Disclosed is a single mode optical waveguide fiber having a segmented core. The relative indexes, the refractive index profiles and the radii of the segments are chosen to provide waveguide fiber properties advantageously used in severe environments, such as, undersea cables. The segmented core waveguide fiber has a negative total dispersion over the operating window of about 1530 nm to 1570 nm, which serves to eliminate soliton formation. The key properties of dispersion zero, cut off wavelength, attenuation, and bend resistance fall within desired ranges. The waveguide also features a low polarization mode dispersion.