GPON anritsufttx

7/30/2019 GPON anritsufttx

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Abstract

References

Advantages of FTTx and PON

Components of a PON System

PON Installation

PON Specifications

PON Measurement Parameters

PON Troubleshooting

Selecting the Right Testing Instrument

Conclusion

Testing fiber-to-the-X (FTTx) networks that include passive optical network (PON) architectures presents unique

challenges to service providers. During installation, the network must meet certain standards parameters. Once the FTTx

network is deployed, each subscriber connection requires additional tests to ensure service quality. Maintaining the

operation of the PON network and troubleshooting potential problems also requires specialized testing procedures and

equipment. Anritsu offers a complete line of FTTx and PON test equipment to ensure your networks will perform at their

highest levels. The MT9083 Series OTDRs are high performance, all-in-one testing tools to ensure the quality of your

optical fibers including PONs featuring up to a 1x128 split. The MT9090A with MU909011A Fault Locator module is the

first tester designed specifically for short fiber such as drop cables.

Table of Contents

Abstract

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B-PON

For more information on ongoing PON Recommendation activities, including Gigabit-PON (G-PON), please check the ITU-T Study

Group 15 website at: www.itu.int/ITU-T/com15

G.983.1 Broadband optical access systems based on Passive Optical Networks

Specifies an optical access system with symmetrical line rates of 155.520 or 622.080 Mbit/s and asymmetrical line rates of 155.520Mbit/s upstream and 622.080 Mbit/s downstream.

G.983.2 ONT management and control interface specification for B-PON

Specifies requirements for the OMCI, managed entities of a protocol-independent Management Information Base and protocol/detailed

messages for the ONT management and control channel.

G.983.3 A broadband optical access system with increased service capability by wavelength allocation

Adds an additional wavelength band to a G.983.1 B-PON to enable the distribution of unidirectional or bidirectional video broadcast or

data services.

G.983.4 A broadband optical access system with increased service capability using dynamic bandwidth assignment

Specifies the enhancements to a G.983.1 B-PON to allow the use of dynamic bandwidth assignment.

G.983.5 A broadband optical access system with enhanced survivability

Specifies protection features for a G.983.1 B-PON.

G.983.6 ONT management and control interface specifications for B-PON system with protection features

Specifies the OMCI for a B-PON system with protection features.

G.983.7 ONT management and control interface specification for dynamic bandwidth assignment (DBA) B-PON system

Specifies the OMCI for a B-PON system using dynamic bandwidth assignment.

G-PON

For more information on ongoing G-PON Recommendation activities, please check the ITU-T Study Group 15 website at:

www.itu.int/ITU-T/com15

G.984.1, Gigabit-capable Passive Optical Networks (G-PON): General characteristics

This Recommendation provides examples of services, User Network Interfaces (UNI) and Service Node Interfaces (SNI) that are

required by network operators. In addition, it shows the principal deployment configuration. Wherever possible, this Recommendation

maintains characteristics from the ITU-T G.982 and G.983.x series Recommendations in order to promote backward compatibility with

existing Optical Distribution Networks (ODN) that comply with these Recommendations.

G.984.2, Gigabit-capable Passive Optical Networks (G-PON): Physical Media Dependent (PMD) layer specificationThis Recommendation specifies the physical layer requirements and specifications for the Physical Media Dependent (PMD) layer. It

covers systems with nominal line rates of 1244.160 Mbit/s and 2488.320 Mbit/s in the downstream direction and 155.520 Mbit/s,

622.080 Mbit/s, 1244.160 Mbit/s and 2488.320 Mbit/s in the upstream direction. Both symmetrical and asymmetrical (upstream /

downstream) Gigabit-capable Passive Optical Network (G-PON) systems are described.

G.984.3, Gigabit-capable Passive Optical Networks (G-PON): Transmission Convergence Layer Specification

This Recommendation specifies the frame format, media access control method, ranging method, OAM functionality and security in G-

PON networks.

References


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Service providers are running optical fiber much deeper into the access network in order to deliver higher bandwidth that

makes it possible to offer multiple high performance voice, video and data services to customers. The diffusion of fiber

into the access network is often called the Fiber-to-the-X (FTTx) network. There are two basic types of FTTx

architectures. In a point to point (P2P) network, laser transmitters in the central office (CO) are dedicated to individual

users. A more popular alternative, because of its high performance to price ratio, is a passive optical network (PON) in

which the transmitters are shared among multiple users.

FTTx networks are designed to deliver high performance Triple Play services to users by bringing fiber directly to or near

the customer premises.

FTTx Acronyms

FTTH - fiber to the home

FTTP - fiber to the premise

FTTU - fiber to the user

FTTC - fiber to the curb/cabinet

FTTB - fiber to the business

FTTN - fiber to the node

The PON architecture is commonly used for FTTx networks because it employs optical splitters to deliver signals to

multiple users without conversion or intervention. Unlike traditional networks where services are direct point-to-point links

between customer and provider, PONs share a common distribution segment before being split to several users,

therefore reducing installation costs. FTTx networks feature active and passive components. The OLT and ONT

segments are active while the PON, as the name states, is passive.

PONs enable service providers to provide virtually unlimited bandwidth for applications such as high definition television

(HDTV), video on demand (VOD), streaming video, gaming and peer-to-peer (P2P) file sharing that require large

amounts of bandwidth. PON equipment costs have dropped to the point where they are competitive with copper

networks and new products such as bend-resistant fibers and easier-to-use cable management systems have simplified

PON installation. With each 1080 pixel HDTV channel requiring up to 6 megabytes, triple play services typically require

about 20 MB per home, just about the limit of what can be provided with copper but well within fiber's capabilities.

ADVANTAGES OF FTTx and PON

FTTx and PON

ADVANTAGES

4 | ADVANTAGES

Internet

Leased Line

Frame/Cell Relay

Passive Optical Splitter

Optical Fiber

Telephone

Interactive Video

Operation System

Service Node

PON

FTTH

FTTB

FTTC

FTTCabONU NT

ONU NT

ONT

ONT

xDSL

Twisted Pair

OLT

Figure 1:

Types of FTTx


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COMPONENTS

www.us.anritsu.com 5


The termination equipment for a PON system in the central office (CO) is called the Optical Line Termination (OLT)

which multiplexes voice and video for downstream transmission to the splitter. The OLT uses a traditional card and

chassis architecture, housing the laser transmitters that are shared among the users. The OLT combines the signals into

a single fiber at the CO using WDM techniques. A fiber distribution frame (FDF) at the CO integrates a number of OLTstogether with splicing trays and connectors that connect the OLT to the backbone network.

Headend(Video)

Residential Residential

High-Rise MDU

Mid-Rise MDU

Horizontal MDU

Low-Rise Garden MDU

FDP Pedestal

DistributionCentral Office

FDH

FEEDER

FIBER ROUTES

DISTRIBUTION

DROP

Figure 2:

Possible PON Architectures


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The distribution cable terminates at the OLT and runs to the pad or pole mounted fiber distribution hub (FDH) which

houses the optical splitter. The splitter is a passive component that requires no maintenance and no power but has a

high relatively high insertion loss, typically 15 dB for 32 port splitter. The FDH typically accommodates up to 10 splitterseach of which typically has up to 32 branches.

Applications where the fiber runs all the way to the customer premise normally use a distribution cable running from the

FDH to the Fiber Distribution Pedestal (FDP) which serves as a splice or connection point close to the customer

premises and contains fiber management. A drop cable with a typical length of several hundred feet runs from the FDP

to the ONT in the customer premises.

The ONT splits the signal into the voice, video and data services used by the customer. The ONT uses various interfaces

including RJ-11 twisted pair jacks for voice service, RJ-45 Ethernet jacks for high speed data and 75 ohm coaxial ports

for video service.

In applications in which the fiber terminates prior to the CP and then converts to some other transmission medium, the

distribution cable runs from the FDH and terminates at an Optical Network Unit (ONU) located at the curb (Fiber to the

Curb (FTTC)) or cabinet (Fiber-to-the-Cabinet or FTTCab). In some cases, the distribution cable is deployed to the

customer premises. In other cases, the drop cable runs all the way from the FDH to the customer premises.

COMPONENTS


CATV - VIDEO EMITTER TRIPLEXER MODULE

DIPLEXER MODULE

OLT SIDE PON ONT SIDE

Figure 3:

Typical PON Layout with a Video Overlay

External

WDM

One SM

Fibre

1 to N

Splitter

Digital

1310 nm

Rx

Digital

1490 nm

Tx

Analog

CATV1550 nmTx

Digital

1490 nm

Rx

Digital

1310 nm

Tx

AnalogCATV

1550 nmRx

6 | COMPONENTS


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Typically PONs are installed in two segments by two different groups with different testing requirements. The first phase

is the installation of the feeder cable from the CO to the FDH or FDP and the distribution cable to the FDP. This segmentis typically installed by a contractor and is certified after installation by measuring the total loss and evaluating splices

and connectors. This segment requires a PON capable optical time domain reflectometers (OTDR) with high dynamic

range and the ability to test multiple wavelengths and provide detailed reporting needed for certification.

The second last mile segment runs from the FDH or FDP to the ONT. Testing during installation and maintenance

typically requires a fault location, connectivity check and isolation. The highly capable instruments used to certify the

feeder cable are not required for testing this segment and so it is possible to use a less expensive and more user-friendly

drop cable fault locator.

PON INSTALLATION

INSTALLATION


FDP

ONT

Feeder Cable Drop Cable

Figure 4:

Possible PON Architecture

OLT


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The International Telecommunications Union Standardization Sector (ITU-T) has created several standards for optical

access systems based on the PON architecture. Broadband PON (BPON) uses Asynchronous Transfer Mode (ATM) cells

for transmission to a maximum of 32 customers and has a maximum access speed of 155 Mbps upstream and 622 Mb/s

downstream. Gigabit PON (GPON) was later developed to increase access speed to 1.2 Gbps downstream and 622

Mbps upstream, making it possible to serve a maximum of 128 customers. The Ethernet PON (EPON) standard uses

standard 802.3 frames with symmetric 1 Gbps upstream and downstream rates. Since EPON is active Ethernet based ituses a powered switch in the outside plant and dedicated switches and fiber runs. Advantages of EPON include the fact

that no encryption is needed since lines aren't shared and that bandwidth can be easily changed. On the other hand,

EPON is more expensive due to switch power costs and dedicated fibers. DPON is a DOCSIS standard based for

multiple system operators (MSOs) that allows use of the current head-end and customer premises equipment.

Video transmission downstream from the CO OLT to the premise ONT is 1550nm at 622Mbits/sec (BPON) or

1.2Gbits/sec (GPON).

Voice/data and IP Video (if used) transmission downstream from the CO OLT to the premise is 1490nm at

622Mbits/sec (BPON) or 1.2Gbits/sec (GPON).

Transmission upstream from the premise ONT to the CO OLT is 1310nm at 155Mbits/sec (BPON) or 622Mbits/sec(GPON).

Most PONs today are using an ATM protocol with access to bandwidth using time division multiple access (TDMA)

upstream and, TDM downstream. IP and Gigabit Ethernet based PON systems are also beginning to see widespread

deployment.

Total End-to-End Optical Budget

25 dB for a Class B PON Network

30 dB for a Class C PON Network

PONs present major testing challenges, largely because the presence of the relatively high-loss optical splitter means that

testing from the CO does not provide a dedicated optical path as with traditional point-to-point fiber networks. The PON is

shared by multiple customers so the situation frequently exists where one or a few customers are down while the rest are

still operating. This makes troubleshooting more difficult to perform because it must be done without disrupting service to

the customers that are up and running. Another complicating factor is that 1490 nm and 1550 nm transmissions are both

possible in the downstream transmission while 1310 nm upstream transmissions are not present unless the downstream

transmission is there to stimulate it.

The Typical Network Planning Specifications for a PON System

PON SPECIFICATIONS

SPECIFICATIONS

8 | SPECIFICATIONS

Figure 5:

PON Architecture (BPON)

Maximum End-to-End Length

20 km determined by the 1310 nm optical budget

25 dB - 12 dB splitter = 13 dB

13 dB - 6 dB (connector and splice loss) = 7 dB

7 dB / 0.35 dB/km (1310 nm fiber loss) = 20 km7dB / 0.20 dB/km (1550 nm fiber loss) = 35 km

FTTH

FTTCab

CENTRAL

OFFICE

Maximum Length: 20 km

155.62/622.08 Mbit/s (1.5 um wavelength)(1.49 um wavelength)

155.52Mbit/s (1.3 um wavelength)

Single Mode Optical Fiber (G.652)

Maximum Divergence Number: 32

Optical Splitter

ATM 25M Etc.

xDSL

OLT

ONU

ONT

NT

NT

NT

Optical Loss Range (Class B:10-25dB, Class C:15-30dB)


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A number of parameters must be measured during installation and maintenance and verified against network

specifications. The end-to-end loss budget of the fiber span at each transmission wavelength is the most crucial

measurement of the physical medium. The measurement should be taken at each transmission wavelength and should

include the end connectors. To ensure accurate results, the test should be performed directionally using a loss test set

(LTS) with the results averaged together to yield the true loss budget.

End connectors should be tested for both loss and reflectance using an OTDR with a lead-in fiber against the individual

connector specifications. If the loss or reflectance of an individual connector does not meet specifications then it should

be repaired or replaced. Documenting the location of each connector is important for future maintenance of the network.

If problems arise on the network, knowing the exact location of each connection point will significantly reduce

troubleshooting time.

Each individual average splice loss should also be verified bi-directionally for maximum loss values, even if the total end-

to-end loss passes the network specification. If the loss of an individual splice does not meet specification, it may signify

a poor quality splice that could cause future problems in the network resulting in network down time and maintenance

costs. This must be done using an OTDR on each feeder fiber before termination to the PON coupler.

The quality of the individual fibers between splice points should be verified to meet average loss specifications from the

supplier at the specified wavelength. Macrobends that may have been introduced during cable installation can be

identified by comparing a shorter 1310 nm OTDR trace with a longer wavelength 1550 nm ODTR trace on the same

fiber. If the losses vary by more than 0.3 dB on the same splice point between different wavelengths, this indicates that

macrobends may be present.


PARAMETERS

Maximum Average Splice Loss (Bi-Directional)(Ea) 0.20 dB

Recommended Splice Loss Specifications

Connector Loss (Each Mated Pair)

Connector Reflectance

Super Polish

Ultra Polish

Angled Polish

0.20-0.50 dB

-45 dB

-50 to -55 dB

-55 to -65 dB

Recommended Connector Specifications

Fiber Type

9/125 Corning (SMF-28e)

1490 nm

0.25-0.35 dB/km

1310 nm

0.33-0.35 dB/km

1550 nm

0.19-0.20 dB/km

Attenuation (dB/km)



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PARAMETERS

10 | PARAMETERS

Optical return loss (ORL) should be measured between the termination fibers located at the customer premise (ONT or

ONU) and the CO (OLT) after the entire network is completed from end to end but before connection to any termination

equipment. Typical ORL specifications values are +30 dB to +35 dB.

In deploying new connections to a live PON system, verify optical power at 1550 and 1490 nm and splice the assigneddrop cables to their respective coupler outputs. At the customer premises, test for live PON receiver power with an

optical power meter at the 1550 nm setting with a 1550 nm pass filter. If the optical power meets the approved -28 dBm

level, connect the ONT. A green light will confirm OLT and ONT communication and equipment operation can be verified.


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If all customers connected to a PON system are out of service, testing can proceed at the CO without danger of

interfering with existing service. System diagnostics will usually detect a problem with the OLT and the solution is

normally a line-card replacement. The OLT manager will usually identify a broken fiber on the main leg as all branches

associated with the OLT will become nonresponsive. Troubleshooting can then proceed with an OTDR or a simpler

break indicator.

Figure 6 outlines a methodology for troubleshooting PON networks in the more difficult situation where one or some

customers connected to the PON are out of service. When a fault occurs in the subscriber's FTTH service, if other

subscribers sharing the OLT are not experiencing the same fault, then the problem is either in the drop cable betweenthe FDH and the ONU/ONT, in the ONU/ONT or in the subscriber's home network. The technician should begin by

disconnecting the optical fiber from the ONU/ONT and checking the optical signal level with a power meter.

If no power is measured on the drop cable, the chances are that the problem is either a break in the fiber or a high loss

event such as a bad splice. Since no power is being received at this ONT location, there is no danger of interfering with

traffic on the PON when testing the fiber using an OTDR. But to be safe it's a good idea to troubleshoot with an OTDR

using the 1650 nm wavelength to avoid interfering with the ONT in the event of a mistake.

If the optical power level is lower than the specification, there is a good chance that that there is a break or damage in

the drop cable. Maintenance of a PON drop cable requires care when the rest of the network is still in service. One

approach is to isolate the drop cable under test from the rest of the network but this is not easy because the connectionsare often high on utility poles and wires, and disconnecting fiber splices is difficult. The solution is to use a short

wavelength OTDR such as the Anritsu MT9090A or MT9083 series with test pulses at a wavelength of 780 nm. Testing

from the subscriber's side at 780 nm has no effect at all on the in-service customers. The dynamic range at 780 nm is 8

dB so faults in a 2 km or shorter drop cable can be accurately pinpointed.

If the power is OK, then test down the stream from the coupler with an OTDR and bare fiber adapter to pinpoint the

attenuation.

PON Troubleshooting


TROUBLESHOOTING

One or more

customers are out

Dispatch

Technician to

Locations in Failure

Connect 780 nm or

1650 nm OTDR to

Fiber at PremiseNo Fiber Issue

Found:Bad Coupler Port

or Connector, Try

Alternate Unused

Splitter Port

Fiber Issue

Found:Repair or Replace

Drop Cable

Clean Connectors

and Connect

the Fiber to the ONT

Connect 1550 nm

OTDR to Distribution

Cable to Locate Fault

Verify Power

at Customer Premise

Power OK

If Still Out of Service

Replace ONT

Power Low

Fault Locate to

Find Fiber Fault

No Power

All ONTs

Are Down

OTDR Test From CO

to Isolate Fiber Fault

on Feeder Cable

All customers out(PON system is in

complete failure)

Figure 6:

PON Troubleshooting Overview


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SELECTION

12 | SELECTION

An OTDR is the universal tool used to pinpoint faults and certify the workmanship in a fiber installation. OTDRs find and

characterize both reflective and nonreflective events in optical fiber runs by sending laser pulses of different widths.

There are two main parameters that measure the performance of an OTDR. The dynamic range determines the length of

fiber link that the OTDR can test - higher values enable testing longer lengths. The event dead zone is the minimum

distance of separation between two different optical reflective events that the OTDR can resolve - shorter values enable

resolving more closely spaced events. Dynamic range and event dead zone both increase with longer pulse widths sotuning the OTDR normally requires a tradeoff between these two parameters.

Not all OTDRs are capable of testing splitter based PONs. To perform well in measuring and certifying PONs, OTDRs

need a small dead zone to allow measurement of near end connectors within the CO in riser cables and at the customer

premises. They also need a high dynamic range in order to measure the high losses that are typically involved in PONs.

Figure 7 compares the measurements provided by a conventional OTDR (blue) and the Anritsu MT9083, a PON capable

OTDR (red). The splitter is easily identified by the large losses at 2.5 km and 2.7 km. The conventional OTDR lacks

dynamic range, resulting in a large amount of noise at distances greater than the splitter and making it impossible to

accurately test through the splitter. On the other hand, the MT9083 OTDR has no difficulty in testing through the splitter.

After initial construction of a PON system it is necessary to accurately and completely characterize the fiber link from the

OLT to the FDH and, most important, to measure loss and ORL. A PON-capable OTDR such as the MT9083 makes this

task easier through its ability to distinguish between the loss properties of the individual PON branches, making it

possible to test the feeder cable from the ONT end.


BLUE:

Normal OTDR

PON Capable OTDR

RED:

Figure 7:

Traces from Traditional and PON-Capable OTDRs

Not OKOK?

OK!

Other OTDRs

Undefined WaveformDue to Poor Dead Zone

Performance

Very sharp waveform,even between close splittersZOOM IN

Figure 8:

MT9083 Offers Excellent Resolution


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SELECTION


A dual mode design enables the MT9083 OTDR series to offer excellent dynamic range and dead zone resolution. The

user can simply select high resolution or enhanced range mode based on the task at hand. When HR mode is

selected, the MT9083 series provides good measurement range with an industry leading deadzone of less than 1 meter.

When ER mode is selected, the MT9083 provides unparalleled performance for measurement distance, measurement

speed and deadzone. The MT9083B and MT9083C provide up to 45 dB dynamic range, providing a measurement range

of over 200 km and making it possible to test a 100 km fiber in less than 10 seconds. The combination of a high dynamic

range with a short pulse makes it possible to test the entire fiber path through the splitter. Splitters up to a single 1x128

or closely spaced, cascaded splitters are completely and accurately measured with industry leading resolution. TheMT9083 series also offers a full SCPI command support for remote operations or automated testing.

Traditional tools have not provided the right solution for the technicians charged with maintaining and troubleshooting

local access networks. Handheld OTDRs and Fault Locators lack the resolution needed for short drop cable spans while

mini-OTDRs were too large, too expensive and too complicated. The new MT9090A from Anritsu finally addresses this

need by providing all of the features and performance required for installation and maintenance of short fibers in a

compact, modular test set. Realizing that short fiber premise applications such as FTTx drop cables, intra-building riser

cables and cell towers have different testing requirements, Anritsu designed the MT9090A from the ground up. It features

5 cm resolution for accurate mapping of events, deadzones of less than 1 meter (3 feet) and a built-in 10 m (30 ft) launch

fiber to ensure everything is evaluated. Since multiple users share the common feed fiber, FTTx maintenance becomes

difficult when only one or two users are down. To address this need, Anritsu also offers a 780 nm Fault Locator module

that can be used to troubleshoot in-service FTTx networks without costly filters and without disruption to other customers.


The MT9083 Series is theonly OTDR That Can Detect

a Fault in This Zone

Figure 9:

MT9083 Offers Excellent Resolution

MT9083 Series MT9090A/MU909011A Fault Locator


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CONCLUSION

FTTx networks with PON architectures provide the opportunity to deliver dramatic increases in bandwidth. Service

providers are using this bandwidth to deliver new value-added services such as HDTV, VOD and gaming to customers.

But the deployment and maintenance of PON architectures presents some significant challenges to service providers.

For example, the presence of the splitter complicates testing because there is no longer a dedicated optical path from

CO to the customer. Installation of a PON requires carefully measuring key performance parameters against network

specifications. Once the FTTP network is deployed, each subscriber connection requires additional tests to ensureservice quality. Overcoming testing challenges is critical to delivering high-performance and reliable service to customers

at a low cost. The correct test equipment and knowledge can quickly result in a trouble-free FTTx network. Anritsu offers

the expertise and the optimized FTTx test equipment to meet these challenges.

Conclusion

14 | CONCLUSION


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11410-00679, Rev. A Printed in United States 2012-12

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