摘要： As seen in the preceding chapters of this book, three major nonlinear effects occurring inside optical fibers—self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM)—are governed by a single nonlinear parameter γ, defined in Eq. (2.3.30). For conventional optical fibers γ has values of ～1 W?1/km. It was realized during the 1990s that this value is too small for optical fibers to be useful as a nonlinear medium for applications requiring short lengths. To solve this problem, several new kinds of fibers with γ > 10 W?1/km were developed; they are collectively referred to as highly nonlinear fibers (HNLFs). This chapter deals with the properties of such fibers. The techniques used to measure the nonlinear parameter are described first in Section 11.1. The following four sections then focus on the four kinds of HNLFs that have been developed to enhance the nonlinear effects. In each case, dispersive properties of the fibers are also described because they play an important role whenever HNLFs are used for practical applications. It will be seen in Chapters 12 and 13 that the combination of unusual dispersive properties and a high value of γ makes HNLFs useful for a variety of novel nonlinear effects. Section 11.6 shows how the design of some HNLFs modifies the effective value of the nonlinear parameter in the case of narrow-core fibers.