If and when fiber optic cables get accidentally severed, they can be joined together again using one of two methods. There’s “termination” and there’s “splicing.” Fiber optic splicing is the preferred method for joining two different types of cable together or when cable runs are considered too long for just a single length of fiber.
Mechanical Versus Fusion Splicing
Speaking of splicing, there are two types: mechanical and fusion. When mechanical splicing is performed, simple alignment devices are used. These hold two fiber ends in such a position that light can pass from one fiber into the other. Fusion splicing, on the other hand, involves a machine that aligns fiber ends while welding them together using heat or electric. Fusion splices result in lower loss light transmissions than mechanical splices do. Cost-wise, mechanical may be a lower investment initially, but then costs per splice are expensive, whereas fusion’s the opposite: a higher investment initially followed by a lower cost per splice.
Depending on the industry, mechanical or fusion splicing both work well. Many telecom/cable companies go with fusion splicing for long haul singlemode networks and then use mechanical splicing for shorter cable runs.
For proper fusion splicing, first the fiber is prepared by removing its protective coatings, jackets, etc. Once it’s just clean, bare fiber showing, it’s time to cleave that fiber in a mirror-smooth manner, perpendicular as possible. Ideally, the cleave angle is at .5 degree or less. Next, to fuse the fiber, alignment occurs followed by using a heat/electrical arc to then melt the fibers, welding them together as intended. Finally, the fiber needs protection from bending and tensile forces, so heat shrink tubing is added, and/or silicone gel/mechanical crimping protectors.
Regarding mechanical splicing, fibers aren’t held together via a permanent bond. Instead, they get aligned at a centerline whereas light can pass through from one to another thanks to a self-contained assembly that links the two pieces of fiber together. Like fusion splicing, the fiber needs to be prepared and cleaved, but then instead of heat, the index matching gel inside the mechanical splice unit ends up helping to couple the fiber together. Finally, the fiber needs protection, and the completed mechanical splice ends up providing it.
Should you ever perform the act of fiber optic splicing, remember that cleanliness is of utmost importance.