Patent ID: 6922513
Filing Date: 2005-07-26
Classification: G02B

Abstract:
1. An optical fiber having a core, an inner cladding and an outer cladding on and surrounding the inner cladding, the cor having a core refractive index and being arranged to permit a light beam to travel therethrough and the inner cladding having an inner cladding refractive index, wherein in a first region the inner cladding refractive index has a first value, and the first value differs from the cor refractive index by an amount of the order of 0.0045 and in an adjoining region which includes a free-space end of said fiber, the inner cladding refractive index, changes along said fiber from the first value to a second value at the free-space end of the fiber, wherein the second value substantially matches the core refractive index, whereby the effective diameter of the core is that of the core plus the inner cladding at the free-space end.