DE3316236A1 - Optical coupler for fibre-optic circuits - Google Patents

Abstract

The invention relates to an optical coupler for fibre-optic circuits. In order to produce a coupling between an end of a light guide and at least two light-transmitting or light-receiving elements, the coupler member (10), which consists of light-transmitting material, has at least two focusing optical surfaces (20, 22) which establish at least two separate optical paths (30, 34) which connect the point (14) of arrangement of an end of a light guide to the optical centres (28, 32) of chambers (16, 18) or holders serving to accommodate the light-transmitting or light-receiving elements. The optical surfaces are constructed as part of the wall surfaces of recesses (24, 26) formed in the coupler member. Use may be made, as the optical surfaces, of reflecting surfaces which generate total internal reflection, for example in the form of ellipsoid or paraboloid surfaces, possibly in combination with a semi-transmitting mirror surface and/or refracting surfaces. <IMAGE>

Description

Aetna Teleconununication Laboratories, 131 Flanders Road, Westboro, Massachusetts 01581, V.St.A,

Optical coupler for fiber optic circuits

The invention relates to an optical coupler according to the preamble of claim 1 for fiber optic circuits.

Such optical couplers are used as a link between fiber optic light guides and light transmitters or -Receivers application to transmit modulated light from a light transmitter to the light guide or light to be transmitted from the light guide to the light receiver. Such couplers can also be used as multiplexers or demultiplexers for modulated light application that can be received by a fiber optic light guide or sent onto it is.

The development of communication technology suggests that such couplers will probably be needed in large numbers in the future, which is why it is desirable

is worth using such a coupler cheaper, high Production techniques that enable quantities with a minimal number of production steps and with one to be able to produce reliable construction anyway. Such couplers must also work properly in work environments function in which changing temperatures or other disruptive effects with regard to the optical properties or the geometric alignment of the coupler and thus with regard to the coupling function prevail.

When installing the coupler, a high level of accuracy is required with regard to the geometric alignment, in order to ensure only low coupling losses between the light guide ends, the light transmitters and the light receivers. Injection molding techniques can be used to manufacture the couplers, but these are often because of the Necessity of laterally movable molded parts to produce all necessary recesses in the coupler body is complicated. It is therefore also desirable to design a coupler so that additional ones can move laterally Avoid molded parts.

Finally, with such a coupler, there are options for keeping the losses small or for achieving flexible uses optical properties desirable that allow focusing, beam splitting or correction of allow spherical aberration and coma.

The invention is based on the object of an optisehen Train couplers of the type in question with regard to the requirements just explained.

This object is achieved according to the invention by the arrangement specified in the characterizing part of claim 1 solved.

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In the coupler according to the invention, an optical coupling is used between the end of a light guide and light receivers and light emitters achieved via one or more focussing surfaces. By training the coupler body as a one-piece plastic part in injection molding technology, with the light guide end and the light transmitter and light receiver are precisely set in molded chambers, becomes a high positioning accuracy and consequently high accuracy of the mutual geometric alignment of the components achieved. The focussing areas, which the light radiation between the light guide end and the light transmitters and light receivers can also be molded in the form of pocket-like recesses or the like in the coupler body. All critical Components of the coupler body are molded together in a single injection molding process, so that an accurate and repeatable coupler production is possible with low manufacturing costs.

In a preferred embodiment of the invention the focusing surfaces of the coupler are reflective surfaces that work according to the principle of total internal reflection work without reflective coatings. These surfaces can be aspherical or spherical, depending on whether correction of spherical aberration and coma is required, or to achieve flexibility with regard to the arrangement of the focussing surfaces. The cost of the injection molds are almost the same in all cases. By arranging all component chambers on two opposite one another Sides of the coupler body can be injection molds with additional, sideways movable mold parts avoid. If desired, the focusing surfaces can be segmented if the beam paths are between the end of the light guide and the light emitters and light receivers should be completely separated. If reflective surfaces

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are used, the coupler is against changes in the refractive index and against temperature-related or by Changes in dimensions and wavelengths caused by other effects are insensitive. 5

In another preferred embodiment, has the coupler has a groove in a beam splitter surface ends. This groove is used to receive and position a light guide with its front end close to the Ray splitter puddle. A beam path leads from Light guide end via a reflection on the beam splitter surface into one for receiving a light transmitter or light receiver serving chamber. The other beam path leads through the beam splitter surface via total internal reflection on an integrally formed focussing surface in another, for receiving a light transmitter or light receiver serving chamber. In this embodiment, too, injection molds with additional sideways Avoid moving moldings.

In yet another preferred embodiment According to the invention, one focusing surface is designed as a reflective surface, while a second focusing surface Surface is designed as a refractive surface.

Some embodiments of the invention are described below with reference to the accompanying drawings describe more in detail, in which shows:

Fig. 1 is a longitudinal section through a coupler

according to the invention with ellipsoidal surfaces for total internal reflection,

Fig. 2 is a longitudinal section through another

Coupler according to the invention with an ellipsoid

areas for total internal reflection,

5 Fig. 3 shows a longitudinal section through a still

further alternative couplers with parabolic surfaces for total internal reflection /

10 Fig. 4 is a plan view of the reflect

the areas according to FIGS. 1, 2 or 3,

Fig. 5 is a plan view of an alternative

Embodiment of reflective 15 areas according to FIGS. 1, 2 or 3,

Figures 6A and

6B in longitudinal section and in plan view

another embodiment of one 20 coupler according to the invention with a

Beam splitter area and one through

total internal reflection focusing

Area,

25 Fig. 7 shows a longitudinal section through a still

another embodiment of a coupler according to the invention with a surface that focusses by refraction and a focussing surface due to total internal reflection,

a plan view of an alternative focusing surface that is used in a Coupler according to the invention is applicable,

a plan view of yet another focussing surface, which in a Coupler according to the invention is applicable, and

30th Fig. 8th 35 Fig. 9

Figures 10A and

Fig. 10B is a partial view and a section

another embodiment of a Coupler according to the invention with a surface that focuses by refraction

and a focusing surface through total internal reflection.

The optical coupler according to the invention has at least two optical surfaces, which are either reflective or diffractive surfaces, which are at least two different, spatially separated beam paths between the end of a fiber optic light guide and active elements, such as light transmitters or light receivers. These reflective or diffractive Areas of the coupler are typically designed as interfaces between the ambient air and a plastic material, from which the coupler body is made.

In a first embodiment of the invention shown in Fig. 1, a coupler body 10 has a Connection stub 12 for connecting an optical fiber connector on, d. H. a plug, in which the end of a fiber optic light guide is captured, around the light guide end to be positioned at an interface 14 of the plastic injection molded coupler body 10. Next is the coupler body 10 provided with recesses in the form of chambers 16 and 18, which in terms of the inclusion and accurate geometrical alignment of light transmitters or light receivers are measured, wherein according to a typical application, one of these chambers is a light transmitter and the other Chamber accommodates a light receiver. The type of light transmitter or light receiver to be used has a central one light-emitting or light-sensitive point. Between the end of the light guide at the interface 14 and the The middle of the chambers 16 and 18 is formed by ellipsoidal surfaces 20

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and 22 each set an optical path. These surfaces run at the critical or a larger angle, to achieve total internal reflection without the need for reflective coatings. These ellipsoidal surfaces 20 and 22 are in the coupler body 10 in the form of bottom surfaces of recesses 24 and 26 molded on. Such aspherical surfaces avoid spherical aberrations. The ellipsoid surface 20 is designed and dimensioned in such a way that the one focal point of the ellipsoid is at a central point with respect to the chamber 16 Point 28 is where light emitted by a light transmitter or light receiver used in this chamber or Will be received. The other focal point of the ellipsoidal surface 22 coincides with the position of the light guide end at the interface 14 together. An optical path 30 thus runs between the end of the light guide and the point 28. The ellipsoidal surface 22 is dimensioned such that the one focal point of the ellipsoid lies at a point 32, which in the chamber 18 on the site the transmission or reception of light by means of a light transmitter or light receiver inserted therein is. The other focal point of the ellipsoidal surface 22 is in turn at the point of the light guide end at the interface 14, so that an optical path 34 is formed between the interface 14 and the point 32. Will the optical Areas 20 and 22 viewed from the interface 14, they basically appear as segments 36 and 38 of the illustration according to FIG. 4. The position of the lowest point 40 of the recess 24 can be changed in order to shift the position of the dividing line 42 between the two segments 36 and 38 and thereby adjusting the relative radiation components which are transmitted via the optical paths 30 and 34. Typically these relative proportions are 50% on each of the two optical paths.

The recesses 24 and 26 can, if desired, also at locations that are angularly offset from one another by 90 with respect to the

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Axis of the connecting piece 12 be arranged to To exclude the influence of light propagating between the points 28 and 32 and thus the accidental Reduce the spread of radiation between these two locations. The surfaces 20 and 22 can both be segmented be to a better separation against crosstalk effects due to in the chambers 16 and 18 emitted or To achieve received light radiation, which is reflected at the interface 14. Such a segmented training is illustrated in FIG. 5, which, similar to FIG. 8, is a top plan view of surfaces 20 and 22 of the interface 14 shows. From this point of view, the surface in the embodiment according to FIG. 5 has a left part and a right part 48, while the surface 20 the central part 50 of the arrangement in the form of a narrow Strip forms.

The coupler body 10 is preferably made of a transparent, injection-moldable plastic such as, for example Lexan. In general, transparent acrylic or polycarbonate plastics have proven particularly useful. The injection molding process required to produce the inner recess areas within the coupler body are known per se. Also the known techniques for making injection molded plastic lenses and other optical forms can be used to make such couplers according to the invention.

An alternative embodiment of an injection molded plastic coupler body 60 is shown in FIG. This coupler body 60 has a connection piece 62 for connecting an optical fiber connector, to center the fiber end with respect to an interface. Between the end of the light guide in the center the interface 64 and the centers of light transmitter or

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Light receiving chambers 70 and 72 run optical paths 66 and 68. These two optical paths 66 and 68 become defined by ellipsoid surfaces 74, 76 and 78, which are marked with work with total internal reflection. The ellipsoid surfaces 74, 76 and 78 all have a common focal point 80, while the other focal point of the ellipsoidal surface 74 at Light guide end at interface 64 and the other focal points of the two ellipsoidal surfaces 76 and 78 at locations 82 and 84, which are centered with respect to chambers 70 and 70, in which light from inserted therein Light transmitters or light receivers is sent or received. The ellipsoidal surfaces 76 and 78 lie respectively centrally between the focal point 8o and the respectively associated other focal point 82 or 84.

The mold for injection molding the coupler body does not require any additional mold parts that can be moved sideways because all the recesses of the coupler body on two opposite sides of the coupler body, namely on its top and bottom, lie. This represents a significant advantage in reducing the Cost and improving the precision of injection molding of such couplers.

Due to the depth of the deepest point 86 of the recess forming the ellipsoidal surface 76, the relative Portions of the radiation on the optical paths 66 and 68 set, typically corresponding to the plan view according to FIG. 4. A segmentation of the reflective surfaces can also be carried out in accordance with the illustration according to FIG. 5 or according to other patterns.

Since each of the two optical paths 66 and 68 has two oppositely directed reflective ellipsoidal surfaces it is possible to focus through

the reflective surfaces in each of the two optical paths with respect to coma and spherical aberration correct.

Fig. 3 shows a third embodiment of a coupler according to the invention with focusing, with inner Total reflection working surfaces in the optical paths between the end of a light guide and light transmitter and Light receiving chambers 96 and 98 of the coupler body. Of the Coupler body 90 in turn has a connection piece 92 for connecting an optical fiber cable terminating Optical fiber connector, around the optical fiber end centrally at an interface 94 of the plastic coupler body 90 to position. The two chambers 96 and 98 are formed on both sides of the connecting piece 92 in the coupler body 90 and serve to optionally accommodate light transmitters or light receivers. Between chambers 96 and 98 and the Light guide ends are optical paths 100 and 102 through collimating, working with total internal reflection Paraboloid surfaces 104 and 106, surface areas 105 of the Coupler body underside and focusing paraboloid surfaces 108 also working with total internal reflection and 110 formed. Because of the focusing property of reflective parabolic surfaces 108 and 110 is their arrangement is not critical and they can be spaced at any desired distance from that associated with the conductor end Interface 94 are arranged. The splitting of the field of view from the point of view of the interface 94, which is caused by the Areas 104 and 106 takes place, can again be varied as required, as above with reference to FIGS. 4 and 5 has been explained.

The casting mold for the coupler body 90 also does not require any additional, laterally movable mold parts. That Injection molding of a coupler according to Fig. 3 can therefore be done in a very economical and accurate manner. the

At

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Couplers according to FIGS. 1 to 3 all operate with reflective surfaces and are therefore all insensitive to fluctuations in the refractive index, the dimensions and the wavelengths.
5

6A and 6B show a second basic embodiment of the invention, in which a beam-splitting, reflective and semitransparent surface for dividing the beam paths between one end of the light guide and the locations of light emitters and light receivers r chambers apply. FIG. 6A shows a coupler body 120 in longitudinal section, while FIG. 6B shows the Shows top 122 of the coupler body in plan view. The coupler body 120 has a groove 124 in which a Unmounted fiber optic light guide is typically cemented in such a way that its end of the conductor is directly in front of a is arranged with a dielectric coating provided beam-splitting inclined surface 126. A first chamber 128 is centrally located directly above the inclined surface 126 and is towards the top 1 of the coupler body open to accommodate a light transmitter or light receiver, so that light is reflected on the inclined surface 126 can be transmitted from the light guide to the chamber or vice versa. That part of the radiation that is due the beam splitting effect of the semitransparent inclined surface 126 obtained by the dielectric coating falls through this, follows an optical path 130, which via total internal reflection at a focusing Surface 132 leads to the center of a further chamber 134 for receiving a light receiver or light transmitter.

The coupler according to FIGS. 6A and 6B can in turn be injection-molded without additional, sideways movable Molded parts are produced. The light guide end can

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if desired, they can be connected to the inclined surface 126 by means of a material which matches the refractive index. The embodiment according to FIGS. 6A and 6B enables a particularly effective coupling of one in the chamber 128 arranged light transmitter to the light guide and also from the light guide to the chamber 134, which is preferably to The inclusion of a light receiver is used.

Both the chamber 128 and the chamber 134 have guide lugs 136 for precise positioning of the light transmitter or light receiver housing.

Fig. 7 shows a third basic embodiment of the invention. According to this illustration, a Coupler body 140 has a connecting piece 142 for receiving an optical fiber plug, around the end of an optical fiber 144 to be positioned at an interface 146 of the coupler body 140. An optical path 148 extends from the end of the light pipe via a surface 150 generating an internal total reflection to a light receiver or light transmitter assembly 152 in a chamber 154. A second optical path 156 leads from the light guide end through a refractive surface 158 to one Light transmitter or light receiver assembly 160 in a second chamber 162 of coupler 140.

In the embodiment according to FIG. 7, light receiver or light transmitter assemblies are the focusing Type with a lens 164 for focusing on a light-sensitive or light-emitting semiconductor element

- falling or emanating light. It's clear, that in the same way other types of light receivers and light transmitters can also be used.

The surfaces 150 and 158 when viewed from the position of the light guide end can have the same character as described above with reference to Figs

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has been. Alternatively, surfaces 150 and be segmented as shown in Fig. 8 and one of the surfaces 150 and 158 corresponding segments 170 and the other of the two surfaces mentioned have corresponding segments 172. In the same way, Fig. 9 shows a segmented arrangement with segments 174 and 176 corresponding to surfaces 150 and 158 or, if necessary, extensions of these areas. Such segmented reflective and refractive surfaces are advantageous for avoiding Back reflections from the interface 146 into the respective opposite chamber and consequently to reduce Crosstalk effects.

FIGS. 10A and 10B show an alternative embodiment of the example according to FIG. 7, in which reflection and refraction are subdivided into two concentric surfaces 180 and 182 within a coupler body 184. 10B shows the coupler body with the reflective surface 182 and the refractive surface 180 in section, whereby two optical paths are formed between a light guide end 186 and chambers 188 and 190 for receiving light transmitters or light detectors. Fig. 10A essentially shows a plan view of these two surfaces.
25th

In the alternative embodiment according to FIGS. 10A and 10B, crosstalk effects between light transmitter and light receiver elements due to reflections at the Interface to the light guide in turn prevented. 30th

Instead of the above-described possibility of preventing cross-talk effects, the above-mentioned Exemplary embodiments find a material that matches the refractive index at the end of the light guide.

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The reflective surfaces 150 and 182 in the embodiments of FIGS. 7 and 10A, 10B are preferred Ellipsoid surfaces with two focal points, which are like this are chosen that the one focal point at the location of the light guide end and the other focal point in the optical Center of the light receiver or light transmitter in question is chamber. The refracting surfaces 158 and 180 are in front preferably Cartesian ovoid surfaces in order to exclude spherical aberrations.

Claims (17)

Patent claims 1 »J Optical coupler for fiber optic circuits, with a fine coupler body with means for connecting a fiber optic light guide, characterized in that the coupler body (10, 60, 90, 120, 140, 184) has at least two chambers (16, 80, 70, 72 , 96, 98, 128, 134, 154, 162, 188, 190) or brackets for positioning and fixing at least two light transmitter and / or light catcher elements, that further the coupler body is made of a translucent material and that the coupler body is at least two optical surfaces (20, 22, 76, 78, 104, 106, 108, 110, 126, 132, 150, 158, 179, 182) which define separate optical paths between each of the chambers or holders and the location of the light guide end . 15th 2. Coupler according to claim 1, characterized in that the coupler body consists of an injection-moldable plastic is made. 3. Coupler according to claim 1 or 2, characterized in that at least one (20, 22, 76, 78, 104, 106, 108, 110, 132, 150, 182) of said optical surfaces generates total internal reflection. 4. Coupler according to claim 1 or 2, characterized in that at least one (126) of said optical Areas acts as a beam splitter. 3315236 5. Coupler according to claim 1 or 2, characterized in that at least one (158, 179) of said optical surfaces generates a refraction of light. 6. Coupler according to one of claims 1 to 5, characterized in that the coupler body consists of an acrylic or Polycarbonate plastic is made. 7. Coupler according to claim 3, characterized in that all optical surfaces (20, 22, 76, 78, 104, 106, 108, 110) generate total internal reflection in the coupler body and define two separate optical paths. 8. Coupler according to claim 7, characterized in that the optical surfaces (20, 22, 76, 78) are ellipsoidal surfaces are. 9. Coupler according to claim 8, characterized in that three ellipsoidal surfaces (74, 76, 78) are provided, each generate total internal reflection, a surface (74) being associated with both optical paths in common and the one focal point of this surface corresponds to a focal point of the other two optical surfaces (76, 78) coincides, while the other focal point is at the location (64) of the light guide end, and the each second focal point of the two other optical surfaces assigned to the two chambers or holders is. 10. Coupler according to claim 7, characterized in that the optical surfaces (104, 106, 108, 110) are paraboloid surfaces are. 11. Coupler according to claim 3, characterized in that the or another optical surface (124) as a beam splitter acts in the form of a semi-transparent mirror surface. 12. Coupler according to claim 11 / characterized in that that means for positioning the light guide end are provided in the immediate vicinity of the beam splitter surface. 13. Coupler according to claim 12, characterized in that that the chamber or holder assigned to the optical path determined by reflection on the beam splitter surface serves to accommodate a light receiver or light transmitter element close to the beam splitter surface. 10 14. Coupler according to one of claims 1 to 13, characterized characterized in that the total internal reflection generating optical surface in the by the beam splitter surface falling through the optical path leading to the other chamber or holder. 15. Coupler according to claim 3, characterized in that the or another optical surface (158, 179) has a refracting surface is. 16. Coupler according to one of claims 1 to 15, characterized in that the optical surfaces as parts of the Wall surfaces of recesses (24, 26) formed in the coupler body are formed, and that these recesses as well further recesses or brackets formed in the coupler body for receiving the light guide and light transmitters or Light receivers are all formed on only two opposite sides of the coupler body. 17. Coupler according to one of claims 1 to 16, characterized in that the optical surfaces are segmented in such a way are designed so that crosstalk effects between the at least two chambers or holders are excluded.