Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/02295—Microstructured optical fibre
  • G02B6/02314—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes
  • G02B6/02319—Plurality of longitudinal structures extending along optical fibre axis, e.g. holes characterised by core or core-cladding interface features
  • G02B6/02338—Structured core, e.g. core contains more than one material, non-constant refractive index distribution in core, asymmetric or non-circular elements in core unit, multiple cores, insertions between core and clad
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
  • G02B6/02—Optical fibres with cladding with or without a coating
  • G02B6/024—Optical fibres with cladding with or without a coating with polarisation maintaining properties

Definitions

• the invention relates to a microstructured optical fiber comprising at least one core having a spatial symmetry of shape comprising at least one axis of symmetry.
• Optical fibers are known and used as a waveguide.
• the microstructured fibers comprise, in section, a matrix of microscopic air holes. These air holes extend over the entire length of the optical fiber. In the center of the optical fiber, one or more air holes are absent so as to form an area having a higher index constituting a light trap and thus a core for the optical fiber.
• the heart of a microstructured optical fiber is therefore the place of propagation inducing a minimum of loss to light.
• the same fiber may have a plurality of cores.
• the non-linearity of an optical fiber depends solely on the material constituting it. Nevertheless, the threshold of appearance of these effects depends on the power density propagating in the heart and thus the confinement of the power throughout its propagation. Moreover, all the parametric effects at the base of complex spectral enlargements require an agreement of the phase velocities of the waves considered and are then sensitive to the polarization effects and thus to the birefringence of the waveguide considered. Indeed, even if a fiber is manufactured to be in isotropic theory, the presence of impurities and physical stresses in the fiber imposes a so-called local or so-called birefringence therein.
• the heart thus formed is therefore substantially elliptical. This results in the appearance of a shape birefringence related to the geometry of the core of the fiber.
• Such a birefringence is independent of the power of the wave propagating in the heart. This birefringence is therefore permanent and is a linear effect.
• microstructured fibers are known from US-2005/105867 and US-2006/088262.
• the elliptical core of the fiber described in the aforementioned publication has a birefringence induced by the geometrical dissymmetry of the guide and can not exceed index variations of the order of about 3.10 "3 to 7.10 " 3 .
• the distribution of the dopant modifies the spatial symmetry of the core, which causes an improved anisotropy of the doped core of the fiber, with respect to the same undoped core.
• the linear birefringence of the optical fiber thus obtained is modified, permanent and potentially improved.
• the introduction of the asymmetry according to the invention also has the advantage of making it possible to shift the dispersion zero of the modes propagating in the core towards the low wavelengths.
• a dopant into the core of a microstructured optical fiber is known per se and makes it possible to amplify an optical signal propagating in the core of the fiber or to exacerbate the non-linear effects.
• Different dopants have been proposed depending on the signal to be amplified and the desired optical effect.
• the dopants are positioned in the center of the heart and symmetrically with respect to axes of symmetry of the heart.
• the dopant is distributed so as to break the symmetry of the core of the fiber.
• the shape birefringence is reinforced by a birefringence induced by the doping geometry.
• An increase in the index of the core in a given zone and asymmetrically allows further asymmetrization of the profile of the mode and thus a modification of the birefringence. Phase agreements that are not accessible without this particular doping are then possible.
• At least one dopant is positioned in a plurality of doping zones of said core, each of the doping zones being distinct, said doping zones being arranged so as to break said spatial symmetry.
• the non-isotropic distribution of the dopant (s) makes it possible to break the symmetry of the core and thus to increase the birefringence effect.
• said core comprises a single dopant, said dopant being positioned in each of said doping zones, the concentration of said dopant being different in each of the doping zones.
• said plurality of doping zones comprises two doping zones.
• the dopant concentrations are distinct within the heart, the symmetry of the heart is broken.
• This embodiment has the advantage of allowing the increase of the birefringence of the heart, while using a type of dopant.
• said core comprises a plurality of dopants, each of the dopants of said plurality of dopants being located in a respective doping zone of said plurality of doping zones.
• said optical fiber may comprise a plurality of cores, each of the cores of said plurality of cores having a spatial symmetry, each of the cores of the plurality of cores comprising at least one dopant arranged so as to break the spatial symmetry.
• This embodiment makes it possible to increase the birefringence of the optical fiber, while allowing the generation of several different spectra according to the opto-geometric characteristics of each of the cores.
• This also makes it possible to produce coupled waveguides by coherently summing several spectra.
• Each wavelength injected into each of the cores can generate a broad spectrum by nonlinear effect independently of the other wavelengths. This makes it possible to obtain at the output of the fiber a spectrum having different characteristics for each core.
• said at least one dopant is a rare-earth ion. This makes it possible to amplify in parallel one or more wavelengths.
• This also makes it possible to obtain a population inversion at different wavelengths to generate a laser effect or a multiple amplification.
• the Applicant has demonstrated that the birefringence was particularly improved when said core is a silica core surrounded by four small diameter air holes and two large diameter air holes, the four small diameter air holes being distributed. in pairs on both sides of large diameter air holes and especially when the small diameter is 2.2 microns, and the large diameter is 4 microns.
• te invention relates ⁇ to ⁇ ⁇ equal "ment ⁇ to ⁇ u ⁇ " method of fabricating a doped optical fiber comprising the steps of:
• microstructured optical fiber having a shape symmetry-shaped core
• FIG. 1 is a section of an optical fiber according to the invention in an XY plane
• FIG. 2 is a section of an optical fiber according to a first embodiment of the invention
• FIG. 3 is a section of a multi-core optical fiber according to the invention
• FIG. 4 is a detailed view of an optical fiber core according to the invention.
• FIG. 1 is a section of an optical fiber 1 according to the invention.
• the optical fiber 1 is a microstructured fiber comprising an array of air holes 2 surrounding intermediate areas of silica 3. This set of holes 2 and silica zones 3 forms a sheath 2, 3 surrounding a fiber core 7.
• This optical fiber 1 is for example manufactured by the known method known as "stack and draw” in English, in which juxtapose silica tubes.
• the diameter of the air holes 2 is about 2.2 micrometers, and the various holes ai ⁇ -c ⁇ ⁇ are esp ⁇ ⁇ a "EES" by ⁇ silica areas of about 2.7 micrometers.
• the core 7 of the fiber 1 is delimited non-symmetrically along the X axis and the Y axis of the reference mark shown in FIG. 1.
• the core 7 is delimited by two holes 4 of diameters greater than the diameters of the holes of the microstructure 2.
• the diameter of the holes 4 along the X axis of the core 7 is about 4 micrometers.
• the core is delimited by holes of the same diameter as the holes 2 of the sheath 2, 3. Due to the presence of the large diameter air holes 4, the core 7 therefore has a shape substantially ellipsoidal.
• the surface of the heart 7 is about 5 microns square.
• the arrangement of the holes delimiting the core 7 thus gives a spatial symmetry to the core 7 along the two axes X and Y. In space, this corresponds to two planes of symmetry.
• the amount of air in the sheath 2, 3 is of the order of 65%.
• the core 7 of the fiber 1 has a size allowing the guiding of six transverse modes of a wave, corresponding to the fundamental mode LP01 with a polarization according to X, to the fundamental mode LP01 with a polarization along Y, to the first higher order mode
• LP1 1 with a central zero in the X or Y direction, and a polarization along X or Y.
• the dispersion zero wavelength is around 770 nanometers for the LP01 mode according to X or Y, and around 560 nanometers for LP1 modes 1.
• the core 7 is non-symmetrically micro-structured and comprises two distinct zones of doping 5 and 6.
• the doping zones 5 and 6 comprise two different materials having different refractive indices.
• the heart 7 is thus separated vertically into two zones ⁇ and 6. This separation can also be vertical.
• these two doping zones 5 and 6 are doped with a different dopant for each doping zone.
• the dopants may be germanium, phosphorus, or rare-earth ions. Germanium and Phosphorus can be introduced more importantly in the fiber than rare earth ions and then allow to obtain a higher birefringence.
• the two doping zones 5 and 6 comprise the same dopant, for example germanium.
• the concentrations of germanium are distinct in zones 5 and 6.
• Zone 5 has a low doping of 3% while the other zone 6 has a higher doping of the order of 10% for example.
• the fiber 1 may comprise a plurality of cores 7, 7A, 7B, 7C, 7D, 7E, 7F, as illustrated in FIG. 3.
• the cores 7A, 7B, 7D and 7E are substantially circular because they are surrounded by air holes 2 of the same diameter. Because of the X-axis presence of the large-diameter air holes 4, the core 7 is substantially ellipsoidal in shape as before, and the holes 7F and 7C are asymmetrical along the X axis, and symmetrical by relative to the X axis.
• doping zones of doping arranged to break a spatial symmetry of the heart are doped.
• At least one spatial symmetry of the core of the fiber is determined, and this core is doped so as to break the spatial symmetry due to the distribution of the fiber. dopant within the heart.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Lasers (AREA)
• Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)
• Agricultural Chemicals And Associated Chemicals (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=37830293

Family Applications (1)

Country Status (5)

Families Citing this family (2)

Family Cites Families (9)

• 2006
  • 2006-12-12 FR FR0610837A patent/FR2909776B1/fr not_active Expired - Fee Related
• 2007
  • 2007-12-12 JP JP2009540814A patent/JP2010512553A/ja active Pending
  • 2007-12-12 US US12/518,934 patent/US20100080523A1/en not_active Abandoned
  • 2007-12-12 EP EP07871847A patent/EP2100175A2/de not_active Withdrawn
  • 2007-12-12 WO PCT/FR2007/002054 patent/WO2008090279A2/fr active Application Filing

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events