Sponsored by:Sponsored by:
Isolating, Testing, and Troubleshooting
FTTx Drops in the Last Mile
November 18, 2015
Sponsored by:Sponsored by:
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.
3
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
4
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
5
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
6
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
7
Document! Document! Document!
Acceptance testing. Performance. Maintenance records. Restoration requirements.
Testing Documentation
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
8
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
9
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
10
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
11
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
12
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
137-10
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
13
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
14
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.
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
15
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
16
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
17
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
18
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
19
Active EthernetP2P Not to Exceed Charts
19
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
20
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
20
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
21
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
22
P2MP Not to Exceed Charts
22
km1310 nm(0.4 dB/km)
+ 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
km1550 nm(0.3 dB/km)
+ 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.
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
23
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?
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
24
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
25
Dynamic range. 35 dB for P2P. 43 dB for P2MP.
Pulsewidth and deadzonelimitations.
ORL and reflectance measurements.
Key Issues for OTDRs
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
26
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
27
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
28
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.
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
29
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
30
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
31
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
32
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
33
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
34
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
35
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
36
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
37
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
38
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
39
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
40
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
Isolating, Testing, and Troubleshooting FTTx Drops in the Last Mile
2015 The Light Brigade, Inc.
41
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
Sponsored by:Sponsored by:
Stay Tuned
Join us for our next webinar when we discussImproving OTDR Accuracy for Emergency Restorations
on January 20, 2016