With so many styles of connectors on the market, choosing a tool kit can be a challenge.
March 1, 2001
Every fiber optic cable that is installed today has a connector on both ends. This may not be big news, but it does mean that connector installation is one of the most important skills an individual can learn in the fiber optic cabling industry.
There are many different styles of connectors available: ST-compatible connectors, SC connectors and several new small form factor (SFF) connector styles. In addition, many different companies manufacture each connector type and this can make choosing a tool kit somewhat difficult.
When you evaluate tool kits, you will probably want to find the connector method that provides you with the greatest amount of flexibility. Will the kit you purchase accommodate many different connector styles? Are the skills you develop for a termination method transferable to other tasks? Does the tool kit require skills that are unique to it? In order to answer these questions, you must have a good understanding of some of the different termination methods that are available.
TO POLISH OR NOT TO POLISH
The most basic distinction that can be made is between termination methods that require the installer to polish the connector, and those that do not. Connectors that require polishing will require the installer to insert a bare fiber through the connector until it comes out of the ferrule at the other end. The bare fiber must then be removed close to the surface of the ferrule with a scribe tool. This can be a challenge for anyone who does not have a steady hand, but it is a skill that can be developed with a little practice. The next step is to polish the ferrule until all of the rough edges are removed and the fiber core and cladding are clear of all imperfections. This is usually done by hand and can be time consuming, but automated polishing machines are also available.
The other termination method involves aligning your piece of optical fiber with a stub that is installed in the ferrule at the factory. The ferrule is already polished, which means time saved in the field. But there is a trade-off, because these connectors will require you to cleave your bare fiber before you insert it into the connector. The cleave will be the most important step, as you need a straight surface on the end of your fiber (so that it will be flush with the fiber stub that is already in the connector). The tool to use in this instance is a score-and-snap cleaver, which looks like a small stapler. With this tool — and a little practice — you will be able to achieve good cleaves on a consistent basis. If you are going to work with many connectors and perform splicing, it is a good idea to invest in a high-quality cleave tool.
Within the basic “polish-no polish” distinction, there are many different varieties of connector termination methods. There are connectors that require epoxy, some that use a crimp mechanism, and one that uses glue. Each of these connectors has its own idiosyncrasies, and these will ultimately affect your purchasing decision.
In earlier days, epoxies were used to lock the fiber in the connector, the fiber was removed from the end of the connector and you would then begin to polish. Many of these connectors are still being installed today. Sometimes the epoxy that is used is composed of two compounds that must be mixed together. The mixture is then drawn into a syringe, and the syringe is used to insert the epoxy into the connector.
One type of epoxy connector uses an oven to heat cure the epoxy before you scribe and polish. The curing time for each connector may be as long as 10 minutes, but curing several connectors in succession and creating a small assembly line can offset this wait. For safety purposes, you must also keep in mind that the oven (and the connectors that come out of it) is very hot.
Another connector uses UV light to cure the epoxy. This epoxy is only one compound and does not require mixing, but it also requires caution because sunlight contains UV rays and they can cause the epoxy to cure. Fortunately, the UV light present in sunlight is not strong enough to be a big problem, and many manufacturers have packaged the epoxy in opaque syringes or bottles to help guard against this. This type of kit includes a high power UV lamp that is used to cure the epoxy once it is in the connector with the fiber; the typical cure time is approximately one minute.
A third type of epoxy is called “anaerobic”, because it cures in the absence of oxygen. This would seem to limit the places in which this connector can be installed, but the epoxy is usually used in conjunction with an accelerant that causes it to cure. In recent years, some companies have changed the formula of this epoxy so that it will cure on its own in a minute or two.
You must remember to change the needle on your bottle of epoxy regularly because it can become clogged when the epoxy in the needle is exposed to the air. This may lead to small pieces of hardened epoxy being injected into the connector and blocking the hole that your fiber is supposed to slide into. This can be a problem for any termination method that uses epoxy. Furthermore, you will need to rotate your inventory on a regular basis, because all epoxies have a limited shelf life. You should also check the expiration date on all consumables kits and bottles of epoxy that you receive from your supplier.
Another termination method to consider involves the use of glue, instead of epoxy, to hold the fiber in the connector. This glue is installed in the connector at the factory, which eliminates the need to mix compounds or use syringes. To terminate a fiber, you must place the connector in an oven for a few minutes until the glue begins to melt. You then insert it into the connector until it comes out the other side. As the connector cools, the glue will harden again and lock the fiber in place. You will complete the installation by scribing and then polishing. One benefit of this method is that there are fewer steps to perform than with epoxy-style connectors. And, in the event of a problem during the termination, it is possible to reheat the connector, remove the fiber and start again. Although the manufacturer of these connectors does not “officially” recommend this, it is often performed with success and can reduce your scrap-rate significantly. This connector method is very popular and will probably continue to be a favourite because its only shortcomings are the safety issues associated with the oven, and the extra time that is required to polish the connectors.
The final type of termination method uses a crimp (instead of glues or epoxies) to lock your fiber in place. This method eliminates the need to use ovens and UV lamps and mix compounds. However, the “polish-no polish” distinction still applies. A crimp connector that requires polishing will lock your fiber in place by grabbing the outside of the optical fiber and coatings as you perform a series of crimps. You will then need to scribe and polish, but this usually requires less time than some of the other termination methods because there is no glue or epoxy to polish away.
The other style of crimp connector involves cleaving your fiber before you insert it into the connector. The optical fiber is crimped in place, once it is aligned with a fiber stub that is already in the connector. These connectors do not require polishing and tend to be the quickest to install. But they are often a little bit more expensive than other connectors, as they require more work on the manufacturer’s part to make them easier for you to install. Due to its simplicity, this methodology has increased in popularity and it is now available from many different manufacturers.
Recently, there has been a move towards the use of SFF connectors. But some things never change, and the basic termination methods still exist. We still have some connectors that use epoxies and require polishing and we have others that use a factory polished stub and crimp mechanism. So, while it may sound like a big change is occu
rring, the tools needed for SFF connectors are usually just a small upgrade to a kit that you are already using to terminate ST-compatible or SC connectors.
Once you have decided which termination methods are appealing, you should examine some of the associated costs. Your tool kit is a one-time expense, although you may have to add things to it in the future. However, many other factors will affect profitability in the future. For instance, what is the price of the connectors for each tool kit you are considering? Which termination methods require consumable items, such as epoxy or polishing paper? Is the connector easy to install? If it is not, you may have to include the cost of extra connectors to cover those that you scrap on the job site, and you may have to spend more money on training. Will you be offering manufacturer certification of the cable system? If so, you will only be able to use their approved connectors and this will limit your choice of tool kits. It will also mean that you must purchase kits from each manufacturer that you will certify installations for.
After carefully reviewing these factors, you may discover that the connector that costs a little more per unit will save you money in other areas. Or, you may find that you personally have more success with one termination method over another. Some people have trouble using the score-and-snap cleaver that is supplied with some crimp-style connectors. Others have difficulty scribing and polishing. If you want to avoid working with messy epoxies, you may want to choose a crimp connector. Perhaps you already have a fiber connector kit but you must work with one of the new SFF connectors. You may be able to save money by buying only a few additional pieces to add to your kit.
There are several other intangibles to look at when deciding which tool kit to purchase. First, you must discover which connector types each kit will accommodate and which types you will need to be able to install. The ST-compatible and SC connectors are still very popular, but not all tool kits will accommodate both. If the tool kit you are considering does not, is there an add-on kit that will allow for this? Can you easily upgrade the kit to accommodate SFF connectors? If the kit requires you to polish connectors, you will also need a microscope to inspect your optical fiber for damage. Many styles of microscopes and levels of magnification are available, but not all kits include one. As you do more work in the industry, you will also need a few extra tools for splicing purposes.
Choosing a connector tool kit can be a difficult decision because there are so many variables. In the best of all possible worlds you would choose more than one kit in order to maximize your flexibility. However, this may not be practical, so your decision must be made cautiously.
You are about to make an investment in your future. As is the case with any investment, you need to evaluate all of your options carefully in order to make an informed decision. CS
Philip Mayson has worked in the cabling industry for 10 years. He is currently an Instructor at the Southern Alberta Institute of Technology (SAIT) in Calgary, where he teaches fiber optic cabling and data communications cabling courses. He can be reached via e-mail at firstname.lastname@example.org.