WO2002079827A1 - Fibre optique a pertes reduites en mode de gaine - Google Patents

Fibre optique a pertes reduites en mode de gaine Download PDF

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Publication number
WO2002079827A1
WO2002079827A1 PCT/US2002/007331 US0207331W WO02079827A1 WO 2002079827 A1 WO2002079827 A1 WO 2002079827A1 US 0207331 W US0207331 W US 0207331W WO 02079827 A1 WO02079827 A1 WO 02079827A1
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WO
WIPO (PCT)
Prior art keywords
core
cladding
stress
flat surfaces
fiber
Prior art date
Application number
PCT/US2002/007331
Other languages
English (en)
Other versions
WO2002079827A8 (fr
Inventor
Abdelouahed Soufiane
Original Assignee
Intelcore Technologies, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US09/922,544 external-priority patent/US6636675B2/en
Application filed by Intelcore Technologies, Inc. filed Critical Intelcore Technologies, Inc.
Priority to AU2002306690A priority Critical patent/AU2002306690A1/en
Publication of WO2002079827A1 publication Critical patent/WO2002079827A1/fr
Publication of WO2002079827A8 publication Critical patent/WO2002079827A8/fr

Links

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
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03694—Multiple layers differing in properties other than the refractive index, e.g. attenuation, diffusion, stress properties
    • 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
    • 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
    • G02B6/036—Optical fibres with cladding with or without a coating core or cladding comprising multiple layers
    • G02B6/03616—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference
    • G02B6/03622—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 2 layers only
    • G02B6/03633—Optical fibres characterised both by the number of different refractive index layers around the central core segment, i.e. around the innermost high index core layer, and their relative refractive index difference having 2 layers only arranged - -
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
    • H01S3/06—Construction or shape of active medium
    • H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
    • H01S3/067—Fibre lasers
    • H01S3/06708—Constructional details of the fibre, e.g. compositions, cross-section, shape or tapering
    • H01S3/06729—Peculiar transverse fibre profile
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/09—Processes or apparatus for excitation, e.g. pumping
    • H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
    • H01S3/094—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light
    • H01S3/094003—Processes or apparatus for excitation, e.g. pumping using optical pumping by coherent light the pumped medium being a fibre

Definitions

  • the invention relates generally to optical fibers and more specifically to optical fibers that maintain the polarization of the incident radiation.
  • optical fibers are used as laser devices in a variety of applications.
  • a fiber produces a lasing effect when light introduced into the fiber interacts with a doped core. As light passes through the core it stimulates the dopants and is amplified.
  • the core is typically surrounded by a pure silica inner cladding having a refractive index less than that of the core, and an outer cladding having an index of refraction less than that of the inner cladding. Therefore, the refractive indices of the layers decrease moving from the core to the outer cladding. This profile causes light pumped into the fiber to be internally reflected within the inner cladding.
  • Laser fibers may be core-pumped or cladding-pumped, depending on where the source light is introduced. In the latter case, light directed into the cladding (e.g., from the side of the fiber) is reflected into the core to cause lasing.
  • the inner cladding may be polygonally (as opposed to circularly) shaped.
  • the non-circular inner cladding causes ray distortion and mode mixing of the incident light, thereby causing the rays to interact with the core more frequently than would be the case in a circular configuration.
  • a circular inner cladding causes light to be continuously reflected in a helical path within the circular cladding and around — rather than into — the core.
  • Single-mode polarization-preserving fibers generally rely on asymmetrical features of the fiber to maintain the polarization of the input light.
  • two orthogonally polarized modes propagate in the fiber, and the asymmetry of the fiber maintains their polarization.
  • One example of this asymmetry illustrated in Figure 1, utilizes an elliptically shaped core 160 disposed within a circular cladding 170.
  • An alternative approach to maintaining polarization is to induce birefringence in the fiber by stressing the cladding in one direction. The component polarized in the direction in which stress is induced is slowed to the point of being eliminated, while the other component is allowed to propagate through the fiber.
  • a linearly polarized incident light decomposes into both x and y polarizations as it propagates down the fiber. Stressing the fiber in the x direction will slow one of the components to the point of virtual elimination. Therefore, the polarization of the incident light is preserved at the end of the fiber.
  • the present invention relates to preserving the polarization characteristics of the incident light and increasing the pumped-radiation absorption efficiency — the amount of absorbed light that interacts with the core — by controlling the shape of the cladding and stress members and their positions relative to each other and the core.
  • the invention relates to an optical fiber including a lasing core that carries radiation.
  • the core has index of refraction n c .
  • the fiber includes a primary cladding with an index of refraction n pc that surrounds the core, a secondary cladding with an index of refraction n sc that surrounds the primary cladding.
  • Within the primary cladding a pair of stress members, each with an index of refraction n sm , are disposed on opposite sides of the core.
  • the stress members have a coefficient of thermal expansion different from that of the primary cladding. This difference induces birefringence within the fiber.
  • Each of the stress members has a flat surface facing the core and the flat surface of the other stress member.
  • the primary cladding has a pair of opposed flat surfaces substantially perpendicular to the stress-member flat surfaces. The stress-member flat surfaces and the primary cladding flat surfaces cooperate to reflect light into the core as it propagates through the fiber.
  • the stress-member flat surfaces have a length at least equal to the core diameter.
  • the cladding flat surfaces have a width dimension at least equal to the core diameter.
  • the stress-member flat surfaces are separated by a distance, and the cladding flat surfaces at least span this distance.
  • the stress members may be solid or fluid (i.e., a liquid, gas, or gel).
  • the present invention relates to a method of maintaining polarization and improving pump-energy efficiency including the step of providing an optical fiber that has a lasing core, a non-circular primary cladding, a secondary cladding, and a pair of stress members disposed within the primary cladding on opposite sides of the core.
  • the primary cladding and the stress members have different coefficients of thermal expansion, thereby resulting in birefringence within the primary cladding.
  • the method includes the step of radially pumping polarized light into the fiber. The birefringence within the primary cladding preserves the polarization of the pumped light, and the non-circular cladding directs the light at the core as the light propagates down the fiber.
  • each of the stress members has a flat surface that faces the core.
  • the primary cladding has a pair of opposed flat surfaces that are substantially perpendicular to the stress-member flat surfaces, thereby cooperating to direct pumped light at the core.
  • the core has an index of refraction n c
  • the primary cladding has an index of refraction n pc
  • the secondary cladding has an index of refraction n sc
  • the stress members have an index of refraction of n sm .
  • the relationships among the indices of refraction are n c > n pc > n sc and n pc > n sm .
  • FIG. 1 is a cross-sectional view of a prior-art polarization-preserving optical fiber.
  • FIG. 2 is a cross-sectional view of an embodiment of the present invention.
  • an optical fiber of the present invention includes a core 200, a primary cladding 210 concentrically surrounding core 200, a pair of opposed stress members 220 within primary cladding 210 and which straddle core 200, and a secondary cladding 230 concentrically surrounding primary cladding 210.
  • Core 200 is typically composed of a silica-based glass doped with a lasing material such as, but not limited to, GeO 2 , P 2 O 5 , TiO , B 2 O 3 , or fluorine.
  • Core 200 has an index of refraction n c associated therewith.
  • primary cladding 210 is composed of an undoped silica-based glass having an index of refraction n pc , which is less than that of core 200.
  • Primary cladding 210 also has a coefficient of thermal expansion ⁇ pc associated therewith.
  • Primary cladding 210 is shaped to define two flat surfaces 250 on opposite sides of core 200, each surface 250 having a length W.
  • a pair of stress members 220 Disposed within primary cladding 210 is a pair of stress members 220, each having an index of refraction n sm5 which is less than that of primary cladding 210, and a coefficient of thermal expansion ⁇ sm which is not equal to that of primary cladding 210.
  • Stress members 220 each have a flat surface 260 of height H. Surfaces 260 are disposed substantially perpendicular to primary cladding flat surfaces 250, facing each other on opposite sides of core 200 and separated by a distance S.
  • Secondary cladding 230 is typically composed of a low index polymeric material or a low index glass composition. Secondary cladding 230 has an index of refraction n sc which is less than those of both core 200 and primary cladding 210.
  • the relationships among the refractive indices and the coefficients of thermal expansion are as follows: n 0 > n pc > n SC; n pc > n sm , and
  • the difference in thermal response between stress members 220 and primary cladding 210 produces the birefringence that preserves the polarization of the incident signal.
  • the non- circular shape of the primary cladding provides ray distortion to direct the pumped light to core 200 of the fiber. Additionally, stress members 220 provide additional ray distortion, thereby increasing the overall pumped-radiation absorption efficiency.
  • cladding flat surfaces 250 and stress-member flat surfaces 260 form a trap to reflect light and direct it toward core 200.
  • the width W of cladding flat surfaces 250 would be at least as great as the separation distance S between stress- member flat surfaces 260 (in other words, the width of the cladding flat surfaces would span the distance S), and the height H of stress members 260 would be such that stress members 260 reach — i.e., span the distance between — cladding flat surfaces 250.
  • the height dimension H is preferably at least equal to the core diameter, but is less than the distance between cladding flat surfaces 250.
  • the width W of cladding flat surfaces 250 is also at least equal to the core diameter, and is desirably at least as great as the distance S.
  • the height H of stress members 220 is 48.44 microns.
  • Core 200 has a diameter of 8.2 microns, and the width W of cladding member flat surfaces 250 are 77.7 microns.
  • Distance S is 29.0 microns, and the diameter of primary cladding 210 is 125 microns.
  • the diameter of secondary cladding 230 is 185 microns.
  • pump energy is radially introduced into secondary cladding 230.
  • the pump light passes through to primary cladding 210 where it undergoes multiple internal reflections because the refractive index n pc of primary cladding 210 is greater than that of secondary cladding n sc .
  • n pc refractive index of primary cladding 210
  • a portion thereof passes through to core 200.
  • that portion of the pump light propagates within core 200 because the refractive index of the core n c is greater than that of primary cladding n pc .
  • the pump light causes lasing to occur through interaction with laser dopants within core 200.
  • stress-member flat surfaces 260 and primary-cladding flat surfaces 250 cooperate to reflect pump light into the core 200, thereby improving the pump-energy absorption efficiency.
  • Stress members 220 and primary cladding 210 have differing coefficients of thermal expansion. As a result, birefringence is created within the fiber. As polarized light propagates through core 200, its polarization is maintained due to this birefringence.

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  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Glass Compositions (AREA)
  • Lasers (AREA)

Abstract

L'invention concerne une fibre optique (200) qui réduit la perte de couplage en mode de gaine (CMCL). La fibre (200) comprend une âme (205), une gaine (220) entourant l'âme de manière concentrique (205) et au moins une région à pertes (215) entourant l'âme de façon concentrique. La région à pertes est disposée à l'intérieur de la gaine (220) et légèrement décalée radialement par rapport à l'âme (205).
PCT/US2002/007331 2001-03-12 2002-03-12 Fibre optique a pertes reduites en mode de gaine WO2002079827A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2002306690A AU2002306690A1 (en) 2001-03-12 2002-03-12 Dual-clad polarization-preserving optical fiber

Applications Claiming Priority (5)

Application Number Priority Date Filing Date Title
US27505601P 2001-03-12 2001-03-12
US60/275,056 2001-03-12
US09/922,544 2001-08-03
US09/922,544 US6636675B2 (en) 2001-03-12 2001-08-03 Optical fiber with reduced cladding-mode loss
PCT/US2002/015449 WO2003098274A2 (fr) 2001-03-12 2002-05-15 Fibre optique a perte reduite en mode de gaine

Publications (2)

Publication Number Publication Date
WO2002079827A1 true WO2002079827A1 (fr) 2002-10-10
WO2002079827A8 WO2002079827A8 (fr) 2003-03-20

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PCT/US2002/007331 WO2002079827A1 (fr) 2001-03-12 2002-03-12 Fibre optique a pertes reduites en mode de gaine

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2445081A (en) * 2006-12-21 2008-06-25 Weatherford Lamb Birefringent waveguide comprising elliptical stress region
US7437044B2 (en) 2006-12-21 2008-10-14 Weatherford/Lamb, Inc. Pure silica core, high birefringence, single polarization optical waveguide

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61215225A (ja) * 1985-03-19 1986-09-25 Fujitsu Ltd 偏波面保存光フアイバの製造方法
JPS63106518A (ja) * 1986-10-23 1988-05-11 Agency Of Ind Science & Technol 光フアイバジヤイロのフアイバコイル
EP0484659A2 (fr) * 1990-11-09 1992-05-13 Corning Incorporated Procédé pour la fabrication d'une fibre à maintien de polarisation
EP0918382A2 (fr) * 1997-11-21 1999-05-26 Lucent Technologies Inc. Structures à fibre pompée à travers le gainage
US5933271A (en) * 1996-01-19 1999-08-03 Sdl, Inc. Optical amplifiers providing high peak powers with high energy levels

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61215225A (ja) * 1985-03-19 1986-09-25 Fujitsu Ltd 偏波面保存光フアイバの製造方法
JPS63106518A (ja) * 1986-10-23 1988-05-11 Agency Of Ind Science & Technol 光フアイバジヤイロのフアイバコイル
EP0484659A2 (fr) * 1990-11-09 1992-05-13 Corning Incorporated Procédé pour la fabrication d'une fibre à maintien de polarisation
US5933271A (en) * 1996-01-19 1999-08-03 Sdl, Inc. Optical amplifiers providing high peak powers with high energy levels
EP0918382A2 (fr) * 1997-11-21 1999-05-26 Lucent Technologies Inc. Structures à fibre pompée à travers le gainage

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 011, no. 053 (C - 404) 19 February 1987 (1987-02-19) *
PATENT ABSTRACTS OF JAPAN vol. 012, no. 350 (P - 760) 20 September 1988 (1988-09-20) *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2445081A (en) * 2006-12-21 2008-06-25 Weatherford Lamb Birefringent waveguide comprising elliptical stress region
US7437044B2 (en) 2006-12-21 2008-10-14 Weatherford/Lamb, Inc. Pure silica core, high birefringence, single polarization optical waveguide
GB2445081B (en) * 2006-12-21 2009-03-25 Weatherford Lamb Pure silica core, high birefringence, single polarization optical waveguide
US7907807B2 (en) 2006-12-21 2011-03-15 Weatherford/Lamb, Inc. Pure silica core, high birefringence, single polarization optical waveguide

Also Published As

Publication number Publication date
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