Patent ID: 6831934
Filing Date: 2004-12-14
Classification: G02B,H01S

Abstract:
Apparatus comprising:a double cladding fiber including, an inner core doped with active species, an inner cladding surrounding the inner core for receiving pumping energy, and transferring said pumping energy to the core; an outer cladding surrounding the inner cladding for protecting the inner cladding and maintain light within the inner cladding; the improvement to a cross-section shape of said inner cladding relative to the outer cladding for minimizing local modes in said inner cladding, the cross-section shape of the inner cladding comprising: a boundary between the inner cladding and the outer cladding with the boundary being at least three arcs; each of the arcs having substantially different arc center; and, each arc having a predetermined radius from the arc center of the arc; wherein the relative size of said inner core and said inner cladding is determined by an inner cladding/inner core area ratio, and wherein said inner cladding/inner core area ratio is selected from a ratio equal to x, where x is between 1 and 200, whereby the local modes in said inner cladding are substantially minimized.