Figure 6-5. - A glass or ceramic alignment tube for mechanical splicing.

diameter of the alignment tube. If the inner diameter is too large, splice loss will increase because of fiber misalignment. If the inner diameter is too small, it is impossible to insert the fiber into the tube.

V-GROOVED SPLICES

Mechanical splices also may use either a grooved substrate or positioning rods to form suitable V-grooves for mechanical splicing. The basic V-grooved device relies on an open-grooved substrate to perform fiber alignment. When you are inserting the fibers into the grooved substrate, the V-groove aligns the cladding surface of each fiber end. A transparent adhesive makes the splice permanent by securing the fiber ends to the grooved substrate. Figure 6-6 illustrates this type of open V-grooved splice.

V-grooved splices may involve sandwiching the butted ends of two prepared fibers between a V-grooved substrate and a flat, glass plate. Additional V-grooved devices use two or three positioning rods to form a suitable V-groove for splicing. The V-grooved device that uses two pois- tioning rods is the spring V-grooved splice. This splice uses a groove formed by two rods positioned in a bracket to align the fiber ends. The diameter of the positioning rods permits the outer surface of each fiber end to extend above the groove formed by the rods. A flat spring presses the fiber ends into the groove maintaining fiber alignment. Trans- parent adhesive completes the assembly process by bonding the fiber ends and providing index matching. Figure 6-7 is an illustration of the spring V-grooved splice. A variation of this splice

Figure 6-6. - Open V-grooved splice.