FR2879307A1 - OPTICAL COUPLING DEVICE - Google Patents

Abstract

The object of the invention is an optical coupling device between an optical waveguide (1) and an optical or optoelectronic component (2), comprising a support (3) and a coupling element (5, 5 '). ), the coupling element being a transparent optical bar having an input face and an output face of the light, forming coupling faces (6, 7, 6 ', 7') between the optical waveguide and the component, for which the input face (6, 6 ', 7, 7') is shaped so that the optical beam entering through this face propagates along an optical axis A and reaches the level of the output face ( 7, 7 ', 6, 6') without being reflected on any surface located between these input and output faces.

Description

OPTICAL COUPLING DEVICE

  The present invention relates to an optical coupling device between a first optical waveguide and an optoelectronic component or a second optical waveguide.

  More particularly, the present invention relates to an optical coupling device between an optical waveguide and an optical or optoelectronic component, comprising a support and a coupling element, the coupling element being a transparent optical bar having a face of input and an output side of the light, forming coupling faces between the optical waveguide and the component.

  One type of embodiment of the optical bar of the prior art is described in US 6,491,443.

  According to this document, a frustoconical shaped bar centers a beam by reflections against the surface defined by a generator of the truncated cone.

  The present invention aims to improve the coupling performance of a device of the type mentioned above.

  To do this, the present invention mainly relates to a coupling device comprising an optical bar, characterized in that the input face of the bar is shaped so that the optical beam entering through this face propagates along an optical axis and reaches the level of the output face without having been reflected on any surface located between these input and output faces.

  The device according to the invention makes it possible to avoid losses at the faces and / or interfaces between the input and output faces.

  According to a particular embodiment, the input face is an aspherical surface centered on an optical axis, this surface having a radius of curvature which increases when one moves away from the optical axis.

  According to another alternative or complementary embodiment, the output face is an aspherical surface centered on an optical axis, this surface having a radius of curvature which increases when one moves away from the optical axis.

  In alternative or complementary embodiment at least one of the faces is a face provided with network diffraction patterns.

  According to a particular embodiment of the invention, at least one of the input-output faces is surrounded by an annular ring.

  More particularly, the annular ring is disposed on the side of the input-output face facing the component and comprises an abutment flange, fitting into a cavity of the component and forming centering and focal length matching means between said facing face and the active element of the component.

  Still according to the invention, the coupling element comprises means for retaining the coupling element in a support body extending radially in a direction perpendicular to said optical axis.

  The retention means comprise in particular an annular ring.

  In a particular embodiment, the support body is molded onto the optical coupling element according to a double injection molding operation. The coupling element more particularly consists of a transparent body having a cylindrical internal section terminating in the input-output faces and a tubular outer section, surrounding the inner section and whose ends constitute reference surfaces relative to each other. at a focusing distance of the input-output faces.

  Other characteristics and advantages of the invention will be better understood on reading the following description of a nonlimiting exemplary embodiment of the invention with reference to the figures which represent: In FIG. 1: a schematic view of a first embodiment of an optical coupling element according to the invention; in FIG. 2: a schematic view of the interception of an optical beam by a face of a coupling element of FIG. 1; in FIG. 3: a view of a variant of the coupling element of FIG. 1; in FIG. 4A: a sectional side view of an exemplary embodiment of an optical coupling device according to the invention comprising the coupling element of FIG. 3; in FIG. 4B: a sectional side view of an exemplary embodiment of an optical coupling device according to the invention comprising the coupling element of FIG. 3 associated with a first optical waveguide.

  In FIGS. 5A and 5B: an exemplary alternative embodiment of an optical coupling element according to the invention and an enlarged view of a coupling face of this element.

  The optical coupling device according to the invention aims to improve the transmission of optical signals in a connection between a transmitter and a receiver and in particular to limit losses at an optical connection between a component 2 and an optical waveguide 1.

  A first exemplary embodiment of a coupling element 5 is shown in FIG. 1. This coupling element comprises two-end input-output faces of a transparent body 100 intended to be inserted into a housing of a housing. coupler.

  The input-output faces of this element 100 are aligned with the active element of an opto-electronic component 2 and with the waveguide 1 which is to be connected to the component.

  The opto-electronic component 21 may be a transmitter such as an electroluminescent diode or a laser diode or it may be a receiver such as a phototransistor or a photodiode while the waveguide is an optical fiber and in particular a fiber single-mode or multi-mode plastic.

  According to this embodiment, the coupling element 5 comprises a bar provided at its ends with input-output faces 6, 7 curves, the two faces being in this case shaped to concentrate the optical beam in the heart of the bar according to a longitudinal optical axis A of the bar and shaped to focus the optical beam at a determined distance (D1, D2) from the bar.

  Depending on the configuration, the face 6 may be an entrance face and the face 7 an exit surface or the opposite. In general, the faces 6 and 7 will be called input-output faces.

  The curvatures of the input-output faces can thus each be adapted to its counter waveguide part 1 and component 2.

  The coupling element 5 of FIG. 1 consists of a transparent body having a cylindrical inner section 13 terminating in the input-output faces 6, 7 and an outer section 14 surrounding the inner section and the ends 15 , 16 extend the bar to form reference surfaces with respect to the focusing distance of the curved faces.

  According to this example, the input-output faces 6, 7 are not necessarily in contact with, on the one hand, the component 2 and, on the other hand, with the waveguide 1, but are far from the latter respectively. a distance D1 and a distance D2, optimal distances with respect to the input-output faces for focusing the beam relative to the waveguide and the component.

  The use of these input-output faces 6, 7 makes it possible to deflect the light rays constituting the optical beam so that they do not intercept the periphery of the bar in its longitudinal direction.

  According to this example, for which the curved faces are aspheric caps of radius of curvature of the order of 1.5 mm, the distance D1 is equal to the distance D2 and of the order of 0.1 mm, the length of the section internal 13 being of the order of 4.8 mm depending on the dimensions of the support body.

  More precisely, the radius of curvature increases as one moves radially away from the optical axis A towards the outside. This arrangement makes it possible to bring the beam back towards the center of the coupling element 5 and to intercept a larger part of the incident beam, as shown in FIG. 2. In fact, in this FIG. 2, are represented by hatched surfaces. , portions of the intercepted beam. These portions would not be intercepted by spherical surfaces having a radius of curvature corresponding to the center of the lens.

  Different focal distances between D1 and D2 for example are possible for the case of optoelectronic components provided with a lens or whose opto-electronic chip is more or less sunk into its case.

  More particularly, as shown in FIG. 1, the curved faces are designed so as to guide the light in the bar in the form of a cylindrical beam F, the beam coming out convergently from the curved faces 6, 7.

  In addition, in the embodiment of FIG. 1, the ends 15, 16 of the tubular outer section 14 protrude with respect to the curved faces 6, 7 and constitute support abutments on one side for the component and on the other. other for the waveguide 1 which avoids any contact of the optical faces between them and separates the optical function of the positioning function and mechanical centering.

  The coupling element is made of an optical material and molded for example by a micro-molding operation.

  FIG. 3 relates to an alternative embodiment of a coupling element 5 'according to which the coupling element comprises two input-output faces 6, 7 curves of which only one is surrounded by an annular ring 8.

  As in the example of FIG. 1, this annular ring 8 comprises an abutment flange 9, which is inserted in a cavity 10 of the opto-electronic component as represented in FIG. 4B and forms centering means and Focal length matching between the curved face 7 and the active element of the component 2.

  The mounting of the coupling member 5 'in a support body 3 forming an optical coupling box here is shown in FIG. 4A.

  According to this figure, the optical coupling device between an optical waveguide 1 and an optical or optoelectronic component 2 comprises a support body 3 provided with a base 4 for receiving a termination of the first waveguide and a receiving channel of the coupling element 5 '.

  The coupling element 5 'according to FIG. 4A is the coupling element of FIG. 3 and of the type comprising a transparent optical rod of generally cylindrical shape, comprising a first curved input-output face 6 of the light and a second light input-output side 7 of said light-forming faces forming coupling faces between the optical waveguide 1 and the component 2.

  The curved faces 6, 7 of the coupling element have a curvature focusing an optical beam at determined distances from the bar and in particular the distance D1 of the curved face 6 to the input / output face of the waveguide 1 and the distance D2 from the curved face 7 of the curved face 7 to the active element of the optoelectronic component 2.

  According to the example of FIG. 4A, only the curved face 7 on the component side is surrounded by an annular ring 8 provided, as explained above, with a stop flange 9 making it possible to center the bar with respect to the component 2.

  The coupling element 5 'has an optical axis A between the two curved faces and means 12 for retaining the coupling element in the support body 3. These means 12 which extend radially in a direction perpendicular to said optical axis comprise according to the example an annular ring.

  Because of the curvature of the faces which contain the beam F in the core of the bar, there is no loss of signal by reflections in the annular ring for holding the bar in the support body.

  The bar can thus be made of transparent plastic material without the need to use a graded index material.

  According to the example of FIG. 4A, the support body 3 can be molded on the optical coupling element 5 'according to a double injection molding operation or molded separately, the bar 5' then being inserted by the outside of the body support until abutment of the annular ring against an internal shoulder to the receiving channel of the bar in the support body.

  According to this example, the support body comprises a stop face 17 for the waveguide 1, this stop face defining the distance D2 of the curved face 7 to the waveguide 1, which avoids providing the bar of two annular crowns.

  The coupling element 5 'consists of a transparent body having a cylindrical inner section 13 terminating in the curved faces and a tubular outer section 14, surrounding the inner section and whose ends 15, 16 constitute reference surfaces by relative to the focusing distance of the curved faces.

  As seen previously, the coupling element 5 'retained in the support body 3 does not need two annular rings as in the example of FIG. 1, one of the stop edges for the component or the fiber being directly realized in the support body 3.

  The abutment face 17 of the support body protects the optical face when the bar is inserted into the support body 3.

  The support body 3 constitutes an optical coupler base provided with holding means 18 of the opto-electronic component.

  These holding means are according to the example a metal cap bearing on the support body and having a spring lug 19 applying the component 2 against the coupling element 5 '.

  The metal cap serves in particular as a shield for the electronic part 5 of the opto-electronic component.

  The support body 3 constitutes a base for receiving a plug 20, known per se and only the general profile is schematized.

  The plug 20 is provided with the optical fiber 1 constituting the optical waveguide and is inserted into the receiving base to make the optical connection.

  The examples of FIGS. 1 to 4B are embodiments for which at least one of the input-output faces 6, 7 is a curved face.

  As has been seen previously, the use of curved faces makes it possible to shape the beam by light refraction at the air-plastic interface and to deflect the beam so that light rays do not intercept the periphery of the bar in its longitudinal direction. .

  The example of FIG. 5A relates to a coupling element also provided with two input-output faces of the light shaped to concentrate the optical beam at the heart of the bar along a longitudinal optical axis A of the bar, but here the principle used is a principle of light diffraction, the faces 6 'and 7' being in this case provided with diffraction patterns 21 in network, an example of which is shown enlarged in FIG. 5B making it possible to re-combine the waves which have traveled a different path and to direct them in the waveguide or in the optoelectronic component.

  The light emitted by the face will be the combination of the recombined beams as represented in FIG. 5B on the graph Intensity I and distance D. A combination of the examples of FIG. 1 and FIG. 5A is possible, one of the faces then being a curved face. the other face is provided with a network diffraction pattern.

  The invention is not limited to the examples shown and is particularly applicable to the connection of two optical fibers to one another, one of the fibers being received in place of the component 2, the support being in this case a support provided with two backplanes to back. The support can also be a connector element provided with electrical contacts for the simultaneous connection of an electrical connector, particularly in the context of applications such as audio-visual devices embedded in automobiles or public transport vehicles.

Claims (1)

9 CLAIMS   1 - Device for optical coupling between an optical waveguide (1) and an optical or optoelectronic component (2), comprising a support (3) and a coupling element (5, 5 '), the coupling element being a transparent optical rod having an input face and an output face of the light, forming coupling faces (6, 7, 6 ', 7') between the optical waveguide and the component, characterized in that the input face (6, 6 ', 7, 7') is shaped so that the optical beam entering through this face propagates along an optical axis (A) and reaches the level of the output face (7, 7 ') , 6, 6 ') without being reflected on any surface between these input and output faces.   2 - Device according to claim 1, wherein the input face (6, 7) is an aspherical surface centered on an optical axis, this surface having a radius of curvature which increases when one moves away from the optical axis .   3 - Device according to one of the preceding claims, wherein the output face (7, 6) is an aspherical surface centered on an optical axis, this surface having a radius of curvature which increases when one moves away from the optical axis.   4 - Coupling device according to one of claims 1 to 3, wherein at least one of the faces (6 ', 7') is a face provided with network diffraction patterns (21).   5 - Optical coupling device according to one of the preceding claims, wherein at least one of the faces (6, 7, 6 ', 7') is surrounded by an annular ring (8).   6 - optical coupling device according to claim 5, wherein the annular ring (8) is disposed on the side of the face (7) facing the component and comprises an abutment flange (9), fitting into a cavity ( 10) of the component and forming centering and focal length matching means between said facing face (7) and the component (2).   7 - optical coupling device according to one of the preceding claims, wherein the faces (6, 6 ', 7, 7') are made so as to guide the light in the bar in the form of a cylindrical beam ( 11).   8 - Optical coupling device according to one of the preceding claims, wherein the coupling element comprises means (12) for retention of the coupling element in a support body, extending radially in a direction perpendicular to said optical axis (A).   9 - optical coupling device according to claim 8, wherein the retention means (12) comprise an annular ring.   - Optical coupling device according to one of the preceding claims, wherein the coupling element (5, 5 ') consists of a transparent body having a cylindrical inner section (13) ending in the input faces- outlet and an outer section (14), surrounding the inner section and whose ends (15, 16) extend the bar to form reference surfaces with respect to a focusing distance of the input-output faces.