Specialty Optical Fibers Handbook

work on the design and fabrication of DCF with negative dispersion and

negative dispersion slope began in the early 1990s [26–29]. Successful large-

scale manufacturing was in place by 1998 [30].

Transmission fibers used in terrestrial applications have positive dispersion

and positive dispersion slopes, as shown in Fig. 5.3. DCFs have high negative

dispersions in the range of 100 to 250 ps=nm-km, as well as negative slopes.

To achieve the negative dispersion and dispersion slope, a large amount of

waveguide dispersion must be added by strongly confining the mode in a narrow

and high D Ge-doped core, surrounded by a low D deeply F-doped trench, with

an additional ring of positive D Ge-doped silica surrounding that. DCF index

profiles may include