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What is Fusion Splicing?

By Larry Ray Palmer
Updated: May 17, 2024

Fusion splicing is a term that comes from the fiber optic communications industry. It refers to the process of joining, or splicing, two optical fibers end-to-end. The fibers are heated to the point that the ends soften and fuse together, thus giving the process its name.

Although the definition of fusion splicing is a very basic explanation of the process, the actual process is slightly more complex. Fiber optic communications rely on the transfer of light throughout the length of the fiber optic cable and its fibers. If fusion splicing is done improperly, it can impede the transfer of light in the optical fiber, thus limiting the usefulness of the fiber or rendering it unusable.

To avoid damage to the sensitive optical fibers during the fusion splicing process, special tools, heat sources and methods are used in the termination and splicing of optical fibers. The process of fusion splicing begins with the stripping of the optic fibers. Stripping refers to the removal of the protective coatings of the optic fiber to ensure that the splice is not contaminated by these protective coatings.

After stripping the coating, the next step in fusion splicing is cleaving the optic fiber. The object of cleaving the optic fiber is to achieve perfectly flat ends that can be spliced together. Cleaving the optic fiber should leave an end surface that is completely perpendicular to the fibers' axis to ensure a proper splice.

The two stripped and cleaved fibers are then inspected under magnification in the fusion splicing apparatus to insure the quality of the cleaving and to align the end faces of the optical fibers for splicing. After these optic fibers have been aligned, they are heated and fused together. In the majority of cases, the heat source used for fusion splicing is an electrical arc, but lasers, gas flames and heated tungsten filaments also provide an adequate heat source for the fusion process.

Following the process of fusion splicing, the optical fibers will require some form of protection. The options for the protection of a fusion splice include recoating with a chemical protectant or the use of a fiber optic splice protector. Recoating is accomplished using a resin that is cured by ultraviolet (UV) light, and this is usually the preferred method of protecting fusion splices as it returns the fiber to its pre-spliced condition.

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