GB1603139A

GB1603139A - Optical conductor junctions

Info

Publication number: GB1603139A
Application number: GB23634/78A
Authority: GB
Original assignee: Felten and Guilleaume Carlswerk AG
Current assignee: Felten and Guilleaume Carlswerk AG
Priority date: 1977-08-24
Filing date: 1978-05-26
Publication date: 1981-11-18
Also published as: NL7808682A; FR2401435B1; DE2738050A1; DE2738050C2; FR2401435A1; SE447512B; SE7808763L

Description

(54) IMPROVEMENTS IN OR RELATING TO OPTICAL CONDUCTOR JUNCTIONS (71) WE, FELTEN & GUILLEAUME CARLSWERK AKTZENGESELLSCHAFT, of Postfach 80 50 01, 5000 Koln 80, Germany, a German Body Corporate, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to optical conductor junctions. Such a junction may have at least three light conducting filaments, wherein, at an end face of a light conducting filament, the light conducting filaments branching off abut thereagainst at one of their end faces.

The invention also relates to methods of producing such optical conductor junctions.

A known optical conductor Junction provides a split light conducting filament which connects one incoming light conducting filament to two outgoing light conducting filaments. Since, however, in this case the two semicircular partial strands of the split light conducting filaments connect directly to a circular cross-section, no light can be fed from the direction of one partial strand into the light conducting filament without half of the light energy being lost.

According to the invention, there is provided an optical conductor junction having at least three light conducting filaments wherein an end face of a first of the light conducting filaments is circular and abuts against the end faces of the other light conducting filaments branching off therefrom, the end faces of the branching-off light conducting filaments forming a circular face having the same diameter as that of the end face of the first light-conducting filament, the branching-off light conducting filaments having mutually abutting inclined plane side surfaces arranged so that the branching-off light conducting filaments taper towards their end faces, each inclined side surface forming a right angle with the end face of the corresponding light conducting filament, the end faces and inclined side surfaces of the branching-off light conducting filaments being ground and polished and the end faces of the branching-off light filaments being connected to the end face of the first light conducting filament by adhesion.

A preferred optical conductor junction uniformly divides the light energy supplied in a light conducting filament to at least two light conducting filaments having the same or a larger cross-section, whereby little or no light energy is lost. A preferred optical conductor junction has a simple construction which is producible in a particularly costfavourable manner.

A preferred junction has a coupling location which consists of two closed end faces and which may be nearly completely without loss of light energy when, according to a preferred embodiment of the invention, the end face formed commonly by the light conducting filaments branching off is constructed to be approximately circular and equal in diameter with the end face of the one light conducting filament. The preferred optical conductor junction permits a multitude of constructional possibilities. In particular, more than two light conducting filaments may be branched off the one light conducting filament, as long as the condition can be fulfilled that the end faces of reduced cross-sectional area of the light conducting filaments branched off together form a closed circular end face. In this case, the cross-section of the light conducting filaments branching off may be the same or even different relatively to each other, depending upon the desired light distribution.

The end regions of the light conducting filaments branching off have inclined side faces which taper towards their end faces, wherein the inclined faces and the associated end face always form a right angle. The longitudinal axes of light conducting filaments branching off and their inclined side faces may be arranged to include an acute angle 2a and the angle region may be filled with a medium which has a smaller refractive index than the light conducting filaments, the end faces including an angle of 90" - ct with the corresponding filament axes.

Preferably the end face of the first light conducting filament has attached thereto two branching-off light conducting filaments each having a semi-circularly constructed end face. This is of advantage in particular for relatively thin light conducting filaments for which a multiple junction is difficult to produce, and obviously also wherever a uniform distribution of the light energy to two wave conductors is demanded.

Coupling together of the light conducting filaments may be realised with different coupling elements. However, the light conducting filaments may be mounted in housing blocks which can be fixed one to the other, the filaments being e.g. cast in, adhesively secured or welded in. In this case, the housing blocks retaining the light conducting filaments branching off may each comprise abutment faces one of which is coplanar with the respective inclined face the other of which is coplanar with the respective end face of the respective light conducting filament, and the housing block retaining the one light conducting filament may comprise an abutment face which is coplanar with the end face of this light conducting filament.

The abutment faces of the housing blocks are placed together and are preferably adhesively secured one to the other, the adhesive used having a refractive index which is smaller than that of the light conducting filaments.

Because of total reflection, no light can issue thereby from the inclined faces. The housing blocks may consist of a synthetic resin, e.g.

moulding resin, or metal. In this case, preference is to be given to housing blocks of a preferably transparent moulding resin, because the accurately coinciding assembly of the inclined faces and the end faces of the light conducting filaments may then be effected visually, under certain circumstances under a microscope. In the case of metal housing blocks it is advantageous that these are provided with inter-engaging adjusting pins and bores.

According to another aspect of the invention, there is provided a method of producing an optical conductor junction according to the invention, in which at least two light conducting filaments are each ground so as to form respective inclined side surfaces arranged so that the two filaments are tapered towards their first ends, and so that, when the two filaments are placed one against the other with their inclined ground faces lying against each other, they form together at the terminal end an end face having substantially the same shape and size as that of the single light-conducting filament, the light conducting filaments being ground at the terminal end, so that their inclined ground faces form with the respective end faces a right angle, and the ground terminal ends together form a plane end face, the light conducting filaments being attached by their plane end face to the end face of the single light conducting filament.

The invention will be further described, by way of example, with reference to the accompanying drawings in which: Figure 1 shows a complete optical conductor junction; Figure 2 is a diagrammatic illustration of an optical conductor junction; Figure 3 shows the end region of a branching-off light conducting filament with an inclined face; Figures 4 to 6 show three possibilities of connecting a branching-off light conducting filament to a housing block to produce an inclined face at the terminal end; Figure 7 is a section on the line VII-VII in Figure 4; and Figures 8 to 10 show respective views of the end faces of branching-off light conducting filaments.

The optical conductor junction illustrated in Figures 1 and 2 provides a connection of a single light conducting filament 1 to two light conducting filaments 2 branching off. A jacket of synthetic resin around the light conducting filament has been removed in the junction region. The light conducting filaments 1 and 2 are arranged in Y-shape with the branching-off light conducting filaments diverging. The junction is formed in that the branching-off light conducting filaments 2 comprise bevels or inclined faces 3, Figure 3, which taper towards the free ends of the filaments, and semi-circular end faces 4 which are disposed at right angles thereto. The semi-circular end faces 4 abut along their diameters at the edges of their inclined faces 3 and thus form together a closed substantially circular end face 5 according to Figure 8, the end face 5 abutting against the end face 6 of the light conducting filament 1. The end faces 5 and 6 have the same diameter, so that a substantially loss-free transfer of the light energy may take place. The light energy may be guided from the light conducting filament 1 into the light conducting filaments 2, or from the latter into the light conducting filament 1, such as is indicated by double arrows in Figure 1.

According to Figure 1, the light conducting filaments 1 and 2 are retained by housing blocks 7 and 8, the housing blocks preferably consisting of a transparent synthetic resin material. The transparent synthetic resin material provides the possibility of adjusting the end faces 5 and 6 relatively to each other in an exactly co-inciding manner by visual observation, so that a maximum throughpassage is obtained. After the respective adjustment, the housing blocks 7 and 8 are securely fixed together. This may be effected by screwing or preferably by adhesive joining, the adhesive 9, to ensure total reflection, preferably having a refractive index which lies below the refractive index of the light conducting filaments 2. The portions of the adjacent faces of the housing blocks 7 distant from the ends of the filaments 2 include an angle therebetween of 2a and contact each other along respective edges nearest the filament 1. In this case each portion of the adjacent face distant from the filament end and the corresponding end face 4 includes an angle 90" - (x. The angle region formed between the housing blocks 7 is filled with a medium which has a lower refractive index than the light conducting filaments. This medium may be e.g. air or an adhesive.

For the purpose of producing the optical conductor junction, the light conducting filaments 2 are first prepared, i.e. the terminal end thereof is ground to the respective desired shape of the end faces 4. The housing blocks are utilized for the purpose of grinding the inclined faces 3 and the end faces 4. In this case every housing block 7 is provided with a continuous groove 10. An end region of the light conducting filament 2 is then laced into the groove 10 and fixed therein by an adhesive or by casting. The light con ducting filament 2 thus retained can then be clamped, together with the housing block 7, in a workpiece holder in a relatively simple manner and treated by grinding and polishing.

According to Figure 4, the housing block 7 has formed therein a straight groove 10, i.e. a groove extending parallel to its surface. The light conducting filament 2 is inclined, being inserted in the groove 10 at a certain angle, and is retained therein in the inclined posi tion by an adhesive mass 11 or the like.

Thereupon a grinding disc is moved in the direction of the arrow A against the housing block 7 and against the light conducting fila ment 2 and these parts are ground away approximately as far as the broken line B.

Thereby the light conducting filament 2 is provided with the inclined face 3 and the housing block 7 is provided with a surface 12 which is in the same plane as the inclined surface 3, such as may be seen from the sec tional illustration according to Figure 7. Af ter the inclined face 3 has been ground, the housing block 7 and the light conducting fila ment 2 are ground in the direction of the arrow C, namely approximately as far as the broken line D. Thereby the light conducting filament 2 is provided with its semi-circular end face 4 and the front wall side 13 of the housing block 7 is provided with a surface in the same plane as the end face 4. Obviously grinding and polishing may be effected first in the direction of arrow C and only then in the direction of Arrow A.

In the illustration according to Figure 5 the housing block 7 has formed therein a groove bottom which extends inclined at a certain angle relative to the surface 12 of the housing block 7 and which receives the light conducting filament 2 in a position which is correspondingly inclined. After the light conducting filament 2 has been fixed in the groove 10 by means of an adhesive mass 11 or the like, the grinding operation and the polishing operation are performed in the same manner as has been explained with reference to Figure 4.

According to Figure 6, the housing block 7 has formed therein a groove 10 which extends parallel to its upper surface. Also the light conducting filament is inserted straight in the groove 10, that is to say extending parallel to the groove bottom. In this case, the inclined face 3 is effected by inclined grinding of the light conducting filament 2 in the direction of arrow A, either the grinding disc being moved thereagainst in an appropriately inclined position, or the housing block 7 being clamped appropriately inclined in the tool holder.

As shown with reference to Figures 9 and 10, it is also possible to provide more than two branching-off light conducting filaments 2. In this case the individual light conducting filaments 2 may even comprise end faces 4 of different construction which are reduced in cross-section. It is only of importance that the end faces 4 together form a closed substantially circular end face 5 owing to appropriately shaped inclined faces 3, the end face 5 having the same diameter as the end face 6 of the light conducting filament 1.

The housing block 8 accommodates the light conducting filament 1 in a centrally arranged through channel 14 in which it is non-displaceably located. In this case, the end face 6 is in the same plane as the outer face of the housing block 8 which face is pressed against the front wall sides 13 of the housing blocks 7 and is e.g. adhesively attached or screwed thereto. The sides of the housing blocks 7 which face each other in the mounted state of the optical conductor junction diverge from their ground-off regions towards the outside, so that a gap 14 is formed which permits the deposition of a sufficiently large quantity of adhesive for securely fixing the housing blocks 7 one relatively to the other. A similar action may be performed also in respect of the housing blocks 7 and 8 one relative to the other.

WHAT WE CLAIM IS: 1. An optical conductor junction having at least three light conducting filaments wherein an end face of a first of the light

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. in an exactly co-inciding manner by visual observation, so that a maximum throughpassage is obtained. After the respective adjustment, the housing blocks 7 and 8 are securely fixed together. This may be effected by screwing or preferably by adhesive joining, the adhesive 9, to ensure total reflection, preferably having a refractive index which lies below the refractive index of the light conducting filaments 2. The portions of the adjacent faces of the housing blocks 7 distant from the ends of the filaments 2 include an angle therebetween of 2a and contact each other along respective edges nearest the filament 1. In this case each portion of the adjacent face distant from the filament end and the corresponding end face 4 includes an angle 90" - (x. The angle region formed between the housing blocks 7 is filled with a medium which has a lower refractive index than the light conducting filaments. This medium may be e.g. air or an adhesive. For the purpose of producing the optical conductor junction, the light conducting filaments 2 are first prepared, i.e. the terminal end thereof is ground to the respective desired shape of the end faces 4. The housing blocks are utilized for the purpose of grinding the inclined faces 3 and the end faces 4. In this case every housing block 7 is provided with a continuous groove 10. An end region of the light conducting filament 2 is then laced into the groove 10 and fixed therein by an adhesive or by casting. The light con ducting filament 2 thus retained can then be clamped, together with the housing block 7, in a workpiece holder in a relatively simple manner and treated by grinding and polishing. According to Figure 4, the housing block 7 has formed therein a straight groove 10, i.e. a groove extending parallel to its surface. The light conducting filament 2 is inclined, being inserted in the groove 10 at a certain angle, and is retained therein in the inclined posi tion by an adhesive mass 11 or the like. Thereupon a grinding disc is moved in the direction of the arrow A against the housing block 7 and against the light conducting fila ment 2 and these parts are ground away approximately as far as the broken line B. Thereby the light conducting filament 2 is provided with the inclined face 3 and the housing block 7 is provided with a surface 12 which is in the same plane as the inclined surface 3, such as may be seen from the sec tional illustration according to Figure 7. Af ter the inclined face 3 has been ground, the housing block 7 and the light conducting fila ment 2 are ground in the direction of the arrow C, namely approximately as far as the broken line D. Thereby the light conducting filament 2 is provided with its semi-circular end face 4 and the front wall side 13 of the housing block 7 is provided with a surface in the same plane as the end face 4. Obviously grinding and polishing may be effected first in the direction of arrow C and only then in the direction of Arrow A. In the illustration according to Figure 5 the housing block 7 has formed therein a groove bottom which extends inclined at a certain angle relative to the surface 12 of the housing block 7 and which receives the light conducting filament 2 in a position which is correspondingly inclined. After the light conducting filament 2 has been fixed in the groove 10 by means of an adhesive mass 11 or the like, the grinding operation and the polishing operation are performed in the same manner as has been explained with reference to Figure 4. According to Figure 6, the housing block 7 has formed therein a groove 10 which extends parallel to its upper surface. Also the light conducting filament is inserted straight in the groove 10, that is to say extending parallel to the groove bottom. In this case, the inclined face 3 is effected by inclined grinding of the light conducting filament 2 in the direction of arrow A, either the grinding disc being moved thereagainst in an appropriately inclined position, or the housing block 7 being clamped appropriately inclined in the tool holder. As shown with reference to Figures 9 and 10, it is also possible to provide more than two branching-off light conducting filaments 2. In this case the individual light conducting filaments 2 may even comprise end faces 4 of different construction which are reduced in cross-section. It is only of importance that the end faces 4 together form a closed substantially circular end face 5 owing to appropriately shaped inclined faces 3, the end face 5 having the same diameter as the end face 6 of the light conducting filament 1. The housing block 8 accommodates the light conducting filament 1 in a centrally arranged through channel 14 in which it is non-displaceably located. In this case, the end face 6 is in the same plane as the outer face of the housing block 8 which face is pressed against the front wall sides 13 of the housing blocks 7 and is e.g. adhesively attached or screwed thereto. The sides of the housing blocks 7 which face each other in the mounted state of the optical conductor junction diverge from their ground-off regions towards the outside, so that a gap 14 is formed which permits the deposition of a sufficiently large quantity of adhesive for securely fixing the housing blocks 7 one relatively to the other. A similar action may be performed also in respect of the housing blocks 7 and 8 one relative to the other. WHAT WE CLAIM IS:

1. An optical conductor junction having at least three light conducting filaments wherein an end face of a first of the light

conducting filaments is circular and abuts against the end faces of the other light conducting filaments branching-off therefrom, the end faces of the branching-off light conducting filaments forming a circular face having the same diameter as that of the end face of the first light-conducting filament, the branching-off light conducting filaments having mutually abutting inclined plane side surfaces arranged so that the branching-off light conducting filaments taper towards their end faces, each inclined side surface forming a right angle with the end face of the corresponding light conducting filament, the end faces and inclined side surfaces of the branching-off light conducting filaments being ground and polished and the end faces of the branching-off light filaments being connected to the end face of the first light conducting filament by adhesion.

2. An optical conductor junction as claimed in Claim 1, in which there are two branching-off light conducting filaments disposed so that their longitudinal axes include an acute angle 2a, the region therebetween being filled with a medium which has a smaller refractive index than the light conducting filaments, each of the end faces including an angle of 90 -a with the axis of the corresponding light conducting filament.

3. An optical conductor junction as claimed in Claim 1 or 2, in which the end face of the first light conducting filament has attached thereto two branching-off light conducting filaments each having semi-circularly constructed end faces.

4. An optical conductor junction as claimed in any one of Claims 1 to 3, in which the light conducting filaments are each mounted in respective housing blocks, the housing blocks being fixable to one another.

5. An optical conductor junction as claimed in Claim 4 in which the housing blocks accommodating the branching-off light conducting filaments each comprise abutment faces one of which is coplanar with the respective inclined face and the other of which is coplanar with the respective end face of the respective light conducting filament, the housing block mounting the first light conducting filament comprising an abutment face which is coplanar with the end face of the first light conducting filament.

6. An optical conductor junction as claimed in Claim 4 or 5, in which the housing blocks mounting the branching-off light conducting filaments are disposed with their edges between the respective abutment faces in contact and are mutually secured together.

7. An optical conductor junction as claimed in Claim 6, in which the housing blocks are adhesively secured together, the adhesive having a refractive index which is smaller than that of the light conducting filaments.

8. An optical conductor junction as claimed in any one of Claims 4 to 7, in whcih the housing blocks consist of a synthetic resin or a metal.

9. A method of producing an optical con- ductor junction as claimed in Claim 1, in which at least two light conducting filaments are each ground so as to form respective inclined side surfaces arranged so that the two filaments are tapered towards their end faces, and so that, when the two filaments are placed one against the other with their inclined ground faces lying against each other, they form together at the terminal end an end face having substantially the same shape and size as that of the single light-conducting filament, the light conducting filaments being ground at the terminal end so that their inclined ground faces form with the respective end faces a right angle and the ground terminal ends together form a plane end face, the light conducting filaments being attached by their plane end face to the end face of the single light conducting filament.

10. A method as claimed in Claim 9, in which two light conducting filaments are ground to provide inclined side surfaces such that each light conducting filament has an approximately semi-circular end face.

11. A method as claimed in Claim 9 or 10, in which the end region of each branching-off light conducting filament is placed in a groove of a housing block and is adhesively secured or cast in this groove, each light conducting filament then being ground to provide the inclined side surface inclined at a pre-defined angle relative to its longitudinal axis, the respective housing block also being ground so as to have an adjacent coplanar surface, and the filament and block being ground in the region of the end of the light conducting filament so that the end of the filament and the adjacent housing block side are coplanar and at right angles to the inclined ground side face.

12. A method as claimed in Claim 9, in which the terminal end of each of the branching-off light conducting filaments is placed in a groove, which is inclined to an axis of and formed in a housing block, is fixed, and thereafter is ground along the said axis together with the block surface.

13. A method as claimed in any one of Claims 9 to 12, in which the edges of the inclined side faces of the branching-off light conducting filaments are placed together and the housing blocks retaining them are securely connected together, whereupon the end face formed by the ends of the light conducting filaments is placed against the end face of the single light conducting filament which is likewise arranged in a housing block, and the housing blocks are securely connected together.

14. An optical conductor junction sub stantially as hereinbefore described with reference to any one of the embodiments illustrated in the accompanying drawings.

15. A method of producing an optical conductor junction, substantially as hereinb efore described with reference to the accom paning drawings.