Few mode optical fibers for mode division multiplexing
AssigneeDraka Comteq B.V.
InventorsPierre Sillard, Denis Molin, Marianne Bigot
Life of this patent
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Abstract
Few mode optical fibers for mode division multiplexing. The Few Mode Fiber supporting 25 or 30 LP guided modes and includes a graded index core with a α-profile, a radius R1 (at 0 refractive index difference) between 23 and 27 μm and a maximum refractive index difference Dn1 between 14·10−3 and 17·10−3, and an end of the α-profile at a radius R1b, with index difference Dn1b; a trench surrounding the core with radius R3 between 30 and 40 μm and refractive index difference Dn3 between −15·10−3 and −6·10−3. Such a FMF shows a specific design of the interface between the core and the cladding such that R1b>R1, Dn1b between −10·10−3 and −3·10−3, and Dn1b−Dn3≥0.9×10−3.
Claims22
An optical fiber comprising a central optical core surrounded by an optical cladding,
- said optical core having a α graded index profile n(r) with α between 1 and 3, α being a non-dimensional parameter that defines an index profile shape of said optical core, that is a function of a radial distance r from the center of said optical core,
- said optical core having a maximum refractive index n0 and an outer radius R1b with a refractive index difference Dn1b=n(R1b)−nCl with respect to said optical cladding having at its outer edge a refractive index nCl,
- said optical core having a radius R1 such that n(R1)=nCl, comprised between 23 μm and 27 μm and a maximum refractive index difference Dn1=n0−nCl between 14·10−3 and 17·10−3,
- said optical cladding comprising a region of depressed refractive index ntrench, called a trench, surrounding the optical core, said trench having an inner radius R1b, and an outer radius R3, with R3>R1b and R3 between 30 μm and 40 μm, and a refractive index difference Dn3=ntrench−nCl between 14·10−3 and 17·10−3,
- said optical cladding comprising a region of depressed refractive index ntrench called a trench, surrounding the optical core, said trench having an inner radius R1b, and an outer radius R3, with >R1b, and R3 between 30 μm and 40 μm, and a refractive index difference Dn3=ntrench−nCl between 15·10−3 and 6·10−3,
- wherein R1b>R1, Dn1b is between −10·10−3 and −3·10−3 and Dn1b−Dn3≥0.9×10−3, said refractive index differences being determined at λ=λC, where λC is a central transmission wavelength of an operating band for which said optical fiber is intended, wherein:
- the optical fiber having a normalized frequency
- V
- =
- 2
-
- π
-
-
- R
- 1
- λ
- c
-
-
- n
- 0
- 2
- -
- n
- Cl
- 2
- that is between 19 and 23.
An optical link comprising N optical fibers, with N≥2, N being an integer, each optical fiber index i ∈ [[1;
- N]] comprising a central optical core and an optical cladding surrounding the optical core, the optical core having a α1 graded index profile ni(r) with αi between 1 and 3, αi being a non-dimensional parameter that defines an index profile shape of the optical core, that is a function of a radial distance r from the center of said optical core,
- and the optical core having a maximal refractive index n0i, and an outer radius R1bi with a refractive index difference Dn1bi=ni(R1bi)−nCli with respect to said optical cladding having at its outer edge a refractive index nCli,
- said optical core also having a radius R1i, such that ni(R1i)=nCli,
- said optical cladding comprising a region of depressed refractive index ntrenchi, called a trench, surrounding the optical core, said trench having an inner radius R1bi, and an outer radius R3i, with R3i>R1bi,
- wherein an average optical core radius R1link for said optical link is comprised between 23 μm and 27 μm where
- R
- 1
-
- link
- =
- ∑
- i
- =
- 1
- N
-
- R
- 1
-
- i
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- i
- with Li a length of optical fiber i in said link, an average maximum refractive index difference Dn1link for said optical link is between 14·10−3 and 17·10−3, wherein
- Dn
- 1
-
- link
- =
- ∑
- i
- =
- 1
- N
-
- Dn
- 1
-
- i
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- i
- with Dn1i=n0i−nCli is the core-cladding index difference for optical fiber i, at λ=λC, where λC is a central transmission wavelength of an operating band for which said optical fiber is intended,
- an average trench outer radius R3link for said optical link is between 30 μm and 40 μm, where
- R
- 3
-
-
- link
- =
- ∑
- i
- =
- 1
- N
-
- R
- 3
-
-
- i
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- I
- with L1 a length of optical fiber i in said link, an average refractive index difference between the trench and the cladding Dn3link for said optical link is between −15·10−3 and −6·10−3, at λ=λC, where
- Dn
- 3
-
- link
- =
- ∑
- i
- =
- 1
- N
-
- Dn
- 3
-
- i
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- i
- with Dn3i=ntrenchi−nCli a refractive index difference between the trench and the cladding for optical fiber i in said link,
- R1blink>R1link, where
- R
- 1
-
- blink
- =
- ∑
- i
- =
- 1
- N
-
- R
- 1
-
- bi
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- i
- with Li a length of optical fiber i in said link is the average refractive index difference between the core at its outer radius and the cladding Dn1blink is between −10·10−3 and −3·10−3, where
- Dn
- 1
-
- blink
- =
- ∑
- i
- =
- 1
- N
-
- Dn
- 1
-
- bi
-
- L
- i
- ∑
- i
- =
- 1
- N
-
- L
- i
- with Li a length of optical fiber i in said link and Dn1blink−Dn3link≥0.9·10−3.
Dependencies are inferred from the claim text.