Now that we have looked at the major pieces of an optic fiber link, the next concern is how to hook them together mechanically and optically. From an optical point of view the challenges are how to launch optical power into a particular type of fiber and how to couple optical power from one fiber into another. Launching light from a source into a fiber entails considerations such as the numerical aperture, core size, and core-cladding refractive index differences of the fiber, plus the size, radiance, and angular power distribution of the optical source. Mechanical factors include highly precise alignment of fibers, low loss and repeatability of connections, and ruggedness of fiber-to-fiber joints.

This chapter first considers the issues involved in coupling light from a source into an optical fiber. The next topic covers the conditions that need to be taken into account in making a fiber-to-fiber joint. Here the difficulty lies in how to precisely align fibers that are roughly the diameter of a human hair (which is 50 to 100 m in diameter) so that only a minute fraction of light is lost across a fiber joint. A further topic notes that no matter what alignment and coupling scheme is used, the end faces of the fiber must be prepared properly. The final two sections deal with connectors and splices. As will be seen in that discussion, a splice is a permanent joint between two fibers, whereas connectors are mounted on the ends of fiber cables so they...