Patent ID: 8107784

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, the refractive index of said outer core region being less than that of said inner core region, the thickness of said outer core region being less than the diameter of said inner core region, and said outer core region extending radially a distance of less than 9 μm and more than 5 μm from said axis, 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 including an outer cladding region having a refractive index less than that of said core region, a pedestal region having a refractive index approximately equal to that of said outer cladding region, an annular inner trench region disposed between said core region and pedestal region, said inner trench region including an annular inner portion and an annular outer portion surrounding said inner portion, the refractive index of said outer portion being greater than that of said inner portion, and an annular outer trench region disposed between said pedestal region and said outer cladding region, said pedestal region have a refractive index greater than the refractive indices of said inner and outer trench regions, 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, and said fiber being configured so that, at a signal wavelength of approximately 1550 nm, an associated bend loss is no more than about 0.1 dB/turn at bend radius of 5 mm and is no more than about 0.02 dB/turn at a bend radius of 10 mm.