TAC42049_V1.1 SG Ed2.0 PDF_CE

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




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.


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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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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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


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


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,


cost of capital in the outside plant. The elimination (or reduction) of repeaters reduces maintenance, power, and operating expenses.

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


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.

Copyright 2013 Alcatel-Lucent. All Rights Reserved.TAC42049_HO01 Edition I2.0

Section 1 Module 1 Page 10

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



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.

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)



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.

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.



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.



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.



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.


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



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.



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



that transmit using analog modulation will typically have a bigger power budget to compensate.

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.



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.



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.



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.



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.



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.



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.



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.



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.



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



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.

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



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



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.

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).



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.



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.

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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.



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.



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.



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.


Section 1 Module 1 Page 39 Section 1 Module 1 Page 39

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.



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



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.



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.



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.



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)

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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.



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.



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.



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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).



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.



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.



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.



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.



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



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.



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

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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

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With a split to 128 users, this actually means 32 alloc-ids can be assigned to a single ONT!



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.

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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



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).

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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)



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.



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.



g p y p y y

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.



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.



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.



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.



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.



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.



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.



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.



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

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