Patent ID: 7421175
Filing Date: 2008-09-02
Classification: H01S

Abstract:
1. Apparatus for providing optical radiation, comprising an optical fibre having a core, a first cladding and a second cladding, and wherein: the core is located within the first cladding; the first cladding is located within the second cladding; in cross section, the first cladding is non-circular; in cross section, the first cladding is defined by an equilateral star and an outer periphery which is polygonal in shape, the polygonal shape being defined by a plurality of intersecting sides, each side comprising a circular arc, all said circular arcs being concave with respect to the core to thereby form a plurality of concave sides; and the circular arcs have centers at vertices of the equilateral star, such that the first cladding has a substantially constant diameter in its cross-section.