Note 1: In silica-based optical fibers, the zero-dispersion wavelength occurs at approximately 1.3 μm, but this wavelength may be shifted toward the minimum-loss window by the addition of dopants to the fiber material during manufacture.
Note 2: Doubly and quadruply clad single-mode fibers have two zero-dispersion points, and thus two zero-dispersion slopes.
Source: from Federal Standard 1037C