Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C13/00—Fibre or filament compositions
  • C03C13/04—Fibre optics, e.g. core and clad fibre compositions
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B37/00—Manufacture or treatment of flakes, fibres, or filaments from softened glass, minerals, or slags
  • C03B37/01—Manufacture of glass fibres or filaments
  • C03B37/012—Manufacture of preforms for drawing fibres or filaments
  • C03B37/014—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD]
  • C03B37/018—Manufacture of preforms for drawing fibres or filaments made entirely or partially by chemical means, e.g. vapour phase deposition of bulk porous glass either by outside vapour deposition [OVD], or by outside vapour phase oxidation [OVPO] or by vapour axial deposition [VAD] by glass deposition on a glass substrate, e.g. by inside-, modified-, plasma-, or plasma modified- chemical vapour deposition [ICVD, MCVD, PCVD, PMCVD], i.e. by thin layer coating on the inside or outside of a glass tube or on a glass rod
  • C03B37/01807—Reactant delivery systems, e.g. reactant deposition burners
• • 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
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/02—Pure silica glass, e.g. pure fused quartz
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
  • C03B2201/12—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/08—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant
  • C03B2201/14—Doped silica-based glasses doped with boron or fluorine or other refractive index decreasing dopant doped with boron and fluorine
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2201/00—Type of glass produced
  • C03B2201/06—Doped silica-based glasses
  • C03B2201/20—Doped silica-based glasses doped with non-metals other than boron or fluorine
  • C03B2201/28—Doped silica-based glasses doped with non-metals other than boron or fluorine doped with phosphorus
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
  • C03B2203/00—Fibre product details, e.g. structure, shape
  • C03B2203/10—Internal structure or shape details
  • C03B2203/22—Radial profile of refractive index, composition or softening point
  • C03B2203/24—Single mode [SM or monomode]

Definitions

• the present invention relates to a single mode fiber for long wavelength
• the effective refractive index of the cladding material is chosen to be substantially less than the refractive index of the core.
• the core region is "up doped” and the cladding region is "down doped” so as to obtain the largest difference in Tefiactive index with the smallest overall fiber diameter.
• the ratio of the cladding diameter D to the core diameter d is useful in determining various performance parameters of optical fiber made from the preform, For example, to obtain optical fiber having desired transmission characteristics, the D/d ratio should be within an acceptable, but relatively narrow, range of values.
• the D/d value also affects the cut-off wavelength of the drawn fiber.
• the cut-off wavelength is the wavelength above which the optical fiber behaves as a step-index multimode fiber and below which behaves as a single mode fiber.
• the D/d ratio affects the mode field diameter (MFD) which is a measure of the width of the light intensity in a single mode fiber - also referred to as the "spot size". In most cases, it is desired to maintain the ratio D/d les,s than 2.5. While this value is acceptable for most short wavelength arrangements, longer wavelengths (e.g., 1550 nm) cannot be supported in such an arrangement.
• the depressed cladding which provides the index difference necessary for a waveguide must be large enough to contain the single mode, while not allowing the energy to leak from the fiber and drastically increase attenuation at the specified wavelength.
• the preform must be designed to have a cutoff wavelength that is relatively close to the operating wavelength to adequately contain the mode.
• the depressed cladding material should have a thickness sufficient to contain the operating wavelength made without suffering from huge bending loss.
• the core is formed from pure silica, with a relatively thick claddmg comprising fluorine-doped silica.
• the addition of the fluorine species serves to reduce the effective refractive index of the cladding material with respect to the pure silica core material.
• approximately 30-90 layers of fluorine-doped silica are deposited within a glass preform tube, with the core material thereafter deposited over the deposited layers of fluorine-doped silica.
• the fiber will be radiation resistant - a necessary feature for some applications.
• the fiber has also been shown to be hydrogen resistant (i.e., performs well in a hydrogen environment) and, therefore, exhibits improved resistance of the hydrogen-induced loss typically seen in harsh environments ("downhole" fibers, for example).
• FIG. 1 illustrates a cross-sectional view and associated refractive index profile for a single mode, long wavelength fiber formed in accordance with the present invention
• FIGs.2 - 5 illustrate an exemplary process for forming the single mode, long wavelength fiber of the present invention.
• FIG. 1 contains a cross-sectional view (FIG, 1 (a)) and associated refractive index profile (FIG. 1(b)) of a long wavelength, single mode fiber 10 formed in accordance with the present invention.
• the fiber comprises a relatively small diameter pure silica core region 12, where the diameter of core region 12 is referred to as "d" in the illustrationa.
• a relatively thick cladding layer 14 surrounds core region 12, where the diameter of cladding layer 14 is defined as "D" in the illustrations.
• cladding layer 1 is doped with fluorine, which functions to lower the effective refractive index of the material, ensuring that most of the propagating signal will remain in the core region.
• FIG. 1(b) illustrates the refractive index profile for fiber 10, where the difference between the refractive index of the core (defined as ni ⁇ ) and the refractive index of the cladding (defined as n ⁇ ) is shown as " ⁇ ", Since the inclusion of fluorine in the cladding layer functions to "depress" the refractive index of the cladding, most of the propagating single mode optical signal will be maintained within core region 12.
• the ratio D/d is controlled to be relatively large, greater than 8.5, and preferably in the range of 9 to 10.
• FIGs. 2 - 5 illustrate an exemplary process sequence that may be used to form the long wavelength, single mode fiber of the present invention.
• the process begins with an exemplary glass tube 20 used to fabricate an optical fiber preform using the well-known "modified chemical vapor deposition" (MCVD) technique.
• Cladding material 22 is then deposited on the inner wall 24 of tube 22, as shown in FIG. 3.
• the cladding is deposited in a number of layers so as to form the desired thickness for the final preform structure.
• the number of layers is controlled (in combination with various process parameters) with respect to the predetermined diameter d of the core region to obtain the desired D/d ratio.
• an HF etch may be used to remove a portion of the deposited cladding material.
• the deposition temperature is preferably within the range of approximately 1920 - 2020 °C
• the fluorine-doped claddmg is formed from precursors of SiF, O 2 , SiCL) and He.
• half of the layers can be deposited in one direction (e.g., from left to right), with the other half then deposited in the opposite direction (e.g., from right to left) so as to "balance" any irregularities in the geometry of the relatively thick deposited cladding material.
• silica core material 24 is deposited on the inner wall 26 of cladding material 22, as shown in FIG. 4. After core material 24 has been deposited, the tube is collapsed to form the preform, as illustrated in FIG. 5.
• a first set of cladding layers (for example, the first 20 - 30 layers) that are deposited may comprise phosphorous as well as fluorine, followed by "fluorine-only" layers, where the presence of only fluorine will maintain the hydrogen stability, as mentioned above.
• MCVD is a preferred technique for forming the fiber preform, any other technique that also is capable of forming a fiber having the desired D/d ratio may be used.

Landscapes

• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Optics & Photonics (AREA)
• Geochemistry & Mineralogy (AREA)
• Materials Engineering (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• General Physics & Mathematics (AREA)
• Glass Compositions (AREA)
• Manufacture, Treatment Of Glass Fibers (AREA)
• Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34992056

Family Applications (1)

Country Status (5)

Cited By (5)

Families Citing this family (13)

Family Cites Families (24)

• 2004
  • 2004-05-06 US US10/840,130 patent/US6947650B1/en not_active Expired - Lifetime
• 2005
  • 2005-05-06 WO PCT/US2005/016045 patent/WO2005109055A2/en not_active Ceased
  • 2005-05-06 JP JP2007511674A patent/JP2007536580A/ja active Pending
  • 2005-05-06 GB GB0624107A patent/GB2430498B/en not_active Expired - Lifetime
  • 2005-05-06 CA CA2565879A patent/CA2565879C/en not_active Expired - Lifetime

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