FOA Basic Skills

Lesson 5: Fiber Optic Termination (Connectors)

Objectives: From this lesson you should learn:
How to identify common fiber optic connectors
How to install connectors using several methods
Adhesive/polish (epoxy, anaerobic and Hot Melt)
Singlemode fiber polishing

Tools And Components Needed
Fiber stripping tools, crimper, Kevlar scissors, etc. or a termination toolkit
Polishing plate, pad, puck and film (12, 3 and 0.3-1micron)
Fiber to splice, preferably a simplex cable or half a zipcord
Download the list of tools and components  needed or refer to the CFOT Certification Lab Manual


Termination refers to the process of installing connectors on the ends of a fiber or fibers in a fiber optic cable. Over the history of fiber optics, there have been over 100 different types of fiber optic connectors designed using at least a dozen ways of attaching the connector to the fiber. Today, factory made connectors use heat-cured epoxy connectors that are generally polished on a machine. Field termination may use adhesive/polish techniques with either heat-cured epoxy, room temperature cured epoxy, anaerobic adhesives or HotMelt ( a 3M product name) or prepolished/splice connectors which have a short stub of fiber inside the connector that are attached with mechanical or fusion splices.

polish connector
Polishing an adhesive/polish connector.

The purpose of this lesson is to show you how to install connectors using the most popular methods. It is recommended that everyone do at least one of the adhesive/polish connectors and one prepolished/splice connector type.

We have provided step-by-step instructions you can follow. If possible, get instructions from the manufacturer of the connectors or the tool kit
you are using and follow them as each manufacturer's connector may have some subtle differences.
Work in a space where you will not be disturbed and avoid distractions. It is important you concentrate on the exercises and follow each step carefully.
Allow plenty of time to complete the exercises without interruption, especially this one on termination. During the termination exercise, you will use adhesives which must be used quickly.


Please Note: This is not the usual online course - it is intended to guide you as you learn new skills - the skills needed to install optical fiber cable plants. It involves using tools and components in a realistic manner. Some of the processes here can be hazardous, like working with sharp scraps of optical fiber and chemicals. The first lesson is about safety - we recommend reading it carefully and posting the safety rules for everyone to see. Always wear safety glasses when doing any of these exercises and dispose of all scraps properly.

These guidelines are strictly the opinion of the FOA provided for educational purposes and the reader is expected to use them as a basis for learning. The FOA assumes no liability for the use of any of this material.

Familiarize yourself with the safety procedures and follow them all the time.

A pair of safety glasses must always be worn.

Be careful when working with sharp tools.

We recommend working on a black table mat to make it easier to see the fiber (and any scraps). It is best to work on tile or concrete floors, not carpet. If you drop fiber scraps into carpet they can be very hard to find or pick up with a vacuum cleaner.
Clean up after your exercises carefully. Some of the scrap you generate can be harmful, such as fiber ends, so we recommend you not work anywhere near food preparation or children’s play areas! Place clean paper over your work area to keep from harming the worktable surface.
Download a FOA safety poster for your work area.

Background Review

This "skills" course assumes you have knowledge of fiber optic termination and splicing. If you are new to fiber optics, you should first complete the "Fiber U Basic Fiber Optics" course before attempting the hands-on exercises here.

Fiber U Basic Fiber Optics: Termination and Splicing 

Hands-On Lab Instructions

Student Assignment:
Watch the videos and/or read the references and complete the exercises. Videos show processes in real time. VHO (virtual hands-on) web pages are step-by-step instructions on how to complete the hands-on projects. Both should be used to learn and do each of the processes.

YouTube Videos
FOA Online Reference
FOA Textbook

Review:  FOA Lecture 7: Fiber Optic Connectors

Adhesive/Polish Connectors:

Fiber Optic Termination, Part 1, Setup & Tools  

Fiber Optic Termination, Part 2, Jacketed Cable Prep  

Fiber Optic Termination, Part 3, Adhesive Prep  

Fiber Optic Termination, Part 4, Stripping Fiber  

Fiber Optic Termination, Part 5, Connector Attachment  

Fiber Optic Termination, Part 6, Polishing  

Fiber Optic Termination, Part 7, Inspection  

Fiber Optic Termination, Part 8, Distribution Cable Termination   

Fiber Optic Connector Polishing Technique 

Prepolished/Splice Connector Termination (Corning Unicam)   

Prepolished/Splice Connector Termination (Panduit OptiCam) 


Splicing and Termination 

Adhesive/polish connectors

Hints For Adhesive/Polish Connector Terminations

Basic termination including testing connectors  (Tutorial)

Adhesive/polish connectors
VHO:  Epoxy/Polish
VHO:  Anaerobic  
VHO:  Hot Melt

Prepolished/splice connectors 
VHO: PPS termination  

Singlemode fiber termination
VHO:  SM termination    

Book Chapters:
FOA Reference Guide to Fiber Optics,
Chapter 7, Connectors and Splices (same in OSP Book)

FOA CFOT Certification Laboratory Manual,
Fiber Optic Cable Termination, p24

Student Hands-On Assignments:
Watch the videos and/or read the references and perform the exercises.
If you are using the FOA CFOT Certification Laboratory Manual, go to Fiber Optic Cable Termination, p24, which gives step by step directions.

Each of these exercises involves terminating a tight buffer fiber or simplex fiber optic cable with a common type of connector.

You should complete the exercises that apply to the work you are doing, although it is recommended that you learn how all these methods are done to understand the complete process of fiber optic termination.

Before starting the hands-on exercises, read these pages:

Adhesive/polish connectors

Hints For Adhesive/Polish Connector Terminations

Download the Fiber Optic Termination Worksheet and answer the questions as you complete each exercise.
General Instructions

Arrange all your tools, components and other items on your work table. Using a black mat (black Naugahyde works well) makes it easier to see the fiber when working. Epoxy and anaerobic adhesive techniques use the same connector type, the basic ceramic ferrule connector. The 3M HotMelt connector is only made by 3M and will require the 3M connectors and oven. Prepolished/splice connectors are available from many manufacturers but will generally require the termination kit from that particular manufacturer.

termination workspace
Termination tools on lab bench

We recommend starting with either SC or ST connectors with a 2.5mm ferrule as they are somewhat easier to terminate. After mastering the techniques, try the LC connectors with smaller ferrules.

connector parts
Parts of an ST connector

Since it is preferred to be able to test each connector as it is made, we recommend starting with a long patchcord, say 5 meters long, then cut it in half and attach your connector to the cut end. That allows testing your connector as soon as it is made using the single-ended (patchcord) test. Record all test data on your connectors.

Adhesive/Polish Connectors
Adhesive/polish connectors all have a similar process (from left): strip the fiber to the proper length, apply adhesive and insert the connector,
after the adhesive sets, cleave the fiber, air-polish to remove most of the fiber stub, final polish on a flat plate with a soft polishing pad.

Fiber Optic Connector Termination

1. Epoxy/polish Connectors

Read: Adhesive/polish connectors
VHO:  Epoxy/Polish

Follow the directions to terminate a fiber or simplex cable. The 8-part videos above give detailed instructions.
The VHO:  Epoxy/Polish web pages show step-by-step instructions that are easy to follow.

Epoxy-polish  connector
Epoxy must be injected into the connector with a syringe.

Inject adhesive until it forms a small bead on the connector ferrule. When this bead hardens, it supports and protects the fiber during polishing to allow a better end finish. This hardened bead of epoxy means the yield of epoxy/polish connectors is nearly 100%. Thus epoxy/polish connectors have the highest yield, best reliability and lowest loss of any termination type.

Epoxy bead
Inject epoxy until you see a small bead of the adhesive on the end of the ferrule.

Many novices think epoxy connectors take too much time - it does take 5-10 minutes to cure epoxy in an oven. But if you are terminating more than one connector, the first connector goes into the oven and will be ready by the time the second or third connector goes in the oven, so the curing time is irrelevant.

Epoxy usually only has a 30 minute life once mixed. If you are working with others, you can share the epoxy to be more efficient.

If you have a curing oven, the epoxy will cure in 5-10 minutes. Room-temperature curing epoxy will need to be left overnight.

2. Anaerobic /polish Connectors

Read: Adhesive/polish connectors
VHO:  Anaerobic

Follow the directions to terminate a fiber or simplex cable. The VHO gives detailed instructions. The
VHO:  Epoxy/Polish web pages show step-by-step instructions that are easy to follow. There are three methods of applying adhesive described here. We recommend you try all three.

Anaerobic-polish connector
One method of applying anaerobic adhesive is to wipe it on the fiber.

Several methods are used for applying an adhesive and some use an “accelerator” or chemical thatmakes the adhesive set instantaneously. These methods are:
  • Inject adhesive into the connector and dip the prepared fiber end into the acceleratorbefore inserting it in the connector. One must work quickly as the adhesive sets in 30 seconds or so, so if trouble getting the fiber intothe connector is encountered, the adhesive may set before the fiber is fully inserted.
  • Inject adhesive into the connector and then insert the prepared fiber end into the connector. Spray or drop theaccelerator on the protruding fiber and move the fiber back and forth to spread the accelerator inside the connector ferrule. It should set in ~30 seconds.
  • Wipe the fiber with the adhesive and insert it in the connector. With noaccelerator, the adhesive will set in 4-5 minutes and be much stronger. If instant adhesion is required, spray or wipe accelerator on theprotruding fiber as above.

The original method developed decades ago was to inject the adhesive in the connector then dip the prepared fiber in the accelerator and insert it. The problem with this method was the adhesive would set so fast that often one could not get the fiber fully inserted in the connector before the adhesive hardened, requiring the connector to be discarded. Try this method also to see if it works for you.

When cleaning fibers for anaerobic connectors (or any connector for that matter), NEVER use regular medical alcohol or alcohol pads. The 30% water content makes the adhesive take much longer to cure (if it ever cures) and makes the bond to the connector ferrule less strong.


3. 3M HotMelt Connectors: 

Read: Adhesive/polish connectors
VHO:  Hot Melt

Follow the directions to terminate a fiber or simplex cable. The VHO gives detailed instructions.
VHO:  Hot Melt 

HotMelt connectors use an adhesive that is applied to the connector at the factory and is then heated up to liquify it to allow insertion of the stripped and cleaned fiber. The connector is then set aside to cool and set for several minutes before the fiber can be polished.

For this exercise, you will need a special 3M Hotmelt oven. HotMelt ovens use a much higher temperature than epoxy overs, so they are not used for any other purpose - the high temperature will ruin epoxy.

3M HotMelt connectors
Inserting a HotMelt connector in a 3M oven

One advantage of the HotMelt connector is you may be able to reuse them. If you break the fiber or have problems in the cleaving or polishing process, you can heat the connector up and remove the fiber and try again. Or you can strip the fiber ~3mm (1/8") longer and after inserting it fully, pull it back 3mm and let it set. If you have problems with
cleaving or polishing, reheat the connector, push the fiber fully in, let it cool and try again.

4. Prepolished/Splice Connectors

Read: Prepolished/splice connectors 
VHO: PPS termination 

Follow the directions to terminate a fiber or simplex cable. The VHO gives detailed instructions. VHO: PPS Termination 

Prepolished/splice connectors are connectors with a short fiber stub already installed in the connector and polished, allowing the connector to be installed on a fiber using a splice. The splice has traditionally been a mechanical splice but fusion splices are now available for use with some connectors, sometimes requiring special splicing machines, sometimes regular fiber splicers.

Each manufacturer's prepolished/splice connector is slightly different. It is important to follow their instructions exactly to get good results.

The most important issue with any prepolished/splice connector is to ensure the fiber is cleaved properly. Many kits for these connectors provides only a simple, cheap cleaver that looks like a stapler. If used properly, these cleavers can provide adequate cleaves, but they require practice and a technique that not every tech can master. More expensive cleavers such as those used for fusion splicing are recommended to prevent problems. 3M has introduced a new cleaver using a diamond wire that is good for only about 100 cleaves, but it works well and is often provided free with a quantity of 3M connectors or splices. (Watch the FOA video on the
3M Easy Cleaver.)  Remember that a poor cleave will not only cause high loss, it usually causes the need to cut off and discard an expensive connector.

5. Singlemode Polishing: Follow the directions to terminate a fiber or simplex cable. The VHO gives detailed instructions.

Read: Singlemode fiber termination
VHO:  SM termination    

Not many techs attempt field installation of singlemode connectors using adhesive/polish techniques. It is very hard to get low loss and especially reflectance with hand-polished SM connectors so most are factory terminated on a pigtail which is fusion spliced onto the fiber in the field. Furthermore, most SM connectors are tested with an interferometer to verify the quality of the end finish. However we offer instructions to those who want to learn how to polish SM connectors.

interference test
Interferometer test of a SM connector

If you do not have access to an interferometer but want to know how good your connectors are, use a reflectance test to check them. Read: Reflectance Testing 


Next:  Lesson 6: Fiber Optic Testing          

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Table of Contents: The FOA Reference Guide To Fiber Optics

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