CA1302135C - Bidirectional coupler for three optical waveguides - Google Patents
Bidirectional coupler for three optical waveguidesInfo
- Publication number
- CA1302135C CA1302135C CA000560201A CA560201A CA1302135C CA 1302135 C CA1302135 C CA 1302135C CA 000560201 A CA000560201 A CA 000560201A CA 560201 A CA560201 A CA 560201A CA 1302135 C CA1302135 C CA 1302135C
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- CA
- Canada
- Prior art keywords
- coupler
- sections
- section
- notch
- optical fiber
- 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 - Lifetime
Links
- 230000002457 bidirectional effect Effects 0.000 title claims abstract description 36
- 230000003287 optical effect Effects 0.000 title claims description 30
- 239000013307 optical fiber Substances 0.000 claims abstract description 80
- 238000005253 cladding Methods 0.000 claims abstract description 36
- 230000000295 complement effect Effects 0.000 claims description 7
- 239000011248 coating agent Substances 0.000 claims 1
- 238000000576 coating method Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 4
- 239000000835 fiber Substances 0.000 description 8
- 239000004033 plastic Substances 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000005083 Zinc sulfide Substances 0.000 description 1
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000007767 bonding agent Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 239000003822 epoxy resin Substances 0.000 description 1
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 description 1
- 229910001635 magnesium fluoride Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229920000647 polyepoxide Polymers 0.000 description 1
- 235000012239 silicon dioxide Nutrition 0.000 description 1
- 239000000377 silicon dioxide Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000004408 titanium dioxide Substances 0.000 description 1
- DRDVZXDWVBGGMH-UHFFFAOYSA-N zinc;sulfide Chemical compound [S-2].[Zn+2] DRDVZXDWVBGGMH-UHFFFAOYSA-N 0.000 description 1
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
- G02B6/2804—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
- G02B6/2817—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 using reflective elements to split or combine optical signals
-
- 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
-
- 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
- G02B6/2852—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 using tapping light guides arranged sidewardly, e.g. in a non-parallel relationship with respect to the bus light guides (light extraction or launching through cladding, with or without surface discontinuities, bent structures)
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Optical Couplings Of Light Guides (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A bidirectional coupler for interconnecting three optical fibers so that signals transmitted by any one of the optical fibers is transmitted through the coupler to the other two optical fibers. The coupler has three optical fiber sections with cores and cladding, two of which sections are axially aligned and one of which has its axis substantially perpendicular to the axes of the other two sections. All of the axes lie in a common plane, and at the point where the axes intersect, or near thereto, there is the peak of a notch in the cores of the two axially aligned sections and either the surfaces of the cores defining the notch are coated with a reflecting material or a wedge-shaped element with reflecting surfaces is inserted in the notch so that part of the signal energy from either of the two sections is reflected to the core of the third section or parts of the energy from the third section are reflected to the cores of the two sections.
A bidirectional coupler for interconnecting three optical fibers so that signals transmitted by any one of the optical fibers is transmitted through the coupler to the other two optical fibers. The coupler has three optical fiber sections with cores and cladding, two of which sections are axially aligned and one of which has its axis substantially perpendicular to the axes of the other two sections. All of the axes lie in a common plane, and at the point where the axes intersect, or near thereto, there is the peak of a notch in the cores of the two axially aligned sections and either the surfaces of the cores defining the notch are coated with a reflecting material or a wedge-shaped element with reflecting surfaces is inserted in the notch so that part of the signal energy from either of the two sections is reflected to the core of the third section or parts of the energy from the third section are reflected to the cores of the two sections.
Description
~0:~135 BIDIRECTIONAL COUPLER FOR THREE OPTICAL WAVEGUI~ES
The present invention relates to a bidirectional coupler between three optical waveguides, also known as optical fibers, and more particularly, it relates to a component for optical circuits which is able to place three optical waveguides into mutual communication in such a way that an optical signal coming from any of said waveguides is transmitted to the other two.
The conventional couplers are only monodirectional or unidirectional.
They are obtained by joining at least two sections of optical fibers in such a manner as to provide a continuous connection between their cores and their claddings and to form three ends. As it is known to those skilled in the art, the terms "core" and "cladding", refer to an optical fiber and indicate, respectively, its radially innermost portion or core and the layer which adheres intimately to the core and surrounds it and which differs from the core by reason of having a lesser index of refraction.
In the conventional couplers, the three ends, the axes of which are coplanar and cross at the same point, have the structure described hereinafter, and in the present specification, the structure will be described as "Y" shaped geometrical configuration.
A first and a second end, hereinafter called "Y armsn, have their axes defining an angle which generally ranges from 3 and 5 degrees, whereas the third end, hereinafter called the "Y stem"
has its axis lying substantially on the prolongation of the bisecting line of such angle.
An example of conventional coupler is described in the article entitled "New Planar Optical Coupler for a Data Bus System with Single Multimode Fibers", published in the magazine ~302~;~S
entitled "Applied Opticsn, vol. 16, No. 8, August 1977.
As stated, all the conventional couplers are monodirectional. In fact, as it can be experimentally ascertained, only the signal sent to the "Y stem~ is transmitted to both of the "Y armsn. On the other hand, a signal sent to one of the "Y arms" is not transmitted to the other arm and is conveyed only to the "Y stemn. At present, when it is desired to connect together three optical waveguides in such a way that a signal coming from one of them may be transmitted simultaneously to the other two, it is necessary to use three conventional couplers forming a structure, described hereinafter, to which the three optical waveguides are connected.
Said structure, which is rather complicated since it is formed by several couplers connected together, has a relatively large overall size as compared to the size of one single coupler.
Furthermore, a structure constituted by several components (as is the case with combined conventional couplers) connected together, is unavoidably subjected to mechanical vibrations which may damage it when it is employed to form optical circuits associated to mechanical plants, machinery, vehicles and the like, with a consequent reduction in the performance of the optical circuits incorporating said structure.
The present invention has, as one object, the provision of a bidirectional coupler between three optical waveguides or fibers which is composed of only one element having an overall size substantially equal to that of a single conventional coupler (which, as stated, is only of the monodirectional type), thereby avoiding the need of providing a structure built up with several components as well as avoiding the above indicated disadvantages relating to said structure.
Accordingly, the subject matter of the present invention is a bidirectional coupler intended to place three optical 1~02~35 waveguides or fibers into mutual communication and which comprises at least two sections of optical fibers secured together to provide a continuous connection between their respective cores and claddings and to form with them three portions with free ends. The coupler is characterized by the fact that the axes of a first and of a second portion are substantially aligned and the axis of the third portion is substantially perpendicular and coplanar to the axes of the other two portions and at the point of intersection of the axes, there is a wedge-shaped notch having two reflecting surfaces at the zone of connection of said sections of optical fibers, said notch interrupting partially the continuity of the core and of the cladding between the first and the second portion and facing at least the core of the third portion, the two reflecting surfaces of the notch being inclined with respect to the axis of the third portion.
The two reflecting surfaces of the wedge-shaped notch, as described hereinafter, may be flat or curved and have equal or different areas.
Alternatively, a wedge-shaped element, complementary to the notch, may be inserted in the notch. In this case, the reflecting surfaces may be the faces of said element which are in contact with the faces of the notch.
Furthermore, when the reflecting surfaces of the coupler are the faces of a wedge-shaped element and the coupler is formed by joining three sections of optical fibers, the joined ends of the element and of the sections of optical fibers have the form of a dihedral angle.
The expression "wedge-shaped notch" as used in the present specification, means a recess whose width decreases in a continuous but not necessarily linear way from the radially outermost surface of the coupler towards the inside of the 1302~35 coupler, said recess having two opposite and converging faces or surfaces which intersect each other along a straiyht line pe:rpendicular to the axes of the three ends, which defines the recess bottom.
According to a broad aspect of the invention there is provided a bidirectional coupler for interconnecting three optical waveguides in mutual communication, said coupler comprising:
first and second sections of an optical fiber with a core having a cladding thereon, with their axes substantially aligned and with one end of the core and cladding of one section meeting and connected respectively to one end of the core and cladding of the other section;
a third section of an optical fiber with a core having cladding thereon, with its axis extending substantially perpendicular to said axes, in the same plane as said axes and intersecting the point of intersection of said axes, said third section having its core and cladding connected respectively to the cores and claddings of said first and second sections;
said first and second sections having a notch between the cores thereof where they meet, said notch having a wider portion at the claddings of said first and second sections and a peak spaced inwardly from the last-mentioned said claddings, said notch having means providing energy reflecting surfaces facing toward the core of said third section and being inclined at an angle to said axis of said core of said third section.
Other objects and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying ~ 4 ...
1~021~S
~7~87-355 drawings in which:
Fig. 1 illustrates diagrammatically and in plan view a structure formed by combining three conventional monodirectional couplers for connecting together three optical waveguides or fibers;
Fig. 2 illustrates in axial section a ~idirectional coupler according to the invention;
Fig. 3 is similar to Fig. 2 and illustrates an alternative embodiment of a coupler according to ~he invention;
Fig 4 illustrates in enlarged scale and in perspective a portion of the bidirectional coupler illustrated in Fig. 3; and Figs. 5, 6 and 7 are similar to Fig. 3 and illustrate further alternative embodiments of bidirectional couplers according to the invention.
As already indicated hereinbefore, when heretofore it has been desired to connect together three optical waveguides in such a way that the optical signals coming from any of them may be simultaneously transmitted to the other two, it has been necessary to use a structure, formed by three conventional monodirectional couplers, such as, for instance, the structure diagrammatically represented in Fig. 1. As it can be seen from said Fig. 1, the structure comprises three monodirectional i302:13S
couplers 1, 2 and 3. Each mo ~ irectional coupler, formed by joining at least two sections of optical fibers in order to ensure a continuity between their cores and claddings, respectively, comprise three ends and has a geometrical "Y"
shape.
In particular, each of couplers 1, 2 and 3 comprises first arms, 4, 5 and 6, respectively, second arms, 7, 8 and 9, respectively, and third stems 10, 11 and 12. In each coupler, the first and the second arms correspond to the arms of the "Y"
shape, while the third stem corresponds to the "Y" stem.
The three couplers are connected together by virtue of the portions forming the "Y" arms.
In particular, in coupler 1, end of the portion 4 is butt joined to end of the portion S of coupler 3 so as to provide continuity in the cores and claddings of the relative ends, whereas the end of the portion 7 is analogously butt joined to end of the portion of the coupler 2.
Furthermore, ends of the portions 8 and 9 of couplers 2 and 3 are butt joined together, still providing the continuity of their respective cores and claddings.
In each coupler 1, 2 and 3, the ends of the third portions or stems 10, 11 and 12, respectively forming the "Y" stem, are butt joined to an optical waveguide, 13, 14 and lS, respectively.
The structure resulting from the assembly of three conventional monodirectional couplers, as diagrammatically represented in Fig. 1, permits the connecting together of three optical waveguides 13, 14 and 15 in such a way that a signal coming from any of them may be simultaneously transmitted to the other two for the reasons explained hereinafter.
An optical signal coming from any of the three optical waveguides (for instance, that indicated with the reference numeral 14, but also any of the other two) enters the coupler ~021~S
connected to said waveguide (coupler 2) and passes through the portion 11 constituting the "Y" stem and is transmitted from the latter to both portions 6 and 9 forming the "Y" arms.
The signals passing through the portions 6 and 9, forming the ny~ arms of coupler 2, are transmitted to the portions 7 and 8, forming one of the two "Y" arms of the other two couplers 1 and 3, which convey them into their own portions 10 and 12 constituting their "Y" stems, and then to the other two waveguides 13 and 15.
A bidirectional coupler according to the invention eliminates the need to carry out a structure as that described above.
A bidirectional coupler according to the invention is built up by joining at least two sections of optical fibers, said joining being able to provide a continuity between the respective cores and claddings and to provide three portions, and having the following basic structure.
The axes of a first portion and of a second portion are substantially aligned, whereas the axis of the third portion is substantially coplanar and perpendicular to the axes of the other two and passes through the point of intersection of the latter axes.
Furthermore, a wedge-shaped notch, having two reflecting surfaces, is present in the zone of connection of the three ends.
In particular, said wedge-shaped notch partially separates the cores and the claddings of the first and of the second portions and faces at least the core of the third portion, so that the two reflecting surfaces, which can have equal or different areas, are inclined with respect to the axis of the third portion. The reflecting surfaces of the wedge-shaped notch may be flat or curved and, in the latter case, they may be concave or convex with respect to the axis of said notch. Moreover, a wedge-shaped ~302135 element, complementary to the notch, can be inserted in the latter, and in this case, the reflecting surfaces can be the surfaces of said wedge-shaped element. As stated, a bidirectional coupler according to the invention is obtained by joining at least two sections of optical fibers while assuring continuity in their respective cores and claddings to provide the above-described basic structure which has substantially a "T"
shaped geometrical configuration. The sections of optical fibers to be used to build up a bidirectional coupler according to the invention may be of any whichever type, their selection depending only on the features of the optical waveguides or fibers which are to be connected by the coupler.
Furthermore, a bidirectional coupler according to the invention, instead of being built up by joining at least two sections of optical fibers, can be obtained by joining together at least two cylindrical filiform elements, having features identical to those of the core of an optical fiber, so as to build up a "T" shaped geometrical configuration, and then by covering the cylindrical surfaces of the filiform elements joined together with a layer having characteristics similar to those of the cladding of an optical fiber.
Fig. 2 illustrates in section one preferred embodiment of a bidirectional coupler according to the invention.
As can be seen in Fig. 2, the bidirectional coupler is formed by joining together two sections of optical fibers 16 and 17 in such a way as to provide continuity between the respective cores 16' and 17' and the respective claddings 16" and 17~ and to provide three portions 18, 19 and 20. In particular, the end of the section of optical fiber 16, connected to the section of optical fiber 17 (in such a manner that, after said connection, the axes of the two sections are coplanar and perpendicular), has the form of a half-cylindrical recess the axis of which is , g ,, ~.3(~2135 perpendicular to the axis of the section 17 and the radius of which is equal to the radius of the core of section of optical fiber 17.
Said core 17' at an intermediate point of its development, has a portion of cylindrical form, equal in length to the diameter of the optical fiber 16, which is devoid of cladding, and, in a diametrically opposite position with respect to said portion, has a wedge-shaped notch 21 having flat surfaces 22 and 23, both of which are reflecting due to the presence on them of a reflecting layer specified hereinafter.
The wedge-shaped notch 21, which partially breaks the continuity of the core of the section of optical fiber 17, has a depth or height h smaller than the value obtained by summing up the thickness o the cladding and the diameter dl of the core of said section and a maximum width V at least equal to the diameter d2 of the core 16' of the section of optical fiber 16.
According to an alternative embodiment (not illustrated) of the structure shown in Fig. 2~ a wedge-shaped element, complementary to the wedge-shaped notch 21 is inserted in the latter and secured to it.
Fig. 3 illustrates in section an alternative embodiment of a bidirectional coupler according to the invention.
As can be seen from Fig. 3, the bidirectional coupler is obtained by joining three sections of optical fibers 24, 25 and 26, each of which corresponds to one portion of the coupler, and a wedge-shaped element 27 having two flat reflecting surfaces 28 and 29.
Each of the sections of optical fibers 24, 25 and 26~ butt joined together to provide continuity between their respective cores 24~ 25~1 26~ and their respective claddings 24n, 25n, 26 have the configuration shown in the perspective view of Fig. 4.
In particular, in each section of optical fiber, the end _ j~ ,,, intended to be joined with the other sections has the form of a dihedral angle with two flat faces 30 and 31, symmetrical with respect to the section axis which form an angle~ of 90 and define an edge 32.
The wedge-shaped element 27 has a structure identical to that of the section of the optical fibers and preferably, although not necessarily, is constituted by a section of optical fiber with an end in the form of a dihedral angle the faces of which are made reflecting due to the presence thereon of reflecting layers 28 and 29 specified below.
The axes 25''' and 26''' of the sections of optical fibers 25 and 26 are aligned with each other and, therefore, are coplanar.
The axis 24''' of the section of optical fiber 24 is coplanar with and perpendicular to the axes of the other two sections, intersecting them at a point 33 lying on a straight line which contains the edges of the dihedral angles of the three sections of optical fibers.
Fig. 5 illustrates a bidirectional coupler according to the invention which is an alternative to the embodiment of the coupler shown in Fig. 3. Also, the coupler illustrated in Fig. 5 is obtained by joining together three sections of optical fibers 34, 35, 36 in such a way as to provide continuity between their respective cores and claddings and with one of their ends shaped as a dihedral angle and by providing a wedge-shaped element 37 having reflecting surfaces 38 and 39.
The coupler illustrated in Fig. 5 differs from the coupler of Fig. 3 by reason of the fact that the dihedral angle of the wedge-shaped element 37, which is symmetrical with respect to the wedge axis, has an angle ~' smaller than 90 in order to create a greater separation between the cores of the sections of optical fibers 34 and 36 the axes of which are aligned.
Consequently, the dihedral angle of the section of optical `` ~30~135 fiber 35, the axis of which is aligned with the axis of the wedge-shaped element 37, is greater than 90, and the dihedral angles of the sections of the optical fibers 34 and 36, the axes of which are aligned, are symmetrical with respect to their own axes.
Furthermore, the dihedral angles of the ends of sections 34, 35 and 36 and of the wedge-shaped element are complementary to one another, meaning that the sum of their angles is 360.
Fig. 6 illustrates a further alternative embodiment of a coupler according to the invention, formed by joining three sections of optical fibers 40, 41 and 42 with a wedge-shaped element 43, which differs from the embodiment of Fig. 5 only because the dihedral angle of said element 43 has an angle ~
greater than 90 so as to create a smaller separation between the cores of the sections of optical fibers 40 and 41.
A still further alternative embodiment of a bidirectional coupler according to the invention is illustrated in Fig. 7.
The bidirectional coupler shown in Fig. 7 is formed by joining three sections of optical fibers 44, 45 and 46, at one of their ends shaped as a dihedral angle, and in such a way as to provide continuity between their respective cores and claddings, with a wedge-shaped element 48, having reflecting surfaces 49 and 50, which have a dihedral angle asymmetrical with respect to axis 48' of the element itself.
The dihedral angle of the wedge-shaped element 48 is an angle ~ ''' different from 90 and also the dihedral angles of the ends of the sections of optical fibers 44 and 45 have a width different from 90. The conditions which are to be respected in connection with the structure of the dihedral angles of the ends of the sections of the optical fibers and of the wedge-shaped element are the following:
the sum of the widths of the dihedral angles is 360;
1~02~3S
the wedge-shaped element 48 has such a depth or height hl such that it breaks partially the continuity between the cores of the sections of optical fibers 44 and 45 the axes of which are aligned;
both faces 49 and 50 of the dihedral angle of the wedge-shaped element 48 are inclined with respect to axis 46' of the section of optical fiber 46 to which said element is facing ; and as in the bidirectional couplers illustrated in the embodiments of Figs. 3, 4, 5 and 7, the axis of the sections of optical fibers and of the wedge-shaped element are coplanar, intersecting at the same point.
In further alternative embodiments of the invention, not illustrated, the couplers have a structure which differs from that of those represented in Figs. 5, 6 and 7 by the fact that the wedge-shaped element is not provided and that the surfaces of the two sections of optical fibers which have their axes aligned and which are not in contact are reflecting surfaces.
In all the above embodiments, as described and as illustrated in the Figs., the wedge-shaped notches and the wedge-shaped elements, when present, have flat surfaces or faces.
However, this must not be considered as restrictive since said wedge-shaped notches or said wedge-shaped elements complementary to them, when present, may have curved surfaces or faces, which can be concave or convex with respect to the axis of their respective notches and of their respective wedge-shaped elements.
As will be apparent from the description of the various embodiments, the characteristic of a bidirectional coupler according to the invention is the presence of two reflecting sur~aces of a wedge-shaped notch or a wedge-shaped element which breaks the continuity between the two portions having their axes in substantial alignment and which face the third portion having ~3()2135 its axis substantially perpendicular and coplanar to the axes of the other two portions.
Said reflecting surfaces can be provided by a metal film formed on the faces of the wedge-shaped notch or on the faces of the wedge-shaped element inserted in said notch or, alternatively, by a reflecting dielectric coa~ing, already known se, formed on said faces, such as for example, a multilayer constituted by alternate layers of silicon dioxide and titanium dioxide or by alternative layers of magnesium fluoride and zinc sulphide.
Another feature of a bidirectional coupler according to the invention is that it is preferably obtained by joining together at least two sections of optical fibers (so as to provide the continuity of the cores and of the claddings, respectively) which have been shaped by cutting by means of templates and the like, the previously shaped sections of optical fibers being placed into molds which keep them in position for the application of the means of mutual connection.
These connection means may be a thermal softening of the parts of the sections of optical fibers and of the wedge-shaped element which are to be joined together, or a transparent bonding agent, such as an adhesive comprising an epoxy resin, interposed between the parts to be joined.
If the bidirectional coupler according to the invention is to be used to connect together optical waveguides or fibers made of plastic material, the sections of optical fibers and the wedge-shaped element constituting the coupler can be made of plastic material and can also be joined together, in addition to the above mentioned ways, by treating the parts to be joined together with a solvent compatible with the plastic material forming the components.
The operation of a bidirectional coupler according to the ~302~5 invention will now be described with reference to the embodiment represented in Fig. 3.
Each free end of the sections of optical fibers 24, 25 and 26 is butt joined with an optical waveguide as indicated in Fig.
1 (not represented).
~ signal coming from the optical waveguide joined to the end of the section of optical fiber 26 is conveyed into the latter and reaches the area where the three sections of optical fibers are connected and where the wedge-shaped element 27 having reflecting surfaces 28 and 29 is disposed.
In said area, the signal is divided into two parts, owing to the presence of the wedge-shaped element 27. One part of the signal is conveyed into the section or end of optical fiber 25, which transmits it to the waveguide connected thereto.
On the other hand, the other part of the signal is reflected by the reflecting surface 29 of the wedge-shaped element 27 and is conveyed into the section of optical fiber 24 and is transmitted to the waveguide connected to the latter.
The same result occurs if the signal enters the bidirectional coupler passing into the section or end of optical fiber 25.
On the other hand, when the signal enters the bidirectional coupler through the end of the section of the optical fiber 24, the following takes place.
The signal, reaching the area where the three sections of optical fibers are joined together and the wedge-shaped element 27 is present, is reflected by the reflecting surfaces 28 and 29 of the latter which divide it into two parts. Such parts are directed to the sections of the optical fibers 25 and 26 which transmit them to the waveguides connected thereto.
In the bidirectional coupler illustrated in Figs. 2 and 3, the signal entering any of the three ends is divided into two f4 ~
213S`
substantially equal parts which are conveyed in the other two ends.
In the embodiments illustrated in Figs. 5, 6 and 7, the signal is divided in a different way according to which end it has entered.
In particular, in the bidirectional coupler of Fig. 5, a signal entering it through the end of the section of optical fiber 34 is divided into two parts of different magnitude. The part having a smaller intensity is transmitted to the optical fiber 36 having its axis aligned with the section 34, whereas the part having a greater intensity is transmitted to the section of optical fiber 35 having its axis perpendicular to the axes of the other section 34 and 36.
The same takes place if the signal comes through the end of the section 36.
On the other hand, if the signal enters the bidirectional coupler of Fig. 5 through the section of optical fiber 35, it is divided into two equal parts by the reflecting surfaces 38 and 39 having an equal area. Said parts are transmitted to the sections of optical fibers 34 and 35.
In the bidirectional coupler of Fig. 6, a signal coming from the section of optical fiber 40 is still divided into two parts of different intensity but, differently from what happens in the coupler of Fig. 5, the signal of greater intensity is transmitted to the section of optical fiber 41 having its axis aligned with end 40, whereas the signal of smaller intensity is transmitted to the section of optical fiber 42. If the signal enters the coupler of Fig. 6 through the section of optical fiber 42, it is divided into two equal parts, which are conveyed to the sections of optical fibers 40 and 41.
Furthermore, in the bidirectional coupler of Fig. 7, the signal is divided in a different way according to the section of 1~02'135 optical fiber through which it enters, and this is a function both of the depth or height hl of the wedge-shaped element 48 and of the symmetry of the latter with respect to its own axis.
From the description given and from the following considerations, it can be understood that a coupler according to the invention accomplishes the objectives of the invention.
In fact, as can be seen from the embodiments described, a coupler according to the invention has an overall size corresponding substantially to the size of a single conventional monodirectional coupler.
Furthermore, a coupler according to the invention permits the connecting together of optical waveguides or fibers in such a way that a signal coming from any one of them can be transmitted simultaneously to the other two, avoiding the need of providing a structure formed by three conventional monodirectional couplers. It follows that, by using a bidirectional coupler according to the invention, which is formed by only one component, it is no longer necessary to resort to the structure of three monodirectional couplers, and that the disadvantage thereof, of possible damage by mechanical vibrations to which is it subjected when used to form optical circuits inserted in machines, motorvehicles and the like, is also eliminated.
Consequently, a bidirectional coupler according to the invention makes it possible to provide optical circuits which are more compact and reliable.
Although preferred embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications may be made without departing from the principles of the invention.
- ~k~--
The present invention relates to a bidirectional coupler between three optical waveguides, also known as optical fibers, and more particularly, it relates to a component for optical circuits which is able to place three optical waveguides into mutual communication in such a way that an optical signal coming from any of said waveguides is transmitted to the other two.
The conventional couplers are only monodirectional or unidirectional.
They are obtained by joining at least two sections of optical fibers in such a manner as to provide a continuous connection between their cores and their claddings and to form three ends. As it is known to those skilled in the art, the terms "core" and "cladding", refer to an optical fiber and indicate, respectively, its radially innermost portion or core and the layer which adheres intimately to the core and surrounds it and which differs from the core by reason of having a lesser index of refraction.
In the conventional couplers, the three ends, the axes of which are coplanar and cross at the same point, have the structure described hereinafter, and in the present specification, the structure will be described as "Y" shaped geometrical configuration.
A first and a second end, hereinafter called "Y armsn, have their axes defining an angle which generally ranges from 3 and 5 degrees, whereas the third end, hereinafter called the "Y stem"
has its axis lying substantially on the prolongation of the bisecting line of such angle.
An example of conventional coupler is described in the article entitled "New Planar Optical Coupler for a Data Bus System with Single Multimode Fibers", published in the magazine ~302~;~S
entitled "Applied Opticsn, vol. 16, No. 8, August 1977.
As stated, all the conventional couplers are monodirectional. In fact, as it can be experimentally ascertained, only the signal sent to the "Y stem~ is transmitted to both of the "Y armsn. On the other hand, a signal sent to one of the "Y arms" is not transmitted to the other arm and is conveyed only to the "Y stemn. At present, when it is desired to connect together three optical waveguides in such a way that a signal coming from one of them may be transmitted simultaneously to the other two, it is necessary to use three conventional couplers forming a structure, described hereinafter, to which the three optical waveguides are connected.
Said structure, which is rather complicated since it is formed by several couplers connected together, has a relatively large overall size as compared to the size of one single coupler.
Furthermore, a structure constituted by several components (as is the case with combined conventional couplers) connected together, is unavoidably subjected to mechanical vibrations which may damage it when it is employed to form optical circuits associated to mechanical plants, machinery, vehicles and the like, with a consequent reduction in the performance of the optical circuits incorporating said structure.
The present invention has, as one object, the provision of a bidirectional coupler between three optical waveguides or fibers which is composed of only one element having an overall size substantially equal to that of a single conventional coupler (which, as stated, is only of the monodirectional type), thereby avoiding the need of providing a structure built up with several components as well as avoiding the above indicated disadvantages relating to said structure.
Accordingly, the subject matter of the present invention is a bidirectional coupler intended to place three optical 1~02~35 waveguides or fibers into mutual communication and which comprises at least two sections of optical fibers secured together to provide a continuous connection between their respective cores and claddings and to form with them three portions with free ends. The coupler is characterized by the fact that the axes of a first and of a second portion are substantially aligned and the axis of the third portion is substantially perpendicular and coplanar to the axes of the other two portions and at the point of intersection of the axes, there is a wedge-shaped notch having two reflecting surfaces at the zone of connection of said sections of optical fibers, said notch interrupting partially the continuity of the core and of the cladding between the first and the second portion and facing at least the core of the third portion, the two reflecting surfaces of the notch being inclined with respect to the axis of the third portion.
The two reflecting surfaces of the wedge-shaped notch, as described hereinafter, may be flat or curved and have equal or different areas.
Alternatively, a wedge-shaped element, complementary to the notch, may be inserted in the notch. In this case, the reflecting surfaces may be the faces of said element which are in contact with the faces of the notch.
Furthermore, when the reflecting surfaces of the coupler are the faces of a wedge-shaped element and the coupler is formed by joining three sections of optical fibers, the joined ends of the element and of the sections of optical fibers have the form of a dihedral angle.
The expression "wedge-shaped notch" as used in the present specification, means a recess whose width decreases in a continuous but not necessarily linear way from the radially outermost surface of the coupler towards the inside of the 1302~35 coupler, said recess having two opposite and converging faces or surfaces which intersect each other along a straiyht line pe:rpendicular to the axes of the three ends, which defines the recess bottom.
According to a broad aspect of the invention there is provided a bidirectional coupler for interconnecting three optical waveguides in mutual communication, said coupler comprising:
first and second sections of an optical fiber with a core having a cladding thereon, with their axes substantially aligned and with one end of the core and cladding of one section meeting and connected respectively to one end of the core and cladding of the other section;
a third section of an optical fiber with a core having cladding thereon, with its axis extending substantially perpendicular to said axes, in the same plane as said axes and intersecting the point of intersection of said axes, said third section having its core and cladding connected respectively to the cores and claddings of said first and second sections;
said first and second sections having a notch between the cores thereof where they meet, said notch having a wider portion at the claddings of said first and second sections and a peak spaced inwardly from the last-mentioned said claddings, said notch having means providing energy reflecting surfaces facing toward the core of said third section and being inclined at an angle to said axis of said core of said third section.
Other objects and advantages of the present invention will be apparent from the following detailed description of the presently preferred embodiments thereof, which description should be considered in conjunction with the accompanying ~ 4 ...
1~021~S
~7~87-355 drawings in which:
Fig. 1 illustrates diagrammatically and in plan view a structure formed by combining three conventional monodirectional couplers for connecting together three optical waveguides or fibers;
Fig. 2 illustrates in axial section a ~idirectional coupler according to the invention;
Fig. 3 is similar to Fig. 2 and illustrates an alternative embodiment of a coupler according to ~he invention;
Fig 4 illustrates in enlarged scale and in perspective a portion of the bidirectional coupler illustrated in Fig. 3; and Figs. 5, 6 and 7 are similar to Fig. 3 and illustrate further alternative embodiments of bidirectional couplers according to the invention.
As already indicated hereinbefore, when heretofore it has been desired to connect together three optical waveguides in such a way that the optical signals coming from any of them may be simultaneously transmitted to the other two, it has been necessary to use a structure, formed by three conventional monodirectional couplers, such as, for instance, the structure diagrammatically represented in Fig. 1. As it can be seen from said Fig. 1, the structure comprises three monodirectional i302:13S
couplers 1, 2 and 3. Each mo ~ irectional coupler, formed by joining at least two sections of optical fibers in order to ensure a continuity between their cores and claddings, respectively, comprise three ends and has a geometrical "Y"
shape.
In particular, each of couplers 1, 2 and 3 comprises first arms, 4, 5 and 6, respectively, second arms, 7, 8 and 9, respectively, and third stems 10, 11 and 12. In each coupler, the first and the second arms correspond to the arms of the "Y"
shape, while the third stem corresponds to the "Y" stem.
The three couplers are connected together by virtue of the portions forming the "Y" arms.
In particular, in coupler 1, end of the portion 4 is butt joined to end of the portion S of coupler 3 so as to provide continuity in the cores and claddings of the relative ends, whereas the end of the portion 7 is analogously butt joined to end of the portion of the coupler 2.
Furthermore, ends of the portions 8 and 9 of couplers 2 and 3 are butt joined together, still providing the continuity of their respective cores and claddings.
In each coupler 1, 2 and 3, the ends of the third portions or stems 10, 11 and 12, respectively forming the "Y" stem, are butt joined to an optical waveguide, 13, 14 and lS, respectively.
The structure resulting from the assembly of three conventional monodirectional couplers, as diagrammatically represented in Fig. 1, permits the connecting together of three optical waveguides 13, 14 and 15 in such a way that a signal coming from any of them may be simultaneously transmitted to the other two for the reasons explained hereinafter.
An optical signal coming from any of the three optical waveguides (for instance, that indicated with the reference numeral 14, but also any of the other two) enters the coupler ~021~S
connected to said waveguide (coupler 2) and passes through the portion 11 constituting the "Y" stem and is transmitted from the latter to both portions 6 and 9 forming the "Y" arms.
The signals passing through the portions 6 and 9, forming the ny~ arms of coupler 2, are transmitted to the portions 7 and 8, forming one of the two "Y" arms of the other two couplers 1 and 3, which convey them into their own portions 10 and 12 constituting their "Y" stems, and then to the other two waveguides 13 and 15.
A bidirectional coupler according to the invention eliminates the need to carry out a structure as that described above.
A bidirectional coupler according to the invention is built up by joining at least two sections of optical fibers, said joining being able to provide a continuity between the respective cores and claddings and to provide three portions, and having the following basic structure.
The axes of a first portion and of a second portion are substantially aligned, whereas the axis of the third portion is substantially coplanar and perpendicular to the axes of the other two and passes through the point of intersection of the latter axes.
Furthermore, a wedge-shaped notch, having two reflecting surfaces, is present in the zone of connection of the three ends.
In particular, said wedge-shaped notch partially separates the cores and the claddings of the first and of the second portions and faces at least the core of the third portion, so that the two reflecting surfaces, which can have equal or different areas, are inclined with respect to the axis of the third portion. The reflecting surfaces of the wedge-shaped notch may be flat or curved and, in the latter case, they may be concave or convex with respect to the axis of said notch. Moreover, a wedge-shaped ~302135 element, complementary to the notch, can be inserted in the latter, and in this case, the reflecting surfaces can be the surfaces of said wedge-shaped element. As stated, a bidirectional coupler according to the invention is obtained by joining at least two sections of optical fibers while assuring continuity in their respective cores and claddings to provide the above-described basic structure which has substantially a "T"
shaped geometrical configuration. The sections of optical fibers to be used to build up a bidirectional coupler according to the invention may be of any whichever type, their selection depending only on the features of the optical waveguides or fibers which are to be connected by the coupler.
Furthermore, a bidirectional coupler according to the invention, instead of being built up by joining at least two sections of optical fibers, can be obtained by joining together at least two cylindrical filiform elements, having features identical to those of the core of an optical fiber, so as to build up a "T" shaped geometrical configuration, and then by covering the cylindrical surfaces of the filiform elements joined together with a layer having characteristics similar to those of the cladding of an optical fiber.
Fig. 2 illustrates in section one preferred embodiment of a bidirectional coupler according to the invention.
As can be seen in Fig. 2, the bidirectional coupler is formed by joining together two sections of optical fibers 16 and 17 in such a way as to provide continuity between the respective cores 16' and 17' and the respective claddings 16" and 17~ and to provide three portions 18, 19 and 20. In particular, the end of the section of optical fiber 16, connected to the section of optical fiber 17 (in such a manner that, after said connection, the axes of the two sections are coplanar and perpendicular), has the form of a half-cylindrical recess the axis of which is , g ,, ~.3(~2135 perpendicular to the axis of the section 17 and the radius of which is equal to the radius of the core of section of optical fiber 17.
Said core 17' at an intermediate point of its development, has a portion of cylindrical form, equal in length to the diameter of the optical fiber 16, which is devoid of cladding, and, in a diametrically opposite position with respect to said portion, has a wedge-shaped notch 21 having flat surfaces 22 and 23, both of which are reflecting due to the presence on them of a reflecting layer specified hereinafter.
The wedge-shaped notch 21, which partially breaks the continuity of the core of the section of optical fiber 17, has a depth or height h smaller than the value obtained by summing up the thickness o the cladding and the diameter dl of the core of said section and a maximum width V at least equal to the diameter d2 of the core 16' of the section of optical fiber 16.
According to an alternative embodiment (not illustrated) of the structure shown in Fig. 2~ a wedge-shaped element, complementary to the wedge-shaped notch 21 is inserted in the latter and secured to it.
Fig. 3 illustrates in section an alternative embodiment of a bidirectional coupler according to the invention.
As can be seen from Fig. 3, the bidirectional coupler is obtained by joining three sections of optical fibers 24, 25 and 26, each of which corresponds to one portion of the coupler, and a wedge-shaped element 27 having two flat reflecting surfaces 28 and 29.
Each of the sections of optical fibers 24, 25 and 26~ butt joined together to provide continuity between their respective cores 24~ 25~1 26~ and their respective claddings 24n, 25n, 26 have the configuration shown in the perspective view of Fig. 4.
In particular, in each section of optical fiber, the end _ j~ ,,, intended to be joined with the other sections has the form of a dihedral angle with two flat faces 30 and 31, symmetrical with respect to the section axis which form an angle~ of 90 and define an edge 32.
The wedge-shaped element 27 has a structure identical to that of the section of the optical fibers and preferably, although not necessarily, is constituted by a section of optical fiber with an end in the form of a dihedral angle the faces of which are made reflecting due to the presence thereon of reflecting layers 28 and 29 specified below.
The axes 25''' and 26''' of the sections of optical fibers 25 and 26 are aligned with each other and, therefore, are coplanar.
The axis 24''' of the section of optical fiber 24 is coplanar with and perpendicular to the axes of the other two sections, intersecting them at a point 33 lying on a straight line which contains the edges of the dihedral angles of the three sections of optical fibers.
Fig. 5 illustrates a bidirectional coupler according to the invention which is an alternative to the embodiment of the coupler shown in Fig. 3. Also, the coupler illustrated in Fig. 5 is obtained by joining together three sections of optical fibers 34, 35, 36 in such a way as to provide continuity between their respective cores and claddings and with one of their ends shaped as a dihedral angle and by providing a wedge-shaped element 37 having reflecting surfaces 38 and 39.
The coupler illustrated in Fig. 5 differs from the coupler of Fig. 3 by reason of the fact that the dihedral angle of the wedge-shaped element 37, which is symmetrical with respect to the wedge axis, has an angle ~' smaller than 90 in order to create a greater separation between the cores of the sections of optical fibers 34 and 36 the axes of which are aligned.
Consequently, the dihedral angle of the section of optical `` ~30~135 fiber 35, the axis of which is aligned with the axis of the wedge-shaped element 37, is greater than 90, and the dihedral angles of the sections of the optical fibers 34 and 36, the axes of which are aligned, are symmetrical with respect to their own axes.
Furthermore, the dihedral angles of the ends of sections 34, 35 and 36 and of the wedge-shaped element are complementary to one another, meaning that the sum of their angles is 360.
Fig. 6 illustrates a further alternative embodiment of a coupler according to the invention, formed by joining three sections of optical fibers 40, 41 and 42 with a wedge-shaped element 43, which differs from the embodiment of Fig. 5 only because the dihedral angle of said element 43 has an angle ~
greater than 90 so as to create a smaller separation between the cores of the sections of optical fibers 40 and 41.
A still further alternative embodiment of a bidirectional coupler according to the invention is illustrated in Fig. 7.
The bidirectional coupler shown in Fig. 7 is formed by joining three sections of optical fibers 44, 45 and 46, at one of their ends shaped as a dihedral angle, and in such a way as to provide continuity between their respective cores and claddings, with a wedge-shaped element 48, having reflecting surfaces 49 and 50, which have a dihedral angle asymmetrical with respect to axis 48' of the element itself.
The dihedral angle of the wedge-shaped element 48 is an angle ~ ''' different from 90 and also the dihedral angles of the ends of the sections of optical fibers 44 and 45 have a width different from 90. The conditions which are to be respected in connection with the structure of the dihedral angles of the ends of the sections of the optical fibers and of the wedge-shaped element are the following:
the sum of the widths of the dihedral angles is 360;
1~02~3S
the wedge-shaped element 48 has such a depth or height hl such that it breaks partially the continuity between the cores of the sections of optical fibers 44 and 45 the axes of which are aligned;
both faces 49 and 50 of the dihedral angle of the wedge-shaped element 48 are inclined with respect to axis 46' of the section of optical fiber 46 to which said element is facing ; and as in the bidirectional couplers illustrated in the embodiments of Figs. 3, 4, 5 and 7, the axis of the sections of optical fibers and of the wedge-shaped element are coplanar, intersecting at the same point.
In further alternative embodiments of the invention, not illustrated, the couplers have a structure which differs from that of those represented in Figs. 5, 6 and 7 by the fact that the wedge-shaped element is not provided and that the surfaces of the two sections of optical fibers which have their axes aligned and which are not in contact are reflecting surfaces.
In all the above embodiments, as described and as illustrated in the Figs., the wedge-shaped notches and the wedge-shaped elements, when present, have flat surfaces or faces.
However, this must not be considered as restrictive since said wedge-shaped notches or said wedge-shaped elements complementary to them, when present, may have curved surfaces or faces, which can be concave or convex with respect to the axis of their respective notches and of their respective wedge-shaped elements.
As will be apparent from the description of the various embodiments, the characteristic of a bidirectional coupler according to the invention is the presence of two reflecting sur~aces of a wedge-shaped notch or a wedge-shaped element which breaks the continuity between the two portions having their axes in substantial alignment and which face the third portion having ~3()2135 its axis substantially perpendicular and coplanar to the axes of the other two portions.
Said reflecting surfaces can be provided by a metal film formed on the faces of the wedge-shaped notch or on the faces of the wedge-shaped element inserted in said notch or, alternatively, by a reflecting dielectric coa~ing, already known se, formed on said faces, such as for example, a multilayer constituted by alternate layers of silicon dioxide and titanium dioxide or by alternative layers of magnesium fluoride and zinc sulphide.
Another feature of a bidirectional coupler according to the invention is that it is preferably obtained by joining together at least two sections of optical fibers (so as to provide the continuity of the cores and of the claddings, respectively) which have been shaped by cutting by means of templates and the like, the previously shaped sections of optical fibers being placed into molds which keep them in position for the application of the means of mutual connection.
These connection means may be a thermal softening of the parts of the sections of optical fibers and of the wedge-shaped element which are to be joined together, or a transparent bonding agent, such as an adhesive comprising an epoxy resin, interposed between the parts to be joined.
If the bidirectional coupler according to the invention is to be used to connect together optical waveguides or fibers made of plastic material, the sections of optical fibers and the wedge-shaped element constituting the coupler can be made of plastic material and can also be joined together, in addition to the above mentioned ways, by treating the parts to be joined together with a solvent compatible with the plastic material forming the components.
The operation of a bidirectional coupler according to the ~302~5 invention will now be described with reference to the embodiment represented in Fig. 3.
Each free end of the sections of optical fibers 24, 25 and 26 is butt joined with an optical waveguide as indicated in Fig.
1 (not represented).
~ signal coming from the optical waveguide joined to the end of the section of optical fiber 26 is conveyed into the latter and reaches the area where the three sections of optical fibers are connected and where the wedge-shaped element 27 having reflecting surfaces 28 and 29 is disposed.
In said area, the signal is divided into two parts, owing to the presence of the wedge-shaped element 27. One part of the signal is conveyed into the section or end of optical fiber 25, which transmits it to the waveguide connected thereto.
On the other hand, the other part of the signal is reflected by the reflecting surface 29 of the wedge-shaped element 27 and is conveyed into the section of optical fiber 24 and is transmitted to the waveguide connected to the latter.
The same result occurs if the signal enters the bidirectional coupler passing into the section or end of optical fiber 25.
On the other hand, when the signal enters the bidirectional coupler through the end of the section of the optical fiber 24, the following takes place.
The signal, reaching the area where the three sections of optical fibers are joined together and the wedge-shaped element 27 is present, is reflected by the reflecting surfaces 28 and 29 of the latter which divide it into two parts. Such parts are directed to the sections of the optical fibers 25 and 26 which transmit them to the waveguides connected thereto.
In the bidirectional coupler illustrated in Figs. 2 and 3, the signal entering any of the three ends is divided into two f4 ~
213S`
substantially equal parts which are conveyed in the other two ends.
In the embodiments illustrated in Figs. 5, 6 and 7, the signal is divided in a different way according to which end it has entered.
In particular, in the bidirectional coupler of Fig. 5, a signal entering it through the end of the section of optical fiber 34 is divided into two parts of different magnitude. The part having a smaller intensity is transmitted to the optical fiber 36 having its axis aligned with the section 34, whereas the part having a greater intensity is transmitted to the section of optical fiber 35 having its axis perpendicular to the axes of the other section 34 and 36.
The same takes place if the signal comes through the end of the section 36.
On the other hand, if the signal enters the bidirectional coupler of Fig. 5 through the section of optical fiber 35, it is divided into two equal parts by the reflecting surfaces 38 and 39 having an equal area. Said parts are transmitted to the sections of optical fibers 34 and 35.
In the bidirectional coupler of Fig. 6, a signal coming from the section of optical fiber 40 is still divided into two parts of different intensity but, differently from what happens in the coupler of Fig. 5, the signal of greater intensity is transmitted to the section of optical fiber 41 having its axis aligned with end 40, whereas the signal of smaller intensity is transmitted to the section of optical fiber 42. If the signal enters the coupler of Fig. 6 through the section of optical fiber 42, it is divided into two equal parts, which are conveyed to the sections of optical fibers 40 and 41.
Furthermore, in the bidirectional coupler of Fig. 7, the signal is divided in a different way according to the section of 1~02'135 optical fiber through which it enters, and this is a function both of the depth or height hl of the wedge-shaped element 48 and of the symmetry of the latter with respect to its own axis.
From the description given and from the following considerations, it can be understood that a coupler according to the invention accomplishes the objectives of the invention.
In fact, as can be seen from the embodiments described, a coupler according to the invention has an overall size corresponding substantially to the size of a single conventional monodirectional coupler.
Furthermore, a coupler according to the invention permits the connecting together of optical waveguides or fibers in such a way that a signal coming from any one of them can be transmitted simultaneously to the other two, avoiding the need of providing a structure formed by three conventional monodirectional couplers. It follows that, by using a bidirectional coupler according to the invention, which is formed by only one component, it is no longer necessary to resort to the structure of three monodirectional couplers, and that the disadvantage thereof, of possible damage by mechanical vibrations to which is it subjected when used to form optical circuits inserted in machines, motorvehicles and the like, is also eliminated.
Consequently, a bidirectional coupler according to the invention makes it possible to provide optical circuits which are more compact and reliable.
Although preferred embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that various modifications may be made without departing from the principles of the invention.
- ~k~--
Claims (10)
1. A bidirectional coupler for interconnecting three optical waveguides in mutual communication, said coupler comprising:
first and second sections of an optical fiber with a core having a cladding thereon, with their axes substantially aligned and with one end of the core and cladding of one section meeting and connected respectively to one end of the core and cladding of the other section;
a third section of an optical fiber with a core having cladding thereon, with its axis extending substantially perpendicular to said axes, in the same plane as said axes and intersecting the point of intersection of said axes, said third section having its core and cladding connected respectively to the cores and claddings of said first and second sections;
said first and second sections having a notch between the cores thereof where they meet, said notch having a wider portion at the claddings of said first and second sections and a peak spaced inwardly from the last-mentioned said claddings, said notch having means providing energy reflecting surfaces facing toward the core of said third section and being inclined at an angle to said axis of said core of said third section.
first and second sections of an optical fiber with a core having a cladding thereon, with their axes substantially aligned and with one end of the core and cladding of one section meeting and connected respectively to one end of the core and cladding of the other section;
a third section of an optical fiber with a core having cladding thereon, with its axis extending substantially perpendicular to said axes, in the same plane as said axes and intersecting the point of intersection of said axes, said third section having its core and cladding connected respectively to the cores and claddings of said first and second sections;
said first and second sections having a notch between the cores thereof where they meet, said notch having a wider portion at the claddings of said first and second sections and a peak spaced inwardly from the last-mentioned said claddings, said notch having means providing energy reflecting surfaces facing toward the core of said third section and being inclined at an angle to said axis of said core of said third section.
2. A coupler as set forth in claim 1 wherein said reflecting surfaces are planar.
3. A coupler as set forth in claim 1 wherein said reflecting surfaces are curved.
4. A coupler as set forth in claim 1 wherein said reflecting surfaces are of different areas.
5. A coupler as set forth in claim 1 wherein said reflecting surfaces are on a wedge-shaped element inserted in said notch and are complementary to the surfaces of said notch.
6. A coupler as set forth in claim 1 wherein said means for providing reflecting surfaces is a reflecting coating on the surfaces of the cores of said first and second sections defining the surfaces of said notch.
7. A coupler as set forth in claim 1 wherein said first and second sections are a single optical fiber with said notch therein, wherein the depth of said notch to said peak thereof is less than the sum of the thickness of the diameter of the core and the cladding of said single optical fiber and wherein said third section is another optical fiber.
8. A coupler as set forth in claim 1 wherein each of said first, second and third sections is a length of optical fiber, wherein the adjoining ends of each length of optical fiber have surfaces forming a dihedral angle, wherein two of the last-mentioned said surfaces of said first section and said second section form the surfaces of said notch and further comprising a wedge-shaped element with dihedral reflecting surfaces in said notch, the dihedral angles of said surfaces at said ends of the lengths of optical fiber and of said reflecting surfaces being complementary.
9. A coupler as set forth in claim 8 wherein each of said dihedral angles is substantially equal to 90°, wherein the vertices of said dihedral angles lie on a straight line perpendicular to said plane of said axes and wherein said axes of said first and second sections and said axis of said third section intersect at said straight line.
10. A coupler as set forth in claims 5 or 8 wherein said wedge-shaped element is a length of optical fiber.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| IT19544A/87 | 1987-03-02 | ||
| IT19544/87A IT1202608B (en) | 1987-03-02 | 1987-03-02 | BIDIRECTIONAL COUPLER BETWEEN THREE OPTICAL WAVE GUIDES |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1302135C true CA1302135C (en) | 1992-06-02 |
Family
ID=11158923
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000560201A Expired - Lifetime CA1302135C (en) | 1987-03-02 | 1988-03-01 | Bidirectional coupler for three optical waveguides |
Country Status (4)
| Country | Link |
|---|---|
| BR (1) | BR8800970A (en) |
| CA (1) | CA1302135C (en) |
| GB (1) | GB2201806B (en) |
| IT (1) | IT1202608B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10557990B2 (en) | 2017-11-27 | 2020-02-11 | Cisco Technology, Inc. | Dynamic photonic waveguide splitter/coupler |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3908530C1 (en) * | 1989-03-16 | 1990-08-09 | Messerschmitt-Boelkow-Blohm Gmbh, 8012 Ottobrunn, De | |
| WO1996007117A1 (en) * | 1994-08-29 | 1996-03-07 | Akzo Nobel N.V. | Connector for polymeric optical waveguide structures |
| US20030072547A1 (en) * | 2001-10-11 | 2003-04-17 | Schott Optovance, Inc. | Three dimensional prism image guide system for optical signal transmission |
| US9658397B1 (en) * | 2016-03-25 | 2017-05-23 | Cisco Technology, Inc. | Embedded universal waveguide optical splitters/couplers |
Family Cites Families (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3901582A (en) * | 1974-11-29 | 1975-08-26 | Us Navy | Mirrored optical connector |
| FR2298806A1 (en) * | 1975-01-22 | 1976-08-20 | Thomson Csf | OPTICAL COUPLING DEVICE FOR INTERCONNECTION OF |
| CH599558A5 (en) * | 1976-03-16 | 1978-05-31 | Patelhold Patentverwertung | |
| US4176908A (en) * | 1977-12-14 | 1979-12-04 | Bell Telephone Laboratories, Incorporated | Devices for monitoring, switching, attenuating or distributing light |
| US4346961A (en) * | 1979-04-02 | 1982-08-31 | The Boeing Company | Fiber optic T coupler |
| GB2059621B (en) * | 1979-09-25 | 1983-09-28 | Standard Telephones Cables Ltd | Optical fibre connector |
| US4447118A (en) * | 1981-09-21 | 1984-05-08 | The Boeing Company | Optical information transfer system |
| FR2525777B1 (en) * | 1982-04-21 | 1985-11-15 | Renault | LATERAL OR TRANSVERSE COUPLER FOR OPTICAL FIBERS |
-
1987
- 1987-03-02 IT IT19544/87A patent/IT1202608B/en active
-
1988
- 1988-02-29 GB GB8804733A patent/GB2201806B/en not_active Expired - Lifetime
- 1988-03-01 CA CA000560201A patent/CA1302135C/en not_active Expired - Lifetime
- 1988-03-02 BR BR8800970A patent/BR8800970A/en not_active IP Right Cessation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10557990B2 (en) | 2017-11-27 | 2020-02-11 | Cisco Technology, Inc. | Dynamic photonic waveguide splitter/coupler |
Also Published As
| Publication number | Publication date |
|---|---|
| IT8719544A0 (en) | 1987-03-02 |
| GB2201806A (en) | 1988-09-07 |
| IT1202608B (en) | 1989-02-09 |
| GB2201806B (en) | 1991-02-27 |
| BR8800970A (en) | 1988-10-11 |
| GB8804733D0 (en) | 1988-03-30 |
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