Siemon Optical Fiber Field Testing Guide

8/3/2019 Siemon Optical Fiber Field Testing Guide

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Siemon Optical Fiber

Field Testing Guide

Edition 1.11


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Optical fiber systems provide users with a high bandwidth, high density platform for network

transmission. Similar to copper cabling systems, optical fiber cabling systems must be field tested

following installation to ensure proper system performance. This supplemental field guide, when used

in conjunction with the Siemon Company Certified Installer Training Manual, has been developed to

provide additional guidance for field testing of optical fiber systems.

Safety

It is very important to be aware of the risks and to utilize good safety practices when interfacing with

optical fiber systems. Handling optical fiber is not inherently dangerous as long as some basic safety

precautions are followed. You can significantly reduce the risk of injury by knowing the risks associated

with working with fiber and following some simple safety guidelines.

Of primary importance during testing is the fact that the light sources used for fiber transmission can

cause damage if viewed, but are not visible to the human eye (see Figure 1). For this reason, never view

directly into a fiber optic connector or adapter unless appropriate protective eyewear is worn or there is

full certainty that the fiber system is not in use.

Figure 1: Visible Spectrum vs Optical Fiber Light Sources

Note that even if performing fiber testing only, the termination process associated with the fiber

installation can leave potential risks within the environment. For example, bare optical fiber fragments

are difficult to see and can easily penetrate the skin. For this reason, the testing environment should be


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inspected and cleaned as necessary. Regardless, it is recommended not to eat or drink in termination

area, nor to touch your eyes when working with fiber systems. Similarly, if wearing protective eyewear,

do not put them down in the local environment.

Field Tester Selection

Siemon requires the use of an Optical Loss Test Set (OLTS) for acceptance testing of optical fiber

systems. This method of testing can be performed by dedicated Power Meter/Light Source testers or

via the use of optical fiber test adapters for many of todays common copper certification testers. As

defined by TIA-568-C.0-2009 Generic Telecommunications Cabling for Customer Premises, Tier 1 testing

specifies attenuation, length and polarity as required test parameters. Such testing should not be

performed with an OTDR as the attenuation is more subjective in nature and can be easily

misinterpreted.

In addition to Tier 1 testing, TIA identifies the use of an OTDR for optional Tier 2 testing. Such testing

can be performed in addition to Tier 1 testing to evaluate attenuation uniformity and the quality of each

connection.

Light Sources

When specifying a light source for the OLTS, Siemon recommends the use of lasers for

singlemode testing and LED based light sources for multimode fiber testing as per IEC 61300-1

Fibre Optic Interconnecting Devices and Passive Components Basis Test and Measurements

Procedures Part 1: General and Guidance. While VCSEL light sources are primarily used for 1

Gb/s and higher applications, and are thus required by users of such applications, they do not

provide the same consistency for field testing.

Mandrels and Encircled Flux Modules

When testing multimode fiber systems, Siemon requires the use of the correct mandrels. Table

1 from TIA-568-C.0-2009 identifies proper mandrel sizes for 50/125 m and 62.5/125 m

multimode fiber. It is important to note that some field testers may utilize internal mandrels

eliminate the need for external mandrels. This should be verified with the field tester

manufacturer prior to use.

Fiber

core/cladding

size

900 m

buffered

fibermm (in.)

2.0 mm

jacketed

cablemm (in.)

2.4 mm

jacketed

cablemm (in.)

3.0 mm

jacketed

cablemm (in.)

50/125 m 25 (0.98) 23 (0.91) 23 (0.91) 22 (0.87)

62.5/125 m 20 (0.79) 18 (0.71) 18 (0.71) 17 (0.67)

Table 1: Acceptable mandrel diameters for common multimode cable types (5 wraps)


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Recently, encircled flux launch cords are now available to the market as a potential alternate to

mandrels. Encircled flux is a new multimode launch-condition metric that improves link-loss

consistency by controlling the number of mode groups during the fiber-testing process. This

launch method is documented in TIA TSB-178 Launch Condition Guidelines for Measuring

Attenuation of Installed Multimode Cabling. It is important to note that this launch condition

method is relatively new within the industry and, while having tremendous potential, is not

currently recognized by Siemon for field testing of multimode systems and should be

approached with caution until the technology is sufficiently mature and proven robust for field

use.

Reference Quality Launch Cords

When testing fiber systems, high quality Test Reference Cords (TRCs) should be used. Per

ISO/IEC 14763-3 Information Technology - Implementation and operation of customer premises

cabling - Part 3 - Testing of optical fibre cabling, TRC reference grade terminations should

achieve insertion losses of better than 0.10 dB for multimode and 0.20 dB for singlemode.

These cords should be replaced at regular intervals as they wear with use and can detrimentally

affect the quality of the resulting tests. The intervals for replacement may vary depending upon

the quality of the TRCs, but as a general rule, they should be replaced after 500

insertion/removal cycles or, if following cleaning and inspection, loss measurements begin ton

consistently increase.

Care should also be taken when handling TRCs. Proper handling and storage of TRCs will serve

to extend the life of their usage. Specifically, do not touch the end faces with your hands as skin

oil can greatly decrease performance and is very difficult to remove. When not connected, TRC

ends should be capped to avoid contamination. TRCs should be also be cleaned before each

use. TRCs are typically available directly from the test equipment manufacturers. Siemon has a

full line of reference quality TRCs available.

Field Tester Preparation

Due to the wide range of field testers and associated usage, the following guidelines are intended to be

somewhat generic in nature. Specific procedures and details should be obtained directly from the

applicable field tester manufacturer.

Field Tester Calibration and Reference

All field testers used must be within factory calibration timeframes. In addition, the field testers

must be field referenced prior to each use based upon the manufacturers requirements. In

some cases, field testers may require a warm up period - please refer to manufacturers

documentation.

Field Tester Inspection


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Optical ports on the test units must be free of contamination to provide accurate test results. If

an inspection probe is available, inspect fiber ports on test equipment. If necessary follow tester

manufacturers cleaning procedures to remove any contaminants present.

All ports on test heads should be covered with protective caps provided with test unit to

minimize contamination when not in use.

Field Tester Setup and Reference

Field testers should be set up and referenced per the instructions provided by the tester

manufacturer. Note that if proper reference values cannot be achieved, this must be resolved

with the field test manufacturer prior to performing any testing.

Note that once TRCs have been referenced out they cannot be unmated from the light source.

If removed, a re-reference of TRCs will be required in order to continue testing.

Simplex/Duplex Fiber System Loss

When calculating system loss for simplex/duplex systems, the following should be used:

System Attenuation (dB) = Total Cable Attenuation (db) + Connector IL (dB) + Splice IL (dB)

where:

Total Cable Attenuation (dB) = Cable Attenuation (dB/km) x Cable Length (km)

Connector IL (dB) = Number of Mated Connectors x Connector Loss (dB)

Splice IL (dB) = Number of Splices x 0.3 dB

Cable Attenuation: 3.5 dB/km @ 850 nm for 62.5/125m or 50/125m multimode cable

1.5 dB/km @ 1300 nm for 62.5/125m or 50/125m multimode cable

1.0 dB/km @ 1310/1550 nm for singlemode inside plant cable

0.5 dB/km @ 1310/1550 nm for singlemode outside plant cable

The system loss calculation is important when using OLTS that simply measure system loss and

must be performed prior to testing. For copper certification testers with optical fiber test

adapters, many of the system loss calculations are performed automatically during setup when

entering the system configuration (see Figure 2). Industry standard cable attenuation and

connector insertion loss (0.75 dB per mated pair) are typically used unless otherwise specified.


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Figure 2: Example of Field Tester System Loss Setup1

Array (Plug & Play) Systems

Figure 3: Array System Model

Multimode array systems are typically configured of (2) array modules connected by a one or

two array cables as shown above in Figure 3. In order to calculate the overall system loss for an

array system, the array cable attenuation and array module insertion loss (IL) for the Siemon

array components are shown below in Table 2.

Fiber Type Performance

Cable

Attenuation*

(dB/km)

MTP IL

(Max.)

LC or SC IL

(Max.)

Total Module

IL

(Max.)

SM XGLO 0.5 / 0.5 0.75 dB 0.40 dB 1.15 dB

50/125 10G XGLO 3.5 / 1.0 0.50 dB 0.25 dB 0.75 dB

50/125 LightSystem 3.5 / 1.0 0.50 dB 0.50 dB 1.0 dB

62.5/125 LightSystem 3.5 / 1.0 0.50 dB 0.50 dB 1.0 dB

* Cable attenuation for singlemode at 1310/1550nm and multimode at 850/1300nm, respectively

Table 2: Siemon Array Module Component Performance

Taking the equation used for simplex/duplex system loss, the following resulting array system

loss is as follows:

1Illustration courtesy of Fluke Networks


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Array System Attenuation (dB) = Total Cable Attenuation (db) + Module IL (dB)

where:

Total Cable Attenuation (dB) = Cable Attenuation (dB/km) x Cable Length (km)

Module IL (dB) = Number of Array Modules x Total Module IL (dB)

Note: For copper certification testers with optical fiber test adapters, a four connector system

loss should be created using the individual component losses noted in Table 2. However, a two

connector system may be utilized for Siemons 50/125 10G XGLO systems as the total array

module IL is equal to the default loss for a single mated pair (0.75 dB).

For simplification of setup when using copper certification testers with optical fiber test

adapters, Siemon will allow the use of a four connector default setting for singlemode array

systems. While the loss limit would be slightly higher than the actual calculated loss (3.0 dB for

Module IL vs 2.3 dB), the resulting system loss would fall within all singlemode application loss

budgets and would be acceptable for the purposes of warranty.

A calculator specific to Siemon duplex and array systems is available by contacting the Siemon

Technical Services team.

Cleaning and Inspection

Due primarily to the increased number of connectors used within array systems, cleanliness of all optical

fiber interfaces is absolutely essential for successful installation and field testing. Contaminants are the

leading cause of high system loss and can be easily transferred between connectors. Even everyday

particles can have detrimental results on optical fiber end faces. Below are several examples of

contaminates under magnification. The cores can easily be seen partially obscured in the images below.

Hand Lotion Dust Particles


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Skin Oil and Dead Skin Flakes Alcohol Residue

Table 3: Examples of Common Contaminants on Fiber End faces2

In addition to contaminating the end face of an optical fiber connector, dust particles can also result in a

disruption of uniform contact in the Z axis as shown below in Figure 4.

Figure 4: Impact of Solid Contaminants on Connector Contact3

Fortunately, by employing proper cleaning procedures and utilizing good preventative measures such as

dust caps, many cases of high loss can be improved or eliminated. Of greatest importance is to ensure

all connector end faces are clean prior to testing. This includes both the optical fiber system as well as

the test cords used for system testing.

Use static minimizing cleaning sticks for both connector end face and bulkhead adaptors. Siemon

recommends the cleaning tools shown below in Figure 5. Simple to use and highly effective at removing

contaminants, these dry cloth cleaning tools are specially designed to clean optical fiber end faces and

are available for multi-fiber MPO connectors as well as LC and SC fiber connectors. The MPO version

cleans both male MPO connectors in array modules and female connectors in adapter plates. LC and SCversions clean installed connectors as well as unmated connectors via an innovative dust cap/adapter.

2Photos and illustrations courtesy of BICSI

3Illustration courtesy of BICSI


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PP-CT-LC .................LC Simplex Dry Cloth Cleaning Tool

PP-CT-SC .................SC Simplex Dry Cloth Cleaning Tool

PP-CT-MTP..............MPO Multi-fiber Dry Cloth Cleaning Tool

Figure 5: Siemon Dry Cloth/Static Removing Cleaning Tools

For significantly contaminated end faces, the use of a specialty wet solvent may be necessary. Siemon

strongly recommends the use of Chemtronics Electro-Wash MX pens. The static bond breaking

properties, and the fact that the Electro-Wash MX unlike isopropyl alcohol - does not leave a residue,

makes it an ideal tool to remove heavy or persistent contamination. Note that, if used, wet solvents

should be used prior to dry cloth cleaning tools as a wet to dry cleaning process is the most

effective.

Ideally, test cord connector end faces should be cleaned between each mating. Contamination from

one port can be carried to the next and spread high loss results to each port tested thereafter. Both

surfaces must be cleaned to neutralize contamination. Continued contamination migration through

multiple matings can result in permanent damage to the end face as can be seen in Figures 6 & 7 below.

Figure 6: Spreading of Contamination with Repeated Mating4

4Images courtesy of BICSI


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Initial End face Contaminated End face Damaged End face

Mated 5 times dirty then cleaned results

in severe permanent damage

Figure 7: Impact of Contamination on Connectors following Repeated Mating5

In addition to the impact of contamination from connector end faces, contamination from

adapter sleeves can also create high loss events known as the Dust Ring effect. As the end faces

are inserted into the adapters, the dust is picked up and pushed to the mated position as can be

seen below in Figure 8.

Figure 8: Dust Ring Effect

Inspection Tools

5Images courtesy of BICSI


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The use of inspection devices is effectively essential in ascertaining whether a connector end

face is sufficiently clean. For this reason, they are highly recommended and the following

options are available.

Optical Scopes

Optical scopes are inexpensive and work well to view the connectors for both fiber patch cords

and pigtails. However, they are limited in that they are unable to view through adapters to

mated connectors.

Video Scopes

Video scopes provide an excellent tool to view the connectors on fiber patch cords, pigtails, and

within adapters. Most field tester manufactures mandate video scope probe inspections of fiber

ports prior to testing. An example of this is provided by Fluke Networks via their Knowledge

Database entry entitled ANSI/TIA-568-C testing LC to LC (Duplex Multimode) DTX-MFM2 which

reads:

Cleaning is critical. It is the single most reason for ending up with negative loss values. You cannot

clean without some means of visually inspecting the end face. This can be anything from a simple Fiber

Viewer to a Video Scope. If you have no inspection device, you cannot proceed.

End Face Conditions

When observing the end faces through the use of magnifying scopes and probes, several

conditions may be seen that can adversely affect performance and may not be improved by

cleaning protocols.

Pits (Permanent Feature)Pits resemble whitish gray irregular dots in the end face. They can be a result of dirty

mating between end faces or can be caused as a natural breakdown of the end faces

from excessive mating cycles. This defect is easy to spot after cleaning since the

features remain in the same place.

Scratches (Permanent Feature)

Scratches usually will run from one side of the end face to the other and can, if over the

core, cause performance degradation. Scratches away from the core may not be of

concern unless they are extremely deep, however deep scratches may collect

contamination and spread it across end face when mated.

Cracks (Permanent Feature)

Cracks resemble scratches in appearance but can extend deep into the connector end

face material. Cracks can become worse with time however, possibly resulting in a

continued drop in performance.


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Chips (Permanent Feature)

Chips are actual pieces of glass or ferrule material that have broken off the connector

resulting in what appears to be large jagged holes in the end face. These can adversely

affect performance when located near the core and can cause serious damage to the

mating surface if dislodged material is present at time of mating.

Imbedded Contamination (Permanent Feature)

Epoxy resin can create a permanent defect in the end face that cannot be cleaned even

with the best cleaning practices. Dirt particles that have been compressed between end

faces, at time of mating, can become permanently embedded in the end face also

resulting in a permanent defect.

Troubleshooting Examples

The following examples are provided as reference to potential resolution methods.

Problem: The fiber link is exhibiting high loss.

Possible Causes:

1. Chances are this is a result of end face contamination. Using recommended procedures listed

above, clean fiber end faces starting with the LC, SC, and ST connectors in TRCs and Array

modules. If test results do not improve, move onto the MPO connections.

2. If cleaning methods listed above do not result in improved numbers it may be necessary to clean

the fiber ports in the field testers fiber modules per manufacturers instructions. Note that re-

referencing of units will be necessary once tester ports have been uncoupled.

3. Excessive mating on TRCs could result in performance issues. Inspection of fiber end face is

recommended. If fiber end face appears compromised with any of the permanent features

noted above, replacement of TRCs may be necessary.

4. If contamination issues continue to be of concern, it is strongly advised to implement the use of

a video scope to ensure cleaning techniques are effective. This can be a helpful tool in

environments containing airborne particles.

Problem: The fiber tester will not link up with remote unit.

Possible Causes:

1. Remote has shut down due to low battery.

2. TRC is on the wrong fiber strand.


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3. Massive end face contamination has totally obscured the fiber core. Refer to and perform

cleaning methods listed above.

4. Improper cabling routing has resulted in damage to fiber link.

5. Connector is not fully mated.

Problem: The tester seems to be exhibiting inconsistent test results that vary each time the same link is

tested.

Possible Cause:

1. In some cases, field testers can begin to exhibit inconsistent results as the battery gets low. If

this occurs, consider performing repeated tests on the same link while keeping all connections

in place to isolate to the field tester. If not realized during testing, this can potentially result in

re-testing, so it is a good practice to monitor battery levels when testing.

Siemon Optical Fiber Field Testing Guide

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