Special Splicing Secrets

As I have described in the previous few columns, splicing fibers is fairly easy. If the installer cleans and cleaves the fibers properly, the machine does the rest. However, the installer’s job is not over at that point.

Once the fibers are spliced, the installer needs to place them into a splice tray that is then placed in an outside plant splice closure or rack, panel or cabinet for premises cabling. During this process, the installer needs skills in managing fibers to ensure their protection.

There are hundreds of splice tray and closure types, varying in fiber capacity, the number or kind of cables, and installation location. The installer needs to know how to manage fibers with the particular splice tray and closures.

Splice trays for single-fiber splices are generally designed to accommodate fibers in multiples of 12 because loose-tube cables have 12 fibers per tube. For 12 fibers, two tubes will come to the tray, one from each of the cables that the installer is splicing. If the splice tray holds 24 splices, it is two tubes from each cable and so on.

The fiber tubes will be attached on one end of the splice tray, and about 1 meter of bare fiber will be left to splice to the appropriate fiber on the other cable. After the installer makes the splice, he or she will neatly coil the bare fibers in the splice tray and place the splice in the holder in the tray’s middle.

Every splice closure has instructions on how long the buffer tubes and bare fibers must be to fit the splices in the trays and the trays in the closure. The fibers will not fit correctly in the splice tray if they are too long. If they are slightly short, they can still fit, but the installer must measure carefully and precisely, because, if the installer has problems with a splice and has to redo it, the cable loses some length.

As the installer prepares to splice the fibers, he or she needs to ensure the proper fibers are spliced to each other. Fibers and tubes are color-coded, so they must match the correct tube and the individual fibers. If the installer is doing a straight-through splice where like colors are spliced, matching fibers is easy. If the installer is splicing cables of different types and fiber counts, he or she needs a table of proper color-code directions to follow and check off when competing each splice.

Once all of the fibers are spliced, the installer will place a cover on the tray before placing it in the closure. It’s important that the fiber coils in the splice tray should be neat, and the installer must be very careful to not pinch or break the fibers when attaching the tray cover. I have seen cracked fibers cause problems long after the splicing is done, and they can be very difficult to find in the middle of a long-distance link.

Ribbon fibers can be quite different to splice and place in a tray or closure. Using special splicers, all the ribbon fibers are fused at once, saving significant time but requiring more care.

Ribbon cables are different from loose-tube cables because there are generally no tubes protecting the fiber ribbons. To handle ribbon cables, it is common to separate the ribbons and slide a plastic tube over one or more to protect them between the cable entry to the closure and the splice tray.

It takes planning to make ribbons fit properly in the splice tray. Ribbons only bend in one direction and cannot cross each other inside the splice tray due to their width. The trick is to fit the ribbons into the tray before splicing. When everything fits, the installer will pull out the two ribbons to be spliced, cut them to the proper length, make the splice and return them to the tray.

Just like single fibers, ribbons require matching color codes. Straight-through splices of identical cables usually mean matching color codes for both the ribbon itself and the individual ribbon fibers. Sometimes you may have to break out individual fibers from the ribbon to splice to fibers in another cable. You must use special tools to break out all of the fibers in the ribbon, so they can be individually matched and spliced to another single fiber.

If you have as much trouble visualizing this process as I have describing it, watch some online splicing videos produced by closure manufacturers. Instructors from the Fiber Optic Association prefer Preformed Line Products, 3M and TE Connectivity. After that, it should make much more sense.

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 www.JimHayes.com .

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