GB2165061A - Optical coupler - Google Patents

Optical coupler Download PDF

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Publication number
GB2165061A
GB2165061A GB08523675A GB8523675A GB2165061A GB 2165061 A GB2165061 A GB 2165061A GB 08523675 A GB08523675 A GB 08523675A GB 8523675 A GB8523675 A GB 8523675A GB 2165061 A GB2165061 A GB 2165061A
Authority
GB
United Kingdom
Prior art keywords
optical coupler
accordance
optical
light
component
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.)
Withdrawn
Application number
GB08523675A
Other versions
GB8523675D0 (en
Inventor
Teddy Wayne Leonard
Anne Bowman Bussard
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.)
International Standard Electric Corp
Original Assignee
International Standard Electric Corp
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 International Standard Electric Corp filed Critical International Standard Electric Corp
Publication of GB8523675D0 publication Critical patent/GB8523675D0/en
Publication of GB2165061A publication Critical patent/GB2165061A/en
Withdrawn legal-status Critical Current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
    • G02B6/24—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
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
    • G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
    • G02B6/29307—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide components assembled in or forming a solid transparent unitary block, e.g. for facilitating component alignment
    • 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
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29304—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating
    • G02B6/29305—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by diffraction, e.g. grating as bulk element, i.e. free space arrangement external to a light guide
    • G02B6/2931—Diffractive element operating in reflection
    • 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
    • G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
    • G02B6/29379—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device
    • G02B6/2938—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Optical Couplings Of Light Guides (AREA)
  • Spectrometry And Color Measurement (AREA)

Abstract

A wavelength division multiplexing or demultiplexing optical coupler of the diffraction grating type includes a pure fused silica optical element (18) having a reflecting, convex toric surface (22) on one end and a diffraction grating (26) on a portion of its other end. The remaining portion of its other end receives a multiple fibre array (14a to d) for transmitting and receiving the light to be multiplexed or demultiplexed. <IMAGE>

Description

SPECIFICATION Optical coupler This invention relates to optical couplers such as optical wavelength division multiplexing or demultiplexing couplers and, more particuiarly, to such couplers of the diffraction grating type.
Diffraction grating couplers used as optical multiplexing or demultiplexing devices take light from the input fibre or fibres, respectively, and couple it back into output fibres or fibre, respectively. These couplers utilise a diffraction grating, that is, an anguiarly dispersive device, that diffracts away incident light at an angle dependent upon the incidence angle and the wavelength of the incident light. For maximum grating efficiency, the incident light is generally collimated.If the coupler is used as a multiplexer, there are a plurality of input fibres each launching a beam of light of a different wavelength into the coupler where the separate beams are combined into a single beam of single output fibre as a single beam of light of different wavelengths; if the coupler is used as a demultiplexer, there is a single input fibre that launches a beam of light of different wavelengths into the coupler where it is separated into light beams of a single wavelength each of which is received on one of a plurality of output fibres.
There are several types of diffraction grating couplers including one that uses a concave diffraction grating, another that uses a radially graded refractive index (GRIN) lens with a plane grating and another disclosed in the copending application of Ann B. Bussard and Robert E. Pulfrey, Serial No.
538,238, filed October 3, 1983 for Wavelength Division Optical Multiplexer/Demultiplexer. In all of these types of coupler it is desirable to reduce the spot size of the light striking or received on the output fibre. By this is meant that all of the rays of all of the light beams received on an output fibre strike the surface of that fibre at points defining an area or spot that is as small as possible and that this spot be smaller than the area of the fibre core.
In this way, no losses are experienced.
According to the invention in its broadest aspect, there is provided an optical coupler comprising an elongated optical component formed of light transmitting material, one end of the component having a convex surface with a toric configuration and the other end having a generally planar surface, one portion of the planar surface having a diffraction grating formed thereon and the remaining portion being adapted to receive a multiple fibre array.
According to another aspect of the invention there is provided an optical coupler comprising an elongated optical component formed of light transmitting material, one end of the component having a convex toric configuration and being coated with a light reflecting material.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a diffraction grating coupler in accordance with this invention; Figure 2 is a front view of the diffraction grating coupler illustrated in Figure 1 with a fibre array coupled to it; and Figure 3 is a top view of the diffraction grating illustrated in Figure 1.
In the drawing there is illustrated a diffraction grating coupler 10 and a multiple fibre array 12. In this embodiment the coupler 10 functions as a multiplexer and, thus, the multiple fibre array includes a plurality of fibres 14a, b, c and d, each connected to a light source (not shown), for example, a laser or a light-emitting diode. It should be understood that any number of fibres can be included in the array. Each light source provides light at a different wavelength region. The light from each fibre is the incident light and is combined by the coupler 10 and coupled into an output or link fibre 16 connected into a fibre optics system.It should be understood that if the coupler 10 is functioning as a demultiplexer, the incident light would include all of the wavelengths and would be transmitted along the fibre 16 to the coupler which would distribute each wavelength to its appropriate fibre 14a through 14d. In this mode, each of the fibres 14a to 14d would be connected to a suitable light detector, for example, an avalanche photodiode or a PIN diode.
The coupler 10 can be seen to include an elongated optical component 18 formed of a good light-transmitting material. In this embodiment the light-transmitting material is glass and is, preferably, pure fused silica. Any of various materials can be used and should have a generally uniform index of refraction. As shown in Figure 1, the optical component 18 has a generally rectangular crosssection, but other shapes are usable.
As also shown in the drawing, the component 18 is actually formed from two blocks of pure fused silica 18a and 18b having generally planar mating surfaces in abutting relationship. The blocks 18a and 18b are fixed together to form a unitary component. Conveniently the blocks 18a and 18b are fixed together by a good optical grade epoxy, i.e., an epoxy that transmits light. The use of two blocks of silica is preferred in some instances since it facilitates the making of coupler 10 as will be clear from later descriptions of the invention. It should be understood that a single block of material could also be used.
One end of the elongated optical component 18 is formed with a convex surface 22 coated with a light-reflecting material. Gold or silver are preferred materials coated on the surface 22 and this surface can be formed by any conventional technique. The configuration of the convex surface 22 is such that it provides a smaller spot size than a spherical surface configuration and this is accomplished by forming the convex surface with a toric shape. The toric-shaped surface is an equilateral zone of a surface generated by a circle rotated about an axis in the plane of the circle that does not intersect the circle and consequently has different focusing power in different meridians.
The other end of the optical component is formed with a generally planar surface 24, one portion of which is formed with a diffraction grating 26. It should be understood that the diffraction grating has a large number of generally parallel grooves as shown in Figure 2 of the drawing. The size of the grooves is greatly exaggerated in Figure 2 for the sake of clarity. The grooves extend across the surface 24 in a direction generally parallel to what could be referred to as the top and bottom surfaces and are generally perpendicular to what will be referred to as the front and back surfaces.
The diffraction grating 26 is also coated with a light-reflecting material such as gold or silver. The remaining portion of the planar surface 24 is that portion to which the multiple fibre array 12 is secured. This can also be accomplished by the use of a suitable optical grade epoxy. The fibre array 12 is arranged so that the fibres are aligned in a row extending between the bottom surface of the grating and the bottom surface of the component 18.
The toric surface 22 has two different radii of curvature, a larger one (R), greatly exaggerated in Figure 2 for the sake of clarity, for the surface when viewed from the front (Figure 2), that is for the surface as it connects with the top and bottom surfaces and a smaller one (R2) for the surface when viewed from the top (Figure 3) so that it connects with the front and back surfaces. Thus, when seen in Figure 2, the surface 22 is flatter than when seen in Figure 3. The radii of curvature R1 and R2 are such that light emitted from the fibre array into the component 18 travels a path to the surface 22 having a length equal to about one focal length.
Thus, the difference between radii RI and R2 is very small. In this way light is collimated by the toric surface 22. The smaller radius of curvature R2 provides a shorter focal length which tends to counteract spreading of the light beam and this, in turn minimizes the spot size.
The diffraction grating 26 can be formed on the planar end surface 24 by a conventional ruling tool, usually a diamond blade. The diffraction grating can also be formed on a wedge which is joined to the planar surface of block 18a with an optical epoxy 20, as shown in Figure 1. It is preferred, however, to replicate the grating 26 on the end face 24. Replication can be accomplished by coating the one portion of the planar surface 24 with a suitable optical grade resin and pressing a master die having the diffraction grating pattern on its contact surface into the resin while it is still soft enough to form. Thereafter, the resin is cured and coated with the reflecting material in accord with conventional techniques. The use of two blocks 18a and 18b is preferred when the diffraction grating 26 is replicated because handling of the material is facilitated.
Various resins can be used and should have an index of refraction when cured, approximately equal to that of the light transmitting material.
Suitable resins are made by Bausch and Lomb, Microscopy and image Analysis Division, located in Rochester, New York.
With reference to Figure 2, it can be seen that incident light travelling down an input fibre is transmitted through the optical component 10 until it strikes the mirrored spherical surface 22 where it is collimated and reflected through the component to the diffraction grating 26. When the collimated light strikes the diffraction grating 26 is diffracted back to the mirrored convex surface 22 where it is reflected and focused into the appropriate output fibre.
As shown in Figure 2, the convex surface 22 is centered with respect to the optical axis A of the component 18. With the surface 22 so centered the planar surface 24 forms an angle T with a iine perpendicular to the optical axis. Angle T is approximately equal to one-half the grating incidence angle required for efficient grating operation.
The outer surfaces of the component 18, excluding surfaces 22 and 24, may have a ground glass finish to decrease internal scattering from the convex surface 22 and from the diffraction grating 26.
The ground glass finished surfaces may be blackened or otherwise treated to enhance their lighttrapping ability.

Claims (13)

1. An optical coupler comprising an elongated optical component formed of light transmitting material, one end of the component having a convex surface with a toric configuration and the other end having a generally planar surface, one portion of the planar surface having a diffraction grating formed thereon and the remaining portion being adapted to receive a multiple fibre array.
2. An optical coupler in accordance with claim 1 wherein the convex surface and the one portion of the planar surface are coated with a light reflecting material.
3. An optical coupler in accordance with claim 1, wherein the optical component is formed of a material having a generally uniform index of refraction.
4. An optical coupler in accordance with claim 1 wherein the optical component is formed of glass.
5. An optical coupler in accordance with claim 1 wherein the other surfaces of the optical component have a ground glass finish and are coated with materials that enhance their light-trapping ability.
6. An optical coupler in accordance with claim 1 wherein the optical component is a single member.
7. An optical coupler in accordance with claim 1 wherein the optical component comprises two blocks of material joined together by an epoxy.
8. An optical coupler in accordance with claim 1 wherein the diffraction grating is formed with aplurality of grooves extending generally parallel to a first pair of opposite surfaces and generally perpendicular to a second pair of opposite surfaces, the toric surface having a first radius of curvature connecting the first pair of surfaces and a second radius of curvature connecting the second pair of surfaces.
9. An optical coupler in accordance with claim 8 wherein the first radius of curvature is larger than the second radius of curvature.
10. An optical coupler in accordance with claim 1 wherein the one portion of the planar surface includes a resin coating in which the diffraction grating is replicated.
11. An optical coupler in accordance with claim 1, wherein the path of light emitted from a multiple fibre array to convex surface is approximately equal to the focal length.
12. An optical coupler comprising an elongated optical component formed of light transmitting material, one end of the component having a convex toric configuration and being coated with a light reflecting material.
13. An optical coupler substantially as described with reference to the accompanying drawings.
GB08523675A 1984-09-26 1985-09-25 Optical coupler Withdrawn GB2165061A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US65435484A 1984-09-26 1984-09-26

Publications (2)

Publication Number Publication Date
GB8523675D0 GB8523675D0 (en) 1985-10-30
GB2165061A true GB2165061A (en) 1986-04-03

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Family Applications (1)

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GB08523675A Withdrawn GB2165061A (en) 1984-09-26 1985-09-25 Optical coupler

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JP (1) JPS61107121A (en)
FR (1) FR2570840A1 (en)
GB (1) GB2165061A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0212438A2 (en) * 1985-08-13 1987-03-04 Firma Carl Zeiss Reflexion diffraction grid operating with a high reflexion coefficient
US4934784A (en) * 1989-03-20 1990-06-19 Kaptron, Inc. Hybrid active devices coupled to fiber via spherical reflectors

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE202008003977U1 (en) 2008-02-26 2009-07-02 Bürkert Werke GmbH & Co. KG microspectrometer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0067972A1 (en) * 1981-06-09 1982-12-29 Licentia Patent-Verwaltungs-GmbH Wavelength multiplexer/demultiplexer
EP0093396A2 (en) * 1982-05-03 1983-11-09 Siemens Aktiengesellschaft Optical wavelength demultiplexer having a diffraction grating
EP0119567A1 (en) * 1983-03-18 1984-09-26 Licentia Patent-Verwaltungs-GmbH Wavelength multiplexer/demultiplexer
GB2147715A (en) * 1983-10-03 1985-05-15 Int Standard Electric Corp Optical coupler

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5587925A (en) * 1978-12-26 1980-07-03 Ritsuo Hasumi Astigmatism correction type spectroscope
FR2537808A1 (en) * 1982-12-08 1984-06-15 Instruments Sa OPTICAL COMPONENT WITH SHARED FUNCTION FOR OPTICAL TELETRANSMISSIONS
FR2543768A1 (en) * 1983-03-31 1984-10-05 Instruments Sa WAVE LENGTH MULTIPLEXER-DEMULTIPLEXER AND METHOD OF MAKING SAME

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0067972A1 (en) * 1981-06-09 1982-12-29 Licentia Patent-Verwaltungs-GmbH Wavelength multiplexer/demultiplexer
EP0093396A2 (en) * 1982-05-03 1983-11-09 Siemens Aktiengesellschaft Optical wavelength demultiplexer having a diffraction grating
EP0119567A1 (en) * 1983-03-18 1984-09-26 Licentia Patent-Verwaltungs-GmbH Wavelength multiplexer/demultiplexer
GB2147715A (en) * 1983-10-03 1985-05-15 Int Standard Electric Corp Optical coupler

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0212438A2 (en) * 1985-08-13 1987-03-04 Firma Carl Zeiss Reflexion diffraction grid operating with a high reflexion coefficient
EP0212438A3 (en) * 1985-08-13 1988-05-04 Firma Carl Zeiss Reflexion diffraction grid operating with a high reflexion coefficient
US4838645A (en) * 1985-08-13 1989-06-13 Carl-Zeiss-Stiftung Reflecting diffraction grating
US4934784A (en) * 1989-03-20 1990-06-19 Kaptron, Inc. Hybrid active devices coupled to fiber via spherical reflectors
WO1990011542A1 (en) * 1989-03-20 1990-10-04 Kaptron, Inc. Hybrid active devices coupled to fiber via spherical reflectors

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Publication number Publication date
JPS61107121A (en) 1986-05-26
GB8523675D0 (en) 1985-10-30
FR2570840A1 (en) 1986-03-28

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732 Registration of transactions, instruments or events in the register (sect. 32/1977)
WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)