Archimedean-lattice microstructured optical fiber

A microstructured optical fiber exhibiting enhanced circularity of the guided light mode is provided. The microstructured optical fiber includes a light-guiding core and a primary cladding surrounding the core wherein the primary cladding has a plurality of holes arranged in hexagonal unit cells defining an Archimedean-like lattice. Preferably, the core is defined by a break in a center of the Archimedean-like lattice, the break being characterised by an absence of at least one of the unit cells. Also preferably, each of the unit cells has seven holes arranged in a centred hexagon. A method of making the microstructured optical fiber is also provided. The method includes fabricating a fiber preform by stacking a plurality of canes around a rod, each cane having a number of holes arranged in a unit cell defining an Archimedean-like lattice, and drawing said fiber preform into the microstructured optical fiber.