Patent ID: 7450806

Claim:
A microstructured optical fiber comprising: a core region having a first refractive index and a cladding region having a second refractive index which is lower than that of the core region such that the light which is to be transmitted through the fiber is retained generally within the core, wherein the cladding comprises at least one region in the cladding comprised of a plurality of non-periodically located closed voids, such that when viewed in cross section said voids are distributed across said cross section, greater than 95 percent of the voids having a maximum diameter of 1550 nm or less, said fiber exhibiting an attenuation at at least one wavelength between 600 and 1550 nm which is less than 500 dB/km, wherein cross sections of said fiber taken at different points along the length of the fiber will exhibit different randomly oriented void patterns and different randomly oriented void sizes.