the recent launch of (HDTV) and other technically complex services such as online gaming, network operators are being encourage to outdo one another by providing more and more bandwidth.

The following table compares PON and AON transmission bandwidth.

Bandwidth2.1.

EFM Active 1 Gbps

EFM Active 100 Mbps

2.4 GPON (32-split)

ADSL2plus

VDSL2BondedADSL2plus

1 2 3 4 5 6[km]

24

45

75

100

1000

[Mb

ps]

Source: DSL Forum, FTTx Summit 2007, Munich

Bandwidth downstream and rangeFigure 5:


2008-05-26 © KEYMILE 2008

To sum up, the PON network’s predefi ned topology makes individual changes more diffi cult. By terminating all the fi bre optics at the OLT, i.e. the same fi bre optic topology as in the AON (point-to-point), this disadvantage can be overcome. Therefore, for future-proof infrastructure investment, reliable point-to-point fi bre optics technology should always be considered.

Security and quality of services2.2. An aspect in public networks that is regaining importance is Quality-of-Service (QoS), which considering today‘s fi nancial restraints is often forced to take a back seat. At the dawn of the ADSL rollout, the majority of services offered took a best effort approach, i.e. the data channel guaranteed neither a minimum band-width, nor any other quality features worth mentioning. As today however, Triply Play services (telephony, data and TV down one single line) are already transmitted to the subscriber, QoS applies more than ever. When surfi ng the Web, short delays of 1 – 2 seconds, e.g. when clicking on a link, do not really matter. During a phone call, this level of delay is however completely unacceptable. When watching TV, it is also no fun if the picture freezes before a goal is scored. As a result, the Triple Play services must be clearly separate and allocated priority.

Although theoretically unlimited bandwidth is available in a fi bre optic line, QoS not be forgotten. Not all QoS aspects can be responded to with bandwidth and neither PON nor AON can really provide unlimited band-width.

Nowadays, the Triple Play offerings, imple-mented via copper wire often consist of two television channels with standard resolution (SDTV), a high-speed Internet connection (>3 Mbps) and at least one POTS or ISDN telephone connection. The current state of the art is that network operators are planning approx. 15 Mbps downlink capacity.

In the future the end customer will be demand-ing high defi nition TV (HDTV). Two simultane-ous TV channels will mean an unacceptable restriction for a family of four in the long term. Furthermore, currently ADSL 16 Mbps Internet access is already being marketed to private customers and including n telephone lines. Online gaming – in the Far East popular for years – is also looking promising in Europe. In this case, top rates of 50 Mbps per subscriber line could easily be reached. Today, standard VDSL2 access would not be able to cope.

The scenario described above indicates what the private consumer will look like in the near future. If such a scenario appears exaggerated, we only have to recall the situation 10 years ago when modern end customers still used 56 kbps dial-up modems to read e-mails, for sending faxes and for home banking. In comparison to today’s standard 3.5 Mbps ADSL connection, the bandwidth has increased 62-fold! Special requirements from business customers, or demands for the backhaul of sub-networks, server connections or high performance IT applications would easily exceed these quality specifi cations and require even greater high quality performance.

AON PON Assessment

Temporary increase in bandwidth (e.g. server back-up over night)

SimpleIn an active access node, traffi c shaping can regulate the bandwidth from the NMS control centre and for example during constant operation be switched to 100 Mbps, or ad-hoc to 1 Gbps.

Diffi cultDue to the TDM procedure, a fi xed time slot is allocated to each customer. The signal must also be separated using a passive splitter, as passive splitters are not manageable. A further allocation of another time slot must be carried out.

AON’s advantageCompared with an AON, the structure of the PON limits the fl exibility to make any changes in bandwidth.

Prioritising services

SimpleStandard mechanisms at Ethernet/IP level can be used.

SimpleStandard mechanisms at Ethernet/IP level can be used.

UndecidedIn this case there are no signifi cant dif-ferences.


2008-05-26 © KEYMILE 2008

AON PON Assessment

Delay, jitter and other effects on quality

LowMainly infl uenced by the design of the core network.

LowMainly infl uenced by the design of the core network.

UndecidedIn this case there are no signifi cant dif-ferences.

Impact of faults in the access node

LowAs n subscribes in an active access node use n optical interfaces and the subscriber density of the interface card is relatively low compared with a PON-OLT, relatively few subscribers are affected if there is a malfunction.

HighIn an OLT, a passive splitter separates the optical subscriber interfaces into 32 or 64 signals. A subscriber subrack usually provides several subscriber interfaces. In comparison with an AON AN, a lot of subscribers are affected if a port, or even a card fails.

AON’s advantageAny faults in the AN affect fewer cus-tomers than in an OLT.

Effect of malfunctions and manipulation

LowThanks to the PTP architecture, each path can be assessed exactly right up to the end customer’s ONT at the very least. In the worst case scenario, the laser on the AN for each subscriber can be deactivated by the control centre.

HighWithin a PON tree, all the subscribers are on the same optical point. If a faulty ONT causes faulty synchronisation, or produces an optically indefi nable signal, a remote localisation of the malfunction in the ONT involved is not possible. As the ONTs are often in the end customer’s home, it is impossible to estimate how long it will take to exchange an ONT.

AON’s advantageIn the worst case scenario, a single ONT can bring an entire PON tree with up to 64 subscribers down if a technical malfunction or deliberate manipulation occurs. A faulty subscriber line on the AON can be very easily identifi ed and eradicated.

Risk of eavesdropping (espionage)

LowEach customer has dedicated fi bre optics. In general, eavesdropping is not possible.

HighA PON tree is known as a shared medi-um, i.e. all subscriber signals are on one fi bre optic terminal point. By allocating the time slot, the data is separated. The setup is in the customer’s network termination.

AON’s advantageThe data in the PON network is en-crypted in a similar way to WLAN, nev-ertheless it is technically still possible to eavesdrop on another subscriber on the same PON tree. However, in-depth technical knowledge is required to do so.

Reliability of the subscriber line (between the customer and AN and passive splitter)

GoodIn an active network, a customer can basically be connected in a ring, or using dual-homing. In other words, a customer can be connected twice.

PoorTo date, there are no plans to connect customers twice in one PON.

AON’s advantageAvailability of the PON, compared with the AON, is much worse.

Reliability of the subscriber line (between passive splitter and OLT, or AN and edge switch)

PoorIf the connection is cut here, several hundred fi bre optics are interrupted and have to be repaired.

GoodIn this case, only one fi bre optic line has to be maintained.

PON’s advantageIn reality cables are cut more often than is generally thought. A PON link between the splitter and OLT consists of a tiny fi bre optic that can be repaired in a few hours.


2008-05-26 © KEYMILE 2008

Business case aspects2.3. Using fi bre optic cable promises virtually unlimited bandwidths, however the network operator only ever has just the copper wire line in the last mile. That means that if the DSL technology is no longer adequate, new optical cables must always be laid.

The high investment costs of this infrastructure, combined with telecommunications providers’ falling revenue at the same time, mean it is often diffi cult to put a business case to inves-tors and network providers’ management boards. Nowadays the ICT industry is spoilt with returns on investment of 1 – 3 years. But when expanding FTTH and FTTC networks, (regardless of whether PON or AON technol-

ogy is used), it sometimes takes more than 10 years.

Nevertheless, depending on the application and conditions at the time, business cases vary greatly, depending on whether passive or active access technology is used for an FTTH rollout. The main differences in investment costs (capital expenses, CAPEX) and operating costs (operational expenses, OPEX) are com-pared with one another below.

Investment costs (CAPEX) comparison2.3.1

AON PON Assessment

Costs of the subscribers’ terminal equipment (CPE)

LowAs standard Ethernet technology can be used. Today, simple ONTs (e.g. Eth-ernet media converters), with functions similar to an ADSL-NT, are available for under $30.

HighAs ONTs in the PON environment are (despite standardisation) not inter-changeable between different manu-facturers. Which means the selection of models is restricted and the savings provided, because a larger number is produced, are negligible.

AON’s advantageThe CAPEX bonus of AON networks should not be underestimated, because the CPE share in the total costs is usu-ally the greatest (often >50 %).

Costs of the network technology (active components)

HighBecause each subscriber has a dedi-cated laser port on the AN. If a fi bre optic path is divided up into several customer connections, additional active equipment is required.

LowAs a single port on the OLT can be shared by several customers. If a fi bre optic has to be shared by several customers, a simple passive splitter can be used.

PON’s advantageBecause optical paths can be used by several subscribers, PON is a bonus because of the price per subscriber.

Costs of the network technology (passive components and infrastructure)

HighBecause of the greater number of opti-cal subscriber interfaces in the access node.

LowAs one laser on the OLT is shared by n subscribers because the passive splitter is used.

PON’s advantageIn this case, passive technology clearly has the upper hand.

Network rollout costs

HighEach subscriber must be connected individually in a star shape.

DifferentDepends on the fi bre optic topology. If the same topology is used as in an AON, the costs are similar (fi bre-rich approach). If the fi bre optic network is tree shaped, cost savings are possible compared with an AON. A PON net-work architecture using a small splitter with 2 or 4 branches allows costs to be shared effi ciently (e.g. in terraced houses).

PON’s advantageDepending on the fi bre optic topol-ogy, PON network architecture can be cheaper in large-scale rollouts.


2008-05-26 © KEYMILE 2008

A comparison of operating expenses (OPEX)2.3.2

AON PON Assessment

Space required for systems technology

HighBecause of the port density of the ac-tive AN, the space required is just as great as for a DSLAM.

LowBecause a single optical port on the OLT for up to 64 customers is used, the space required at the OLT for systems technology is very low. Over 8,000 subscribers can be placed on a single rack using today’s technology.

PON’s advantagePON’s space-saving potential in the col-location room is greater compared with AON. Due to the wide ranges of PON paths, in comparison with copper wire, some MDF sites may not be necessary at all.

Space required by cable

GreatOne fi bre optic cable at the AN per subscriber.

LowOne fi bre optic cable can supplied to up to 64 subscribers.

PON’s advantageThe space PON saves in fi bre optic cable is particularly critical in central OLT locations.

Energy consumption

HighBecause of the high number of laser interfaces.

LowBecause of the passive splitting.

PON’s advantageBecause of the passive splitter and higher subscriber density on the OLT, the PON is much better in this case.

Level of maintenance

HighActive access nodes require an external power supply, plus battery to supply emergency electricity. This is a disad-vantage, above all in FTTC networks, where the AN is on the outdoor cabinet.

LowIn an outdoor cabinet, the passive splitter needs virtually no maintenance. External power supply is not required. Malfunctions are very seldom.

PON’s advantageIn this case, the PON is also at an ad-vantage because there are fewer active components in the network.

Level of diffi culty in identifying and eradicating malfunctions

LowBecause in AON networks it is easy to carry out an end-to-end diagnosis right into the subscriber's home, due to the PTP topology and the possibility of as-sessing the dedicated optical transmis-sion path via the NMS.

HighAs in the worst case scenario, a faulty ONT cannot be deactivated by the NMS centre. A local visit to the cus-tomer is required. Depending on the accessibility of the ONT, this can take a long time.

AON’s advantageIdentifying and eradicating faults in the AON is a lot easier than in the PON, due to the PTP topology. Nevertheless, in the PON the ability to analyse faults by using monitoring systems can be improved.

Follow-up costs for upgrades

LowBecause of the better granularity of the ANs and the separation of the custom-ers (PTP), individual upgrades can be carried out in the AON and for example CPE can be exchanged.

HighAn entire PON tree is affected by an upgrade. All ONTs have to be exchanged at the same time. As a result, individual upgrades are virtually precluded.

AON’s advantageBecause of the greater individual fl ex-ibility, AON has an advantage where upgrades are concerned.


2008-05-26 © KEYMILE 2008

AON PON Assessment

Suitability for connecting up housing estates (green fi eld)

SatisfactoryThe requirements for rolling out active networks are higher.

GoodThe fi bre optic infrastructure is simpler. The requirements for passive splitters in outdoor cabinets are low (no power needed, no problems with heat/cold).

PON’s advantageBecause of the lower requirements, a PON network can be installed more quickly and cheaply.

Level of suitability for connecting large-scale/business customers

Very goodIn this case advantages on fl exibility, se-curity and performance really pay out. A router or switch can be used as an optical network termination to separate services.

PoorThe customers in a PON tree are all treated the same. Individual features can only be implemented at protocol level above layer 3.

AON’s advantageRequirements from bulk customers are always special, PON network concepts tend to be more static. Therefore, in this case the active approach is a lot better.

Level of suitability to provide telephony and high-speed Internet (HIS) at the same time

GoodNo major restrictions.

GoodNo major restrictions.

UndecidedFrom a technical point of view, both PON and AON can be used here with-out any problems.

Level of suitability to provide telephony, HSI and television (Triple Play) at the same time

GoodFor transmitting n HDTV channels, AON can also mobilise enough bandwidth reserves.

SatisfactoryPON does have the advantage that some systems are capable of transmit-ting analogue TV (similar to a CATV network), however the usual bandwidth for broadcasting several HDTV channels might not be suffi cient.

AON’s advantageAn optical network rollout is a long term investment. If we assume that HDTV will be the standard format in the future, active networks have the upper hand, due to their high levels of bandwidth reserves.

Suitability to provide additional services

GoodAON technology can be adapted to suit individual requirements.

PoorThe range of specialised terminal equipment is very limited because of dependency on manufacturers. The rather infl exible bandwidth manage-ment, based on TDM procedures, is a disadvantage.

AON’s advantageThe requirements for additional and possibly new services when designing a new network are often not specifi ed to the last detail. PON's limits could signifi cantly inhibit business cases in the future.

Flexibility of usages as regards optical network termination

GoodAs AON uses standardised Ethernet interfaces, a variety of different devices can be used for network termination.

PoorToday there is no real interoperability between rival PON technologies, even within the same PON technology. Operators are forced to purchase the ONTs and ONUs from the OLT supplier (dependency).

AON’s advantageIn this case, the operator of an AON network can act more fl exibly and make use of real price savings. When using feature-rich IP equipment instead of an ONT, the provider can expand his range of services by leasing addi-tional features (additional VPNs, hosted PBX…)

Ranges (max. length of the subscriber access line)

Very goodMaximum of about 70 km without repeaters.

GoodUp to 20 km depending on passive splitter.

AON’s advantageOptical components can be selected individually

Backhaul of sub-networks and network elements

GoodA normal AN subscriber interface can also be used for backhaul jobs (e.g. of a DSLAM, radio equipment etc).

PoorA PON interface board can only be used for implementing PON trees.

AON’s advantageAs an active access node is similar to an Ethernet switch in the way it works and provides standard Ethernet interfaces, it can also be used for various backhaul jobs.

Flexibility and scope for usage2.4. Previous fi ndings in the comparison of AON and PON have already highlighted key differ-

ences. Apart from technological differences, there are further differences between the two optical access technologies, depending on the operator’s business strategy.


2008-05-26 © KEYMILE 2008

Finally we should not forget that a generic comparison of technologies, such as this one, cannot always apply in all cases. The balance can easily shift from one side or the other depending on statutory, commercial or struc-tural constraints.

Basically, passive optical networks are a better choice for network operators who want to supply a very large number of subscribers, like the (previous) network operators who had a monopoly. These operators tend to aim more for the mass and private customer market. In this case, PON can throw its commercial benefi ts into the balance and at the end of the day compensate for various operational disadvantages.

Active optical technology is more suitable for private network operators, that either lay their own fi bre optic infrastructure, or use debun-dled fi bre optic lines (Fibre Local Loops).

AON is perfect for high-profi t end customer segments (such as for example business

customers, multi-dwellings, universities, local authorities etc…), as in these cases fl exibility, quality and security are demanded. And because of the way they are structured, PON networks struggle to fulfi l these requirements. As standardised ONTs are used, the commer-cial aspects of supplying households on a large scale should be weighed up too and can compete with PON systems.

Nevertheless, as PON networks are on the increase, it is likely that some of the disadvan-tages of PON listed here will gradually be eliminated. However some of the inherent features of a PON will remain. But one thing is almost certain, the fi bre optic based access network, and therefore end customer products too, will constantly be upgraded to handle more than 50 Mbps. The whole issue is set to stay an exciting one

Summary3.

Requirement AON’s suitability

PON’s suitability

Individual assessment

Bandwidth

Bandwidth allocation ☺Maximum bandwidth per subscriber ☺Bandwidth increase ☺Security and quality servicesTemporary increase in bandwidth e.g. Overnight server mirroring ☺Prioritising services ☺ ☺Delay, jitter and other effects on quality ☺ ☺Impact of malfunctions in the access node ☺Effect of malfunctions and manipulation ☺Risk of eavesdropping (espionage) ☺Transmission reliability, I. ☺Transmission reliability, II. ☺Operating costs (OPEX)Place required for systems technology ☺Room required by cable ☺Energy consumption ☺Level of maintenance ☺Level of diffi culty in identifying and eradicating faults ☺Follow-up costs for upgrades ☺Investment costs (CAPEX)Costs of the subscribers’ terminal equipment (CPE) ☺Costs of the network technology (active components) ☺


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Requirement AON’s suitability

PON’s suitability

Individual assessment

Costs of the network technology (infrastructure) ☺Rollout costs

Flexibility and scope for usageSuitability for connecting up housing estates (green fi eld) ☺Suitability for connecting bulk/business customers ☺Suitability for providing telephony and high-speed Internet (HSI) ☺ ☺Suitability for providing telephony, HIS and TV ☺Suitability for providing additional services ☺Flexibility of usage re optical network termination ☺Ranges ☺ ☺Backhaul of sub-networks and network elements ☺

Glossary4.

Abbreviation Description

100BaseTx 100Mbit/s Ethernet, copper interface

3G Third generation of the mobile telephony standard

4G Fourth generation of the mobile te-lephony standard

ADSL Asymmetrical DSL

AN Access node

AON Active Optical Network

APON ATM PON

ATM Asynchronous Transfer Mode

BPON Broadband PON

CaTV Cable television

CO Central Offi ce

DSL Digital Subscriber Line

DSLAM DSL Access Multiplexer

EFM Ethernet First Mile

EPON Ethernet PON

FTTC Fiber-to-the-Curb

FTTE Fiber-to-the-Exchange

FTTH Fiber-to-the-Home

GEPON Gigabit Ethernet PON

GPON Gigabit PON

HDTV High Defi nition TV

ICT Information Communication Technology

IP Internet Protocol

IPTV Television over IP

Abbreviation Description

ISDN Integrated Services Digital Network

ITU-T International Telecommunication Union, Telecommunication Standardisation Sector

LTE Long Term Evolution

MDF Main Distribution Frame

MDU Multi Dwelling Unit

MSAN Multi-Service Access Node

NMS Network Management System

OLT Optical Line Termination

ONT Optical Network Termination

P(A)BX Private (Automatic) Branch Exchange

PMP Point-to-Multipoint

PON Passive Optical Network

POTS Plain Old Telephony Service

PTP Point-to-Point

QoS Quality of Service

SAL Subscriber access line

SDTV Standard Defi nition TV

TDM Time Division Multiplex

VDSL Very high-speed Digital Subscriber Line

WiMAX Worldwide Interoperability for Microwave Access


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