The letter treats a doubly clad dielectric optical fibre. We assume that the core refractive index is greater than the outer-cladding refractive index, which is greater than the inner-cladding refractive index. This optical fibre, if properly designed, has an anomalous or negative normalised guide dispersion (ω2/β)d2β/dω2 that compensates typical glass dispersion. Single-mode operation of this doubly clad fibre can be obtained with the core radius appreciably larger than that of a singly clad fibre with the same core and outer-cladding refractive indices.