Isolating testing troubleshooting FTTx Drop in Lastmile

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Isolating, Testing, and Troubleshooting

FTTx Drops in the Last Mile

November 18, 2015


Todays speaker is

Larry JohnsonDirector and Founder

of Light Brigade

Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile

2015 The Light Brigade, Inc.

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For your convenience, this presentation will be available on demand within 24 hours after we conclude today at www.lightwaveonline.com.

I encourage you to ask questions using the Ask a Question box that you should see on the left-hand side of your screen. To keep a consistent flow we will answer those questions at the end of the presentation.

If you have a tech support issue, you can alert us through this question box as well.

Some Housekeeping Issues



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The Light Brigade was established in 1986 to fill a growing need for fiber optic training.

Since that time, we have grown to become the industry leader and provide courses worldwide, either directly or under license.

We have delivered fiber optic training for more than 50,000 people.

Our goal has always been to give our students mastery over multiple fiber optic disciplines, each from the perspective of a specific role: designers, planners, engineers, technicians, installers, splicers, and those who operate and maintain optical communication systems.

Fiber Optic Training History



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This session is to review common problems in FTTx installations and how they are located using various types of fiber optic test equipment.

The focus will primarily be on Passive Optical Networks (PONs) but can apply to Active Ethernet or other fiber optic networks.

Objective



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Test equipment. Test disciplines.

Testing. Troubleshooting. Maintenance. Restoration.

Point-to-point systems (P2P). Active Ethernet. Home Run PON.

Point-to-multipoint-systems (P2MP). Passive Optical Networks.

Introduction



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Document! Document! Document!

Acceptance testing. Performance. Maintenance records. Restoration requirements.

Testing Documentation



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Physical Plant Equipment

Attenuation. OTDR. Power meter. Optical loss test set.

Reflection. OTDR.

Power. Power meter.

Surface quality. Inspection scope.

Continuity tester. Visual laser.

Test Equipment



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Connections Are Critical

FTTH and FTTB. Transmitters and receivers.

Optical line terminals (OLT). Optical network terminals (ONT).

Active Ethernet. CO to/from cabinet. Cabinet to/from subscriber. SFP modules.

OSP. Fiber distribution hubs (FDH). Fiber access terminals (pedestals). Multiport service terminals (MST). Transition boxes (NIU).

System Test Points



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Knowing the Outside Plant

Span continuity. End to end attenuation.

OTDR signatures. Splice attenuation.

Location. Splitter attenuation. Optical return loss (ORL).

Spans. Reflectance.

Component.

Testing for FTTx



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Find the Common Element

P2MP PON.

P2P active Ethernet. Fiber outage between CO and AE cabinet.

Use OTDR to locate damage. Fiber outage between cabinet and subscriber ONT.

Truck roll.

FTTx Outages

32 ONTs Fiber CO to FDH Use OTDR16 ONTs 1:16 splitter or fiber/connection to splitter Truck roll

8 ONTs 1:8 splitter or fiber/connection to splitter Truck roll4 ONTs 1:4 splitter or fiber/connection to splitter Truck roll1 ONT ONT or drop cable Truck roll



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Prior to service activation the optical power levels should be documented for all transmitters and receivers.

Acceptance testing of transmitter output power (in dBm). 1490 nm for downstream Basicband.

OLTS must operate in-line for upstream power measurements from ONT.

Testing OLT Downstream Transmitter Output Power



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One of the first tests using the optical power meter (OPM) is at the subscribers optical network terminal (ONT or SFP for Active Ethernet systems).

If the receivable optical power level is lower than the initial measurements. Identify the amount of change. Start working upstream to next

connector point with the OPM. If the power level is the same the

problem is in the transmission equipment and not the OSP.

Photodetectors

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Testing Receiver Input Power

Testing receiver input power in dBm. 1490 nm Basic band from OLT. 1550 nm Enhancement band for RF

overlay.

Testing upstream optical power levels requires an inline OPM.

Most OPMs can only measure downstream optical power levels due to automatic upstream laser shutdown function in ONTs.



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The most difficult test to perform is the upstream ONT power level.

Wavelength isolating power meters provide this ability.

Notice that when the connection is disconnected the upstream laser shuts down.

Once the PON OPM is connected in-line the upstream transmission is reestablished.

Testing Upstream Power Levels



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Testing ONT Tx and Rx

Operates inline and can measure bidirectional OLT and ONT power levels.

Uses in-line tap coupler with attenuation subtracted from displayed power level.

Calibrated for 1310 nm, 1490 nm, and 1550nm wavelengths.

B-PON, G-PON and EPON protocol selects.

Optical return loss. Data storage.

PON Power Meters



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All Power Levels are Recorded in dBm

ONT #Downstream Upstream dB Loss

1490 nm 1550 nm 1310 nm 1310 nm 1490 nm 1550 nm

1

2

OLT #Downstream Upstream dB Loss

1490 nm 1550 nm 1310 nm 1310 nm 1490 nm 1550 nm

1

2

Header required for detail criteria.

FTTx Optical Power Test Record



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Once the optical power levels have been confirmedthen the focus changes to locating the problem in the OSP.

The Physical Layer Operations, Administration, and Maintenance (PLOAM) function of the OLT and its management system will determine the extent of the fault.

Knowing how ONTs are offline will assist in locating the common points to investigate.

E.g. 32 ONTs are offline. OTDR testing of that fiber from C.O. Input power level at splitter port.

Compare to original power level. Too low problem is prior. Good problem is in splitter.

One ONT is offline. Fiber cut. Power failure.

Focusing on the Outside Plant



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Active EthernetP2P Not to Exceed Charts

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km1310 nm(0.4 dB/km)

+ Splice qty 0.1 dB With patch panel Total

10 4.0 0.3 0.5 4.80

20 8.0 0.5 0.5 9.00

40 16.0 0.8 0.5 17.30

60 24.0 1.1 0.5 25.60

80 32.0 1.4 0.5 33.90

km1550 nm(0.25 dB/km)

+ Splice qty 0.1 dB With patch panel Total

10 2.50 0.3 0.5 3.30

20 5.00 0.5 0.5 6.00

40 10.00 0.8 0.5 11.30

60 15.00 1.1 0.5 16.60

80 20.00 1.4 0.5 21.10



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20 km distance limitation. Fiber attenuation.

0.3 dB/km at 1490/1550 nm (downstream). 0.4 dB/km at 1310 nm (upstream).

Splitter attenuation. Theoretical 1:32 = 15 dB. Practical 1:32 = 15.8 dB.

Connections are 0.5 dB each. Splices are 0.1 dB each.

PON Loss Budgets

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1:32 Splitter example

If the problem may be at the optical splitter one person with a optical power meter can measure and confirm if one or more ports are at fault.

Measure the receive optical power at the input port in dBmand zero the meter (dB).

Measure the outputs. The loss should be over 15 dB per port but will average 15.8 dB per the ITU-T G.671 passive optical components standard.

Insertion LossSplit Average1:2 3.4 dB1:4 6.6 dB1:8 9.7 dB

1:16 12.9 dB1:32 15.8 dB1:64 19.2 dB

Splitter Not to Exceed Values



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P2MP Not to Exceed Charts

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+ Splice qty 0.1 dB

With patch panel* With splitter

Total,in dB

1 0.4 0.4 3.5 15.8 20.1

5 2.0 0.4 3.5 15.8 21.7

10 4.0 0.6 3.5 15.8 23.9

15 6.0 0.8 3.5 15.8 26.1

20 8.0 1.0 3.5 15.8 28.3


+ Splice qty 0.1 dB

With patch panel* With splitter

Total, in dB

1 0.3 0.2 3.5 15.8 19.8

5 1.5 0.4 3.5 15.8 21.2

10 3.0 0.6 3.5 15.8 22.9

15 4.5 0.8 3.5 15.8 24.6

20 6.0 1.0 3.5 15.8 26.3

*Seven connections at 0.5 dB each.



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When is it used? Before, during, and after the installation of the fiber spans. Confirmation of the splice losses during the joining of the spans. The entire connected span. When all ONTs on a fiber are offline.

Where is it used? (Wherever there are connectors). Central office. Fiber Distribution Hubs. Fiber Access Terminals (Pedestals). Multiport Service Terminals.

The closer the fault is to the subscriber the less effective the OTDR is.

What about the OTDR?



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The OTDR is critical to locating where and the extent of the damage.

If the cable is damaged more than one PON can be affected. Concern is when the fault is localized around splitters, splices

and connection points.

Care should be taken not to increase possible damage to adjacent fibers.

Using visible lasers may be helpful. Continuity test between ONT and splitter location or MST. Splitter locations.

OLT and ONT power levels will be checked using the OPM.

Finding the Fault



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Dynamic range. 35 dB for P2P. 43 dB for P2MP.

Pulsewidth and deadzonelimitations.

ORL and reflectance measurements.

Key Issues for OTDRs



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Use the 1550 nm wavelength to locate stresses before and after the break.

Use real-time function to identify fiber with Fresnel reflection. Use two-point measurement to determine the extent of the damage

(from each end).

Use vertical and horizontal resolution. Measure the location of the stresses/breaks from previous splice

locations.

Finding the Fault



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Connection Points are Key for Fiber Access

OTDR Testing of Splices

Test with short/medium

pulsewidth

Test with short/medium

pulsewidth

Test with short pulsewidth and high averaging

Test with medium pulsewidth

Test with short pulsewidth and high averaging



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Reflective OTDR Signatures

Connectors. Open fibers. Fiber end with UPC connection.

59 dB reflective. Notice the slight Fresnel

reflection at the end of the OTDR trace.



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Fiber Roll-off

Caused by nonreflectiveevents at fiber end. Breaks. Extreme macrobend. Water. Cable gel.

Other non-reflective signatures. Fusion splices. Macro and microbends.

Nonreflective OTDR Signatures



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Correct Identification

Where is the splitter? Where are the fiber ends? What is the reflectance? What about non-equal splits? What about similar length

drop cables?

For those new to testing optical splitters using the OTDR, understanding the OTDRs specifications is key.

Splitter Signatures



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Drop cable lengths are shorter than conventional spans.

OTDR with standard dynamic range may not be able to measure past the splitter. OTDR with higher dynamic range

required.

Testing of drop cables might be easier by standard optical loss testing. Light source and optical power meter. Or dBm readings at splitter and ONT.

Visual laser for quick continuity testing.

Testing Drop Cables



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When to Use (or Not Use) the OTDR

Testing drop cables. Short spans. Keep it simple. OPM using dBm power

levels. dBm (Tx) minus dBm

(Rx) = dB. Drop cable attenuation

is almost always less than 1 dB.

Visual lasers for simple continuity check.

Testing active Ethernet SFP drop cables uses the same technique.

Troubleshooting PON and AE Systems



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Troubleshooting. Isolate the trouble.

Feeder, distribution, drop. From ONT to FDH.

OPM. Visible laser.

Initial installation. With an OTDR.

From CO to FDH, FAT, or ONT. With an OLTS (dB) or OPM (dBm).

From CO to splitter. From splitter to ONT. From CO to ONT

FTTx Troubleshooting for PON Networks



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Red light has limited range and operates out of band from the detectors used in OLTs and ONTs.

Visual. Excellent for quick continuity

testing for drop cables.

Close-in faults. Pigtail splices. Connectors. ONT to FDH. Tie wraps (microbends). Bend radius (macrobends). Splitters.

Troubleshooting with a Visual Fault Locator



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Visual Inspection Equipment

Damaged connectors would need to be replaced.

Contaminated connectors can be cleaned.

Digital inspection scopes. Can be used to store, transmit and

compare images. Can inspect ferrule endfaces and

internal adaptor plug endfaces. Are safer.

Connectors Damage or Contaminated



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Fresnel reflections affect laser operation, and therefore affect signal quality. BER, latency.

Connectors are the major cause. Open ports and splitter pigtails can also have high Fresnel

reflections.

Optical terminators can be used to resolve reflection problems. Cleanliness and cleaning materials affect reflectance. ORL is the sum of all reflections.

Rayleigh, Fresnel. Reflectance is the term for an individual component.

Reflection Testing



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Using the OTDR

Match connector type, fiber type, and polish.

Reflectance. Components.

ORL. System.

Options: Two deadzone boxes. One deadzone box on the

front end and optical terminators at the far location.

How to Measure ORL and Reflectance



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Measuring Reflectance with a Deadzone Box

Testing the front end connection. Two deadzone boxes. Allows for measuring attenuation and reflectance at both ends of the span.

Connections can be tested for attenuation

and reflectance.

Deadzone box

Deadzone box



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The FTTx systems alarms should identify the scope of the problem.

Eliminate the transmission equipment using the OPM. Use the OTDR only when all ONTs in a PON are in alarm. Use the OPM to eliminate segments by using dBm power levels. Good initial documentation will assist by making comparison

measurements.

Summary



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Get Troubleshooting a Fiber Optic Link DVD for $99 each through December 2 with code DVD99 at lightbrigade.com.

The Light Brigade can develop and deliver a custom onsite course specific to your needs and application. Let us create a course to meet your desired skill level and to focus on specific subject matter.

Question and Answer Period



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For any questions on this presentation or other fiber optic related topics, feel free to contact us.

Email: [email protected] Call: 1 800 451 7128 (from inside the United States)

+1 206 575 0404 (from outside the United States)

To contact me directly, please send email to [email protected]

Question and Answer Period


Stay Tuned

Join us for our next webinar when we discussImproving OTDR Accuracy for Emergency Restorations

on January 20, 2016

Isolating testing troubleshooting FTTx Drop in Lastmile

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