WO2003019254A1 - Etablissement de dispositif photonique a travers le revetement de fibre dopee aux terres rares - Google Patents

Etablissement de dispositif photonique a travers le revetement de fibre dopee aux terres rares Download PDF

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Publication number
WO2003019254A1
WO2003019254A1 PCT/AU2002/001189 AU0201189W WO03019254A1 WO 2003019254 A1 WO2003019254 A1 WO 2003019254A1 AU 0201189 W AU0201189 W AU 0201189W WO 03019254 A1 WO03019254 A1 WO 03019254A1
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WO
WIPO (PCT)
Prior art keywords
optical fibre
core
rare earth
wavelength
earth element
Prior art date
Legal status (The legal status 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 status listed.)
Ceased
Application number
PCT/AU2002/001189
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English (en)
Inventor
Justin Blows
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
University of Sydney
Original Assignee
University of Sydney
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 AUPR7420A external-priority patent/AUPR742001A0/en
Priority claimed from AU2002950074A external-priority patent/AU2002950074A0/en
Application filed by University of Sydney filed Critical University of Sydney
Publication of WO2003019254A1 publication Critical patent/WO2003019254A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • 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
    • G02B6/02057—Optical fibres with cladding with or without a coating comprising gratings
    • G02B6/02076—Refractive index modulation gratings, e.g. Bragg gratings
    • G02B6/02123—Refractive index modulation gratings, e.g. Bragg gratings characterised by the method of manufacture of the grating
    • G02B2006/02161—Grating written by radiation passing through the protective fibre coating

Definitions

  • the present invention relates to a method of fabricating an in-fibre photonic device structure, such as a Bragg grating and to a photonic device when fabricated by the method.
  • Bragg gratings are important components of photonic networks, including WDM optical networks because they form the basis of many in-fibre wavelength selective components. Such gratings are typically written with UV light having a wavelength of 244nm because germanium doped silica fibre is
  • grating 20 grating may be written using 244nm UV light, because even the most UV transmissive coatings are highly absorptive at this wavelength.
  • the problem with this is that the mechanical stripping of optical fibre reduces its strength by a factor of -2.5 and decreases, its long-term 25 reliability. Chemical stripping does largely preserve the fibre strength but takes more time to complete. Furthermore, it is generally necessary to recoat a stripped section of an optical fibre following the writing of a required structure, this adding further complexity and time
  • gratings can be written using radiation having a wavelength longer than that of UV radiation, i.e. near UV light emitted by argon ion lasers or frequency tripled Nd:YAG lasers.
  • the latter lasers have a significantly lower power consumption ( ⁇ 2 kW) compared to frequency doubled argon ion lasers (>10 kW) which typically are used to write gratings.
  • they can be air cooled, eliminating the need for expensive and complicated water cooling systems.
  • Such a laser source is therefore very attractive for industrial applications, and if a high repetition rate laser is used there is no damage to the fibre core resulting from the pulsed output.
  • the writing of gratings at 355nm is now feasible because appropriate sources of sufficient power have become available .
  • UV light having a wavelength longer than that of UV offers the possibility for writing gratings through coatings that are transparent to that radiation.
  • the photosensitivity of germanium doped silica fibre to near-UV radiation, or to radiation have a wavelength even longer than that, is much lower than that for UV radiation at 244nm.
  • Writing gratings using radiation having a wavelength longer than that of UN radiation therefore has a disadvantage in that a much higher dose of radiation is required to write gratings having sufficient (ie, acceptable) strength.
  • the present invention seeks to avoid this disadvantage by providing a method of creating a structure having a varying refractive index within an optical fibre that has a polymeric coating without stripping the coating from the optical fibre.
  • the method comprises the steps of:
  • optical fibre with a light transmitting core doped with at least one rare earth element that is selected to increase the photosensitivity of the core to light having a wavelength in the visible to near-UV spectral region
  • optical fibre • providing the optical fibre with a polymeric coating that is substantially transparent to light having a wavelength in the visible to near-UV spectral region
  • the invention may also be defined in terms of a photonic device comprising or incorporating an optical fibre having a structure created by the above-defined method.
  • the invention may be defined in an alternative way as providing a photonic device incorporating or comprising an optical fibre having a light transmitting core, a cladding surrounding the core and a polymeric coating surrounding the cladding, wherein the core is doped with at least one rare earth element that is selected to increase the photosensitivity of the core to light having a wavelength in the visible to near-UV spectral region and wherein a structure having a varying refractive index is written into the core by irradiation of the optical fibre through the coating using light having a wavelength in the visible to near-UV spectral region.
  • the structure that is written into the optical fibre will normally, but need not necessarily, be in the form of a Bragg grating.
  • the or each rare earth element within the core may be selected as one which absorbs the structure writing radiation and transfers energy to the core material so as to create a localised increase in refractive index.
  • the or each rare earth element preferably is selected as a rare earth element dopant that does not change its oxidation state significantly when exposed to the writing radiation.
  • the or each rare earth element dopant preferably has a valence value of about 3+, and in particularly preferred forms of the invention the or each rare earth element dopant comprises Ho 3+ and/or Tu 3+ ions .
  • the or each rare earth element dopant preferably is substantially transparent at optical communication wavelengths.
  • the method of the present invention may include the additional step of hydrogenating the optical fibre prior to irradiation.
  • the method may also comprises the step of annealing the optical fibre subsequent to the step of writing the structure.
  • the irradiation of the optical fibre preferably is effected by near UV radiation.
  • the radiation most preferably has a wavelength within the range of 300 to 360 nm.
  • the source of the radiation preferably is a frequency tripled Nd:YAG laser.
  • the invention effectively involves the three-step process of: providing the optical fibre with a light transmitting core which is doped with at least one rare earth element that serves to increase the photosensitivity of the core to light having a wavelength in the visible to near-UV spectral region (such as light having a wavelength of 300 - 700nm) , providing the optical fibre with a polymeric coating that is substantially transparent to light having a wavelength in the visible to near-UV spectral region, and writing a grating structure into the core by a process that involves irradiating the optical fibre through the coating with light having a wavelength in the visible to near-UV spectral region.
  • Germano-silicate optical fibres have been formed and doped with Ho 3+ and Tm 3+ ions.
  • the concentrations of the rare earth dopants in the fibres were estimated by comparing absorption spectra with those of spectra published in
  • the Ho 3+ concentration is approximately 3600 ppm in a core of 12 mol . % Ge0 2 and the Tm 3+ concentration is approximately 900 ppm in a core of 10 mol. % of Ge0 2 .
  • Gratings were created in the cores of the optical fibres by irradiating the optical fibres through their claddings.
  • Near-UV radiation of wavelength in the order of 355 nm was provided by a frequency tripled Nd:YAG laser which was run at 15 kHz with an output power of 1 W and focused using a cylindrical lens with a focal length of 89 mm onto the fibres through a phase-mask to effect direct writing of the Bragg grating.
  • the irradiance at the fibres was approximately 200 Wcm "2 and a 1 mm slit was placed in the beam so that the length of the grating in each case was lmm. Due to the presence of the slits the optical fibres were subjected to a power of less than 1 W.
  • the transmission versus wavelength plots shown in the drawing were recorded using a tungsten white light source and an optical spectrum analyser before and after the gratings were written.
  • the drawing shows the measurements for the Bragg gratings written into a boron doped fibre 10, a Ho 3+ doped fibre 20 and a Tm 3+ doped fibre 30.
  • the plots indicate that the gratings written into the fibres doped with Ho 3+ and Tm 3+ have a strength of approximately -7.5 dB, which is superior to the strength of the boron doped fibre (-5.5 dB) .
  • the increased strengths of the gratings written into the Ho 3+ and Tm 3+ doped fibres demonstrates that these gratings have increased refractive index contrasts.
  • the gratings were subsequently annealed for 10 min at temperatures ranging from 50°C to 300°C, and it was determined that the relative decay of grating strength as a function of annealing temperature of the Tm 3+ and Ho 3+ doped gratings was similar to that of the boron doped grating. This indicates that no lifetime penalty is incurred by introducing the rare earth dopants.
  • each optical fibre was stripped prior to exposure to the radiation. Such stripping was required because the fibres were coated with a near UV opaque material of a type that is routinely used for such fibres.
  • a near UV opaque material of a type that is routinely used for such fibres.
  • the present invention will be embodied in an optical fibre that has a polymeric coating that is substantially transparent to light having a wavelength in the visible to near-UV spectral region, and in such case the polymeric coating will not be stripped from the optical fibre.
  • coating materials are vinyl ether and a aliphatic urathane acrylate .

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Lasers (AREA)
  • Optical Fibers, Optical Fiber Cores, And Optical Fiber Bundles (AREA)

Abstract

L'invention concerne une fibre optique dopée à un ou plusieurs éléments des terres rares, sélectionnés de manière à augmenter la photosensibilité du coeur pour atteindre une longueur d'onde située dans la zone spectrale allant du visible à l'UV proche. Il s'agit d'une fibre à revêtement polymère transparent aux longueurs d'onde dans la région spectrale considérée. On établit un dispositif photonique dans le coeur, sans ôter le revêtement de la fibre optique, par irradiation de cette fibre avec de la lumière dont la longueur d'onde est située dans la zone spectrale allant du visible à l'UV proche. Parmi les variantes de l'invention figurent les réseaux de Bragg, établis dans des fibres en germanosilicate dopées aux ions d'holmium (20) ou de thulium (30), fournissant une puissance de signal environ égale à 7,5db.
PCT/AU2002/001189 2001-08-31 2002-08-30 Etablissement de dispositif photonique a travers le revetement de fibre dopee aux terres rares Ceased WO2003019254A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
AUPR7420A AUPR742001A0 (en) 2001-08-31 2001-08-31 Method of fabricating a structured photonic device using near-uv radiation
AUPR7420 2001-08-31
AU2002950074A AU2002950074A0 (en) 2002-07-05 2002-07-05 Method of fabricating a structured photonic device using near-uv radiation
AU2002950074 2002-07-05

Publications (1)

Publication Number Publication Date
WO2003019254A1 true WO2003019254A1 (fr) 2003-03-06

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Application Number Title Priority Date Filing Date
PCT/AU2002/001189 Ceased WO2003019254A1 (fr) 2001-08-31 2002-08-30 Etablissement de dispositif photonique a travers le revetement de fibre dopee aux terres rares

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Country Link
WO (1) WO2003019254A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2281787A (en) * 1993-09-09 1995-03-15 Northern Telecom Ltd Optical waveguide gratings
WO2000036714A1 (fr) * 1998-12-16 2000-06-22 Mitsubishi Cable Industries, Ltd. Egaliseur de gain, amplificateur de lumiere et systeme optique de communication
US6240224B1 (en) * 1998-10-16 2001-05-29 University Of Southhampton Coated optical fiber
WO2001057571A1 (fr) * 2000-02-03 2001-08-09 The University Of Sydney Changement d'indice de refraction par differenciation des rayonnements

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2281787A (en) * 1993-09-09 1995-03-15 Northern Telecom Ltd Optical waveguide gratings
US6240224B1 (en) * 1998-10-16 2001-05-29 University Of Southhampton Coated optical fiber
WO2000036714A1 (fr) * 1998-12-16 2000-06-22 Mitsubishi Cable Industries, Ltd. Egaliseur de gain, amplificateur de lumiere et systeme optique de communication
WO2001057571A1 (fr) * 2000-02-03 2001-08-09 The University Of Sydney Changement d'indice de refraction par differenciation des rayonnements

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