The present invention is directed to a universal channel dispersion
compensating fiber (CDCF) for WDM channel compensation that provides
essentially zero dispersion slope over the wide wavelength band used in
state-of-the-art transmission systems. It allows compensation of a large
number of channels using a single fiber design. The improved optical
fiber of the invention exhibits a dispersion slope at 1550 nm: <0.02
ps/nm2-km, preferably <0.01 ps/nm2-km, and a maximum variation of
dispersion per km over the S-, C-, and L- bands of preferably less than
2.0 ps. In a preferred embodiment, the index profile of these fibers
comprises a simple three layer design, which includes an up-doped central
core, surrounded by a down-doped trench region, further surrounded by an
up-doped ring region.