Mechanical Splice

A mechanical splice is a junction of two or more optical fibers that are aligned and held in place by a self-contained assembly (usually the size of a large carpenter's nail). The fibers aren't permanently joined, just precisely held together so that light can pass from one to another.
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Of optical fibers, a splice, i.e. , permanent joint, accomplished by aligning the mating fibers in some kind of mechanical fixture. Note 1: The fibers may be secured by mechanical means or with an optical adhesive. Note 2: When the fibers are secured by mechanical means, the gap between them is usually filled with an index-matching gel to reduce Fresnel reflection. Likewise, the optical adhesives that are used in conjunction with mechanical splices are formulated to have a refractive index that approximates that of the glass, and also serve to reduce Fresnel reflection. [After FAA]