Active versus passive optical fibre network architectures

1. White Paper
AON vs. PON –
A comparison of two optical access network technolo-
gies and the different impact on operations
2008-05-26 © KEYMILE 2008

2. White Paper
AON vs. PON
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
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3. White Paper
AON vs. PON
AON vs. PON
The telecommunications industry has had more alleled success story. Today, considering all the
than ten years of experience with active and new services like high definition IPTV, online
passive optical networks and debates about gaming and remote surveillance, ICT service
their advantages and disadvantages have been providers are well advised to seek access
running for that long at the very least. Fibre network solutions with even more bandwidth
optic networks can be laid directly to house- for the post-DSL era. However, due to the
holds (Fibre-to-the-Home [FTTH]) by using physical properties of copper wire in the last
Passive Optical Networks (PONs) and Active mile, VDSL2 has reached its limits, even if
Optical Networks (AONs). In the mid 1990s, technology called DSM (Dynamic Spectrum
the first large-scale PON installations were Management) is being developed to boost the
commissioned in Japan. In many other parts of transmission capacity on copper. Communica-
the world, FTTH concepts were a long way off. tion solutions like WiMAX, or LTE in mobile
The Internet was still in its infancy, attractive telephony, reach the limits of their capabilities
online offerings for private customers were even more quickly because of poorer physical
practically non-existent and the technology was transmission properties (in comparison with
much too expensive in any case. As a result, copper). To date, the only solution for seem-
most end customers did not require more ingly infinite bandwidths has been the optical
bandwidth (i.e. more than ISDN was capable of wave guide, also called fibre optics.
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-
1. Basic facts
The key technical difference between active close as possible, ideally right into the sub-
and passive access technology is that a passive scribers’ houses and apartments. This FTTH-
splitter is used for passive optical networks. solution is technically the best option with
The splitter is basically a kind of multi-mirror respect to the transmission quality and the
that distributes the optical signal for the bandwidth.
subscriber line to fibre optic routes without any
electrical current (which is why it is called
passive). 1.1. Passive Optical Networks (PONs)
The first active optical access networks used As regards the core network, the first network
TDM technology. The first passive optical element of a PON network is the OLT (Optical
networks on the other hand used ATM for voice Line Termination Unit), that provides n x 1 Gbps
and data traffic (APON, BPON, ITU-T Standard and n x 10 Gbps Ethernet interfaces to the core
G.983). Because early PON systems could network and the PON interfaces to the sub-
already transmit a TV broadcast signal on a scriber. The PON types used here today are
separate wavelength in the optical spectrum, usually Ethernet-PON (EPON), Gigabit-PON
simultaneously to the voice-data signal, they (GPON) or Gigabit-Ethernet-PON (GEPON).
were popular in cable TV networks. The Ethernet technology is the common denomina-
topologies of PON and CATV networks are also tor in all these technologies. Nowadays,
very similar to one another, so existing cable EPON installations tend to occur more in the
lines, or ducts can be used and costs saved in Far East and GPON more in the USA and
the network rollout. The objective of both Europe. Consequently, we will be looking at
PON and AON is to get the fibre optics as the GPON-type (ITU-Standard G.984) below.
2008-05-26 © KEYMILE 2008 Page 3

4. White Paper
AON vs. PON
1.2. Active Optical Networks (AONs)
ket AON is a point-to-point network structure
Pac twork (PTP), i.e. each subscriber has their own fibre
Ne optic line that is terminated on an optical
concentrator (Access Node [AN]).
ket
Line OLT) Pac twork
ical ( Ne
Opt ination
Te rm
ical
opt
sive litter
Pas Sp rk
two
ica l Ne ation
n
Opt Termi NT)
(O ode
essN
Acc
Figure 1: Subscriber line in a PON
et
ern
GPON’s current standard can provide a maxi- al Eth
Optic wor
k
mum of 2.5 Gbps towards the subscriber Net n
i cal inatio
(downlink) and 1.25 Gbps towards the core Opt Term NT)
(O
network (uplink) per PON interface on the OLT.
To the subscriber, a passive splitter, that is
Figure 2: Subscriber line in an AON
either fitted to an outdoor cabinet in a colloca-
tion room, or in the end subscriber’s premises, This type of AN can be designed differently,
multiplies the signal on the fibre optics into n depending on specifications. Usually Metro-
optical subscriber branches. In other words, Ethernet-Switches, IP-Edge routers or Multi-
the network structure is a point-to-multipoint Service Access Nodes (MSANs) with optical
structure (PMP). The structure is similar to a Ethernet interfaces are used in this case. The
tree, colloquially called a PON tree, or a twig or fibre optics can be terminated by an ONT here
branch is referred to in the subscriber access too, but also by any Ethernet switch or IP router
line (see figure 1). with an optical uplink interface. If the last mile
In an FTTH network architecture, subscriber to the subscriber is to be bridged using copper
access is implemented using optical network wire, DSLAMs or other MSANs are used. When
termination (ONT) that terminates the optical MSANs are used, both copper and optical lines
signal and converts it into one or more electri- can be used for the last mile from the same
cal interfaces, such as for example 100BaseTx, access node.
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 fibre 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.
2008-05-26 © KEYMILE 2008 Page 4

5. White Paper
AON vs. PON
1.3. Network topologies with PON and AON
ket LT
Pac t O CO
ne
ket T tter ON
U MDF
Pac t OL
Curb
Spli
ne
MDU
ket
Pac twork DN
olds
ne S/IS plus
POTDSL2
useh
OLT A
tter e
Ho k typ
ket Spli
Pac t OLT
wor
ne U NT
ON
Net
U
ON
ket E
Pac twork
ne lus
L2p L2
NT FTT
NT
OLT DN ADS VDS NT
ase
FX S/IS plus
00B POTDSL2 DSL2 B
nx
10
r
A V
NT FTT
tte
Spli
tter
Spli C
bps
,5 G bps ON
T FTT
nk 2 25 G
wnli nk 1,
Do Upli H Copper double pair
ON
T FTT Optical fibre
H
FTT
Figure 3: Overview of network topologies in PON networks
As figure 3 and 4 show, PON and AON can be last mile with copper wire. For PON this can
used to implement all network topologies, be implemented directly from the OLT, or in
starting with Fibre-to-the-Exchange (FTTE), to AON from the access node. Optical Network
Fibre-to-the-Curb (FTTC), Fibre-to-the-Building Units (ONUs), or DSL Access Multiplexers
(FTTB) and Fibre-to-the-Home (FTTH). (DSLAMs) can be integrated to provide the
POTS or ISDN interfaces for telephony and
Both technologies have to take the fibre optics
various DSL types for High-Speed Internet (HSI).
to the end subscriber, but can also bridge the
ket
Pac work CO
net
ket et
ern h AN
MDF
Pac work Eth Switc
net
Curb
MDU
ket et AN
Pac work ern h
Eth Switc DN
S/IS plus
olds
net
POTDSL2
useh
A
Ho type
ket
Pac work
net NT
w ork
Net
AN
AM
ket et DSL
Pac work ern h E
net Eth Switc
AN lus
L2p L2
NT FTT
NT
AN DN ADS VDS NT
seF
X S/IS plus
0Ba POTDSL2 DSL2 B
nx
100 A V
NT FTT
C
nk
wnli ps ON
T FTT
/Do Mb
Up link ≥100
H Copper double pair
ON
T FTT Optical fibre
H
FTT
Figure 4: Overview of network topologies in AON networks
Despite the obvious aspects both technologies PON and AON technology is so widespread
have in common, there are variations inherent and changing from one to the other is costly,
in the systems that affect operations, costs and operators should be aware of all the facts. The
the value they provide differently. Because main differences are shown below.
2008-05-26 © KEYMILE 2008 Page 5

6. White Paper
AON vs. PON
2. Comparison of the technologies AON vs. PON
2.1. Bandwidth The trend towards increasing bandwidth
1000
continues unabated. Due to the launch of
EFM Active 1 Gbps TV-over-IP (IPTV) there is no sign of the increase
100
in bandwidth tailing off, in fact quite the
EFM Active 100 Mbps opposite. Because of the recent launch of
75 (HDTV) and other technically complex services
2.4 GPON (32-split)
such as online gaming, network operators are
45
Bonded being encourage to outdo one another by
VDSL2
24
ADSL2plus providing more and more bandwidth.
[Mbps]
ADSL2plus
The following table compares PON and AON
[km] 1 2 3 4 5 6 transmission bandwidth.
Source: DSL Forum, FTTx Summit 2007, Munich
Figure 5: Bandwidth downstream and range
AON PON Assessment
Bandwidth allocation
Good Average AON’s advantage
The amount allocated to the subscriber The GPON interface on the OLT AON clearly has the edge because of
is governed by the interface type, or nowadays is 2.5/1.25 Gbps (downlink/ its flexibility. Due to the static splitting
traffic shaping on the access node and uplink). The bandwidth per subscriber is factor and the interfaces on the OLT,
is therefore adjustable in kilobit incre- determined by the splitting factor (usu- PON is at a disadvantage.
ments. 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.
Maximum bandwidth per subscriber
Good Satisfactory AON’s advantage
As each subscriber is connected with With regard to the PON standards AON technology is clearly better as
their own fibre optics, bandwidth can available today, the maximum feasible regards the bandwidth per subscriber.
today be implemented at between capacity of fibre optics is the same The maximum bandwidth per sub-
100 Mbps and 1 Gbps per household or as the total capacity of an OLT port, scriber is a lot higher. The flexibility to
company. i.e. 2.5 Gbps (PTP connection without allocate different bandwidths to indi-
a splitter). Therefore, realistically the vidual subscribers is also greater (e.g.
bandwidth with splitter and a separa- for corporate customers) than when
tion of usually 1:32 is 78 Mbps, or at PON systems are used. Depending on
1:64 39 Mbps (all figures relate to the splitting factor, a PON connection
downstream). via fibre optics supplies less bandwidth
than a VDSL2 connection via copper
wire.
Increasing bandwidth
Simple Difficult AON’s advantage
As the active access node has a Depending on the systems technology, In this case, the PTP architecture is
modular structure, subscriber interfaces it would be feasible in the future to superior to the PON’s PMP architecture.
can be upgraded to include more bundle several time slots and therefore, Just by converting boards, subscribers
bandwidth. It is often sufficient to just at the cost of the maximum number can obtain an upgrade, without the net-
switch the fibre optic lead to be able to of subscribers per PON branch, to work architecture or the service of other
operate it again. increase individual bandwidth by a fac- subscribers having to be changed.
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).
2008-05-26 © KEYMILE 2008 Page 6

7. White Paper
AON vs. PON
To sum up, the PON network’s predefined Nowadays, the Triple Play offerings, imple-
topology makes individual changes more mented via copper wire often consist of two
difficult. By terminating all the fibre optics at television channels with standard resolution
the OLT, i.e. the same fibre optic topology as in (SDTV), a high-speed Internet connection
the AON (point-to-point), this disadvantage can (>3 Mbps) and at least one POTS or ISDN
be overcome. Therefore, for future-proof telephone connection. The current state of the
infrastructure investment, reliable point-to- art is that network operators are planning
point fibre optics technology should always be approx. 15 Mbps downlink capacity.
considered.
In the future the end customer will be demand-
ing high definition TV (HDTV). Two simultane-
2.2. Security and quality of services ous TV channels will mean an unacceptable
restriction for a family of four in the long term.
An aspect in public networks that is regaining Furthermore, currently ADSL 16 Mbps Internet
importance is Quality-of-Service (QoS), which access is already being marketed to private
considering today‘s financial restraints is often customers and including n telephone lines.
forced to take a back seat. At the dawn of the Online gaming – in the Far East popular for
ADSL rollout, the majority of services offered years – is also looking promising in Europe. In
took a best effort approach, i.e. the data this case, top rates of 50 Mbps per subscriber
channel guaranteed neither a minimum band- line could easily be reached. Today, standard
width, nor any other quality features worth VDSL2 access would not be able to cope.
mentioning. As today however, Triply Play
services (telephony, data and TV down one The scenario described above indicates what
single line) are already transmitted to the the private consumer will look like in the near
subscriber, QoS applies more than ever. When future. If such a scenario appears exaggerated,
surfing the Web, short delays of 1 – 2 seconds, we only have to recall the situation 10 years
e.g. when clicking on a link, do not really ago when modern end customers still used
matter. During a phone call, this level of delay 56 kbps dial-up modems to read e-mails, for
is however completely unacceptable. When sending faxes and for home banking. In
watching TV, it is also no fun if the picture comparison to today’s standard 3.5 Mbps ADSL
freezes before a goal is scored. As a result, the connection, the bandwidth has increased
Triple Play services must be clearly separate 62-fold! Special requirements from business
and allocated priority. customers, or demands for the backhaul of
sub-networks, server connections or high
Although theoretically unlimited bandwidth is performance IT applications would easily
available in a fibre optic line, QoS not be exceed these quality specifications and require
forgotten. Not all QoS aspects can be even greater high quality performance.
responded to with bandwidth and neither PON
nor AON can really provide unlimited band-
width.
AON PON Assessment
Temporary increase in bandwidth (e.g. server back-up over night)
Simple Difficult AON’s advantage
In an active access node, traffic shaping Due to the TDM procedure, a fixed Compared with an AON, the structure
can regulate the bandwidth from the time slot is allocated to each customer. of the PON limits the flexibility to make
NMS control centre and for example The signal must also be separated any changes in bandwidth.
during constant operation be switched using a passive splitter, as passive
to 100 Mbps, or ad-hoc to 1 Gbps. splitters are not manageable. A further
allocation of another time slot must be
carried out.
Prioritising services
Simple Simple Undecided
Standard mechanisms at Ethernet/IP Standard mechanisms at Ethernet/IP In this case there are no significant dif-
level can be used. level can be used. ferences.
2008-05-26 © KEYMILE 2008 Page 7

8. White Paper
AON vs. PON
AON PON Assessment
Delay, jitter and other effects on quality
Low Low Undecided
Mainly influenced by the design of the Mainly influenced by the design of the In this case there are no significant dif-
core network. core network. ferences.
Impact of faults in the access node
Low High AON’s advantage
As n subscribes in an active access In an OLT, a passive splitter separates Any faults in the AN affect fewer cus-
node use n optical interfaces and the the optical subscriber interfaces into tomers than in an OLT.
subscriber density of the interface 32 or 64 signals. A subscriber subrack
card is relatively low compared with a usually provides several subscriber
PON-OLT, relatively few subscribers are interfaces. In comparison with an AON
affected if there is a malfunction. AN, a lot of subscribers are affected if a
port, or even a card fails.
Effect of malfunctions and manipulation
Low High AON’s advantage
Thanks to the PTP architecture, each Within a PON tree, all the subscribers In the worst case scenario, a single
path can be assessed exactly right up are on the same optical point. If a faulty ONT can bring an entire PON tree with
to the end customer’s ONT at the very ONT causes faulty synchronisation, up to 64 subscribers down if a technical
least. In the worst case scenario, the or produces an optically indefinable malfunction or deliberate manipulation
laser on the AN for each subscriber can signal, a remote localisation of the occurs. A faulty subscriber line on the
be deactivated by the control centre. malfunction in the ONT involved is not AON can be very easily identified and
possible. As the ONTs are often in the eradicated.
end customer’s home, it is impossible
to estimate how long it will take to
exchange an ONT.
Risk of eavesdropping (espionage)
Low High AON’s advantage
Each customer has dedicated fibre A PON tree is known as a shared medi- The data in the PON network is en-
optics. In general, eavesdropping is um, i.e. all subscriber signals are on one crypted in a similar way to WLAN, nev-
not possible. fibre optic terminal point. By allocating ertheless it is technically still possible to
the time slot, the data is separated. eavesdrop on another subscriber on the
The setup is in the customer’s network same PON tree. However, in-depth
termination. technical knowledge is required to do
so.
Reliability of the subscriber line (between the customer and AN and passive splitter)
Good Poor AON’s advantage
In an active network, a customer can To date, there are no plans to connect Availability of the PON, compared with
basically be connected in a ring, or customers twice in one PON. the AON, is much worse.
using dual-homing. In other words, a
customer can be connected twice.
Reliability of the subscriber line (between passive splitter and OLT, or AN and edge switch)
Poor Good PON’s advantage
If the connection is cut here, several In this case, only one fibre optic line has In reality cables are cut more often
hundred fibre optics are interrupted to be maintained. than is generally thought. A PON link
and have to be repaired. between the splitter and OLT consists
of a tiny fibre optic that can be repaired
in a few hours.
2008-05-26 © KEYMILE 2008 Page 8

9. White Paper
AON vs. PON
2.3. Business case aspects ogy is used), it sometimes takes more than 10
years.
Using fibre optic cable promises virtually
unlimited bandwidths, however the network Nevertheless, depending on the application
operator only ever has just the copper wire line and conditions at the time, business cases vary
in the last mile. That means that if the DSL greatly, depending on whether passive or
technology is no longer adequate, new optical active access technology is used for an FTTH
cables must always be laid. rollout. The main differences in investment
costs (capital expenses, CAPEX) and operating
The high investment costs of this infrastructure, costs (operational expenses, OPEX) are com-
combined with telecommunications providers’ pared with one another below.
falling revenue at the same time, mean it is
often difficult 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-
2.3.1 Investment costs (CAPEX) comparison
AON PON Assessment
Costs of the subscribers’ terminal equipment (CPE)
Low High AON’s advantage
As standard Ethernet technology can As ONTs in the PON environment are The CAPEX bonus of AON networks
be used. Today, simple ONTs (e.g. Eth- (despite standardisation) not inter- should not be underestimated, because
ernet media converters), with functions changeable between different manu- the CPE share in the total costs is usu-
similar to an ADSL-NT, are available for facturers. Which means the selection ally the greatest (often >50 %).
under $30. of models is restricted and the savings
provided, because a larger number is
produced, are negligible.
Costs of the network technology (active components)
High Low PON’s advantage
Because each subscriber has a dedi- As a single port on the OLT can be Because optical paths can be used by
cated laser port on the AN. If a fibre shared by several customers. If a several subscribers, PON is a bonus
optic path is divided up into several fibre optic has to be shared by several because of the price per subscriber.
customer connections, additional active customers, a simple passive splitter can
equipment is required. be used.
Costs of the network technology (passive components and infrastructure)
High Low PON’s advantage
Because of the greater number of opti- As one laser on the OLT is shared by n In this case, passive technology clearly
cal subscriber interfaces in the access subscribers because the passive splitter has the upper hand.
node. is used.
Network rollout costs
High Different PON’s advantage
Each subscriber must be connected Depends on the fibre optic topology. Depending on the fibre optic topol-
individually in a star shape. If the same topology is used as in an ogy, PON network architecture can be
AON, the costs are similar (fibre-rich cheaper in large-scale rollouts.
approach). If the fibre 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 efficiently (e.g. in terraced
houses).
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10. White Paper
AON vs. PON
2.3.2 A comparison of operating expenses (OPEX)
AON PON Assessment
Space required for systems technology
High Low PON’s advantage
Because of the port density of the ac- Because a single optical port on the PON’s space-saving potential in the col-
tive AN, the space required is just as OLT for up to 64 customers is used, the location room is greater compared with
great as for a DSLAM. space required at the OLT for systems AON. Due to the wide ranges of PON
technology is very low. Over 8,000 paths, in comparison with copper wire,
subscribers can be placed on a single some MDF sites may not be necessary
rack using today’s technology. at all.
Space required by cable
Great Low PON’s advantage
One fibre optic cable at the AN per One fibre optic cable can supplied to The space PON saves in fibre optic
subscriber. up to 64 subscribers. cable is particularly critical in central
OLT locations.
Energy consumption
High Low PON’s advantage
Because of the high number of laser Because of the passive splitting. Because of the passive splitter and
interfaces. higher subscriber density on the OLT,
the PON is much better in this case.
Level of maintenance
High Low PON’s advantage
Active access nodes require an external In an outdoor cabinet, the passive In this case, the PON is also at an ad-
power supply, plus battery to supply splitter needs virtually no maintenance. vantage because there are fewer active
emergency electricity. This is a disad- External power supply is not required. components in the network.
vantage, above all in FTTC networks, Malfunctions are very seldom.
where the AN is on the outdoor
cabinet.
Level of difficulty in identifying and eradicating malfunctions
Low High AON’s advantage
Because in AON networks it is easy to As in the worst case scenario, a faulty Identifying and eradicating faults in the
carry out an end-to-end diagnosis right ONT cannot be deactivated by the AON is a lot easier than in the PON,
into the subscriber's home, due to the NMS centre. A local visit to the cus- due to the PTP topology. Nevertheless,
PTP topology and the possibility of as- tomer is required. Depending on the in the PON the ability to analyse faults
sessing the dedicated optical transmis- accessibility of the ONT, this can take a by using monitoring systems can be
sion path via the NMS. long time. improved.
Follow-up costs for upgrades
Low High AON’s advantage
Because of the better granularity of the An entire PON tree is affected by Because of the greater individual flex-
ANs and the separation of the custom- an upgrade. All ONTs have to be ibility, AON has an advantage where
ers (PTP), individual upgrades can be exchanged at the same time. As a upgrades are concerned.
carried out in the AON and for example result, individual upgrades are virtually
CPE can be exchanged. precluded.
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11. White Paper
AON vs. PON
2.4. Flexibility and scope for usage ences. Apart from technological differences,
there are further differences between the two
Previous findings in the comparison of AON optical access technologies, depending on the
and PON have already highlighted key differ- operator’s business strategy.
AON PON Assessment
Suitability for connecting up housing estates (green field)
Satisfactory Good PON’s advantage
The requirements for rolling out active The fibre optic infrastructure is simpler. Because of the lower requirements, a
networks are higher. The requirements for passive splitters PON network can be installed more
in outdoor cabinets are low (no power quickly and cheaply.
needed, no problems with heat/cold).
Level of suitability for connecting large-scale/business customers
Very good Poor AON’s advantage
In this case advantages on flexibility, se- The customers in a PON tree are all Requirements from bulk customers are
curity and performance really pay out. treated the same. Individual features always special, PON network concepts
A router or switch can be used as an can only be implemented at protocol tend to be more static. Therefore, in
optical network termination to separate level above layer 3. this case the active approach is a lot
services. better.
Level of suitability to provide telephony and high-speed Internet (HIS) at the same time
Good Good Undecided
No major restrictions. No major restrictions. From 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
Good Satisfactory AON’s advantage
For transmitting n HDTV channels, AON PON does have the advantage that An optical network rollout is a long
can also mobilise enough bandwidth some systems are capable of transmit- term investment. If we assume that
reserves. ting analogue TV (similar to a CATV HDTV will be the standard format in
network), however the usual bandwidth the future, active networks have the
for broadcasting several HDTV channels upper hand, due to their high levels of
might not be sufficient. bandwidth reserves.
Suitability to provide additional services
Good Poor AON’s advantage
AON technology can be adapted to The range of specialised terminal The requirements for additional and
suit individual requirements. equipment is very limited because of possibly new services when designing
dependency on manufacturers. The a new network are often not specified
rather inflexible bandwidth manage- to the last detail. PON's limits could
ment, based on TDM procedures, is a significantly inhibit business cases in the
disadvantage. future.
Flexibility of usages as regards optical network termination
Good Poor AON’s advantage
As AON uses standardised Ethernet Today there is no real interoperability In this case, the operator of an AON
interfaces, a variety of different devices between rival PON technologies, even network can act more flexibly and make
can be used for network termination. within the same PON technology. use of real price savings. When using
Operators are forced to purchase the feature-rich IP equipment instead of
ONTs and ONUs from the OLT supplier an ONT, the provider can expand his
(dependency). range of services by leasing addi-
tional features (additional VPNs, hosted
PBX…)
Ranges (max. length of the subscriber access line)
Very good Good AON’s advantage
Maximum of about 70 km without Up to 20 km depending on passive Optical components can be selected
repeaters. splitter. individually
Backhaul of sub-networks and network elements
Good Poor AON’s advantage
A normal AN subscriber interface can A PON interface board can only be As an active access node is similar to an
also be used for backhaul jobs (e.g. of a used for implementing PON trees. Ethernet switch in the way it works and
DSLAM, radio equipment etc). provides standard Ethernet interfaces,
it can also be used for various backhaul
jobs.
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12. White Paper
AON vs. PON
3. Summary
Finally we should not forget that a generic customers, multi-dwellings, universities, local
comparison of technologies, such as this one, authorities etc…), as in these cases flexibility,
cannot always apply in all cases. The balance quality and security are demanded. And
can easily shift from one side or the other because of the way they are structured, PON
depending on statutory, commercial or struc- networks struggle to fulfil these requirements.
tural constraints. As standardised ONTs are used, the commer-
cial aspects of supplying households on a large
Basically, passive optical networks are a better
scale should be weighed up too and can
choice for network operators who want to
compete with PON systems.
supply a very large number of subscribers, like
the (previous) network operators who had a Nevertheless, as PON networks are on the
monopoly. These operators tend to aim more increase, it is likely that some of the disadvan-
for the mass and private customer market. In tages of PON listed here will gradually be
this case, PON can throw its commercial eliminated. However some of the inherent
benefits into the balance and at the end of the features of a PON will remain. But one thing is
day compensate for various operational almost certain, the fibre optic based access
disadvantages. network, and therefore end customer products
too, will constantly be upgraded to handle
Active optical technology is more suitable for
more than 50 Mbps. The whole issue is set to
private network operators, that either lay their
stay an exciting one
own fibre optic infrastructure, or use debun-
dled fibre optic lines (Fibre Local Loops).
AON is perfect for high-profit end customer
segments (such as for example business
Requirement AON’s PON’s Individual
suitability suitability assessment
Bandwidth
Bandwidth allocation ☺
Maximum bandwidth per subscriber ☺
Bandwidth increase ☺
Security and quality services
Temporary 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 difficulty 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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13. White Paper
AON vs. PON
Requirement AON’s PON’s Individual
suitability suitability assessment
Costs of the network technology (infrastructure) ☺
Rollout costs
Flexibility and scope for usage
Suitability for connecting up housing estates (green field) ☺
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 ☺
4. Glossary
Abbreviation Description Abbreviation Description
100BaseTx 100Mbit/s Ethernet, copper interface ISDN Integrated Services Digital Network
3G Third generation of the mobile telephony ITU-T International Telecommunication Union,
standard Telecommunication Standardisation
Sector
4G Fourth generation of the mobile te-
lephony standard LTE Long Term Evolution
ADSL Asymmetrical DSL MDF Main Distribution Frame
AN Access node MDU Multi Dwelling Unit
AON Active Optical Network MSAN Multi-Service Access Node
APON ATM PON NMS Network Management System
ATM Asynchronous Transfer Mode OLT Optical Line Termination
BPON Broadband PON ONT Optical Network Termination
CaTV Cable television P(A)BX Private (Automatic) Branch Exchange
CO Central Office PMP Point-to-Multipoint
DSL Digital Subscriber Line PON Passive Optical Network
DSLAM DSL Access Multiplexer POTS Plain Old Telephony Service
EFM Ethernet First Mile PTP Point-to-Point
EPON Ethernet PON QoS Quality of Service
FTTC Fiber-to-the-Curb SAL Subscriber access line
FTTE Fiber-to-the-Exchange SDTV Standard Definition TV
FTTH Fiber-to-the-Home TDM Time Division Multiplex
GEPON Gigabit Ethernet PON VDSL Very high-speed Digital Subscriber Line
GPON Gigabit PON WiMAX Worldwide Interoperability for Microwave
Access
HDTV High Definition TV
ICT Information Communication Technology
IP Internet Protocol
IPTV Television over IP
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14. White Paper
AON vs. PON
Publisher
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2008-05-26 © KEYMILE 2008 Page 14