Before we begin to dive into that question let’s get a brief understanding on what a fusion splicer is. If you are in the fiber optic world you will definitely know what a fusion splicer is and most likely will have used one or will be using one. A fusion splicer is a machine that fuses or welds two different pieces of fiber optic glass cables together to become one with an electric current also known as an arc. Most fusion splicers have an attached shrink oven that the protection sleeve is placed into to complete the process. Some splicers do not have an attached shrink oven and an external separate shrink oven will be needed for the application. As mentioned, fiber optic cable is made of glass and glass, especially how thin optical fiber is, will be very brittle and can very easily break. When this fusion of glass is completed, this is where our friend, the fusion protection sleeve steps in.
You may be asking, what is a fusion splice protection sleeve? Well that is a great question! A fusion protection sleeve is used to protect the fusion splice where the two separate pieces of fiber optic cable have been joined into one. A protection sleeve is made up of three parts: An outer shrinkable tube made of heat shrink plastic, an inner tube or fiber tube where the fiber is placed, and a strength member, either made of stainless steel or ceramic, more on this later. The protection sleeve ensures a consistent and reliable means of protection of the fiber when heat is applied from the splicer oven or external oven. Have you ever broke an arm or bone or knew someone who has? When this happens a cast is applied to the broken area. The cast can be interpreted as the protection sleeve and the broken bone area is the fiber optic cable. The cast protects the broken bone as the protection sleeve protects the fused fiber cable.
Fusion protection sleeves can be broken down into basically two categories: single splice protection sleeves and ribbon splice protection sleeves and will most commonly be 40mm or 60mm in length and are normally made of a clear outer tube so you can view the fiber when inside the sleeve for regular inspection and/or maintenance to the cable inside. A single splice protection sleeve is just that, a sleeve that will accommodate a single piece of fused fiber. A ribbon splice sleeve can accommodate multiple fiber splices ranging from 2-12 fibers inside the sleeve. As mentioned above, protection sleeves will either have a stainless steel or ceramic strength member that runs the entire length on the side of the protection sleeve and there is a definitive reason there are two different types of strength members. Fiber optic cable uses light to transmit data and light and glass to not conduct electricity. If a contractor is specifically using fiber optic cable in the application there should be no worry in using a protection sleeve that contains a stainless steel strength member. On the other hand if the fiber optic application will be next to or near any copper/conductive type material, the contractor may consider a splice sleeve that contains the ceramic strength member so there is no electrical disturbance between the copper cable or conductive material and the strength member.
Before the splice sleeve is applied to the fusion splice and the cable, the splice sleeve itself should be inspected before installation. This is done to ensure the sleeve is free from deformity and is clean both on the outside and the inside of the sleeve. The inspection and cleaning process is vital in any fiber optic application ranging from cleaning connector ends to making sure your equipment is clean from any contaminants. Not cleaning your fiber optic accessories and equipment is the leading cause of attenuation in the cable. Attenuation is the measurable loss of signal strength along the cable and it is measured in decibels. Inspecting the inside of the sleeve to make sure it is free of contaminates along with cleaning the fiber before installing the sleeve is a good practice as the slightest bit of contaminates could and most likely will cause attenuation. When not using the sleeves, they should be stored in a clean plastic zip bag for protection during storage.
Aside from the importance of cleaning there are other factors to consider before your splice sleeve installation. As mentioned earlier, protection sleeves are used when fusion splicing. Your fusion splicer has many different settings that can be chosen when splicing and may differ from manufacturer to manufacturer. Fiber tension is one setting that may need to be adjusted in this process. Improper fiber tension can result in an improper or uneven shrink when the protection sleeve is placed in the shrink oven. It is essential to maintain proper tension on the cable and not to twist the fiber when placing in and removing from the oven.
Another factor to consider in this process is actually the type of cable you’re using to splice with. Some fiber optic cables contain a gel similar to petroleum jelly that is contained on the inside jacket of the fiber. This gel will need to be cleaned off of the cable with a special degreaser wipe to ensure the proper fit and finish of the application of the splice sleeve. Inspecting the splice sleeve after it is removed from the heating oven is another good practice as the heat setting may be to high resulting in a split in the sleeve itself or the heat may be to low resulting in an improper shrink to the sleeve. If either of these are observed you may need to adjust the heat setting on the oven itself.
Once all of these installation practices are meet, the protection sleeve along with the attached cable are usually placed in a splice tray. A splice tray is a tray or container that prevents spliced fibers from being damaged or misplaced after splicing. If the cable and protection sleeve will be placed in a splice tray the protection sleeve should have the strength member pointing down, you should not be able to see the strength member when looking at a protection sleeve when it is in a splice tray.
As small as the fusion protection sleeve may be, it is a huge importance to the fusion splicing world of fiber optics. When all of these practices are met, you will be successful when you decide to try your hand at fusion splicing with the added protection of fusion protection sleeves added to your fiber optic cable installation arsenal.