Optical Communications Essentials

A key issue in the successful widespread application of any emerging technology is the implementation of cost-efficient component production. Whereas it is acceptable to use highly expensive custom-made devices for proving that the technology works, the cost of components must be reduced significantly when bringing systems into the field. This is especially challenging in optical communications where new concepts have been appearing rapidly and standards are not fully mature in many areas. Ways of achieving this include adapting semiconductor manufacturing techniques, setting up automation processes, and devising reliable optoelectronic packaging methods.
This chapter looks at a few of the many issues associated with optical fiber and component production. First, Sec. 20.1 describes methods for producing optical fibers. Next, Sec. 20.2 discusses some component design issues, such as integration of various functions on planar lightwave circuits and athermal package designs. An important step in manufacturing is the connector and component polishing process, which is critical for high light coupling efficiency and low optical return loss. Section 20.3 describes some factory automation equipment to achieve this. Finally, Sec. 20.4 addresses various component packaging issues such as package designs, bonding of metallized fibers, and hermetic sealing.
Modern optical fibers are made of highly pure silica (SiO 2) to which certain impurities, such as germanium or boron, have been added to induce slight changes in the value of the refractive index. These fibers are produced principally by what is called a vapor-phase oxidation process. In this method, highly...