A microstructured optical fiber for transmitting optical signals comprised of light, the optical fiber comprising: a core region disposed about a longitudinal centerline and having a refractive index profile with a first refractive index, and a cladding region surrounding the core region, the cladding region comprising an annular void-containing region comprised of non-periodically disposed voids; wherein maximum void diameter in nm is given by Dmax and the maximum void length in cm is not greater than 2.5×105×(dmax)−1.7.