Stick 'em Up Using Epoxy

I am always amused when I hear, “No one uses heat-cured epoxy connectors anymore.” In fact, about 95 percent of all connectors, including every factory-made patchcord, uses heat-cured epoxy for its ease of use, low cost and high reliability. Granted, only the most skilled techs use them in the field, but they know the secrets of working with these connectors.

To terminate fiber with epoxy/polish connectors, you only need a basic tool kit and an epoxy-curing oven, which is a temperature-controlled, electric oven that cures epoxy in about five minutes. Most of these ovens require alternating current (AC) power, which is no problem in most premises applications, but, as I bragged in an earlier column, I invented one that works on battery and AC power for use anywhere. It’s still available.

When you arrive at a work site, set up your workspace. Plug in the oven to let it heat up fully. In most cases, you need ample room for all of your tools and a small folding table covered with a black plastic mat so you can see the fiber more easily. Once you become experienced, you will develop strong preferences for tool placement and creation of the most efficient workspace.

Experienced techs know to use only the proper adhesives in the specified manner. Much research has gone into finding the right kind of adhesive to bond glass fibers to ceramic ferrules in connectors, including how to apply the adhesive and how to cure it. 

Only buy your epoxy from a quality fiber optic distributor. Ensure the adhesive is fresh (it’s dated like food, and you should store it in the refrigerator), and mix it thoroughly to ensure the adhesive and hardener are fully combined.

After mixing, the adhesive is poured into a syringe with a flat-ended needle. Most adhesives have only about 30 minutes of working life, so you need to plan ahead to get the most use out of the epoxy. If all of your cables are prepared with only the tight-buffered fibers left to strip, you can get more than a dozen connectors from one batch of epoxy.

The syringe squeezes adhesive into the connector. Insert the needle into the back of the connector, hold the flat-tipped needle against the end of the ferrule and squeeze gently until you see a small bead of adhesive on the end of the ferrule. Back the syringe out a bit, and squeeze just a tiny bit more into the back of the connector. If adhesive runs out the back of the connector, you overdid it. Remove the syringe, and place it on the table on top of a lint-free wipe.

Inserting the fiber into the connector is easy once you get the hang of it, even if the fiber and the hole in the ferrule are the size of a human hair. Connector manufacturers have thought about that, so there is a chamfer on the hole to guide the fiber.

Here is another trick. While you insert the fiber, slowly rotate the connector back and forth to spread the adhesive evenly. The surface tension of the adhesive will “float” the fiber into the center of the hole in the ferrule, improving fiber alignment in the connector and improving the polishing process. That trick will noticeably reduce your connectors’ loss.

If you are terminating tight-buffer fiber (the fiber with the 900-micron plastic coating), all that is left is to slip on the boot and place the connector in the oven to cure. If you are using a jacketed cable, crimp the strength members to the connector, slide the boot on the connector and place it in the oven.

Here is where epoxy/polish connector critics get confused in talking about termination times. You don’t wait around for that connector to cure before polishing it. You prepare another connector and put it in the oven, then another and another. Most ovens have about 20 positions for connectors (the oven I designed holds six connectors). By the time you get the sixth connector in the oven, the first one is ready to come out. If you are terminating a number of connectors, the oven curing time is irrelevant. You simply go on to the next connector. The curing time only matters when you are only doing one or two connectors.

With epoxy, connectors come out of the oven ready to polish—a process that takes less than a minute. Setting up a production line will enable a tech to easily complete a dozen connectors an hour, twice that if they are skilled and in a hurry.

Next month, the process continues.

Only buy your epoxy from a quality fiber optic distributor. Ensure the adhesive is fresh 
(it’s dated like food, and you should store it in the refrigerator), and mix it thoroughly to ensure the adhesive and hardener 
are fully combined.

About the Author

Jim Hayes

Fiber Optics Columnist and Contributing Editor
Jim Hayes is a VDV writer and trainer and the president of The Fiber Optic Association. Find him at .

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