Fiber Optic Cleaving – Key to Quality Connectors and Splices

Joe Loucks

On June 6th In Installation & Cabling, IP Tech Tips

To prepare a fiber end for a connector or splice, the end of the fiber must be cleaved to a 90 degree flat end. This is needed because when a fiber end is inserted into a connector or splice, it is going to butt up against another fiber which is usually perfectly 90 degrees flat. If the inserted fiber has been cut with a razor or standard knife the end of the core/cladding combination will have an irregular face which won’t allow the light energy to pass from the fiber strand into the connector or splice.

For technicians the problem is that the end of the fiber strand is so small that it is impossible to tell with the naked eye whether the strand has a flat end – it’s just too small to see. So it’s important to use the proper tool with good technique to consistently achieve a 90 degree flat end. If you don’t achieve the proper flat end, you won’t know until you test the connector or splice and find out that it’s no good.  And then you will have to start the whole process over.

Whatever vendor or type of fiber optic cleaver you use, they all perform basically the same function. To achieve the 90 degree flat end, the fiber is scored or scratched at a specific length. The cleaver doesn’t cut the fiber; if you cut the fiber with the cleaver, you will need to redo the operation. After the fiber has been scored, operation of the cleaver by the technician will either bend or pull the fiber end, stressing the fiber. This stress will cause the fiber to break at the score mark, leaving a 90 degree flat end if all goes well. So the cleaver doesn’t cut the fiber; it breaks the fiber at a specific length.

There are two broad categories of fiber optic cleavers, cheap ones and precision cleavers. While both types perform the functions above, the difference between the two categories of cleavers is the percentage yield of good cleaves. An experienced fiber optic technician will achieve approximately 90% good cleaves with a cheap cleaver, while the precision cleaver will produce 99% good cleaves. The difference doesn’t seem like much but since you cannot see whether a cleave is good or not, it is best to invest in the precision cleaver. The time saved in redoing bad connectors made with cheap cleavers will quickly make the precision cleaver a better investment.

Above is the Leviton FastCAM Connector Tool Kit, which includes a fiber stripping tool and precision cleaver. ADI part #LV-49800SMK.

Before cleaving the fiber it is very important to clean the stripped fiber end using a fresh alcohol pad. This cleaning is necessary to remove any microscopic debris left on the side of the fiber from the stripping process. When cleaning the fiber technicians should squeeze the fiber end with the alcohol pad with some pressure. This will stress the fiber before the cleaving process. In the event that the fiber core/cladding was inadvertently nicked during the stripping process, squeezing the fiber with the alcohol pad and pulling it through will cause it to break in the pad. If the fiber has been nicked we want it to break now, before we do the cleaving and connector/splice installation. It’s quite possible that a nicked fiber that isn’t stressed with the cleaning pad before installation will break at some inopportune time in the future.

Once the fiber is cleaned, the strand is placed into the cleaver so that a specific length of stripped fiber extends from the remaining 900 micron jacket to the cleaved end and the cleave process is performed.

With a properly cleaved fiber end, the connector or splice is ready to be done.

ADI offers a number of training opportunities throughout the year that provide tips for easier installations. Click here to check out the upcoming training events taking place at your local ADI branch