Patent ID: 8326106

Claim:
An optical fiber comprising: a core region having a longitudinal axis, said core region including an inner core region and an annular outer core region surrounding said inner core region, said inner core region having a radial width in the range of approximately of 8 to 10 μm, the refractive index of said outer core region being less than that of said inner core region and the radial thickness of said outer core region being less than a width of said inner core region and being in the range of approximately 1-5 μm, the difference in refractive index between said inner core region and said outer core region being in the range of approximately 0.003-0.007, and a cladding region surrounding said core region, said core and cladding regions configured to support and guide the propagation of signal light in a fundamental transverse mode in said core region in the direction of said axis, said cladding region comprising: an outer cladding region having a refractive index less than that of said core region, the difference in refractive index between said core region and said outer cladding region being approximately 0.003-0.006, and the refractive indices of said outer cladding region and said outer core region being within approximately 0.002 of one another, an annular pedestal region having a radial thickness of said pedestal region is approximately 1-4 μm, the refractive indices of said core region and said pedestal region being within approximately 0.003 of one another, an annular inner trench region disposed between said core region and pedestal region, said inner trench region having a refractive index less than that of said outer cladding region, and an annular outer trench region disposed between said pedestal region and said outer cladding region, said outer trench region having a refractive index less than that of said outer cladding region, the refractive index difference between said core region and at least one of said trench regions being greater than approximately 0.007, and the interface between said outer cladding region and said outer trench region being located at a radius r out of approximately 17-23 μm, said pedestal region being configured to resonantly couple at least one transverse mode of said core region, other than said fundamental mode, to at least one transverse mode of said pedestal region.