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WO2003098294A1 - Fibre optic connector - Google Patents

Fibre optic connector Download PDF

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Publication number
WO2003098294A1
WO2003098294A1 PCT/GB2003/001988 GB0301988W WO03098294A1 WO 2003098294 A1 WO2003098294 A1 WO 2003098294A1 GB 0301988 W GB0301988 W GB 0301988W WO 03098294 A1 WO03098294 A1 WO 03098294A1
Authority
WO
WIPO (PCT)
Prior art keywords
fibre
single core
multicore
cores
grin lens
Prior art date
Application number
PCT/GB2003/001988
Other languages
French (fr)
Inventor
James Gordon Burnett
Original Assignee
Qinetiq Limited
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
Application filed by Qinetiq Limited filed Critical Qinetiq Limited
Priority to AU2003240998A priority Critical patent/AU2003240998A1/en
Publication of WO2003098294A1 publication Critical patent/WO2003098294A1/en

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
    • G02B6/02042—Multicore optical fibres
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers
    • G02B6/2848—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals forming multipart couplers without wavelength selective elements, e.g. "T" couplers, star couplers having refractive means, e.g. imaging elements between light guides as splitting, branching and/or combining devices, e.g. lenses, holograms
    • 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
    • G02B6/24—Coupling light guides
    • G02B6/26—Optical coupling means
    • G02B6/32—Optical coupling means having lens focusing means positioned between opposed fibre ends

Definitions

  • the invention concerns a method of connecting each core of a multi-core optical fibre to the core of a single core optical fibre, and to a connector for connecting such two fibre types.
  • a connector allows for the simultaneous interrogation of N cores in the multicore fibre through a common single-mode fibre download.
  • Optical fibres are known components having a core along which light can pass either in single mode or multi mode transmission, surrounded by an optically insulating sheath.
  • the fibre may be single or multicore.
  • the fibre cores are of a glass material having a diameter of several microns upwards, e.g. 50 to 500 ⁇ m.
  • the cores may be several tens of ⁇ m apart, e.g. 30 to 100//m apart.
  • the above problem is solved by use of two similar GRIN lenses optically connected together through a diffractive optical element and connecting the multicore fibre to one GRIN lens and a single core fibre to the other .
  • GRIN lens optically connected together through a diffractive optical element and connecting the multicore fibre to one GRIN lens and a single core fibre to the other .
  • a method of coupling cores in a multicore optical fibre to a single core of a single core fibre includes the steps of: -
  • a connector for coupling cores in a multicore optical fibre to a single core of a single core fibre includes: -
  • a diffractive optical element connecting optically to both GRIN lenses for splitting incident wavefronts from N different cores into N ⁇ 1 -order wavefront pairs
  • the optical fibres transmit visible light and/or other wavelengths such as IR and UV.
  • the diffractive optical element may be formed by holographic techniques. For example it may be formed from a photoresist material on one end of a GRIN lens illuminated by light from a multicore fibre fixed to the other end of the lens.
  • the invention may also be used to connect a plurality of single core optical fibres to the multicore optical fibre.
  • the DOE needs to be different to that used for a single fibre.
  • GRIN lenses are known commercially obtainable optical components; for example obtainable from Nippon Sheet Glass Company.
  • the GRIN lenses are described as being of 0.25 pitch. This is the theoretical ideal, true at one wavelength; in practice deviation from the ideal is satisfactory.
  • 0.25 pitch and substantially 0.25 pitch is to be taken to include 0.25 pitch and functionally equivalent or similar pitches.
  • the term pitch relates to the number of cycles that are associated with the sinusoidal trajectory of an optical ray propagating from the input face of the GINR lens to its output face.
  • the sinusoidal trajectory of an optical ray propagating along a GRIN lens is a consequence of the quadratic refractive index profile of the GRIN lens.
  • An optical ray that propagates along a ray path trajectory equal to one cycles of a sinusoid has a pitch of 1.0.
  • a 0.25 pitch lens will propagate rays through a quarter of a sinusoid cycle and therefore all rays emanating from a point on the input face of a 0.25 GRIN lens (provided these ray propagate within the numerical aperture of the GRIN lens) will exit the GRIN lens at its output face co-linearly (i.e. they will describe a collimated beam).
  • Figure 1 is a diagrammatic view of a connector between a multicore optical fibre and a single core optical fibre;
  • Figure 2 is an enlarged end view of the multicore fibre having four cores on a square grid
  • Figure 3 is an enlarged end view of the single core fibre
  • Figure 4 is a schematic view of Figure 1 showing wave traces.
  • the connector 1 of Figures 1 , 2 comprises a first graded index (GRIN) lens 2 connected optically to a second GRIN lens 3 through a diffractive optical element (DOE) 4.
  • a multicore optical fibre 5 having N cores is connected optically to the first GRIN lens.
  • Both GRIN lens 3, 4 are 0.25 pitch length.
  • An optical fibre 10 having a single core 11 is connected optically to the second GRIN lens 3.
  • the whole assembly of GRIN lenses 2, 3 and fibres 5, 10 may be held in position by optical cement and all contained in a potting material for robustness.
  • the components may be held in position by a holder 12, which may in two parts 13, 14 separable for connecting to different elements.
  • the DOE 4 is arranged to split an incident wavefront light into N ⁇ 1 -order wavefront pairs, Figure 4. Each wavefront pair has a predetermined tilt offset leading to 2N images on the GRIN lens 2 surface butted to the multicore fibre 5.
  • light 15 from the single core fibre 6 is diffracted into two paths 16, 16' into two opposite cores 6, 8 of the multicore fibre 5.
  • light 17 from core 6 is diffracted into two paths 18 one into the single core 11 and the other path 18' onto the end face of the second GRIN lens 3.
  • light 19 from core 8 is diffracted into two paths, one 20 onto the single core 11 and the other path 20' onto the end face of the second GRIN lens 3.
  • the DOE 4 may be formed by holographic techniques. For example a layer of a photoresist material may be spun onto the end of a GRIN lens. On the other end is fixed the multicore fibre 5, Light is directed down the multicore fibre 5, through the GRIN lens onto the photoresist to form interference patterns in the photoresist. The photoresist is then photographically developed by selective removal of exposed/non- exposed (?) material and hardened by a fixture material. The second GRIN lens 3 is then attached to the DOE 4. Other known techniques may also be used; for example if the dimensions of the fibre 5 is known accurately, then the interference pattern may be calculated using known formulae and a DOE 4 produced.
  • the two cores 8, 9 may be used as two arms of a Michelson interferometer in which case the end of the multicore fibre 5 is cleaved square and coated to maximise reflectivity back along the fibre.
  • Light is directed from the single core fibre 10 into both cores 8, 9.
  • Light travels to the end of the cores 8, 9 arranged within a component whose bending is to be detected. Bending of these cores 8, 9 will produce changes in their relative length.
  • light is coupled into the single core fibre and transported back to a detector where interference gives rise to a signal which is a function of the optical path difference between the two cores 8, 9 and hence the amount of bend.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)

Abstract

A method and a connector for coupling cores in a multicore optical fibre (5) to a single core of a single core fibre (10) employs a first GRIN lens (2) of 0.25 pitch for connecting to the multicore fibre (5), a second GRIN lens (3) of 0.25 pitch for connecting to the single core fibre (10)and a diffractive optical element (4) connecting optically to both GRIN lenses for splitting incident wavefronts from N different cores into N ± 1-order wavefront pairs, whereby output from a plurality of cores within the multicore fibre (5) is received by the core of the single core fibre (10).

Description

Fibre Optic Connector
The invention concerns a method of connecting each core of a multi-core optical fibre to the core of a single core optical fibre, and to a connector for connecting such two fibre types. Such a connector allows for the simultaneous interrogation of N cores in the multicore fibre through a common single-mode fibre download.
Optical fibres are known components having a core along which light can pass either in single mode or multi mode transmission, surrounded by an optically insulating sheath. The fibre may be single or multicore. Typically the fibre cores are of a glass material having a diameter of several microns upwards, e.g. 50 to 500μm. In a multicore fibre the cores may be several tens of μm apart, e.g. 30 to 100//m apart.
One use of multicore fibres is in the monitoring of structures where the fibre is incorporated into the structure to measure bend. It is necessary to read the outputs from different cores to obtain a bend measurement. One problem concerns coupling light from the cores to other fibres leading to detectors and other components for calculating bend etc. One arrangement for connecting a multiple core optical fibre to single core fibres is described in US patent 6,078,708.
According to this invention the above problem is solved by use of two similar GRIN lenses optically connected together through a diffractive optical element and connecting the multicore fibre to one GRIN lens and a single core fibre to the other . GRIN lens.
According to this invention a method of coupling cores in a multicore optical fibre to a single core of a single core fibre includes the steps of: -
providing a first GRIN lens of 0.25 pitch for connecting to the multicore fibre;
providing a second GRIN lens of 0.25 pitch for connecting to the single core fibre; and
providing a diffractive optical element connecting optically to both GRIN lenses for splitting incident wavefronts from N different cores into N ± 1 -order wavefront pairs,
whereby output from a plurality of cores within the multicore fibre is received by the single core of the single core fibre.,
According to this invention a connector for coupling cores in a multicore optical fibre to a single core of a single core fibre includes: -
a first GRIN lens of 0.25 pitch for connecting to the multicore fibre;
a second GRIN lens of 0.25 pitch for connecting to the single core fibre; and
a diffractive optical element connecting optically to both GRIN lenses for splitting incident wavefronts from N different cores into N ± 1 -order wavefront pairs,
whereby output from a plurality of cores within the multicore fibre is received by the core of the single core fibre.
The optical fibres transmit visible light and/or other wavelengths such as IR and UV.
The diffractive optical element may be formed by holographic techniques. For example it may be formed from a photoresist material on one end of a GRIN lens illuminated by light from a multicore fibre fixed to the other end of the lens.
The invention may also be used to connect a plurality of single core optical fibres to the multicore optical fibre. In this case the DOE needs to be different to that used for a single fibre.
GRIN lenses are known commercially obtainable optical components; for example obtainable from Nippon Sheet Glass Company. The GRIN lenses are described as being of 0.25 pitch. This is the theoretical ideal, true at one wavelength; in practice deviation from the ideal is satisfactory. In this specification the term 0.25 pitch and substantially 0.25 pitch is to be taken to include 0.25 pitch and functionally equivalent or similar pitches.
The term pitch relates to the number of cycles that are associated with the sinusoidal trajectory of an optical ray propagating from the input face of the GINR lens to its output face. The sinusoidal trajectory of an optical ray propagating along a GRIN lens is a consequence of the quadratic refractive index profile of the GRIN lens. An optical ray that propagates along a ray path trajectory equal to one cycles of a sinusoid has a pitch of 1.0.
A 0.25 pitch lens will propagate rays through a quarter of a sinusoid cycle and therefore all rays emanating from a point on the input face of a 0.25 GRIN lens (provided these ray propagate within the numerical aperture of the GRIN lens) will exit the GRIN lens at its output face co-linearly (i.e. they will describe a collimated beam). The invention will now be described, by way of example only, with reference to the accompanying drawings in which:
Figure 1 is a diagrammatic view of a connector between a multicore optical fibre and a single core optical fibre;
Figure 2 is an enlarged end view of the multicore fibre having four cores on a square grid;
Figure 3 is an enlarged end view of the single core fibre; and
Figure 4 is a schematic view of Figure 1 showing wave traces.
The connector 1 of Figures 1 , 2 comprises a first graded index (GRIN) lens 2 connected optically to a second GRIN lens 3 through a diffractive optical element (DOE) 4. A multicore optical fibre 5 having N cores is connected optically to the first GRIN lens. Both GRIN lens 3, 4 are 0.25 pitch length. In the specific example N=4, and the four cores 6, 7, 8, 9 are arranged on a square grid with each core offset from fibre axis by δ as seen in Figure 2. An optical fibre 10 having a single core 11 is connected optically to the second GRIN lens 3.
The whole assembly of GRIN lenses 2, 3 and fibres 5, 10 may be held in position by optical cement and all contained in a potting material for robustness. Alternatively the components may be held in position by a holder 12, which may in two parts 13, 14 separable for connecting to different elements.
The DOE 4 is arranged to split an incident wavefront light into N ±1 -order wavefront pairs, Figure 4. Each wavefront pair has a predetermined tilt offset leading to 2N images on the GRIN lens 2 surface butted to the multicore fibre 5. In the specific example, light 15 from the single core fibre 6 is diffracted into two paths 16, 16' into two opposite cores 6, 8 of the multicore fibre 5. Similarly, light 17 from core 6 is diffracted into two paths 18 one into the single core 11 and the other path 18' onto the end face of the second GRIN lens 3. Likewise, light 19 from core 8 is diffracted into two paths, one 20 onto the single core 11 and the other path 20' onto the end face of the second GRIN lens 3.
The DOE 4 may be formed by holographic techniques. For example a layer of a photoresist material may be spun onto the end of a GRIN lens. On the other end is fixed the multicore fibre 5, Light is directed down the multicore fibre 5, through the GRIN lens onto the photoresist to form interference patterns in the photoresist. The photoresist is then photographically developed by selective removal of exposed/non- exposed (?) material and hardened by a fixture material. The second GRIN lens 3 is then attached to the DOE 4. Other known techniques may also be used; for example if the dimensions of the fibre 5 is known accurately, then the interference pattern may be calculated using known formulae and a DOE 4 produced.
One use of the connector shown is in a bend sensor as described in WO 9859219A2. The two cores 8, 9 may be used as two arms of a Michelson interferometer in which case the end of the multicore fibre 5 is cleaved square and coated to maximise reflectivity back along the fibre. Light is directed from the single core fibre 10 into both cores 8, 9. Light travels to the end of the cores 8, 9 arranged within a component whose bending is to be detected. Bending of these cores 8, 9 will produce changes in their relative length. On reflection from the core ends, light is coupled into the single core fibre and transported back to a detector where interference gives rise to a signal which is a function of the optical path difference between the two cores 8, 9 and hence the amount of bend.

Claims

Claims.
1. A method of coupling cores in a multicore optical fibre to a single core of a single core fibre including the steps of: -
providing a first GRIN lens of substantially 0.25 pitch for connecting to the multicore fibre;
providing a second GRIN lens of substantially 0.25 pitch for connecting to the single core fibre; and
providing a diffractive optical element connecting optically to both GRIN lenses for splitting incident wavefronts from N different cores into N ± 1 -order wavefront pairs,
whereby output from a plurality of cores within the multicore fibre is received by the single core of the single core fibre.
2. The method of claim 1 wherein the diffractive optical element is formed by exposure of light from the cores of the multicore optical fibre and through the GRIN lens onto a layer of photoresist material followed by development of the photoresist material.
3. A connector for coupling cores in a multicore optical fibre (5) to a single core of at least one single core fibre (10) including: -
a first GRIN lens (2) of substantially 0.25 pitch for connecting to the multicore fibre (5);
a second GRIN lens (3) of substantially 0.25 pitch for connecting to the single core fibre (10); and
a diffractive optical element (4) connecting optically to both GRIN lenses (2, 3) for splitting incident wavefronts from N different cores into N ± 1 -order wavefront pairs,
whereby output from a plurality of cores (6, 7, 8, 9) within the multicore fibre (5)is received by the core (11) of the at least one single core fibre (10).
4. The connector of claim 3 wherein the optical fibres (5, 10) and GRIN lenses (2, 3) are supported within a holder (12).
5. The connector of claim 3 wherein the connector couples to the single core of a single core fibre (10).
6. The connector of claim 3 wherein the connector couples to the single core of a plurality of single core fibres (10).
PCT/GB2003/001988 2002-05-18 2003-05-07 Fibre optic connector WO2003098294A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU2003240998A AU2003240998A1 (en) 2002-05-18 2003-05-07 Fibre optic connector

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0211446.0 2002-05-18
GB0211446A GB2388670A (en) 2002-05-18 2002-05-18 Coupling multicore optic fibre cores to one single core optic fibre

Publications (1)

Publication Number Publication Date
WO2003098294A1 true WO2003098294A1 (en) 2003-11-27

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
DE102007018354A1 (en) * 2007-04-18 2008-10-30 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Device and method for coupling light into a fiber
US8295662B2 (en) 2008-12-12 2012-10-23 Samsung Mobile Display Co., Ltd. Laser system
CN104536100A (en) * 2014-12-15 2015-04-22 哈尔滨工程大学 Multi-core optical fiber connector based on gradient refractive index lenses
US9377565B2 (en) 2012-08-10 2016-06-28 Corning Cable Systems Llc Processing of gradient index (GRIN) rods into GRIN lenses attachable to optical devices, components, and methods

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN112162365B (en) * 2020-10-27 2021-05-04 武汉长盈通光电技术股份有限公司 Single-mode fiber and multi-core fiber rapid coupling device and method
EP4254825A1 (en) * 2022-04-01 2023-10-04 Microsoft Technology Licensing, LLC Optical transmitter unit, optical receiver unit and optical transceiver unit

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EP0802432A1 (en) * 1994-05-24 1997-10-22 Asahi Kasei Kogyo Kabushiki Kaisha Plastic fiber bundle for optical communication

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JPS55106406A (en) * 1979-02-09 1980-08-15 Mitsubishi Electric Corp Photo circuit element
US4626069A (en) * 1979-04-21 1986-12-02 U.S. Philips Corporation Optical power divider
EP0802432A1 (en) * 1994-05-24 1997-10-22 Asahi Kasei Kogyo Kabushiki Kaisha Plastic fiber bundle for optical communication
US5657155A (en) * 1996-08-16 1997-08-12 Jds Fitel Inc. Optical tap coupler device

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102007018354A1 (en) * 2007-04-18 2008-10-30 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Device and method for coupling light into a fiber
US8295662B2 (en) 2008-12-12 2012-10-23 Samsung Mobile Display Co., Ltd. Laser system
US9377565B2 (en) 2012-08-10 2016-06-28 Corning Cable Systems Llc Processing of gradient index (GRIN) rods into GRIN lenses attachable to optical devices, components, and methods
CN104536100A (en) * 2014-12-15 2015-04-22 哈尔滨工程大学 Multi-core optical fiber connector based on gradient refractive index lenses

Also Published As

Publication number Publication date
AU2003240998A1 (en) 2003-12-02
GB0211446D0 (en) 2002-06-26
GB2388670A (en) 2003-11-19

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