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GB1558643A - Optical couplers - Google Patents

Optical couplers Download PDF

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Publication number
GB1558643A
GB1558643A GB1553077A GB1553077A GB1558643A GB 1558643 A GB1558643 A GB 1558643A GB 1553077 A GB1553077 A GB 1553077A GB 1553077 A GB1553077 A GB 1553077A GB 1558643 A GB1558643 A GB 1558643A
Authority
GB
United Kingdom
Prior art keywords
fibres
epoxy
tube
mixing rod
light
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.)
Expired
Application number
GB1553077A
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.)
STC PLC
Original Assignee
Standard Telephone and Cables PLC
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 Standard Telephone and Cables PLC filed Critical Standard Telephone and Cables PLC
Priority to GB1553077A priority Critical patent/GB1558643A/en
Priority to BR7802336A priority patent/BR7802336A/en
Publication of GB1558643A publication Critical patent/GB1558643A/en
Expired legal-status Critical Current

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Classifications

    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24Coupling light guides
    • G02B6/36Mechanical coupling means
    • G02B6/38Mechanical coupling means having fibre to fibre mating means
    • G02B6/3801Permanent connections, i.e. wherein fibres are kept aligned by mechanical means
    • GPHYSICS
    • G02OPTICS
    • G02BOPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B6/00Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
    • G02B6/24Coupling light guides
    • G02B6/26Optical coupling means
    • G02B6/28Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
    • G02B6/2804Optical 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
    • G02B6/2808Optical 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 using a mixing element which evenly distributes an input signal over a number of outputs

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

Description

(54) IMPROVEMENTS IN OR RELATING TO OPTICAL COUPLERS (71) We, STANDARD TELE PHONES AND CABLES LIMITED, a British Company, of 190 Strand, London, W.C.2, England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to couplers for coupling light from a number of separate single optical fibres and thus making that light available to all those fibres or to the fibres of another set of separate single optical fibres.
According to the present invention there is provided an optical coupling arrangement which includes a mixing rod to one end of which the ends of a number of separate single optical fibres are terminated so that light from a said fibre can enter said mixing rod and so that light from the mixing rod can pass to all of said fibres, and a mirror at the opposite end of the rod from the fibre ends, said mirror reflecting light incoming from one of the fibres in such a way that that light spreads over the ends of the fibres so as to propagate thereinto, wherein the mixing rod consists of a glass or silica tube containing a light transmissive medium, the refractive indices of the tube and of the contents thereof being so chosen that the numerical aperture of the mixing rod matches that of the fibres.
The same basic arrangement can be used in a so-called transmissive coupler, the one referred to in the preceding paragraph being a reflective coupler. Therefore the present invention also provides an optical coupling arrangement which includes a mixing rod to one end of which there is terminated a first set of separate single optical fibres so that light from any one of said fibres can enter said mixing rod, and a second set of separate single optical fibres terminated to the other end of said mixing rod so that light from the fibres of said second set can enter said mixing rod, the arrangement being such that light from any one of the fibres of the first set passes to all of the fibres of the second set via the mixing rod and that light from any one of the fibres of second set passes to all of the fibres of the first set via the mixing rod, wherein the mixing rod consists of a glass or silica tube containing a light transmissive medium, the refractive indices of the tube and of the contents thereof being so chosen that the numerical aperture of the mixing rod matches that of the fibres.
Embodiments of the invention will now be described with reference to the drawings accompanying the Provisional Specifications, ill which: Figure 1 is a cross-section of a bundle of seven single optical fibres.
Figure 2 is a sectional view of an optical coupling arrangement of the reflective type which embodies the invention.
Figure 3 is a view similar to Figure 2 of another optical coupling arrangement of the reflective type which embodies the invention.
Figure 4 is a sectional view of an optical coupling arrangement of the transmissive type which embodies the invention.
Figure 5 is a sectional view of a further optical coupling arrangement embodying the invention.
In the couplers to be described herein, each of the sets of optical fibres consists of seven fibres arranged in a dose-packed bundle as shown in Figure 1. As will be seen from the other drawings these fibres spread out as one moves away from the coupler, as each one is connected to a different distant terminal. In practice a third layer of fibres can be added, giving a total of 19.
The first arrangement to be described is shown in Fig. 2, in which the mixer region is a glass or silica tube 1, filled with an epoxy 2. The refractive indices of the epoxy 2 and the tube 1 are so chosen that the numerical aperture of the coupler matches that of the fibres.. The lower end of the tube 1 is attached to a substrate 3 bearing a mirror 4, and the fibres are sealed to the upper end of the mixing rod by epoxy 5. The nominal numerical aperture of a step index waveguide is given by: (N,2 ~ N22)+ where N, and N2 are the refractive indices of the core and the cladding respectively.
TABLE
CORE: - CLADDING Refractive Refractive Numerical Material Index Material Index Aperture 305 Epoxy 1.511 Pyrex 1.479 0.30 301 Epoxy 1.539 Pyrex 1.479 0.42 305 Epoxy 1.511 Silica 1.46 0.39 301 Epoxy 1.539 Silica 1.46 0.49 The material referred to in the above Table, and also below, as Pyrex is a borosilicate glass, Pyrex being a Registered Trade Mark. The word Teknis used below to identify the type of epoxy material which we have used is also a Registered Trade Mark.
The above table shows the range of numerical apertures which can be achieved by using two readily available epoxy resins with either silica or Pyrex tubing. For example Chance-Pilkington fibre type HYTR AN 50 has a numerical aperture of 0.48 and from the Table it can be seen that this could be matched by using Teknis epoxy type 301 in a silica tube. In Fig. 2 the fibres are parallel to the axis of the silica tube 1 and the mirror 4 which is gold coated is perpendicular to the axis. It will be noticed that the ends of the fibres are not in the same plane as this was found to be an advantage when assembling the unit.
An improved coupling arrangement is shown in Fig. 3. There the fibres are located inside the silica tube 10 by a length of glass rod 11 whose refractive index matches that of the epoxy resin 12. For example Change-Pilking- ton glass type LBC 541595 with refractive index of 1.541 would match the refractive index of 1.539 of Teknis 301 epoxy. Since the rod 11 would be virtually invisible in the epoxy 12 it need not be a close fit in the silica tube 10.
As can be seen from Fig. 3 the main purpose of the rod is to locate the ends of the fibres inside the silica tube, the rod being surrounded by epoxy resin.
The loading of the fibre bundle into the silica tube can be simplified if the end of the tube is flared, which is shown in Fig. 4 for a transmissive coupler, although it will be appreciated that the flare can also be used in reflective couplers. Fig. 4 shows such a flared tube together with an arrangement which gives a transmissive type of coupler as opposed to the reflective type in Figs. 2 and 3. It will be seen that the reflective types in Fig. 2 and 3 could be converted to transmissive types.
Another coupler which could be called a tapered coupler is shown in Fig. 5. In this case a bundle of individual optical fibres is fused as shown at 30 and drawn into a taper.
To avoid the entrainment of bubbles in the taper it is desirable to draw the taper in vacuum. This taper 36 is surrounded by the optically-matched epoxy 31.
If the fibres are unclad, i.e. composed of one material only, drawn into the gradual taper, and inserted into a matching epoxy as shown in Fig. 5 the principle of operation is relatively straight-forward when it is realized that there is no optical discontinuity between the taper and the surrounding epoxy. Unfortunately if any of the matching epoxy reaches the fibres outside the silica tube, and it would in fact be difficult to avoid this, there would be an unacceptably high loss of light This problem is overcome by using clad fibres, but the operation of the device is more difficult to understand and the surrounding epoxy need not be matched to either the core or the cladding of the fibres. Note that a transmissive coupler could be constructed by having two taper arrangements as shown in Fig. 5, in which case the mirror is omitted.
The units would be housed is suitable containers and the fibres would end either singly or in groups in conventional optical connectors.
WHAT WE CLAIM IS: 1. An optical coupling arrangement which includes a mixing rod to one end of which the ends of a number of separate single optical fibres are terminated so that light from a said fibre can enter said mixing rod and so that light from the mixing rod can pass to all of said fibres, and a mirror at the opposite end of the rod from the fibre ends, said mirror reflecting light incoming from one of the fibres in such a way that that light spreads over the
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. TABLE CORE: - CLADDING Refractive Refractive Numerical Material Index Material Index Aperture 305 Epoxy 1.511 Pyrex 1.479 0.30 301 Epoxy 1.539 Pyrex 1.479 0.42 305 Epoxy 1.511 Silica 1.46 0.39 301 Epoxy 1.539 Silica 1.46 0.49 The material referred to in the above Table, and also below, as Pyrex is a borosilicate glass, Pyrex being a Registered Trade Mark. The word Teknis used below to identify the type of epoxy material which we have used is also a Registered Trade Mark. The above table shows the range of numerical apertures which can be achieved by using two readily available epoxy resins with either silica or Pyrex tubing. For example Chance-Pilkington fibre type HYTR AN 50 has a numerical aperture of 0.48 and from the Table it can be seen that this could be matched by using Teknis epoxy type 301 in a silica tube. In Fig. 2 the fibres are parallel to the axis of the silica tube 1 and the mirror 4 which is gold coated is perpendicular to the axis. It will be noticed that the ends of the fibres are not in the same plane as this was found to be an advantage when assembling the unit. An improved coupling arrangement is shown in Fig. 3. There the fibres are located inside the silica tube 10 by a length of glass rod 11 whose refractive index matches that of the epoxy resin 12. For example Change-Pilking- ton glass type LBC 541595 with refractive index of 1.541 would match the refractive index of 1.539 of Teknis 301 epoxy. Since the rod 11 would be virtually invisible in the epoxy 12 it need not be a close fit in the silica tube 10. As can be seen from Fig. 3 the main purpose of the rod is to locate the ends of the fibres inside the silica tube, the rod being surrounded by epoxy resin. The loading of the fibre bundle into the silica tube can be simplified if the end of the tube is flared, which is shown in Fig. 4 for a transmissive coupler, although it will be appreciated that the flare can also be used in reflective couplers. Fig. 4 shows such a flared tube together with an arrangement which gives a transmissive type of coupler as opposed to the reflective type in Figs. 2 and 3. It will be seen that the reflective types in Fig. 2 and 3 could be converted to transmissive types. Another coupler which could be called a tapered coupler is shown in Fig. 5. In this case a bundle of individual optical fibres is fused as shown at 30 and drawn into a taper. To avoid the entrainment of bubbles in the taper it is desirable to draw the taper in vacuum. This taper 36 is surrounded by the optically-matched epoxy 31. If the fibres are unclad, i.e. composed of one material only, drawn into the gradual taper, and inserted into a matching epoxy as shown in Fig. 5 the principle of operation is relatively straight-forward when it is realized that there is no optical discontinuity between the taper and the surrounding epoxy. Unfortunately if any of the matching epoxy reaches the fibres outside the silica tube, and it would in fact be difficult to avoid this, there would be an unacceptably high loss of light This problem is overcome by using clad fibres, but the operation of the device is more difficult to understand and the surrounding epoxy need not be matched to either the core or the cladding of the fibres. Note that a transmissive coupler could be constructed by having two taper arrangements as shown in Fig. 5, in which case the mirror is omitted. The units would be housed is suitable containers and the fibres would end either singly or in groups in conventional optical connectors. WHAT WE CLAIM IS:
1. An optical coupling arrangement which includes a mixing rod to one end of which the ends of a number of separate single optical fibres are terminated so that light from a said fibre can enter said mixing rod and so that light from the mixing rod can pass to all of said fibres, and a mirror at the opposite end of the rod from the fibre ends, said mirror reflecting light incoming from one of the fibres in such a way that that light spreads over the
ends of the fibres so as to propagate thereinto, wherein the mixing rod consists of a glass or silica tube containing a light transmissive medium, the refractive indices of the tube and the contents thereof being so chosen that the numerical aperture of the mixing rod matches that of the fibres.
2. An optical coupling arrangement which includes a mixing rod to one end of which there is terminated a first set of separate single optical fibres so that light from any one of said fibres can enter said mixing rod, and a second set of separate single optical fibres terminated to the other end of said mixing rod so that light from any one of the fibres of said second set can enter said mixing rod, the arrangement being such that light from any one of the fibres of the first set passes to all of the fibres of the second set via the mixing rod and that light from any one of the fibres of the second set passes to all of the fibres of the first set via the mixing rod, wherein the mixing rod consists of a glass or silica tube containing a light transmissive medium, the refractive indices of the tube and of the contents thereof being so chosen that the numerical aperture of the mixing rod matches that of the fibres.
3. An arrangement as claimed in claim 1, wherein the tube from which the mixing rod is made consists of silica or a borosilicate glass, and wherein the light transmissive medium is an epoxy resign.
4. An arrangement as claimed in claim 1, 2 or 3, wherein the tube from which the mixing rod is made consists of silica or a borosilicate glass, and wherein the light trans missive medium is a glass rod located within said tube and spaced therefrom by epoxy resin.
5. An arrangement as claimed in claim 1 or in daim 2 or 3 with claim 1 and wherein said rod is shorter than said tube, so that the fibre ends are enclosed within the end of said tube.
6. An arrangement as claimed in claims 1, 2, 3, 4 or 5, wherein the optical fibres terminated to the or each said end are seven in number, and are secured to the end of the mixing rod by an epoxy resin.
7. An arrangement as claimed in any preceding claim, and in which the or each said end of the tube is flared, and in which the end of the tube into which the fibres fit is flared.
8. An arrangement as claimed in claim 1 or 2, wherein the fibres terminated on said mixing rod are fused together and drawn into a taper, and wherein the taper extends into said light transmissive medium.
9. An optical coupling arrangement substantially as described with reference to Fig.
2, 3 or 5 of the drawings.
GB1553077A 1977-04-14 1977-04-14 Optical couplers Expired GB1558643A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
GB1553077A GB1558643A (en) 1977-04-14 1977-04-14 Optical couplers
BR7802336A BR7802336A (en) 1977-04-14 1978-04-14 IMPROVEMENTS IN OR RELATING TO OPTOCOUPLERS

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB1553077A GB1558643A (en) 1977-04-14 1977-04-14 Optical couplers

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GB1558643A true GB1558643A (en) 1980-01-09

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2119959A (en) * 1982-05-12 1983-11-23 Bicc Plc Optical fibre duplex coupler
US4530566A (en) * 1982-05-12 1985-07-23 Bicc Public Limited Company Optical fiber duplex coupler
GB2219869A (en) * 1988-06-15 1989-12-20 British Telecomm Optical waveguide coupling device
WO2000075701A2 (en) * 1999-06-03 2000-12-14 Hutchinson Technology Incorporated Fiber optic light mixer
US6481899B1 (en) 1999-06-03 2002-11-19 Hutchinson Technology Incorporated Optical connector latching mechanism for a spectrophotometric instrument
US6892006B2 (en) 2002-11-05 2005-05-10 Hutchinson Technology Incorporated Fiber optic light mixer
US7525647B2 (en) 2005-09-08 2009-04-28 Vioptix, Inc. Medical device probe with source and detector sensors
US8290558B1 (en) 2009-11-23 2012-10-16 Vioptix, Inc. Tissue oximeter intraoperative sensor
US8938279B1 (en) 2009-01-26 2015-01-20 VioOptix, Inc. Multidepth tissue oximeter
US20220197008A1 (en) * 2020-12-18 2022-06-23 Precision Optics Corporation, Inc. System and method for treating ends of optical fibers for use in an endoscope

Cited By (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2119959A (en) * 1982-05-12 1983-11-23 Bicc Plc Optical fibre duplex coupler
US4530566A (en) * 1982-05-12 1985-07-23 Bicc Public Limited Company Optical fiber duplex coupler
GB2219869A (en) * 1988-06-15 1989-12-20 British Telecomm Optical waveguide coupling device
GB2219869B (en) * 1988-06-15 1992-10-14 British Telecomm Optical coupling device
WO2000075701A2 (en) * 1999-06-03 2000-12-14 Hutchinson Technology Incorporated Fiber optic light mixer
WO2000075701A3 (en) * 1999-06-03 2001-08-23 Hutchinson Technology Fiber optic light mixer
US6481899B1 (en) 1999-06-03 2002-11-19 Hutchinson Technology Incorporated Optical connector latching mechanism for a spectrophotometric instrument
US6487343B1 (en) 1999-06-03 2002-11-26 Hutchinson Technology Incorporated Fiber optic light mixer
US6892006B2 (en) 2002-11-05 2005-05-10 Hutchinson Technology Incorporated Fiber optic light mixer
US7796247B2 (en) 2005-09-08 2010-09-14 Vioptix Inc. Tissue oximeter with source and detector sensors
US7525647B2 (en) 2005-09-08 2009-04-28 Vioptix, Inc. Medical device probe with source and detector sensors
US10709367B1 (en) 2009-01-26 2020-07-14 Vioptix, Inc. Multidepth tissue oximeter
US8938279B1 (en) 2009-01-26 2015-01-20 VioOptix, Inc. Multidepth tissue oximeter
US11564601B1 (en) 2009-01-26 2023-01-31 Vioptix, Inc. Multidepth tissue oximeter
US8527022B1 (en) 2009-11-23 2013-09-03 Vioptix, Inc. Tissue oximeter intraoperative sensor
US9060720B1 (en) 2009-11-23 2015-06-23 Vioptix, Inc. Tissue oximeter intraoperative sensor
US9351686B1 (en) 2009-11-23 2016-05-31 Vioptix, Inc. Tissue oximeter intraoperative sensor
US9706954B1 (en) 2009-11-23 2017-07-18 Vioptix, Inc. Tissue oximeter intraoperative sensor
US10165970B1 (en) 2009-11-23 2019-01-01 Vioptix, Inc. Tissue oximeter intraoperative sensor
US10624565B1 (en) 2009-11-23 2020-04-21 Vioptix, Inc. Tissue oximeter intraoperative system
US8290558B1 (en) 2009-11-23 2012-10-16 Vioptix, Inc. Tissue oximeter intraoperative sensor
US11284822B1 (en) 2009-11-23 2022-03-29 Vioptix, Inc. Tissue oximeter intraoperative system
US20220197008A1 (en) * 2020-12-18 2022-06-23 Precision Optics Corporation, Inc. System and method for treating ends of optical fibers for use in an endoscope

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Publication number Publication date
BR7802336A (en) 1979-02-13

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PCNP Patent ceased through non-payment of renewal fee