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Cabling Installation

Cable box or reel should be marked with same identifier as end of cable. Footage marker on end of cable should be recorded. Cross out previous identifier and footage markings. Fish tapes, pull strings, ropes, Kellem grips and pulleys can be used for pulling cables When using fish tape or rope, strength member used Strip back 4-6 inches of outer jacket, fold the aramid yarn through eye of rope or tape and apply electrical tape around folded head of yarn Cable should be laid into cable tray. If it cannot, it should be pulled. Cable pulled slowly through pathway so as not to cause friction.

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Cabling Installation

Cable should eliminate slack, reduce strain on the cable, and prevent cable from getting caught against objects If cable pulled in stages, slack should be piled in a figure-8 pattern at junction Pull string be pulled in with the cable Allow for slack at both ends of the cable At least 3 meters (10 feet) of slack in Telecommunications Room At least 1 meter of slack at Work Area outlet

Cable Installation

Cable Preparation and Tools

Cable Installation

Pulling Practice

• Utilize Pulling Grip and Swivel

• Allows cable to freely spin decreasing chances of causing high cable

attenuation due to cable twist

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Cable Installation

Distribution Cable with and without central strength member

Cable Installation

Pulling Eye Installation on Armored Cable

Step 1: Remove Armoring and strip buffer to expose Kevlar and fiber

cabling

Step 2: Tape entire section of exposed armor and Kevlar

Step 3: Slide pulling eye over taped area of Kevlar and armoring

Step 4: Begin taping just previous to the taped section and continue the full length of the pulling grip up to the

pulling eye

Step 5. Final taping should have entire pulling grip covered along with

approx. 12” of cable. Swivel can now be attached to pulling eye.

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Cable Installation

Pulling Eye Installation on Armored Cabling

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Cable Installation

Twist in the cable causing high attenuation

OTDR trace before

Cable Installation

With twist in cable relieved

OTDR trace after

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Fiber #6

Fiber #10

Cable Installation

Improper Pulling Consequences

Damage and twist to outer sheath

Twisting of inner buffer tubes

Resulting OTDR traces

Cable/Fiber Management

for Enclosure less Systems

• Utilize FQCRCM (QuickNet)

Rear Manager

• Utilize fingers provided in the cabinet’s vertical manager to assist

with managing trunk cable or individual flat ribbons

Fiber Installation Training Checklist Check Endface of connectors

o Use visual inspection scope or video probe to ensure the endface of the infrastructure and patch cords being used are clean and free of damage

o If contamination is found, clean utilizing the dry clean method o If you must wet clean, remember to dry clean to remove excess alcohol o Re-inspect after cleaning o If contamination cannot be removed, replace the cords

Check Test gear

o Ensure test gear is calibrated and software releases are up to date o Ensure the test heads are clean and free of contamination

o Inspect utilizing Video Probe o Ensure Reference quality cords are being utilized for testing

o Are the reference cords still within reference specifications? o Inspect end face of reference cords to ensure there are no pits, signs of wear. o If signs of wear, replace the reference cord

Obtain Test Results

o Obtain “raw” fluke files (*.flw) so all data can be checked o If “raw” data not available, *.PDF of data files is acceptable, but needs to be each test, not a

summary page of the tests.

Check integrity of cabling infrastructure o 6F or 12F cable has a tendency to twist during installation causing possible high attenuation,

even inside armored cabling. o Check fiber run if possible for twist or scraping to the cabling which would show possible

excessive stress applied to cable during installation o OTDR cable from both directions to check the connections and integrity of the cable o Check cable attenuation against the specified attenuation from the manufacturer

Bad connectors

o Was connector scoped and cleaned? o Ensure questionable connector or connectors are preserved o Refer to “Check integrity of cabling infrastructure” for possible cabling issue o On a trunk assembly, remove at least 2m of cable after the transition to establish where the

damage has occurred during investigation of the issue o On an Opticam or Field polish connector ensure at least 0.5m of fiber is still attached to

connector for investigation Bad cassettes

o Are the discrete connector endfaces clean (MPO, LC, SC, ST)? o Need to inspect with a Video probe

o Is there external damage to the cassette? o Broken connectors, broken housings?

Depending on the OTDR, there will be different settings. I suggest that the Auto Test feature is utilized for testing the cable for attenuation.

1. Utilize a 50m or longer MM launch cord with pre-terminated reference connectors on both ends. If one is not available, fusion splice pre-terminated pigtails onto a long MM fiber.

2. Terminate a connector on the end of the fiber under test. This can be either a bare fiber adapter or a mechanical type connector for quick, easy measuring. You just need to ensure that this connection is a good. A bad first will cause major reflection back into the OTDR resulting in an erroneous trace.

3. Inspect the end faces of the launch cords to ensure they are free of contamination. 4. Connect the Launch cord to the output of the OTDR and to the connector attached to the fiber

under test utilizing an adapter with a zirconia ceramic sleeve. 5. Push the test button on the OTDR. This will test both the 850nm and 1300nm wavelengths and

give a resulting graphical representation of the link. 6. In order to calculate the attenuation of the cable, the A cursor has be past the tail of the first

connection and the B cursor has to be just before the beginning of the rise of the end of the cable (this is the beginning of the reflection of the end event). See the trace below for setting of the cursors. The black trace represents 850nm and the red trace represents 1300nm.

The following trace shows high fiber attenuation and therefore something wrong with the fiber cable.

7. The fiber attenuation in dB/km will be shown on the OTDR display when the cursors are placed at the correct positions.

8. Compare the dB/km reading from the OTDR with the specification of the cable specified below:

Optical Time-Domain Reflectometer (OTDR) Best Practices Purpose

The purpose of this document is to explain the best practices associated with utilizing an OTDR and analyzing the traces obtained while utilizing an OTDR during Tier II testing. What is an OTDR?

An OTDR is an Optical Time-Domain Reflectometer. The OTDR transmits optical pulses through the fiber under test and measures the amount of light that is reflected back to the source over time. The OTDR can determine fiber and connection losses (Rayleigh and Fresnel reflections) by comparing the amount of light reflected back at different times. Common Terms Associated with the OTDR

Reflective Event: Any event where there is a discontinuity in the fiber segment causing a change in the refractive index. These events include fiber breaks, connectors or mechanical splices.

Non-reflective Event: An event where there are no discontinuities in the fiber segment. These events

include fusion splices, macro bends or APC connectors. Index of Refraction (IOR): The ratio of light velocity in a vacuum to its velocity in a given transmission

medium (Typical glass value of 1.46). See manufacturer’s specification on glass for the IOR will differ. Insertion Loss: The amount of loss introduced to a link by the addition of a connector or splice. Optical Return Loss: The measurement of the difference between the amount of light the source sends out

and the amount of light that returns to the source. This may also be referred to as a back reflection. Ghost: Apparent feature or event on OTDR trace caused by the launched pulse reflecting off features in the

fiber Dynamic Range: Determines the range and speed of the OTDR. It is defined as the dB difference between

the initial power level reflected from the fiber under test and the value equal to the noise floor of the detector within the OTDR.

Range: The distance the OTDR will acquire data samples. The longer the range is set, the farther the

measurement. Best practice is to set the range at twice the link length that is to be tested. Pulse Width: The duration of the amount of light injected by the OTDR into the fiber. The longer the pulse

width, the greater the light level generated into the fiber and the farther the distance the OTDR will accurately measure.

Rayleigh Reflection: When the light introduced to the fiber is scattered in randomly throughout the fiber due

to microscopic particles within the fiber. These particles are embedded in the fiber during manufacturing and are graphically represented by the slopping of the fiber trace over the entire span. (This is the reason for cable attenuation)

Fresnel Reflection: When the light introduced to the fiber comes in contact with air, or another media such

as a splice of fiber connector. This is referred to as an event. Events are both reflective (connector) and non-reflective (splice or APC connector) events.

Event Dead Zone: This refers to the minimum distance required for consecutive reflective events to be

Identifiable. If a reflective event is within the event dead zone of the previous event, it will not be detected.

Attenuation Dead Zone: This refers to the minimum distance required, after a reflective event, for the OTDR

to measure another reflective or non-reflective event loss.

Quick Measuring Tips

1. Utilize a 50m or longer launch cord with a reference grade connector on the end that will attach to the link under test. This will ensure the first connection point is measureable and the least amount of back reflection will occur possibly causing an erroneous trace.

2. Utilize a 50m or longer receive cord with a reference grade connector that will attach to the link under test should be utilized if the last reflective event needs to be measured.

3. A small pulse width will allow for more distinguishable trace, but usually needs a longer averaging time. A long pulse width will allow the OTDR signal to travel further and is usually used to quickly find a fiber break.

4. The range on the OTDR should be set to approx. 2x the length of the cable being measured. Example of a Trace

Measuring Fiber Cable Attenuation

When measuring the attenuation of a length of fiber cable, the cursors need to be place just after the launch event and just before the final reflective event. As shown below, the “A” cursor is placed just after the tail of the first connector (this is the connection between the launch cord and the first connector in the fiber cable under test). The “B” cursor is placed just before the beginning of the last reflective event (This can be a connectorized end of the cable or a bare fiber end.

Launch

Non-Reflective Event

Reflective Event End

Reflection

Noise

A B

Measuring Loss of a Reflective Event (Connector or Mechanical Splice)

When measuring the loss of a reflective event, the cursors need to be place just before the event and after the tail end of the reflective event (where the trace levels off). As shown below, the “A” cursor is placed just before the start of the reflective event and the “B” cursor is placed just after the leveling of the signal after last reflective event. The difference in the two points “x” is the insertion loss of the reflective event.

Measuring Loss of Non-Reflective Event (Fusion Splice)

When measuring the loss of a non-reflective event, the cursors need to be place at the start and end of the event. As shown below, the “A” cursor is placed at the start of the non-reflective event and the “B” cursor is placed at the end of the non-reflective event. The difference in the two points “x” is the insertion loss of the non-reflective event.

Measuring Return Loss of a Reflective Event

When measuring return loss of a reflective event (the reflectance measurement must be selected on the OTDR) the “A” cursor should be placed just before the reflection and the “B” cursor should be placed on the peak of the reflection. Keep in mind that calculating reflectance manually with an OTDR is a complicated process and the measurements have a fairly high measurement uncertainty; the higher the peak, the higher the reflectance value. In order to measure reflectance, the peak must not saturate the OTDR receiver, indicated by a flat-topped reflectance peak.

A B

X

X

A B

Reflectance

A B