Large core holey fibers
Holey fibers provide optical propagation. In various embodiments, a large core holey fiber comprises a cladding region formed by large holes arranged in few layers. The number of layers or rows of holes about the large core can be used to coarse tune the leakage losses of the fundamental and higher modes of a signal, thereby allowing the non-fundamental modes to be substantially eliminated by leakage over a given length of fiber. Fine tuning of leakage losses can be performed by adjusting the hole dimension and/or spacing to yield a desired operation with a desired leakage loss of the fundamental mode. Resulting holey fibers have a large hole dimension and spacing, and thus a large core, when compared to traditional fibers and conventional fibers that propagate a single mode. Other loss mechanisms, such as bend loss and modal spacing can be utilized for selected modes of operation of holey fibers.
1. An optical fiber for propagating a single optical mode, said optical fiber comprising:
a cladding region comprising a plurality of cladding features disposed in a matrix, said plurality of cladding features having an average spacing, Λ, and an average size, d, said plurality of cladding features being substantially arranged in a plurality of layers, N; and
a core region surrounded by said cladding region, said plurality of cladding features substantially confining propagation of said single optical mode to said core region, said plurality of cladding features having (i) sufficient average spacing, Λ, to provide an increased effective core size, 2ρ, and (ii) a sufficient average size, d, to provide substantial confinement of light having a wavelength, λ, within said core region,
wherein said average size, d, and said average spacing, Λ, have values at least about 20 micrometers to provide an effective core size of at least about 20 micrometers;
wherein d/Λ is at least about 0.6, and said optical fiber is configured to propagate said single optical mode in said core region and to suppress higher order modes based on selective adjustment of values of d, Λ and/or the number of layers, N,
wherein said number of layers N is less than or equal to about 4, and λ/Λ is less than or equal to about 0.3.
2. The optical fiber of claim 1 , wherein said average size, d, and said average spacing, Λ, have values of at least about 30 micrometers.
3. The optical fiber of claim 1 , wherein said average size, d, and said average spacing, Λ, have values of at least about 40 micrometers.
4. The optical fiber of claim 1 , wherein said effective core size is at least about 30 micrometers and less than about 150 micrometers.
5. The optical fiber of claim 1 , wherein said effective core size is at least about 40 micrometers.
6. The optical fiber of claim 1 , wherein said effective core size is at least about 60 micrometers.
7. The optical fiber of claim 1 , wherein said effective core size is at least about 80 micrometers.
8. The optical fiber of claim 1 , further comprising dopants that provide gain.
9. The optical fiber of claim 1 , wherein the wavelength, λ, is in a range from 1 micrometer to 1.55 micrometer, thereby producing a ratio λ/Λ which is less than 0.075 with said average size, d, and said average spacing, Λ, and wherein the number of said layers is in the range from 1 to 3.
10. The optical fiber of claim 1 , wherein d/Λ is at least 0.75.
11. The optical fiber of claim 1 , wherein said core region comprises a doped region, said optical fiber further comprising an outer cladding having a plurality of holes.
12. A cladding pumped fiber amplifier or cladding pumped fiber laser, comprising:
the optical fiber of claim 11 ; and
a pump source optically connected to said optical fiber.