In the early 80's, pioneers in the interconnection industry developed a basic method to attach a connector to a length of fiber optic cable. That method was the use of epoxy, applied onto the fiber with a cotton swab or toothpick. The coated fiber was inserted into the connector, the epoxy was cured, the fiber was cleaved, and finally a few polishing steps were performed to get the fiber smooth and flat (relative to the end of the connector). The time to do all that was 15 - 20 minutes per connector.

Similar methods are still being used today. The epoxies have been refined, the method of applying the epoxy has been facilitated, and the polishing films/tools optimized. In addition, many new connector designs and termination methods have been developed that enable a connector to be installed onto a fiber cable in less than two minutes!

In this article, we will examine several termination methods and the advantages/disadvantages of each.

First of all, the basic steps for using epoxy as a termination method are as follows (after the cable has been stripped down to the bare fiber):

Mix the two components of the epoxy (resin and hardener). The epoxies these days have just the right viscosity to allow it to flow nicely between the very small space between the fiber and the connector ferrule hole and they also can be cured at various temperatures/times to enable excellent resistance to temperature extremes. Also, the mixing is made quite simple.

Pre-mixed and pre-loaded epoxy is also available, in a syringe. This type of packaging requires that the pre-loaded syringes be kept frozen until ready for use, but the use of dry ice makes that relatively convenient and the advantages are that no mixing is required and the epoxy is devoid of air bubbles.

Load the mixed epoxy into a syringe (unless it's pre-loaded of course).

Inject the epoxy into the back end of the connector ferrule.

Insert the prepared cable into the connector such that the bared fiber is inserted into the ferrule hole. Insert until the cable seats inside the connector. The fiber will be protruding out the front of the ferrule by typically ½ inch.

Crimp: If the connector is being installed onto jacketed fiber, a crimping operation is required to retain the connector onto the cable strength members and jacket. This is usually accomplished via use of a crimp sleeve and, in order to retain the connector onto the cable's strength members as well as the jacket, two crimps are typically required.

Install the connectorized cable into a curing holder (which serves to protect the protruding fiber from the damage that could occur from handling during the next step, curing the epoxy).

Cure the epoxy: Place the connectorized cable & curing holder into an oven. There are curing ovens designed specifically for this purpose which are basically a hot plate with 12 - 20 holes in it which the connector/curing holder fits into. However, any kind of oven will work, as long as it is capable of achieving the proper temperature for the right amount of time. Hint: if a "conventional" oven is used, be sure to position the connector/curing adapter such that the mating end of the connector is facing the floor.

This will avoid what is called "wicking", which refers to the flowing of epoxy out the back end of the connector and into the strength member strands (which can cause a brittle condition that will degrade the cable retention).

Cleave the protruding fiber (using a pocket pen style scriber) as close to the ferrule tip as possible and remove this excess fiber with a straight, non-twisting pull.

Dispose of the fiber by depositing it onto a piece of tape (regular masking tape works fine) or into a debris container that is set up for that purpose. This may seem overly cautious but if a piece of fiber gets stuck onto your finger or flies up into the air, it can end up in your skin or in your eye.

Polish: This process is critical to optical performance& ..if a smooth finish is not achieved on the fiber, the light rays will be lose some power passing through the first connector and into the one mated to it. The first polishing step is intended to remove the excess epoxy from the ferrule tip via use of a relatively coarse grit polishing film. The subsequent polishing steps use increasingly finer grit films so as to gently create the desired smoothness on the fiber.

Clean the ferrule tip/fiber. There are various methods of cleaning the polished ferrule tip. The method that gets the ferrule/fiber the cleanest is via use of a lint-free "wipe" that has been dipped into alcohol (use of 99% reagent-grade alcohol is recommended), followed immediately by a dry lint-free wipe, and finally to blow-dry using a can of clean, compressed air. The other methods are less effective but are generally sufficient (especially if the fiber is multimode, rather than singlemode):

Clean the ferrule tip/fiber.

using the same alcohol-soaked wipe method as noted above but eliminating the blow-dry step is a good alternate;

use of an available cleaning "box" that contains a special dry, lint-free cleaning tape on a reel is good, albeit expensive; 3-there's also an inexpensive sticky-tape product available that basically does the job; i.e., it generally produces sufficient cleanliness for multimode applications.

Inspect: It is important to look at what has been accomplished during the polishing and cleaning steps. If the polishing was not done well (i.e., neither the ferrule nor the fiber were polished sufficiently smooth) and this connector was then mated to another, good connector, it is possible that the good connector could be damaged via the fiber being scratched by the "bad" connector.

Inspect: There are several microscopes available that make this inspection quite easy. They are designed to hold the connector in a position to enable simple focusing, and to magnify the polished ferrule tip sufficiently to enable seeing the ferrule tip and fiber well enough to be able to judge its quality (typically 100X; sometimes 200X).

Test: Optical testing is the only way to assure that the quality of your terminated connector is good enough to transmit voice, data, or video signals without excessive degradation. For multimode, the only required test is Insertion Loss (a measure of how much light is passing through the connection). However, for singlemode, Return Loss must also be tested (a measure of how much light is being reflected as a result of the connection).

Termination

Method

Typical Time to Field

Terminate onto Buffered

Fiber (1)

(Minutes per Connector)

Time Allowed to

Insert Cable

Source of

Epoxy/Adhesive

Cure

Heat-Cured Epoxy 10 + 30 (cure time) 2 hours Oven

Room Temp-Cured

Epoxy

10 + 120 (cure time) 15 minutes Air

Pre-Injected

Epoxy

8 + 30 (cool down time) 1 minute Oven

UV Adhesive 5 30 seconds UV Light

Cyanoacrylate

Adhesive

3 < 5 seconds Air

Anaerobic

Adhesive

3 5 seconds Activator

Acrylic

(LightSpeed TM)

Adhesive

2.5 30 seconds Activator

Crimp 2 No limit Not Applicable

No Epoxy/No

Polish

1.5 No limit Not Applicable

Termination

Method

Relative Connector Cost Special Tools

Required(2)

Environmental

Resistance

Heat-Cured Epoxy Low Curing oven Excellent

Room Temp-Cured

Epoxy

Low None Good

Pre-Injected

Epoxy

Medium Heating oven, cooling stand Good

UV Adhesive Medium UV curing light Fair

Cyanoacrylate

Adhesive

Low None Fair

Anaerobic

Adhesive

Low None Fair

Acrylic

(LightSpeed TM)

Adhesive

Low None Good

Crimp High Special installation tool Fair

No Epoxy/No

Polish

High Special cleaver & crimp tool

1) The time to field terminate as noted is based on use of manual polishing techniques (where applicable). If an Automated Field Polisher is used (such as Siemon part number FPOL) for the adhesive and crimp methods, 0.5 to 1.0 minute can be saved relative to the manual times noted above.

(2) The following tools are considered standard for fiber connector termination (i.e., not special): jacket stripper, buffer stripper, industry-standard crimp tool with two hexagonal cavities, high-quality scissors (able to cut aramid strength members), scriber, manual polishing puck, polishing film (usually two grits), polishing pad, dry wipes, safety glasses, debris container (or masking tape), marker pen, microscope (100X minimum).

Note that the cost of the special tools as noted for the crimp and no epoxy/no polish methods can vary from manufacturer-to-manufacturer. Some of the tools have an insignificant cost, some cost a few hundred dollars.

The Crimp style termination method typically does not need an industry-standard crimp tool because the installation tool includes the required crimp cavities.

The No epoxy/No polish termination method does not require the following "standard" tools: industry-standard crimp tool (all crimping is performed via the installation tool), scriber, manual polishing puck, polishing film, polishing pad, microscope.

Connector Types

This procedure is a general guide for the use, care, and maintenance of fiber jumpers sold by The Siemon Company and is included on each fiber jumper/pigtail bag.

• Keep all connectors clean. Replace protective dust caps on connectors when not in use.

• Clean the connector ferrule with a lint-free wipe soaked in isopropyl alcohol, followed with a dry lint-free wipe.

• Do not touch the connector ferrule tip prior to installation.• Observe a minimum bend radius of 30mm (1.2 in.) during

handling, installation and use.