How to handle optical fiber and connectors



Fiber damage caused by improper handling is very costly in wasting time and ruining components but can be almost completely avoided. The procedures below describe the safe way to handle, clean and install fiber optic components.

About the fibers
General handling guidelines for fiber optic components
Removing components from their packing containers
Fiber optic connector cleaning and maintenance
Cleaning the bulkhead mating adapters
Cleaning the cable connectors
Fiber optic cable installation
Connecting fiber optic cables with bulkhead adapters

About the fibers

The typical diameter of standard bare telecommunications fiber is approximately 125 micrometers (10-6 meters) -about the same size as a human hair. The strength of this glass fiber, however, exceeds that of an equivalently sized strand of steel бн that is, unless the glass surface is scratched.

Typical telecommunications fiber is composed of three basic parts: a core (5-8 um) that carries the light, a cladding (125 um), and an outer coating (see Figure 1). The core and cladding are made of high purity glass, while the outer "primary" coating is made from a polymer (Acrylate or polymide) that serves as a protective barrier (or sometimes it can be epoxy resin). Careful handling, however, is still required to prevent fiber damage.

The three major causes of fiber damage: scratching, bending, and pulling

Scratching is, by far, the most common cause of fiber breakage. Handle fibers only in areas that are very clean and do not contain sharp objects.

Bending is another common cause of fiber damage. The typical minimum bend radius for uncoated telecommunication fiber is about 17mm -approximately the size of a standard pen. If it is bent more than this (see Figure 2), it will likely break. Also, power loss in the fiber will increase with smaller bending radius. Coiling and twisting the fiber will also result in polarization dependent loss due to induced fiber birefringence.

Loops the fiber in a large radius before the final packaging process. However, if the loop becomes tangled, carefully unwind it, avoiding any small diameter radius bends -if the fiber breaks, the component may be unusable.

Pulling on the fiber is the third major cause of breakage. The fibers are attached to the assemblies with either epoxy, solder (for metallized pigtails) or sometimes glass. While these bonding methods are very strong, improper handling can result in the fiber "pulling out" of the component package. To prevent this, avoid handling the component by the fiber.

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General handling guidelines for fiber optic components

Optical fiber is very strong in some ways, but since it contains a very thin strand of glass, it is also quite delicate. Treat it like fine crystal, follow the handling procedures outlined here, and you will minimize the time and expense associated with broken component fibers.

    * Wear finger cots or gloves. Your hands may look clean, but dirt and oils on them can damage the fiber and contaminate connectors.

    * Never use the fiber pigtail to pick up or support the weight of the device. Keep both the device and the optical connector together in your hand(s)

    * The fiber is made of a very pure, expensive glass. Treat it with the same care that would be used when handling expensive crystal glass.

    * Do not allow kinks or knots to develop in the fiber.
            o Carefully work out any tangles-patience will save time and money
            o Do not pull on the fiber when kinks or knots are present. Pulling will only cause knots, kinks, and curls to tighten, increasing the chance of breakage.

    * Always use the correct tools for stripping and cleaving the fiber. It will save time and reduce breakage caused by scratches.

    * Follow all ESD precautions and approved fiber cleaning procedures.

    * Always read and comply with the handling instructions on the shipping container Removing components from their packing containers

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Removing components from their packing containers

Fiber optic component containers usually specially designed to prevent damage during shipping. Use these following procedures to remove the components.

    * From cardboard shipping carton:
            o First, release and lift out the connector using one hand.
            o Then, use the other hand to carefully uncoil the fiber from its oval recess
            o If the fiber snags, gently work the fiber toward the center of the oval, then lift.
            o Once the fiber is completely uncoiled, lift the device out of the shipping box.

    * From clear molded plastic shipping container:
            o First, separate the flat top from the recessed plastic bottom.
            o Then, remove the plastic foam surrounding the device package and the large foam inserts covering the coiled fiber.
            o Gently uncoil the fiber. If there are kinks, tangles, or knots - DO NOT PULL.
            o Once both sides are uncoiled, gently lift the device package from the container and place it on a clean surface away from sharp objects.

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Fiber optic connector cleaning and maintenance

Connectors and bulkhead adapters should be cleaned before interconnection. A microscopic bit of dirt or contamination can damage the connector or degrade performance. In high power systems this dirt can act as a lens to focus the high power and actually 'burn' the interconnection.

Warning! To prevent serious eye damage, never look directly into a fiber optic cable connector or mating adapter. Never assume laser power is turned off or the fiber is disconnected at the other end.

Warning! Always handle, use and dispose of chemicals and other cleaning materials in accordance with manufacturer's instructions.

Note: Always perform the cleaning procedure described below for cable connectors prior to fiber optic cable installation. Whenever possible, inspect each connector before connecting it to its mating adapter.

Cleaning materials
    * Reagent grade isopropyl alcohol in an alcohol dispenser.
    * Lint free laboratory wipes, such as Kimwipesä tissues.
    * Clean, dry, oil-free compressed air.
    * NTT-ME Corp. Optical fiber connector cleaner ("CLETOP REEL Type A" or similar)

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Cleaning the bulkhead mating adapters

When cleaning a cable connector/ bulkhead mating adapter pair, clean the mating adapter first. The mating adapter should not require cleaning if it has been used with clean, defect free fiber connectors and capped when not in use. However, if the adapter is suspected of being dirty, use only clean, dry, oil-free compressed air and follow these steps:

Step 1: Aiming away from the adapter, release a short blast of compressed air to remove any dust inside the nozzle of the compressed air can.

Step 2: Use three to four short blasts of air directed at the adapter to remove dust.

Follow the manufacturer's instructions for use of compressed air. Improper use of compressed air can result in contamination of the adapter.

A more thorough cleaning requires disassembly of the part and should only be done by a n specially trained technician.

Note: Use a clean dust cap on adapter ports and fiber connectors when not in use.

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Cleaning the cable connectors

Step 1: Fold a clean wipe several times, to get a pad of 6 to 8 layers of material.

Step 2: Remove the protective cap on the optical fiber cable connector.

Step 3: Dampen (but do not soak) a corner of the pad with alcohol using the alcohol dispenser.

Step 4: Firmly press the tip of the ferrule into the alcohol-moistened area of the wipe. Pinch the wipe firmly with your fingers against the ferrule and twist the ferule. Repeat three times, using a clean area of the wipe. Clean the tip and as much of the outside of the ferrule as possible.

Step 5: Press the ferrule tip into a clean, dry spot of the wipe, pinch, and twist once.

Step 6: Discard the used wipe.

Step 7: (Optional) Use clean, dry, oil-free compressed air to remove tissue fragments that may have been deposited on the tip of connector.

Step 8: Whenever possible, inspect the ferrule end-face. If it is still dirty, repeat steps 1 through 8. If the ferrule is damaged it may need to be replaced. Contact producer technical product support. Defects on the fiber cable connector can damage the mating connector and repair can be costly.

Step 9: If the ferrule end-face is clean and damage-free, place the connector into the matching, clean, mating adapter.

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Fiber optic cable installation

Warning! Follow all directions and warning labels when working with optical fiber cables and adapters. To prevent serious eye damage, never look directly into an optical fiber cable connector or mating adapter.

Note: Electrostatic Discharge protection (such as ESD wristbands) is necessary when working with modules containing electrical connections.

Note: Always clean before making the connection with the mating adapter. One missed cleaning may allow a piece of grit to permanently damage the fiber inside the unit.

Note: Make sure that the connector type matches that of the bulkhead adapter (e.g., SC/UPC). Mismatches will result in damage.

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Connecting fiber optic cables with bulkhead adapters

Step 1 Place the cable connector in front of the bulkhead adapter on the front panel of the device. Refer to the device test data for a detailed description of the inputs and outputs.

Step 2 Align the keyed ridge of the cable connector with the slot in the receiving adapter.

Step 3 Gently push the cable connector into the adapter. For SC/UPC, you will hear the click of the latching mechanism.

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