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7302-7360 ISAMGPON Basic ConfigurationStudent Guide
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Course outline
1. Technologies
1. GPON Technology
2. NE Operation
1. GPON Basic Configuration
Welcome to 7302-7360 ISAM
GPON Basic Configuration
1. Technologies
1. GPON Technology
2. NE Operation
1. GPON Basic Configuration
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4COPYRIGHT ALCATEL-LUCENT 2013. ALL RIGHTS RESERVED.
Course objectives
Upon completion of this course, you should be able to:
Explain which components are used in an optical relay system
internal reflection, transmitter, amplifier, receiver, splitter,
,
Explain the basic properties of a passive optical network,
Describe the functions of the components present in a PON based
network, Describe the different standardizations in GPON and XGPON,
Know the PON evolution, Describe the embedded OTDR, Correctly use
basic PON terminology, Describe the different ways in provisioning
an ONT and provision an ONT, Manage the ONT Software.
7302-7360 ISAM
GPON Basic Configuration
Upon completion of this course, you should be able to:
Explain which components are used in an optical relay system
internal reflection, transmitter, amplifier, receiver, splitter,
,
Explain the basic properties of a passive optical network,
Describe the functions of the components present in a PON based
network,
Describe the different standardizations in GPON and XGPON,
Know the PON evolution,
Describe the embedded OTDR,
Correctly use basic PON terminology,
Describe the different ways in provisioning an ONT and provision
an ONT,
Manage the ONT Software.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.
Your feedback is appreciated!
Please feel free to Email your comments to:
[email protected]
Please include the following training reference in your
email:
TAC42049_V1.1-SG Edition 2.0
Thank you!
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Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0Section 1 Module 1 Page 1
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Document History
Edition Date Author RemarksEdition Date Author Remarks
01 Last name, first name First edition
02 Sept/2013 ALU-University Madrid [[R4.5/R4.6 AMS R9.2.30]]
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Edition I2.0Section 1 Module 1 Page 2
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Page
1 Fiber Principles 71.1 Advantages of fiber 81.2 Optical fiber
structure 91.3 Optical fiber classification 101.4 Optical fiber
types 111.5 Reflection and refraction 121.6 Total internal
reflection 131.7 Scattering 141 8 Absorption 151.8 Absorption 151.9
Attenuation as function of wavelength 161.10 Fiber optic relay
system 171.11 Transceiver 181.12 Light wave modulation 191.13 Fiber
interconnections 201.14 Joining fibers Fiber alignment 211.15
Joining fibers Fiber orientation 221.16 Joining fibers Connectors
231 17 Connectors - Couplers 241.17 Connectors Couplers 241.18
Joining fibers Splices 251.19 Enclosures and Splice Trays 261.20
Splice and Splice Trays 272 GPON fundamentals 282.1 What is GPON
used for? 292.1 What is GPON used for? 302.3 GPON, where? 312.4 PON
deployment scenarios FTTx 322.5 Two Basic FTTH technologies 332.6
Definition - Feeders, Distribution, Drops 342.7 PON properties
352.8 PON lambdas 362.9 Splitter - Types 372.10 Splitters Example
382.11 Optical Power budget loss 392.12 Splitter Optical Budget
412.13 Data transceiver specifications (class B+) 422.14 Optical
power budget Data 432 15 Data transceiver specifications (class C+)
442.15 Data transceiver specifications (class C+) 442.16 Video
transceiver specifications 452.17 Optical power budget Video 462.18
Maximum range per splitter - configuration 472.19 GPON protocol
layers and formats 482.20 Data Transmission : DOWNSTREAM 492.21
Data Transmission : UPSTREAM 502.22 Distance ranging Why? 512.23
Distance ranging explained 522 24 GPON frame format 532.24 GPON
frame format 532.25 DOWNSTREAM : Continuous mode operation 542.26
GPON frame format Downstream 552.27 GPON frame format Downstream
562.28 GPON frame format Downstream 572.29 UPSTREAM : Burst mode
operation 582.30 GPON frame format Upstream 592.31 GEM
encapsulation 602.32 The solution(s) in brief 612.33 Data solution
Data over ethernet 62
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Page
2.34 Voice solution 1 VoIP using SIP phones 632.35 Voice
solution 2 SIP@ONT 642.36 Voice solution 3 MEGACO@ONT 652.37 Video
solution 1 Inband video 662.38 Video solution 2 Outband video
672.39 MBH-Mobile Backhaul solution(s) 682.40 GPON vs EPON 693 PON
standardization: GPON-XGPON 703 1 PON flavors over time 713.1 PON
flavors over time 713.2 ITU-T standards for GPON 723.3 ITU-T
G.984.x framework 733.4 ITU-T standardization build-up 743.5
Summary standards view 753.6 General Characteristics 763.7 Physical
Layer 773.8 Transmission Convergence Layer 783.9 REFERENCE
SCENARIOS 793 10 OMCI ONT Management Control Interface 803.10 OMCI
ONT Management Control Interface 803.11 OMCI layer 813.12 OMCI and
interoperability 823.13 Reach Extender and Long Reach 833.14
Redundancy 843.15 Redundancy: Graphical view 853.16 ALU Feeder
Redundancy 864 More info on the PON evolution 874.1 Trends towards
next generation PON 884.2 Pushing the envelope of PON now : Moving
up Capacity, Reach & Split 894.3 Readiness for Next Generation
PON 904.4 Upgrade for 10G GPON Wavelength overlay in both uplink
and downlink 914.5 10G GPON evolution 924.6 G.987.3: XGPON TC-layer
characteristics 934.7 G.987.3: T-CONT & GEM port concepts 944.8
G.987.3 : Comparison between GPON & XGPON1 954.9 Bandwidth
Management 964.10 Bandwidth Management: Upstream DBA 974.11 ITU-T
G.984.5: reference diagram 985 Embedded OTDR 995 Embedded OTDR
995.1 Fiber physical layer problems What can go wrong? 1005.2
Optical Supervision and Diagnosis (with OTM and eOTDR) 1015.3
Embedded OTDR : overview -Today 1025.4 Embedded OTDR : distribution
of sub functions 1035.5 Optical Transceiver Monitoring (OTM) 1045.6
Traditional OTDR vs ALU eOTDR Solution 1055.7 Embedded OTDR :
integrated solution 1065.8 Embedded OTDR : measurement principal
1075 9 OTDR Building blocks 1085.9 OTDR Building blocks 1085.9 OTDR
Building blocks 109
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Let's begin with the advantages of fiber.
Fiber has an extremely high bandwidth. Fiber today has bandwidth
capability theoretically in excess of 10Ghz and attenuations less
than 0.3 db per kilometer of fiber. The limits on transmission
speed and distance today lie largely with the laser, receiver, and
multiplexing electronics. With the future advent of stable narrow
line single-mode lasers and coherent optics, 10 to 100 Gb/s
transmission is possible.
Fiber has a smaller diameter with lighter weight cables compared
to copper cable Even when fibers areFiber has a smaller diameter
with lighter weight cables compared to copper cable. Even when
fibers are covered with protective coatings, they still are much
smaller and lighter than equivalent copper cables.
Fiber also has negligible crosstalk. In conventional circuits,
signals often stray from one circuit to another, resulting in other
calls being heard in the background. This crosstalk is negligible
with fiber optics even when numerous fibers are cabled
together.
Fiber optic cables are immune to interference caused by
lightning, nearby electric motors, relays, and dozens of other
electrical noise generators that induce problems on copper cables
unless shielded and filteredof other electrical noise generators
that induce problems on copper cables, unless shielded and
filtered.
Fiber is a high quality transmission media. Fiber provides
communication quality much more than copper or microwave. This is a
result of the noise immunity of the fiber transmission path. The
BER or Bit Error Rate for fiber is 10 to the -9 up to 10 to the -11
compared to copper or microwave which is 10 to the -5 up to 10 to
the -7.
Fiber has low installation and operating costs. Low loss
increases repeater spacing, therefore reducing the cost of capital
in the outside plant. The elimination (or reduction) of repeaters
reduces maintenance, power,
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0Section 1 Module 1 Page 8
cost of capital in the outside plant. The elimination (or
reduction) of repeaters reduces maintenance, power, and operating
expenses.
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These are the different parts of a fiber.If you look closely at
a single optical fiber, you will see that it has [2] the core which
is the thin glass center of the fiber, where the light travels
transmitting the corresponding data. Cladding is the outer optical
material surrounding the core that reflects the light back into the
core.The plastic coating protects the fiber from damage such as
abrasion crushing chemicalsThe plastic coating protects the fiber
from damage, such as abrasion, crushing, chemicals, moisture, etc.
Hundreds or thousands of these optical fibers are arranged in
bundles in optical cables. The bundles are protected by the cable's
outer covering, called a jacket.This is a fiber ending in a special
connector (in this case SC type) to connect to the equipment
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0Section 1 Module 1 Page 9
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Fiber can be classified by the material used in the core and the
cladding. There are glass, plastic, and plastic-clad silica
fibers.The glass fiber has the lowest attenuation and is the one
used in telecommunications. The core and cladding are made of
silica glass.The plastic fiber has the highest attenuation, with
the core and cladding made up of plastic. This is the cheapest
fiber. Since it does not have to go long distances, the high
attenuation isThis is the cheapest fiber. Since it does not have to
go long distances, the high attenuation is not a problem. The
plastic fiber is used in the automotive industry.The plastic-clad
fiber has a glass core and plastic cladding. It has intermediate
attenuation compared to the other two. This fiber can be used, for
example, in connecting the network within a building.The glass used
in a fiber-optic cable is ultra-pure, ultra-transparent silicon
dioxide or fused quartz. During the glass fiber-optic cable
fabrication process, impurities are purposely added to the pure
glass to obtain the desired indices of refraction needed to guide
light. Germanium, titanium, or phosphorous is added to increase the
index of refraction. Boron or fluorine is added to decrease the
index of refraction. Other impurities might somehow remain in the
glass cable after fabrication. These residual impurities can
increase the attenuation by either scattering or absorbing
light.
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Section 1 Module 1 Page 10
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Here we see that there are two types of fibers, according to the
mode.
The MMF ( Multi Mode Fiber) described in the ITU recommendation
G.651 was the first fiber mode created having a core of a diameter
ranging from 50 to 62.5 microns, operating at wavelengths between
850 and 1,300 nanometers. It uses low-cost electronics such as LEDs
(Light emitting diodes) or VCSELs (Vertical-Cavity Surface-Emitting
Lasers). This wider core in the multi mode produces various rays,
thus the name multi mode, with different incident angles,the multi
mode produces various rays, thus the name multi mode, with
different incident angles, finite ones and specific ones according
to the Maxwell Law. These rays will be kept inside the core by the
cladding, reflecting each ray within the core. Due to these multi
modes, the transmission in this type of fiber can only go short
distances, such as within a building to connect LANs.
The other fiber type is the SMF (Single Mode Fiber), described
in the ITU recommendation G 652) with a core diameter between 8 and
10 microns Hair diameter is around 100 micronsG.652), with a core
diameter between 8 and 10 microns. Hair diameter is around 100
microns.
The Single Mode Fiber has wavelengths between 1200 and 1600
nanometers. Such a narrow core will have one incident angle. This
type of fiber acts as a waveguide. With these types of
characteristics (that is only one ray and acting as a waveguide)
the SMF is used for long distances. It is the most prominent type
used in the telecommunication sector. There is a new SMF fiber,
usually used indoors, which complies with the ITU 657, defining
minimum bending
di f 7 5 d 10
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Edition I2.0
Section 1 Module 1 Page 11
radius of 7.5mm and 10mm.
For data center premise cables, the jacket color depends on the
fiber type in the cable. For cables containing SMFs, the jacket
color is typically yellow, whereas for cables containing MMFs, the
jacket color is typically orange. For outside plant cables, the
standard jacket color is black.
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How is it that the light travels within the fiber with all the
curves it might have? This can be attributed to the Snell law which
is a formula which describes the angles of incidence and refraction
of light or other waves as it travels through two mediums which
have different refraction indices.
The Snell law indicates that if n1 is greater than n2, then a2
is greater than a1. In other d if th t i l 1 hi h i thi i th fib h
g t f ti i d words, if the material n1, which in this case is the
fiber core, has a greater refraction index
than the n2 material, in this case it is the fiber cladding,
then the angle a2 caused by the refracted ray will always be
greater than angle a1 caused by the incident ray. This means that
when a1 increases, a2 will reach 90 degrees before a1. If a1 keeps
increasing, a2 cant be more than 90 degrees, therefore there will
be no ray in n2 and at this point there will be total reflection.
This will be the ideal situation of transmitting light through the
fiber.
The lasers used in the fiber will be adjusted so the light
transmitted inside the fiber will be greater than angle a1 (called
the critical angle). This way there will always be total reflection
and no refraction. Refraction will be a loss of the light
transmitted.
Therefore to have total reflection the fiber core refraction
index must be greater than the fiber cladding and the incident
angle must be greater than the critical angle.
There are other known mediums with different refraction indexes.
The water refraction index is greater than ice, and both of these
are greater than air. So if someone is under the water with a laser
pointed towards the air someone outside will see a laser ray
(refraction)
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 12
water with a laser pointed towards the air, someone outside will
see a laser ray (refraction) and the one under the water will also
see the ray reflecting. But as the angle is changed in such a way
that it becomes greater than the critical angle, the one outside
will no longer see a ray and the one under the water will see the
reflecting ray, but this time more intense, since it has total
reflection. This means there is no loss since there is no
refraction.
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The light in a multi-mode fiber-optic cable travels through the
core by constantly bouncing from the cladding (mirror-lined walls),
a principle called total internal reflection.
Because the cladding does not absorb any light from the core,
the light wave can travel great distances. However, some of the
light signal degrades within the fiber, mostly due to impurities in
the glass.
The extent that the signal degrades depends on the purity of the
glass and the wavelength The extent that the signal degrades
depends on the purity of the glass and the wavelength of the
transmitted light (for example, 850 nm = 60 to 75 percent/km; 1,300
nm = 50 to 60 percent/km; or 1,550 nm is greater than 50
percent/km). Some premium optical fibers show much less signal
degradation, less than 10 percent/km at 1,550 nm.
The difference in refraction index between the core and cladding
will create this total internal reflection. However if the angle at
which a beam of light hits the cladding is just below the critical
angle, it is possible that part of the energy will be lost in the
cladding. This is based on Snells LawThis is based on Snells
Law.
The fact that we need to maintain a certain angle, creates an
acceptance cone, an area where all lasers will work to have total
reflection and absolutely no refraction.
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Edition I2.0
Section 1 Module 1 Page 13
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Scattering (called Rayleigh scattering) is one of the two major
attenuations inside the fiber, affecting shorter wavelengths (below
800 nanometers).
If the scattered light maintains an [2] angle that supports
forward travel within the core, attenuation does not occur. If the
light is scattered at an [3] angle that does not support continued
forward travel, the light is diverted out of the core and
attenuation occurs. Depending on the incident angle, some portion
of the light propagates forward and the other part deviates out of
the propagation path and escapes from the fiber core.
Since an increase in temperature of the fiber will increase the
movement of electrons, the temperature will influence the
attenuation through the fiber.
Some scattered light is reflected back toward the light source.
This is a property that is used in an Optical Time Domain
Reflectometer (OTDR) to test fibers. The same principle applies to
analyzing loss associated with localized events in the fiber, such
as splices.
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Section 1 Module 1 Page 14
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Absorption is the other major attenuation inside the fiber which
affects the longer wavelengths more (that is wavelengths above 1700
nanometres').
Material absorption occurs as a result of the imperfection and
impurities in the fiber. The most common impurity is the hydroxyl
(OH-) molecule, which remains as a residue, despite stringent
manufacturing techniques.
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Edition I2.0
Section 1 Module 1 Page 15
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This graph is for a specific fiber of a specific manufacturer.
It indicates the attenuation (dB/km) in relation to the wavelength.
The extreme attenuation on the left of the graph is caused by
scattering (low wavelengths) and the extreme attenuation on the
right is caused by infrared absorption (high wavelengths).
*The indicated wavelengths in the graph are the ones used in the
GPON and XGPON networks. There is 1310nm, 1490nm for GPON and
1270nm, 1578nm for XGPON with an optional one (1550nm) used to
transmit overlay video (Analog or Digital Terrestrial TV). There
are studies to use this optional wavelength (1550nm), if not for
video overlay, then to transmit more IPTV channels. The attenuation
of light through glass depends on the wavelength of the light as
shown on the graph. For the kind of glass used in fibers, the
attenuation is shown in decibels per linear kilometer of fiber. The
figure shows the near infrared part of the spectrum, which is
normally used. Visible light has slightly shorter wavelengths, from
0.4 to 0.7 microns (1 micron is 10 to -6 meters).
When attenuation for a fiber-optic cable is dealt with
quantitatively, it is referenced for operation at a particular
optical wavelength, a window, where it is minimized. The most
common peak wavelengths are 780 nm, 850 nm, 1310 1550 d 1625 *Th
850 i i f d t th fi t i d ( it d i iti ll 1310 nm, 1550 nm, and
1625 nm. *The 850-nm region is referred to as the first window (as
it was used initially because it supported the original LED and
detector technology). *The 1300-nm region is referred to as the
second window, and *the 1550-nm region is referred to as the third
window.
Three wavelength bands are used for communication. They are
centered at 0.85, 1.30 and 1.55 microns, respectively. The latter
two have good attenuation properties (less than 5 percent loss per
kilometer). The 0.85 micron band has higher attenuation, but the
nice property at that wavelength is that the lasers and electronics
can be made from the same material (gallium arsenide). All three
bands are 25,000 to 30,000 GHz wide.
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Section 1 Module 1 Page 16 Section 1 Module 1 Page 16
Typical low loss fibers have attenuations of between 0.3 to
3dB/km. Contrast this attenuation with the ones for coaxial cable!!
For fibers and coaxial cables alike, the losses are a function of
the frequency of the signal carrier. Coax attenuation varies as the
square of frequency with signal carriers in the DC to hundreds
megahertz range.
-
The basic function of an optical fiber relay system (or optical
fiber link) is to transport a signal from some piece of electronic
equipment (e.g., a computer, telephone or video device) at one
location to corresponding equipment at another location with a high
degree of reliability and accuracy.
The optical fiber is one of the most important elements in an
optical link. A variety of fiber types exist, and there are many
different cable configurations, depending on whether the cable is
to be installed inside a building, in underground pipes, outside on
poles, or under water.
Basically, a fiber-optic system simply converts an electrical
signal to an infrared light signal, launches or transmits this
light signal onto an optical fiber, and then captures the signal on
the other end, where it reconverts it to an electrical signal.
Even though miniature or tiny light sources and detectors are in
use, optical fibers are so small that special connectors must be
used to couple the light from the source to the fiber and from the
fiber to the detector The optical fiber provides a low loss path
for the light to follow from the fiber to the detector. The optical
fiber provides a low-loss path for the light to follow from the
light source to the light detector. In a sense it is a waveguide
that carries optical energy.
When the link becomes too long, the fiber will attenuate the
light waves traveling down it so that the light waves cannot be
distinguished from noise. Today the range goes to tens of
kilometers before amplification is necessary.
Even with the highest-intensity light sources and the
lowest-loss fibers, the light waves finally become so weak or dim
from absorption and scattering that they must be regenerated. At
this
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 17
become so weak or dim from absorption and scattering that they
must be regenerated. At this point, a repeater must be placed in
the circuit. This device consists of a light receiver, pulse
amplifier, regenerator, and a light source. Together they rebuild
the pulses to their former level and send them on their way.
-
The transceiver is one of the connectors mostly used in
connecting the equipment to the network via fiber. It converts the
electrical signal to laser form and vice versa. The transceiver is
of the type SFP or Small Form factor pluggable. The fiber will
connect to this SFP using LC connectors. This SFP normally has two
fibers, one for transmission and the other for reception.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 18
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Two types of light wave modulations are possible, analog or
digital .
In analog modulation, the intensity of the light beam from the
laser or LED is varied continuously. That is, the light source
emits a continuous beam of varying intensity. This will typically
be used for the video overlay service.
In digital modulation, conversely, the intensity is changed
impulsively, in an on/off fashion. The light flashes on and off at
an extremely fast rate. In the most typical system Pulse-Code
Modulation PCM the analog input signals are sampled for wave
height. For voice signals, this is usually at a rate of 8000 times
a second. Each wave height is then assigned an 8-bit binary number
that is transmitted in a series of individual time slots or slices
to the light source In transmitting this binary number a 1 can be
represented as a pulse of lightlight source. In transmitting this
binary number, a 1 can be represented as a pulse of light and a 0
by the absence of light in a specific time slice.
Digital modulation is far more popular, as it allows greater
transmission distances, with the same power, than analog
modulation.Noise (attenuation) has a bigger impact onto analog
transmission. Therefore the components that transmit using analog
modulation will typically have a bigger power budget to
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 19
that transmit using analog modulation will typically have a
bigger power budget to compensate.
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A significant factor in any fiber optic system installation is
the requirement to interconnect fibers in a low-loss manner. These
interconnections occur at the optical source, at the photo
detector, at intermediate points within a cable where two fibers
join, and at intermediate points in a link where two cables are
connected. The technique selected for joining the fibers depends on
whether a permanent bond or an easily demountable connection is
desired. A permanent bond (usually within a cable) is referred to
as a splice,
h d t bl j i t t th d f bl i k t whereas a demountable joint at
the end of a cable is known as a connector.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 20
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In fiber, there must be good alignment in the connectors and in
the fiber joining or splices. A bad alignment will have high
attenuation. Today, with modern equipment, the alignment in the
splices is done automatically. Back then; this was done by the
operator, using a special microscope which could have less
perfection compared to the automatic one, resulting in high
attenuation.
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Edition I2.0
Section 1 Module 1 Page 21
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Optical Return Loss (ORL) is caused by the imperfect alignment
of the connection. The PC has greater Optical Return Loss than the
APC, in other words, more back reflection.
The fiber connectors also have ORL.
Optical return loss is caused by several factors. It can be
caused due to collisions of photons with impurities in the fiber,
some are reflected back. Physical contact splices also cause huge
optical return losses.huge optical return losses.
ORL can even damage the transmitter when the signal is powerful,
for example video in overlay.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 22
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Now, lets discuss the properties of a connector and its
different types. The connectors have a loss of around 0.3dB. The
connectors are classified by the housing type and the polishing
type. The slide displays various polishing types and the return
loss of each with the corresponding housing colors.APC is the
Angle-Polished Contact with an ORL of -60dBSPC is the
Straight-Polished contact with an ORL of -40dBSPC is the
Straight-Polished contact with an ORL of -40dBPC or Physical
Contact has an ORL of -30dB and UPC or Ultra-Polished Contact has
an ORL of -40dB.
Which one to use will depend on the ORL desired.
Here you will see the different housing types such as FC LC SC
MT and so on Which one toHere you will see the different housing
types such as FC, LC, SC, MT, and so on. Which one to use will
depend on the size and mating cycles which is the number of times
connect and disconnect occurs before it introduces a higher loss
greater than 0.3 dB. The connector type will be defined by
indicating the housing type and polishing type. The first two
letters indicate the housing type and the letters after a forward
slash indicate the polishing type.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 23
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Now lets discuss the different types of connectors.
As weve seen in the previous slide, the different housing types
are
FC (Ferrule Connector) which has a screw type coupling, SC
(Square Connector) which has a snap or push-pull type coupling and
LC (Little Connector) which also has a snap or push-pull type
coupling used in SFPs.
The MT-RJ (Mechanical Transfer Registered Jack) which has an
RJ-45 structure and similar to the LC has a snap or push-pull type
coupling with RJ-45 type latching. Unlike the rest of the
connectors it uses rectangular ferrules instead of round ones.
ST (Straight Tip) connectors have a keyed bayonet-push-in &
twist coupling type like a BNC.
The MU (Miniature Unit coupling) connector is similar to the SC
but is miniature, sometimes called small SC called small-SC .
Two of these occupy the space of an SC. This has widespread
usage in WDMs since there are a lot of fiber connections within
small areas, twice the port density on a face plate.
There are no Female connectors, so Couplers have to be used,
connecting two pieces of fiber, ending in a male connector.
A coupler will make a connection with a loss of around
0.6dB.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 24
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Mechanical splices just lay the two carefully cut ends next to
each other on a special sleeve and clamp them in place. The
alignment can be improved by passing light through the junction and
then making small adjustments to maximize the signal. Mechanical
splices take trained personnel about 5 minutes, and result in a 10
percent light loss.
Two pieces of fiber can be fused or melted to form a solid
connection. A fusion splice is l t d i l d fib b t h ll t f tt
tialmost as good as a single drawn fiber, but even here, a small
amount of attenuation occurs.
For both kinds of splices, reflections can occur at the point of
the splice, and the reflected energy can interfere with the
signal.
Fiber-optic cables might have to be spliced together for a
number of reasonsfor example, to realize a link of a particular
length. Another reason might involve backhoe fade, in which case a
fiber-optic cable might have been ripped apart due to trenching
work. The network installer might have in his inventory several
fiber-optic cables, but none long enough to satisfy the required
link length. Situations such as this often arise because cable
manufacturers offer cables in limited lengthsusually 1 to 5 kms. A
link of 10 kms can be installed by splicing several fiber-optic
cables together. The installer can then satisfy the distance
requirement and avoid buying a new fiber-optic cable. Splices might
be required at building entrances, wiring closets, couplers, and
literally any intermediate point between a transmitter and
receiver.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 25
Connecting two fiber-optic cables requires precise alignment of
the mated fiber cores or spots in a single-mode fiber-optic cable.
This is required so that nearly all the light is coupled from one
fiber-optic cable across a junction to the other fiber-optic cable.
Actual contact between the fiber-optic cables is not mandatory.
-
This is an example of splice enclosure, composed of a box, cable
entrances, splice trays, [5] splice-holder, and
splice-protectors.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 26
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This is the inside view of a Splice tray. This could be in the
basement of a building. As you can see, the Fiber tube is coming
from the network and the patch cords are going to each individual
subscriber.
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Edition I2.0
Section 1 Module 1 Page 27
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Edition I2.0
Section 1 Module 1 Page 28
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The ISAM-PON (Passive Optical Network) node has the same usage
as the Litespan (xDSL) (x Digital Subscriber Line) and the
ISAM-xDSL, in other words, it is used to transmit the Triple Play
Services to the subscriber in the access side, but via Fiber. The
PON node (as well as the Litespan and ISAM) is the last step of
transmission between the Service providers and the subscribers.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 29
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Lets first look at the whole picture. The ISAM-PON (GPON) node
has the same usage as the Litespan (xDSL) and ISAM-xDSL. In other
words, it is used to transmit the Triple Play Services to the
subscriber on the access side, but via Fiber. The GPON node (as
well as the Litespan and ISAM nodes) is the last step of
transmission between the Service providers and the subscribers.
Why is this? Why not? Fiber offers an extremely high bandwidth
with no crosstalk and no interference. It is a high quality
transmission media.
But why are we delivering fiber to the user now if we have the
different XDSL flavors to transmit the Triple Play service?There
are two reasons to deliver Fiber To The User/Fiber To The Home
(FTTU or FTTH):
The services that will be offered to the subscriber will require
more bandwidth, with one of them being the High Definition TV. One
HD 1080p) channel in MPEG4 (which has been used since 2008)
occupies 10Mb/s to 11Mb/s (17M with 5 audio channels or a 3D
channel 36M) compared to a normal channel with 3.2Mb/s. Operators
dont need to worry about the bandwidth required for the future
services to come. They are future safe for many years In the future
they can increase the bandwidth by changing the Tx and Rx while
leaving the fiberyears. In the future, they can increase the
bandwidth by changing the Tx and Rx while leaving the
fiberinstallation as is. The most expensive job is changing the
wiring installation.
The other reason is that the lasers, fibers, connectors, and
devices to splice the fiber are more precise and cheaper than many
years ago.
In the graph we also see the different technologies used in the
copper pair along with the fiber, which indicates bandwidth versus
distance (or the distance between the house and the node). Most of
us will probably have one of the ADSLs. The first ADSL is roughly 8
Mb/s and with a distance of approximately 3 to 4 km. After that
distance, those 8 Mb/s drop as the distance increases. If the
distance is less than 1.5 km, then ADSL2+ can be used, with a
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 30
those 8 Mb/s drop as the distance increases. If the distance is
less than 1.5 km, then ADSL2 can be used, with a 24 Mb/s bandwidth.
However, if that copper pair length is less than 1 km, then VDSL2
can be used with a 52 Mb/s bandwidth. Typically, VDSL2 is used most
often in FTTB or C (Fiber To The Building or Curb) deployment. This
brings the node closer to the subscribers premises by placing it
inside the building (for example, a parking basement) or curb. But
look at the fiber. It can provide service at 100 Mb/s for a 20 km
distance.
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Where exactly is the GPON technology located?
The GPON spans from the GPON node to the NT in the subscribers
home. More precisely, it is from the GPON part of the LT to the
GPON part of the NT. Therefore, both these units have to comply
with the GPON standard.
Also, as the name implies (GPON: PASSIVE Optical Network) it is
a passive network, in other words, there are no power devices (no
electronics) within the network. This is a reduction in the
OPEX---operating and maintenance costs. The only elements which are
active are the Equipment side(LT) and the subscriber y q p (
)side(NT).
Also as shown in the diagram the GPON is a Point-Multipoint
layout. One port of the GPON node is divided in multiple users.
This reduces the electronics: one transceiver for a number of
NTs.
It also reduces the number of fibers
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 31
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A Passive Optical Network (PON) consists of an optical line
terminator (OLT) located at the Central Office (CO) and a set of
associated optical network terminals (ONTs) located at the
customers premise. Between them lies the optical distribution
network (ODN) comprised of fibers and passive splitters or
couplers.
The application of PON technology for providing broadband
connectivity in the access network to homes, multiple-occupancy
units, and small businesses commonly is called fiber-to-the-x. This
application is given the designation FTTx. *Here x is a letter
indicating how close the fiber endpoint comes to the actual user.
This is illustrated in the drawing. Among the acronyms used in the
technical and commercial literature are the following:g y g
*FTTB fiber-to-the-business or building, refers to the
deployment of optical fiber from a central office switch, directly
into an enterprise or apartment building.
FTTC fiber-to-the-curb, describes running optical fiber cables
from central office equipment to a communication switch located
within 1000 ft (about 300m) of a home or enterprise. Coaxial cable,
twisted pair copper wires (e.g. for DSL), or some other
transmission medium is used to connect the curbside equipment to
customers in a building.
FTTH fiber-to-the-home, refers to the deployment of optical
fiber from a central office environment directly into a home. The
difference between FTTB and FTTH is that, typically, business
demands larger bandwidths over greater part of the day than do home
users. As a result, a network service provider can collect more
revenues from FTTB networks and h h i ll i h f FTTH kthus recover
the installation costs sooner than for FTTH networks.
FTTO fiber-to-the-office, is analogous to FTTB in that an
optical path is provided all the way to the premises of a business
subscriber.
FTTP fiber-to-the-premises, has become the prevailing term that
encompasses the various FTTx concepts. Thus FTTP architectures
include FTTB and FTTH implementations. An FTTP network can use
BPON, EPON or GPON technology.
FTTU fiber-to-the-user, is the term used by Alcatel-Lucent to
describe their products for FTTB and FTTH applications.*
As we see in the picture, the shaded part is the GPON. The fiber
can terminate in an ONT, in the subscribers premises, or in an ONU
(Optical Network Unit-it has several ports, a port per subscriber)
where from here copper pair using VDSL2 or m lti ADSL ill connect
to the s bscribers VDLS2 or m lti ADSL CPE This co ld be done for e
ample to re se the copper
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 32
multi-ADSL will connect to the subscribers VDLS2 or multi-ADSL
CPE. This could be done, for example, to reuse the copper pairs
which exist in the building.
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There are two basic FTTH technologies as shown. The first is a
one to one relationship (P2P:Point to Point). In other words, each
port from the equipment is one subscriber.
The second one is most often used in the GPON method. It is a
Point to Multipoint connection where one port of the equipment can
have up to 128 subscribers, using splitters*. This results in less
space, fewer fibers, and a smaller duct size. Since one fiber is
used both to transmit and receive, there are two lambdas, one for
upstream at 1310 nanometers), and the other is for *downstream (at
1490 nanometers).
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 33
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Feeder section: stretch from CO (Central Office) to first
splitting point
The OSP (OutSide Plant) of a FTTH network typically looks like
this with approximate distances.
Independant of what kind of technology will be used, there will
always be a need to transmit the signals from the CO (Central
Office) to the CPE (Customer Premises Equipment).
In a Fiber Optic network, the infrastructure needs to be in
place in order to carry the signals to the end user.
The FTTH infrastructure is not much different from a country
road map.
We need highways, secondary roads, and driveways to the house.
In this case, we have the feeders, the distribution, and the
drops.
We start in the POP (Point of Presence), where the GPON is
located.
The Feeder section is a stretch from the CO to the first
splitting point.
The Distribution section is where the fiber is split in a ratio
of 1:4, 1:8 or 1:16.
Finally, the Drop is where the fiber is again split, in a ratio
of 1:4, 1:8, or 1:16, and connected to the y p g psubscribers CPE
(in this case the ONT).
The combination of the two splits will give a total of 32, 64,
or 128 subscribers for one fiber in the Feeder section.
This architecture could change by omiting the Secondary
Flexibility point.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 34
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Depending on the capabilities of the optical transmitters and
receivers, the GPON recommendation specifies maximum transmission
distances of 10 or 20 km. For a GPON the minimum number of
splitting paths is 64.
---
The 60 km max. distance is also referred to as a logical
distance: this is related to the ranging procedure (see further),
where an ONT (Optical Network Terminal) will add some equalisation
delay depending on the distance the ONT is away from the OLT
(Optical Layer Transport). This leads to all ONTs being virtually
away 60 km from the OLT.
About the split: the standards already took care of having a
split of up to 128 subscribers, which is sometimes referred to as a
logical split.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 35
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The nominal line rates are specified as 1.25 Gbps (1244.160
Mbps) and 2.5 Gbps (2488.320 Mbps) in the downstream direction, and
155 Mbps, 622 Mbps, 1.25 Gbps, and 2.5 Gbps in the upstream
direction. The data rates can be either symmetrical (the same rate
in both directions) or asymmetrical, with higher rates being sent
downstream from the OLT to the ONTs.
In practice, all vendors implement only 2.5 Gbps in downstream
and 1.25 Gbps in upstream.
The wavelengths are specified to be in the range 1480 to 1500 nm
for downstream voice and data traffic and The wavelengths are
specified to be in the range 1480 to 1500 nm for downstream voice
and data traffic and 1260 to 1360 nm for its corresponding upstream
traffic. Thus, the median values are the standard 1490nm and 1310nm
wavelengths as used in BPON and EPON systems. In addition, the
wavelength range 1550 to 1560 nm can be used for downstream video
distribution.
Video can be transported in two different ways:
1. Video overlay: a separate (3rd party) device, called V-OLT
(Video OLT), using a separate wavelength (lambda) to modulate the
analogue video directly onto the PON system. The V-OLT will use a
analogue modulation technique.
2. IPTV system: the digital video signals (encoded further in
the network) will be sent as data over the PON system, using the
same wavelength, in this case 1490 nm, since video is typically
only sent in downstream direction.
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Edition I2.0
Section 1 Module 1 Page 36
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Section 1 Module 1 Page 37
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The connectorized splitters will be a lot more flexible, but
they come at a extra cost in attenuation, some 0.6 dB extra
compared to spliced variant.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 38
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These are the typical losses in fiber.
Even though this is fiber it still has a loss per km usually
around 0.42db/km. The aging also adds some loss which usually is
calculated around 1dB.
The connectors and splices also add more losses: 0.3dB per
connector and 0.1dB per splice.
The splitter is the component which is responsible for the
greatest loss since it splits the The splitter is the component
which is responsible for the greatest loss since it splits the
light. A one to two ratio will have a 3dB loss since it splits the
light in two.
The other major loss is caused by the impurities inside the
fiber but only at certain wavelengths. This is caused by scattering
and infrared absorption which effects mostly the lowest and highest
wavelengths. This is why all equipment using fiber will use
wavelengths in certain ranges called 2nd and 3rd window; this point
was explained previously in the graph attenuation vs
wavelength.
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Edition I2.0
Section 1 Module 1 Page 39 Section 1 Module 1 Page 39
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Here we see all the components that will introduce losses inside
the PON network. The sum of these losses will determine the
distance between the GPON node and the CPE (Customer Premises
Equipment), called the ONT (Optical Network Termination).
The biggest loss in a PON network is the splitter. It will
depend on whether we have a 32, 64, or 128 split. With a split of
64, there is a loss of 18dB (10 log 64). Since it is not a perfect
split, there is an extra loss of 1 to 3dBsto 3dBs.The other loss
would be caused by the fiber, which depends on the lambda used, as
seen previously in the graph and the quality of the fiber. Since
there are two lambdas (plus an optional one), the worst case is
used which is the upstream lambda of 1310 nano meters with a loss
of 0.42dB/km.
The connectors which connect the fiber to the equipment and the
ONT will have a 0.3dB loss per connector. There could be more, for
example in the optical distribution frame, both at the Central
Office and the Customer Premises.Any splices which join different
fiber sections present through out the path will introduce a 0.1dB
loss per splice.The WDM (Wave Division Mux) coupler will only be
needed if video overlay is used. This will add a 1.3 dB loss.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 40
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Issue: the optical power budget
The loss budget requirement for the PON, based on ITU
Recommendation G.983.4, is 22 dB total loss budget for Class B PON
and 27 dB for Class C PON. What differentiates Class B and Class C
PON is the power of the laser used and, marginally, the quality of
the optical components. This loss budget is really tight,
especially when high-port-count splitters are used in the design.
The splitters in a PON cause an inherent loss because the input
power is divided between several outputs. Splitter loss depends on
the split ratio and is about 3 dB for a 1 x 2 splitter, increasing
by 3 dB each time the number of outputs is doubled. A 1 x 32
splitter has a
litt l f t l t 15 dB Thi l i f b th d t d t i l C bi th l
splitter loss of at least 15 dB. This loss is seen for both
downstream and upstream signals. Combine the losses of the WDM
coupler, splices, connectors and fiber itself, and it is easy to
understand why a precise bidirectional measurement of end-to-end
optical loss at the installation is a must.
In addition to the optical loss, the end-to-end link optical
return loss (ORL) is very important to measure. Undesirable effects
of ORL include:
Interference with light-source signals
Higher bit error rate in digital systems
Lower system optical signal to noise ratio Lower system
optical-signal-to-noise ratio
Strong fluctuations in the laser output power
Permanent damage to the laser
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 41
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The loss budget requirement for the PON, based on ITU
Recommendation G.983.4, is 22 dB total loss budget for Class B PON
and 27 dB for Class C PON. What differentiates Class B and Class C
PON is the power of the laser used and, marginally, the quality of
the optical components. This loss budget is really tight,
especially when high-port-count splitters are used in the design.
The splitters in a PON cause an inherent loss because the input
power is divided between several outputs. Splitter loss depends on
the split ratio and is about 3 dB for a 1 x 2 splitter, increasing
by 3 dB each time the number of outputs is doubled. A 1 x 32
splitter has a splitter loss of at least 15 dB. This loss is seen
for both downstream and upstream signals. Combine the losses of the
WDM coupler, splices, connectors and fiber itself, and it is easy
to understand why a precise bidirectional measurement of end-to-end
optical loss at the installation is a and it is easy to understand
why a precise bidirectional measurement of end-to-end optical loss
at the installation is a must.
In addition to the optical loss, the end-to-end link Optical
Return Loss (ORL) is very important to measure. Undesirable effects
of ORL include:
Interference with light-source signals
Higher bit error rate in digital systems
Lower system optical-signal-to-noise ratio
Strong fluctuations in the laser output power Strong
fluctuations in the laser output power
Permanent damage to the laser
Path penalty: compensates for dispersion over certain distances.
More info can be found on:
http://en.wikipedia.org/wiki/Dispersion_%28optics%29Here we see the
calculation for the 28dB power budget for class B+ laser.Looking at
the downstream, there is a minimum power transmission of +1.5 dB
with a -27 dB sensitivity on the reception side and a 0.5dB path
penalty. This will give a power budget, also called loss budget of
28 dB.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 42
In the upstream, there is a minimum of +0.5dB as power
transmission, a -28dB sensitivity on the reception side, and a
0.5dB path penalty. This will also give a power budget of 28dB.
The path penalty is caused by dispersion over certain
distances.
-
A system is limited in the distance you can send signals and the
maximum number of times you can split the signal to go to different
subscribers. The main problem is usually that the signal level
drops too low to be usable. Other considerations sometimes
dominate.
Fiber loss per km is 0.25 dB (1550 nm) to 0.4 dB (1260 - 1360
nm)
As seen before, every time the signal is split two ways, half
the power goes one way and half goes the other. So each direction
gets half the power, or the signal is reduced by
10log(0.5)=3 dB. In reality we see that the loss is closer to
3.5 dB.
Broadcast analog video actually sets the distance (see next
slide)
Class A 5-20 dB
Class B 10-25 dB
Class C 15-30 dB
The power budget available (for data) on a particular PON
depends on the class of laser used: e.g. for class B+ it is 28
dB
The power budget available (for video) on a particular PON is
lower than this.p g ( ) p
We see an example of calculating the maximum distance between
the GPON node and the ONT. The result is 24 km, considering a power
budget of 28dB and all the losses shown, which includes a 1dB loss
due to fiber aging.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 43
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The same power calculation for the class B+ is used for the
class C+ laser.
Path penalty: compensates for dispersion over certain distances.
More info can be found on:
http://en.wikipedia.org/wiki/Dispersion_%28optics%29
Since a class C+ can be used to reach longer distances, we add
some additional path penalty (1dB, compared to 0.5dB with B+).
(**) ONT sensitivity in C+ mode with FEC (which gives a gain of
3dB, so a virtual minimum of -30dB). The FEC could have been added
in the class B+ power budget calculation.
FEC (Forward Error Correction): Can be activated per PON in the
downstream and per ONT in the upstream. Since it corrects
Transmitted data there is a gain of 3dB which means an increased
split, and longer range.
There are very slight disadvantages which are: Reduced capacity
(minimum) available for service transport that causes a need for
additional header for
the FEC. There will be a very slight delay to process the
FEC.
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Section 1 Module 1 Page 44
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Section 1 Module 1 Page 45
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A system is limited in the distance you can send signals and the
maximum number of times you can split the signal to go to different
subscribers. The main problem is usually that the signal level
drops too low to be usable. Other considerations sometimes
dominate.
Fiber loss per km is 0.25 dB (1550 nm) to 0.4 dB (1260 - 1360
nm)
Every time the signal is split two ways, half the power goes one
way and half goes the other. So each direction gets half the power,
or the signal is reduced by
10log(0 5)=3 dB 10log(0.5) 3 dB.
Broadcast analog video actually sets the distance (see next
slide)
---
Class A 5-20 dB
Class B 10-25 dB
Class C 15-30 dB
The power budget available (for data) on a particular PON
depends on the class of laser used: e.g. for class B+ it i 28 dBit
is 28 dB
The power budget available (for video) on a particular PON is
lower than this.
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Section 1 Module 1 Page 46
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This is a rough estimation on maximum range per
splitter-configuration using a B+ laser. Better results are
achieved using a C+ laser.
Splitters are the main part of the loss in the link between OLT
and ONT. We have to consider that a split of 1:2 will have a 3dB
loss or we can calculate the loss by this formula: 10log the split
number. For example, a split of 64 will have a loss of 18 dB.
Also, we have to take into account the attenuation of fiber per
Km (around 0.3, 0.4dB/Km), the number of splices in the fiber (each
splice has a 0.1dB loss), and the number of connectors (a 0.3dB
loss per connector). We will have 2 connectors minimum, one in the
OLT and another one in the ONT, but can have more, like in the
distribution frame inside the CO and others inside the building of
the subscriber. Considering all this, a table is shown to indicate
roughly the distance between OLT and ONT in function of the
splitters used.
A splitter configuration can be one splitter or several
splitters in cascade.
The splitter configuration 1:8 can be one splitter of 1:8, or
one splitter of 1:4 and one splitter of 1:2.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
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Section 1 Module 1 Page 47
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According to the GPON Service Requirements (G.984.1), a GPON
must be a full-service network, which means that it should be able
to carry all service types.
These include 10- and 100-Mbps Ethernet, legacy analog
telephone, digital T1/E1 traffic (I.e., 1.544 and 2.028 Mbps),
155-Mbps asynchronous transfer mode (ATM) packets, and higher-speed
leased-line traffic.
AAL2 and AAL5 are indicated between square brackets, as they are
optional (and actually no-one is implementing ATM)implementing
ATM)
AAL = ATM Adaptation Layer
AAL2 = adaptation for e.g. voice (CBR style of connection)
AAL5 = adaptation for data
We can use GEM to encapsulate either data traffic or voice over
the optical access network between ONT and OLT, as shown in the
picture.
GEM t Eth t t ffi t t f d tGEM supports Ethernet traffic
transport for data.
GEM also provides a mechanism to map TDM traffic; for example to
carry voice from a PABX.
ATM is an alternative medium defined in the standard (but
actually no vendor is implementing ATM). In this case, voice is
mapped using Adaptation Layer 2 and data with Adaptation Layer
5.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
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Section 1 Module 1 Page 48
---
Depending on who you are talking to, people talk about Generic
Encapsulation Method or GPON Encapsulation Method.
-
GPON has a many benefits, but the shared medium also presents us
with some difficulties. Since we are using a point-to-multipoint
topology, a specific transmission mechanism has to be implemented
in order to benefit fully from this architecture.
In the downstream direction, the transmission is defined as
being broadcast. In other words, the same information is sent to
all connected ONTs. For security reasons, this information can be
encrypted. On top of that, the information contains a specific
destination to allow each ONT to decide whether to accept or reject
the packet.
The broadcast traffic is continuous, i.e., there is always a
signal on the fiber. We need to do this in order to allow the ONT
to synchronize with the central office.
As extra security, AES (Advanced Encryption Standard) could be
activated per service. OLT requests the encryption key to the ONT.
The ONT generates the key and sends it to the OLT and the OLT will
indicate to the ONT to activate the encryption. This encryption key
automatically changes every x-time (called churning).
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
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Section 1 Module 1 Page 49
-
In the upstream direction, the situation is a bit more complex.
We only have 1 fiber and all ONTs use the same wavelength (1310
nm)
Imagine a street with 64 houses. Each family uses a car to go
shopping on Saturday morning. Imagine they all leave whenever they
want without looking left or right. It is obvious that eventually
there will be accidents (collisions). The same scenario is true for
the GPON network (upstream)
How do we solve this problem ? Well, we install a policeman and
he decides when each family has access to the street.
Telecom-wise, the policeman will be the central office. The OLT
decides when each ONT can send traffic in the upstream
direction.
An important parameter in this decision process is the distance
between the ONT and the central office. We know the speed (1.25 G),
so if we know the distance, we can generate time windows in which
the ONTs can send information.
The process of determining the distance between ONT and OLT is
called distance ranging (during this time, the PON light on the ONT
will be blinking)
The process of determining timeslots for each ONT s called
access granting
Thats the concept behind TDMA : Time Division Multiple Access
(using different timeslots on the same medium)
So TDMA is implemented by using these three factors:
The distance from the ONT to the OLT must be measured.
Then timeslots are allocated to the ONT according to the
distance.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
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Section 1 Module 1 Page 50
The ONTs send data upstream only in their assigned timeslot.
-
To better understand the concept of logical distance we are
going to review the concept of distance ranging and why we need it
in GPON technologies.
In normal network conditions, ONTs are located at different
distances from the OLT. This results in transmission phase
differences and the OLT may receive overlapping transmissions from
the different ONTs. The PON concept has a specific method for
synchronising the ONT transmissions, called ranging. First, an ONT
synchronises itself to the downstream frame headers and waits for
the ranging window to open. When the window opens, the network
enters into the ranging procedure, during which the delay and phase
differences b t th OLT d ll ti ONT d t i d A lt th ONT dj t th i t
i i h between the OLT and all active ONTs are determined. As a
result, the ONTs adjust their transmission phases and grants
accordingly.
The overall ranging scheme is presented in the picture above.
The ranging is operated by the OLT, which opens a ranging window
between configurable time periods. This means that the OLT sends a
ranging grant and stops the traffic in the network and waits for
the ONTs to send their ranging PLOAMs. The ranging window should be
large enough to cover propagation and processing delays of all the
ONUs, including the farthest ONU. The window size can be programmed
to support transport distances up to 20 kilometres (B-PON).
During the ranging procedure, each active ONU receives a PON-ID
from the OLT, which uses the IDs to send data to each ONT
individually. Moreover, the OLT measures the arrival phases of the
ONU ranging cells, calculates the required equalisation delays and
communicates the information to the ONTs. The ONTs adjusts their
transmission phases according to the determined values. After
initialisation, each active ONT can transmit data according to the
given grants.
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Section 1 Module 1 Page 51
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This shows how ranging is done.
1 The P-OLT sends out a Ranging-Grant message on the PON.
2 The newly connected ONT listens to this message and processes
it (this takes some time).
3 The ONT sends an acknowledgement to the P-OLT, including the
time needed to process the message.
4 The P-OLT calculates the time it took for the ranging grant to
reach the ONT (roundtrip delay minus the process time (t) divided
by 2, assuming the result is 75 s.
Based on the speed of light in fiber, which is 200,000 km/s, the
distance of the ONT can be calculated resulting in the P-OLT
assigning the corresponding equalization delay to the ONT.
Assigning an equalization delay to each ONT makes all ONTs
virtually located at the same distance.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 52
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The GPON frame format is specified as part of ITU-T
recommendation G.984.3: GTC GPON transmission convergence.
This recommendation is equivalent to layer 2 (the data
transmission layer) in the OSI reference model, and besides the
GPON frame format also describes the media access control protocol,
the ranging scheme, operations and maintenance processes, and the
information encryption method.
The picture shows the GPON frame format, which has a fixed 125-s
length. The frame consists of a physical control block (PCB) and a
payload composed of a pure ATM segment and a GEM segment. The PCB
section contains the physical layer overhead information to control
and manage the network. For example this is where the OLT grants
the ONTs to transmit upstream. Note that the optional ATM segment
is defined for compatibility, but its not used by any vendor.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 53
-
For the downstream, we have Continuous mode operation. A signal
is always present, even when no data is transmitted. So the laser
is always on, but can be turned off administratively. We have to
consider two elements:
continuous mode transmitter, no need to adapt power level
continuous mode receiver, clock extraction
P l l id tiPower level considerationIn continuous mode
operation, the power level is high enough to reach all subscribers.
Each ONT gets this signal, although attenuated differently because
they all are at different distances from the central office.
The attenuation shouldnt be too big, so there still is enough
power in the signal left. The attenuation shouldnt be too small
either, because then the power level of the signal going out of the
fiber would be too big and this might damage the optical
receiver.
When the power level is in the dynamic range of the receiver,
the ONT can easily do the clock extraction and pick up the data
destined for it.p p
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 54
-
In the downstream direction the PCBd (physical control block for
frames going downstream) contains the following information:
a 4-byte frame synchronization field (Psync).
a 4-byte segment (Ident) that contains an 8-kHz counter, a
downstream FEC status bit, an encryption key switchover bit, and 8
status bits reserved for further use.
a 13-byte downstream physical layer OAM (PLOAMd) message, which
handles functions such as OAM-related alarms or threshold crossing
alertsrelated alarms or threshold crossing alerts.
a 1-byte bit interleaved parity (BIP) field, used to estimate
the bit error rate.
a 4-byte downstream payload length indicator (Plend), which
gives the length of the upstream bandwidth (US BW) map and the size
of the ATM segment. The Plend field is sent twice for extra
redundancy and error robustness.
the N x 8-byte US BW map allocates N transmission time slots to
the ONTs.
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Section 1 Module 1 Page 55
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The US BW map contains N entries associated with N time-slot
allocation identifications for the ONTs. As the picture shows, each
entry in the US BW map or access structure consists of:
a 12-bit allocation identifier (AllocID) that is assigned to an
ONT (will represent services on the ONT, see later)
twelve flag bits that allow the upstream transmission of
physical layer overhead blocks for a designated ONT (see slide p.
43)
a 2-byte start pointer (SStart) that indicates when the upstream
transmission window starts This time is a 2 byte start pointer
(SStart) that indicates when the upstream transmission window
starts. This time is measured in bytes; the beginning of the
upstream GTC frame is designated as time zero.
a 2-byte stop pointer (SStop) that indicates when the upstream
transmission window stops.
a 1-byte CRC that provides a 2-bit error detection and 1-bit
error correction on the bandwidth allocation field
---
The AllocID identifies the T-CONT (Traffic container)
The Port-ID identifies the queue on the ONTThe Port-ID
identifies the queue on the ONT
---
With a split to 128 users, this actually means 32 alloc-ids can
be assigned to a single ONT!
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Edition I2.0
Section 1 Module 1 Page 56
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This slide gives an example of time-slot allocations for three
ONTs. Here there are three entries in the US BW map field. The
AllocID of the ONTs are 1, 2, and 3 for ONT1, ONT2, and ONT3,
respectively. The center part of the picture shows start and stop
time slots listed in the downstream US BW map field during which
the various ONTs are allowed to transmit. The lower part of the
picture shows the general format of the ensuing upstream
information stream form the three ONTs. An appropriate guard time
is placed between packets from different ONTs.
---
So a GPON system allocates time slots for each ONT to ensure
that the data of each ONT is received independently at the OLT.
A system of pointers is used. The PCB holds the grant
bytes/messages, which defines which ONU should use which
time-slots/bytes in the upstream frame.
This allocation can change frame after frame, so bandwidth is
allocated dynamically.
downstream framegrantg
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ONU1 ONU2 ONU3 ONU4 ONU5
r s t
upstream frame
u v w x y z
-
On the upstream we have Burst mode operation. Theres only a
signal when an ONT needs to send information. A guard time of 26 ns
is needed between 2 consecutive bursts. We have to consider two
elements: burst mode transmitter and burst mode receiver.
The transmitter operates in burst mode. It has three modes: no
light, logic 0, and logic 1. In contrast to point-to-point systems,
ONUs which are not permitted to transmit must turn off their
lasers.
There is a burst mode receiver resync on every single burst
coming in.
Power level considerationPower level considerationAssume all
ONTs send their upstream data using the same power level. Due to
the fact they are all at different distances, the attenuation
imposed will be different for all of them. It even is possible that
the power level of a logic 0 from a near ONT exceeds the power
level of a logic 1 from a far ONT! So the receiver at the OLT has a
hard time to distinguish a logical 1 from a logical 0. In order to
do that, the receiver has to measure the power levels of a 0 and a
1 (amplitude ranging), and adapt the detection thresholds
accordingly. And this has to happened for each burst coming in!
Thats the reason why every burst of information is prepended with
some bits/bytes referred to as burst overhead (BO).
---
The transmitter operates in burst mode. It has three modes: no
light, logic 0 and logic 1. In contrast to point-to-point systems,
ONTs which are not permitted to transmit must turn off their
lasers. At the input to the OLTs receiver, the light corresponding
to a logic 0 from a near ONU could well exceed the light
corresponding to a logic 1 from a far ONU. (chapter 60/4 of
Telecommunications engineers reference book, second edition)
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 58
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Upstream GPON traffic consists of successive transmissions from
one or more ONTs. As the picture on previous slide illustrates, the
particular sequence of frames is based on the transmission
time-slot allocations developed by the OLT. To allow proper
reception of the individual burst-mode frames, a certain amount of
burst-overhead is needed at the start of an ONT upstream burst. The
slide on this page shows the format of an upstream frame, which
consists of up to four types of PON overhead fields and a
variable-length user data payload that contains a burst of
transmission. The upstream header fields are the following:
the physical layer overhead (PLOu) at the start of an ONT
upstream burst contains the preamble, which ensures proper physical
layer operation (e.g., bit and byte alignments) of the burst-mode
upstream link.
the upstream physical layer operation, administration and
management (PLOAMu) field is responsible for management functions
such as ranging, activation of an ONT, and alarm notifications. The
13-byte PLOAMu contains the PLOAM message as defined in G.983.1 and
is protected against bit errors by a cyclic redundancy check (CRC)
that uses a standard polynomial error detection and correction
code.
the dynamic bandwidth report (DBRu) field informs the OLT of the
queue length of each AllocID at an ONT. This allows the OLT to
enable proper operation of the dynamic bandwidth allocation
process. The ONT. This allows the OLT to enable proper operation of
the dynamic bandwidth allocation process. The DBRu is protected
against bit errors by a CRC.
Transmission of the PLOAMu, PLOu, and DBRu fields are optional
depending on the downstream flags in the US BW map.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 59
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GPON encapsulation method (GEM) is used to accommodate all types
of services (e.g. ATM, TDM, and Ethernet) efficiently. This method
is based on a slightly modified version of the ITU-T recommendation
G.7041 Generic Framing Procedure, which gives the specifications
for sending IP packets over SONET or SDH networks.---
The GPON encapsulation method works similar to ATM, but is uses
variable-length frames instead of fixed-length cells as in ATM.
Thus, GEM provides a generic means to send different services over
a GPON. The encapsulated payload can be up to 1500 bytes long. If
an ONT has a packet to send that is larger than 1500 bytes, the ONT
must break the packet into smaller fragments that fit into the
allowed payload length. The destination equipment is responsible
for reassembling the fragments into the original packet format.
The picture above shows the GEM segment structure, which
consists of four header fields and a payload that is L bytes long.
The header fields are the following:
A 12-bit payload length indicator (PLI) that gives the length in
bytes of the GEM-encapsulated payload.
A 12-bit port identification number that tells which service
flow this fragment belongs to.
A 3-bit payload type indicator which specifies if the fragment
is the end of a user datagram, if the traffic flow is congested, or
if the GEM payload contains OAM information.
A 13-bit cyclic redundancy check for header error control that
enables the correction of two erroneous bits and the detection of
three bit errors in the header
A key advantage of the GEM scheme is that it provides an
efficient means to encapsulate and fragment user information
packets. The reason for using encapsulation on a GPON is that it
allows proper management of the multiple service flows from
different ONTs that share a common optical fiber transmission link.
The purpose of fragmentation is to send packets from a user
efficiently regardless of their size and to recover the original
packet format reliably from the physical layer transmission windows
on the GPON.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 60
g p y p y y
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Here is the whole solution using the GPON.
The NMS (Network Management System) is the operators interface,
called the AMS (Advance Management System), used to manage the
node.
At the right side of the picture are the different ONT
families.
For the Single Family Homes, there are the O (outdoor) and I
(Indoor) series. There are different ones depending on what type of
ports they have for the subscribers; 2 to 4 Ethernet ports (RJ45),
1 or 2 phone ports (RJ11) and some will also have an F connector (a
coaxial Siemens connector) for the analogue/digital ports (RJ11),
and some will also have an F connector (a coaxial Siemens
connector) for the analogue/digital TV.
The Business series ONTs are for the Small Medium Enterprises.
Besides having more Ethernet ports and phone ports compared to the
O/I series, they also have E1 (2Mbps) connections.
The M (Modular) series for the MDUs (Multi-Dwelling Units) will
have numerous (24) Ethernet and phone ports to connect various
subscribers.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 61
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Here is the HSI solution using the GPON. The subscribers
computer is connected to one of the ONTs Ethernet ports, or via
Wi-Fi if the ONT has it. Some operators will put a modem-router
between the ONT and PC so as to have router capabilities at the
subscribers premises, since most of the ONTs are only layer 2 (a
switch).
You see in the diagram that the traffic is inserted over GEM.
This is the encapsulated method used in GPON, GEM (GPON or Generic
Encapsulation Method). They are frames with its own header to
control the ONTs data, downstream and upstream. It is a variable
size frame, which depends what is being exchanged and on the number
ONTs available.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 62
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This is the solution for VoIP using the SIP protocol. In this
case, *the phone is connected to the Ethernet port of the ONT. It
is a phone which has intelligence and communicates with the SIP
proxy.
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Edition I2.0
Section 1 Module 1 Page 63
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In this scenario, the ONT can be considered as a the Media
Gateway for the *plain old telephone (black phone). This telephone
will be connected via its UTP (unshielded twisted pair) wire to the
RJ11 port of the ONT. In this case the ONT has the intelligence and
signals all telephone events (off-hook, on-hook, digits dialled,
etc) to the SIP proxy. The ONT will also apply all different types
of signals to the phone indicated by the SIP proxy; ringing
current, busy tone, call waiting tone, etc.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 64
-
In this scenario, the ONT can also be considered as the Media
Gateway for the plain old telephone (black phone), but this time
using the Megaco or H248 protocol.
This will be the same as the previous slide. The phone is
connected to the RJ11 port of the ONT. The ONT monitors all states
of the phone so as to indicate it to the softswitch, and also
applies all sorts of signals to the phone; ringing current, call
waiting tone, busy tone, etc.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 65
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Here is the solution for the IPTV service.
This is the same solution as the data solution, but instead of
connecting the ONT to the PC, it is connected to the STB (Set Top
Box). The (mpeg) encoded video leaves the video-server at the top
left as a stream of UDP packets, which are passed onto the OLT and
further sends the video stream onto the ONT and on to the STB.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 66
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This is the solution for the analogue or Digital TV (the DTV
Digital Terrestrial Tv) also called the outbandvideo.
In this case, the V-OLT receives an incoming 1550 wavelength
optical signal with embedded video channels from the cable TV
head-end equipment.
The video signal is amplified and split in the V-OLT, then
routed to a WDM.
The TV is connected to the ONT using a coaxial cable to the F
connector of the ONT.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 67
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Finally this is the solution for the Mobile Backhaul using the
GPON.
The functions of the B (business)-ONT are the following:
It Packetizes/De-packetizes the E1/DS1s from/to the base station
and in/out to the pseudowires.
It receives the clock reference from the OLT and forwards it to
the Base Stations through the E1/DS1 interfaces the E1/DS1
interfaces.
It Supports an Ethernet interface to backhaul Wimax and 3G data
traffic and provides the GPON connection.
These are the functions of the GPON OLT:
It Forwards traffic with the right QoS so delay and jitter is
minimized
It receives the clock reference in its BITS interface and
forwards it along the PON i If SDH GPS l k f i il bl l k
connection. If no SDH or GPS clock reference is available, a clock
recovery gateway co-
located with the OLT recovers the clock reference provided by
the RNC/BSC and feeds it into the OLT over the BITS interface.
The PWE3 (Pseudo Wire Emulation Edge to Edge) transports E1s
according to the Metro Ethernet forum (MEF)-8 which defines Circuit
Emulation Service over Ethernet.
Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01
Edition I2.0
Section 1 Module 1 Page 68
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Here we see the difference between GPON and EPON.
The first formal PON activity was initiated in the Spring of
1995 when a group of seven major network operators established the
Full Service Access Networks (FSAN) consortium. This groups goal
was to define a common standard for PON equipment so that equipment
vendors and operators could come together in a competitive market
for PON equipment. The result was first APON then BPON and around
2001 GPON with a downstream rate of of 2.5Gb/s and 1.25Gb/s
uplink.
On a parallel track, in early 2001, the IEEE established the
Ethernet in the First Mile (EFM) group, realizing the enormous
prospect that lies ahead in the optical access market. The EFM
standardized a 1.25 Gb/ssymmetrical system for Ethernet transport
only-EPON.
EPON dominates in Asia; Japan, South Korea and China with a mix
o