APPLYING AN OPTICAL FIBER TO A SUBSTRATE

Abstract: In applying an optical fiber (1) to a substrate (3) coated with an adhesive, a supply of the optical fiber is located wound around a reel (13). The optical fiber is fed in a loose loop (17) providing a fiber magazine from the reel (13) to a collet (9) or nozzle, from which the optical fiber is passed to a hold-down means (11) having a non-rotating bottom surface. The hold-down means (11) presses the fiber against the surface of the substrate (3). The reel (13), collet (9) and the holding-down means (11) are moved so that the contact point at the substrate surface is moved along a desired path, where the optical fiber (1) is to be placed. This allows that the fiber is applied with small radii of curvature and with a minimum of mechanical stress. A fiber cutter (23) is provided upstream the collet (9) and it can cut the fiber at the places where it is to end so that no loose fiber end portions are produced. A fiber feeder (21) is provided behind the cutter (23) to feed more fiber after it has been cut.

Description: APPLYING AN OPTICAL FIBER TO A SUBSTRATE TECHNICAL FIELD The invention relates to a method and a device for applying an optical fiber to a substrate, in particular for making optical waveguide fiexfoils, i.e. flexible sheets having optical waveguides arranged therein or thereon, using optical fibers as the waveguides. BACKGROUND Future demands on communication systems include an increased density of components used and higher band widths. Due to restriction in space and the high impedance characteristics of thin electrical lines, increased component density on printed circuit boards, PCBs, renders difficulties in providing a sufficient number of electrical connections to an electrical backplane, BP, and from one circuit board to another through such a backplane. Due to the large bandwidth and low signal loss exhibited by optical fibers, the use of optical interconnections for inter board communication and intra board communication may reduce these problems. However, a large number of loose fibers mounted on or connected to PCBs or BPs will give an unmanageable building practice. Optical fiber management is one of the key factors that have to be solved in order to successfully implement the use of short range optical interconnections. The short range optical interconnect medium here presented consists of optical fibers mounted on a flexible substrate, i.e. an optical fiber flexfoil. The optical flexfoil technique has been presented by the company AT&T, see U.S. patent No. 5,259,051 for Burack et al. This patent describes how optical fibers are routed using a rotatable wheel on a surface of a substrate coated with an adhesive. The rotatable wheel has three parallel grooves and is mounted at the lower end of a manipulator, i.e. a robot arm. The fiber is fed from a reel through a fiber guide to pass over a lower portion of the wheel in one of the grooves to be deflected at the wheel by an angle of about 45°. When the manipulator is moved down to the flat surface having an adhesive coating, the wheel will press the piece of optical fiber at its lower surface and partly inside the groove against the surface to make the fiber stick to the surface. By moving the robot arm and thus the wheel over the surface it is possible to place the optical fiber along any desired path. The optical fiber is placed on the surface in one whole length of fiber. After placing the fiber on the surface, the substrate is cut to provide accessible fiber ends at the cutting lines, the whole length of fiber then being separated into a plurality of individual fiber pieces. It is also mentioned that the optical fiber can be severed after each interconnection made, i.e. after applying the optical fiber between e.g. a start tab and an end tab. The patent also describes how the optical fiber is encapsulated between two plastic foils, the surface having the adhesive coating being an inner surface of one of the foils. Before applying the other foil the optical fibers applied are encapsulated by a layer of a thermoplastic material. Another patent for the company AT&T, U.S. patent No. 5,204,925, focuses on optical fiexfoils comprising connectorised tongues, i.e. tongues provided with optical connectors. In this case, the tongues extend from the flexfoil, beyond the edges thereof. SUMMARY It is an object of the invention to provide a method and a device for making fiexfoils using optical fibers allowing that individual pieces of an optical fiber are applied to a base foil or sheet. It is another object of the invention to provide a method and a device for making fiexfoils using optical fibers allowing that a single fiber is applied substantially only at positions where it is needed, thus not requiring any fibers loops exterior to the flexfoil base. It is another object of the invention to provide a method and a device for making fiexfoils using optical fibers allowing that the fibers are applied with small curvatures at fiber bends and with a minimum of mechanical stress on the fibers. It is another object of the invention to provide a method and a device for making fiexfoils using optical fibers allowing fiber cross-overs to be produced also for small angles between crossing fibers. Thus, the problem to be solved by the invention is how to apply an optical fiber to a base flexfoil only at positions where it is needed for forwarding light and in an accurate manner with a good control of the applied fiber and with as small curvatures as possible with a minimum mechanical stress to the fiber during the application thereof. In applying an optical fiber to a substrate, such as producing a flexfoil structure having optical waveguides located between two flexible plastics sheets which are laminated to each other, the substrate being one of the two foils to be laminated, this substrate is assumed to be coated with a suitable adhesive or at least to have a surface to which the optical fiber adheres when pressed against it. A supply of the optical fiber is located wound around a reel and the optical fiber is fed in a loose loop providing a fiber magazine from the reel to a collet or nozzle, giving the fiber located in front of or downstream the outlet of the collet a definite, accurately defined direction. From the outlet of the_ collet the optical fiber is passed as freely extending fiber portion, not in contact with the substrate surface or anything else, to a hold-down means having a fixed bottom surface or pressing surface located at a small distance of the outlet of the collet. The hold-down means presses at its bottom or pressing surface the fiber against the surface of the substrate, the collet and its outlet then being located at some small distance from the substrate surface. The reel, collet and the holding-down means are moved so that the contact point at the substrate surface is moved along a desired path, where the optical fiber is to be placed. A fiber cutter is located upstream the collet and it can cut the fiber at the places where it is to end so that no loose fiber end portions are produced. A fiber feeder is provided behind the cutter to feed more fiber after it has been cut. The important features comprise firstly that in the laying-out-operation of the optical fiber the direction is defined by a device, the outlet of the collet, and the pressing operation of the fiber against the substrate is performed by a separate device, the hold-down means, or that the optical fiber is fed from the supply to contact, with a top side portion of the fiber, all the time the same bottom surface of the hold-down means and that simultaneously a bottom side portion of the fiber, which is opposite the top side portion, is pressed by the bottom surface to contact the surface of the substrate. The bottom surface is thus a fixed portion of the fixed hold-down means meaning that the fiber will all the time contact the same definite area of the bottom surface. The bottom surface is thus not rotatable or a portion of some rotatable body. It has a generally straight configuration of its lower-most part as see from the outlet of the collet, no guiding means being arranged in or at the bottom surface for maintaining the fiber in contact with the definite area of the bottom surface, the definite area being the central part of the lower-most portion of the bottom surface. The fiber is thus not guided in lateral directions of the fiber at the bottom or pressing surface of the hold-dow means, the lateral directions here being taken as directions parallel to the substrate surface and perpendicular to the longitudinal direction of the fiber. The bottom or pressing surface has no groove or any other guiding means, but it may be curved, as seen in the fiber direction, and straight, as seen in a direction perpendicular to the fiber direction along the substrate surface, or generally be part of a circular-cylindrical surface having its axis parallel to the substrate surface and a diameter of typically 10 - 20 mm. The direction of the fiber along the substrate surface when it is applied thereto, is only defined by the collet and the rigidity of the fiber between the outlet of the collet and the pressing surface. The distance between the outlet of the collet and the pressing surface is selected to be sufficiently small, so that the rigidity of the optical fiber will substantially maintain the direction given by the collet up to the pressing surface. It will then be advantageous if the optical fiber when being feed from the outlet of the collet up to the pressing surface of the hold-down means will not be sharply deflected at the "pinch" between the pressing surface and the substrate surface. If it was too sharply deflected it could, owing to the bending and elastic forces in the fiber, easily loose its definite direction and slip away from the central portion of the pressing surface. Therefor, the free portion of fiber between the outlet of the collet and the pressing surface is made to form a small angle to the substrate surface, the angle being chosen to be as small as possible considering the necessary dimensions of the collet and the free portion of the fiber from the collet to the bottom surface. In particular an angle of 5 - 15° , preferably an angle of 5 - 10°, can be used. The distance from the outlet of the collet to the substrate surface, also called the height of the outlet, will then be equivalently small, e.g. about 0.2 - 0.5 mm, for a free portion of the fiber of about 3 - 5 mm, preferably substantially 4 mm between the outlet of the collet and the central point of the pressing surface. Since the width of the pressing surface or bottom surface of the hold-down means, as seen in the fibe direction, can suitably be about 3 - 4 mm, this means that the distance from the collet outlet to the most adjacent portion of the pressing surface is about 2 mm or generally 1.5 - 2 mm. The height of the collet outlet above the substrate surface should be as small as possible still allowing that the collet will not contact optical fibers earlier placed on and adhering to the substrate. The free portion of the fiber between the outlet of the collet and the pressing surface is selected to be as small as possible, considering that the collet should not touch earlier placed fibers and that the rigidity of the this portion should be sufficient to guide the fiber to the same central area at the lowest surface of the pressing means. A second feature comprises the cutting operation which can be performed at any place at the substrate and thus allows fiber pieces to start and end at any desired places. Thirdly, the magazine portion of the optical fiber between the supply and the contact point configured as a loosely hanging or suspended portion having a curvature allows a rapid feeding of the optical fiber at the contact point subjecting the fiber to a minimum of mechanical stress during the fiber-placing operation and in particular at bends of the laid- out fiber and at starts and stops. This is in contrast to the teachings of the first cited U.S. patent 5,259,051 assigned to AT&T which among other things does not include any fiber cutting facility. Instead, the AT&T patent describes how the fiber is routed as a continuous loop having portions placed outside the actual flexfoil area to be used causing substantial lengths of fiber to be spent in relation to the actually used fiber lengths in the finished flexfoil. The patent states that this is an advantage since it then is possible to determine the quality of all the fiber routed in one measurement sending light through the fiber prior to cutting the foil and the fibers to define the usable area of the flexfoil. However, this is only an advantage if damage to the fiber by the routing is likely to occur. Possibly, also the lamination of the top foil could be performed before the cutting operation and in the lamination process then also there could be a risk a causing damage to the place fiber. Using the lamination method described in the simultaneously filed International patent application entitled "Lamination of optical fiber fiexfoils" together with the routing method as described herein, the risk of such damage is virtually eliminated. The remaining risk of damage or malfunctioning will then reside in the activities made for connecting the optical fibers to external devices. However, such malfunctioning can only be detected by loss measurements on the individual fiber pieces in the finished flexfoil structure. The fiber routing method and device described herein have the capability of routing fiber for forming cross-overs even though the angle between the two fibers crossing each other is small. If the fiber routing device is equipped with a grooved wheel, as suggested by the cited first patent assigned to AT&T, low angle fiber cross-overs may be difficult to achieve. The fiber-carrying grooved wheel may be blocked by the adjacent fiber. If the wheel would be moved in the Z-direction or height direction away from the substrate surface, the fiber may loose track due to the small and shallow key way on the wheel and the elasticity of the fiber at the rather sharp bend at the wheel. However, this patent describes that the wheel is spring-loaded in order to allow cross-overs what will make sharp cross-overs even more difficult. Further, in order to route fiber curvatures with small radii, the radius of the wheel must be small. Depending on the depth of the groove in the wheel, the radius of this wheel may need to be smaller than the smallest routing radius used. If the smallest radius used is close to the mechanical safe bending limit of approximately 5 mm for conventional glass fiber, that is only valid for short time periods of bending - for longer periods substantially larger bending radii are only allowed, the bending radius during routing due to the wheel may be harmful to the fiber. In the method and device as described herein, the placement definition and the actual attachment are separated into two parts by the collet and the sleigh or hold-down means instead of being provided by a single part performing simultaneously or integrated both functions, the grooved wheel. This avoids all problems associated with using a grooved wheel as described above. The use of the pre-cut fiber method as described above allows the use of fiexfoils having internal tongues without having to get numerous redundant fiber portions in the production of the foil which would be the case using continuous routing as in the cited prior art. The advantages of internal tongues are described in the simultaneously filed International patent application "Fiexfoils having connector tabs" . Finally, in the cited U.S. patent 5,259,051 assigned to AT&T the fiber being routed is directly pulled from a reel possessing a significant moment of inertia what requires a rather constant speed of feeding fiber from the reel and does not allow rapid stops and starts and what can also produce unnecessary tensions in the fiber when making bends. Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the methods, processes, instrumentalities and combinations particularly pointed out in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS While the novel features of the invention are set forth with particularly in the appended claims, a complete understanding of the invention, both as to organization and content, and of the above and other features thereof may be gained from and the invention will be better appreciated from a consideration of the following detailed description of non- limiting embodiments presented hereinbelow with reference to the accompanying drawings, in which: - Fig. 1 is a perspective view of an apparatus for applying an optical fiber to a substrate, and - Fig. 2 is a schematic cross-sectional view of the apparatus of Fig. 1 , - Fig. 3 is a cross-sectional view showing schematically a lower portion of a cutting tool, and - Fig. 4 is a cross-sectional view showing schematically a lower portion of a feeding unit. DETAILED DESCRIPTION In Fig. 2 a schematic cross-sectional view of an apparatus for routing optical fiber 1 on a surface of a substrate 3 is shown, the apparatus being shown also in a perspective view in Fig. 1. The surface of the substrate is made to adhesive to an optical fiber to be applied such as by coating with a suitable adhesive or subjecting the surface to some other suitable treatment. A vertical flat house 5 is mounted on a robot arm 7 of a manipulator, not shown. A feeding collet 9 is attached at a low position of the house 5. A hold-down means or sleigh 11 is mounted at the lower end of the robot arm 7, so that the nozzle, outlet or mouth of the collet 9 is located at a small distance from and directed towards the bottom surface of the sleigh 11. The bottom surface has a part-cylindrical shape, the cylindrical surface thus being directed downwards and the axis of the part-cylindrical surface being perpendicular to the direction of a fiber passing through the collet 9 to the part-cylindrical surface and also horizontal and thus substantially parallel to the top surface of the substrate 3. The manipulator is capable of moving the arm 7 in parallel to the top surface of the substrate 3 located underneath the apparatus, the adhesive top surface being horizontal and extending in the X-Y-plane. The manipulator is also capable of moving the arm 7 in the vertical direction or Z-direction perpendicular to said surface and of rotating it in the ^-direction about a vertical axis passing through the center of the generally vertical arm 7, through the contact point of a routed fiber drawn from the collet 9 and the bottom side of the sleigh 11. At the top edge of housing 5 a reel 13 having the optical fiber wound thereon is mounted. A motor unit 15 is attached to the reel 13 and has control means allowing the fiber to be automatically unwound from the reel 13. From the reel 13 the fiber is fed inside and in parallel to the vertical large surfaces of the house 5 in a specially designed path comprising first a loose, freely hanging or freely suspended loop 17, generally a free, non-straight portion having a curvature, and from that, as guided by a border 19 of the house 5, that projects laterally or in a horizontal direction from the large surfaces of the house 5, to the inlet of the feeding collet 9. A high precision fiber feeding unit 21 and a fiber cutting tool 23 are attached to the plate 5 behind or upstream the feeding collet 9. The fiber feeding unit 21 feeds the fiber or fiber-end region before and during the actual fiber routing. The house 5 thus has the shape of a basically inverted, triangular main body having a horizontal upper side and containing the fiber freely hanging loop 17. The reel 13 is attached to the front upper corner of the triangular shape. From the rear upper corner of the triangular shape a channel projects for guiding the fiber to the feeding unit 21 , the channel being limited in the forward direction of the house by the border 19 and extending first in a vertical direction to finish in a curved portion having a forward bend to end in a small angle to the horizontal plane. A steel plate 24 connects the main triangular body of the house 5 and the channel portion for stabilizing the channel portion. A lower portion of the cutting tool 23 is shown in Fig. 3. It comprises a housing in which a cylindrical channel 31 is arranged for guiding the optical fiber 1 through the tool. A knife 33 is arranged in the housing in order to be moved, as driven by a suitable motor, not shown, see the arrow 34, in a direction perpendicular to the that of the channel 31 for cutting the optical fiber when required. A cleaning channel 35 is provided from the outside of the housing to the edge of the knife 33. Particles which can be formed in the cutting operation can be sucked out through this channel. The front mouth of the fiber channel 31 is connected to the nozzle 9, not visible in Fig. 3. In the same way a lower portion of the feeding unit 21 is shown in Fig. 4. It has a housing in which a cylindrical channel 41 is arranged for guiding the optical fiber 1 through the unit. Two rollers 43, acting on opposite sides of the optical fiber to be transported, are arranged inside the housing. The rollers 43 can rotate freely or be rotated by being driven by a motor, not shown, when required, for feeding the optical fiber in the channel 41 , both when introducing a new piece of optical fiber and after cutting the optical fiber in the cutting tool 23. s Now the routing of a piece of optical fiber will be described. First the optical fiber is manually unwound from the reel 13 and positioned in the desired path inside the house 5, first in the loosely hanging loop 17 and then along a semi-circular path having its central point located highest, the border 19 and thus the channel portion of the house being configured correspondingly. From the semi-circular path the fiber is placed along a o vertical path and is then bent to a direction which is nearly horizontal and is therefrom inserted in the inlet of the fiber feeding unit 21. The fiber feeding unit 21 senses the inserted fiber end and feeds, by activating its motor acting on the rollers 43, a piece of fiber through the cutter 23 and the collet 9 and up to the central, lowest point of the bottom or pressing surface of the sleigh 11. s When the end of the fiber is in this position at the profiled bottom surface of the sleigh 11 , the manipulator moves the arm 7 downwards, so that the sleigh 11 is moved towards the adhesive-made upper surface of the substrate 11 with the lowest points of its bottom surface forming a straight line parallel to the substrate surface. Then the bottom surface presses the fiber against the substrate surface, so as to make the fiber 1 adhere to the 0 adhesive surface of the substrate 11. The thickness of an adhesive coated on the substrate surface and/or the pressure are adjusted so that the bottom surface of the sleigh 11 never touches the adhesive and only the upper side of the fiber 1. The manipulator then moves the robot arm 7 in parallel to the upper surface of the substrate 3. As the robot arm 7 moves, the optical fiber 1 adheres to the substrate along a selected path determined by the 5 movement of the arm 7 in relation to the substrate 3. The friction or adhesive forces between the pressed-down fiber 1 and the adhesive surface causes the optical fiber to be automatically fed from the loose loop 17 inside the housing 5 and further through the feeding collet 9. As has already been described, the robot arm 7 is rotatable in the φ- direction about its vertical central axis which passes through the contact point between the 0 sleigh 11 and the fiber 1 during the pressing operation. A change in the direction of the path of the fiber to be placed on the adhesive surface requires a rotation of the robot arm 7 as well as a change of the velocity of its movement in the X- and Y-directions. The amount of the rotation (movement in the ^-direction) of the robot arm 7 in each instant is determined by the radius of the fiber path curvature. When the robot arm 7 rotates around 35 its vertical central axis, also the house 5 and its attached components rotate, i.e. the reel 13, the fiber feeding unit 21 , the fiber cutting tool 23 and the feeding collet 9, and of course also the sleigh 11 which is rigidly attached to the robot arm 7. When nearly all of the required length of optical fiber has been routed in the desired path, the cutting tool 23 is activated for cutting off the fiber by moving the knife 33. The robot arm 7 then continues its horizontal movement along a short additional path so that the fiber piece between the sleigh 11 and the edge of knife 33 in the cutting means 23 is expelled from the feeding collet 9 and is pressed on to the coated top surface. Thus a piece of optical fiber has been placed at the coated surface in a desired path. Then, the robot arm 7 is moved upwards, in the Z-direction from the top surface of the substrate 3. After the sleigh 11 has lost contact with the upper side of the routed fiber, the robot arm 7 is free to move to a new starting point for another piece of optical fiber to be routed, i.e. to perform a movement in the X- and Y-directions. At this starting point additional fiber is fed automatically by the feeding unit 21 by activating the motor acting on the rollers 43 through the cutting tool 23 and the feeding collet 9 in order to place the fiber end in a suitable start position centrally at the bottom surface of the sleigh 11. The robot arm 7 is then moved downwards, in the Z-direction towards the substrate surface, which causes the fiber at the lower surface of the sleigh 11 once again to adhere to the surface of the substrate 3. Now, a movement of the robot arm 7 in the X- and/or Y-directions causes new fiber to be routed, etc. In the operation described above, when a fiber is routed, friction between the coated surface of the substrate 11 all the time causes additional, new fiber 9 to be automatically and successively fed from the feeding collet 9, the rollers 43 of the feeding unit 21 then rotating freely, not interfering with the transport of new fiber. Then new fiber is fed from the loop 17 of fiber which loosely hangs down from the reel 13. Because of this loose loop, the tension exerted on the fiber during the fiber routing is low enough not to damage the fiber and the moment of inertia of the reel 13 does not influence the automatic fiber feeding operation at the bottom surface of the sleigh 11 when it is moved pressing the fiber 1 to contact the coated surface. Using this apparatus having the described cut-and- place function requires also a quick stopping and starting of the fiber feeding process and of the movement of the arm 7. A control and sensing unit 25 is mounted at a vertical side of the house 5 at the location of the loosely hanging fiber loop 17 and it is arranged to control the amount of fiber contained in this loop. When a certain amount of fiber has been fed from the loop 17, the control and sensing unit 25 starts the motor 15 attached to the reel 13 for feeding a predetermined length of fiber from the reel 13 to restore the original shape of the loosely hanging loop 17. This can made by arranging e.g. two sensors 27, 29 such as photodetectors at different heights in the area of the loosely hanging loop 17. The upper sensor 27 signals when the loosely hanging loop has 17 been used sufficiently for feeding more fiber from the reel 13 and the lower sensor 29 signals that sufficient new fiber has been fed from the reel 13. A fiber crossing an already placed fiber may be routed even though the angle between the two fibers is small. If a fiber is to cross an adjacent fiber, the manipulator moves the robot arm 7 in the Z-direction upwards from the substrate surface at the starting point of the fiber crossover. When the bottom surface of the sleigh 11 does not any more press the currently routed fiber against the substrate surface it moves in an oblique direction, i.e. simultaneously both in parallel with as well as perpendicular to, the adjacent fiber. When the fiber has been crossed, the manipulator moves the arm 7 in the Z-direction towards the substrate surface which causes the fiber at the bottom surface of the sleigh 11 once again to adhere to the substrate surface. Attached to the robot, that carries the manipulator, is a unit, not shown, that makes alignment marks on the substrate. When the manipulator moves in the X- or Y-direction to the substrate surface, it moves relative to the alignment marks. The alignment marks are used as reference points in the coordinate system used by a control system using video cameras and controlling the manipulator in the same way as in automatic component mounting machines for e.g. surface mounting of electronic components. The alignment marks thus allow that a low accuracy is used when the substrate is placed in a fixture in the fiber routing apparatus. The fibers placed on a substrate as described above are then, for forming a flexfoil, encapsulated by a top substrate, not shown, placed on top of the fibers and of the substrate 11 and adhering to the fibers and the substrate, the substrates then usually comprising flexible plastic sheets. The flexfoil thus formed may then be subjected to a cutting operation for adjusting the shape of the flexfoil and for forming tongues, not shown, used for external optical connections. If the cutting machine is equipped with a vision system that locates the alignment marks on the substrate, the punching/cutting process may be performed using the internal coordinate system given by the alignment marks. The fiber routing technique here described allows a large number of fibers of arbitrary lengths to be routed on a substrate surface, i.e. arbitrary lengths in sense of several fibers having predetermined lengths or also one continuous fiber. The technique may be used for any kind of optical fiber, e.g. optical glass fibers and plastics or polymer optical fibers. While specific embodiments of the invention have been illustrated and described herein, it is realized that numerous additional advantages, modifications and changes will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details, representative devices and illustrated examples shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. It is therefore to be understood that the appended claims are intended to cover all such modifications and changes as fall within a true spirit and scope of the invention.

Claims: CLAIMS 1. A method of applying an optical fiber to a substrate, the method comprising the steps of: - providing a substrate having a substrate surface, to which an optical fiber to be applied thereto, adheres, - providing a supply of the optical fiber, from which the optical fiber can be drawn as required, - feeding the optical fiber from the supply so that always a portion of the optical fiber is located at a pressing surface facing the substrate surface, - moving the pressing surface to make the portion of the optical fiber at the pressing surface contact the substrate surface and be adhered to the substrate surface and then moving the pressing surface along a pattern at the substrate surface keeping successively new portions of the optical fiber at the pressing surface and in contact with the substrate surface so that the successively new portions adhere to the substrate surface and so that the optical fiber is drawn from the supply, characterized by - controlling all the time the direction of the optical fiber at an outlet portion of the optical fiber located at a predetermined distance before the portion of the optical fiber which is located at the pressing surface, so that the direction is towards the pressing surface, - making a free portion of the optical fiber between the outlet portion and the portion of the optical fiber which is located at the pressing surface pass through a distance without contacting the substrate surface being only guided as to its direction by its connection to the outlet portion owing to the rigidity of the optical fiber, and - when moving the pressing surface keeping successively new portions of the optical fiber at the pressing surface and in contact with the substrate surface the successively new portions of the optical fiber located after the distance and at the pressing surface against the substrate surface being only guided along the pressing surface in lateral directions by the connection of the successively new portions to the free portion owing to the rigidity of the optical fiber. 2. A method according to claim 1 , characterized in that in making the free portion of the optical fiber pass through a distance without contacting the surface of the substrate the free portion is made to form a small angle to the substrate surface, in particular an angle of 5 - 15° , preferably an angle of 5 - 10 \ c 3. A method according to any of claims 1 - 2, characterized in that in controlling all the time the direction of the optical fiber at the outlet portion of the optical fiber the outlet portion is made to have a small distance from the substrate surface, in particular a distance of less than 0.5 mm, preferably in the range of 0.2 - 0.5 mm. 4. A method according to any of claims 1 - 3, characterized in that in feeding the optical fiber from the supply the optical fiber is fed through a collet and placing the collet at a smallest possible height over the substrate surface, the smallest possible height being selected so that the collet will not contact optical fibers possibly earlier placed on the substrate surface. 5. A method of applying an optical fiber to a substrate, the method comprising the steps of: - providing a substrate having a substrate surface, to which an optical fiber to be applied thereto, adheres, - providing a supply of the optical fiber, from which it can be drawn as required, - feeding the optical fiber from the supply to adhere to the substrate surface, characterized in - that in feeding the optical fiber it is fed through a collet defining accurately the direction of the optical fiber at an outiet of the collet, in order for the optical fiber to contact, with a top side portion of the optical fiber located at a distance from the outlet of the collet, a bottom surface of a hold-down means at a contact portion of the bottom surface, and - moving the bottom surface to make a bottom side portion of the optical fiber, which is opposite the top side portion, contact the substrate surface and be adhered to the substrate surface and then moving the pressing surface along a pattern at the substrate surface keeping successively new portions of the optical fiber at the pressing surface and in contact with the substrate surface so that the successively new portions adhere to the substrate surface and so that the optical fiber is drawn from the supply, - the contact portion all the time being substantially the same portion or substantially a fixed portion of the bottom surface, the bottom surface and the bottom surface of the hold-down means all the time being the same or fixed. 6. A method according to claim 5, characterized in that for bringing a bottom side portion of the fiber to contact a surface of the substrate the hold-down means are arranged to press in a direction towards the substrate surface. 7. A method according to any of claims 5 - 6, characterized in that the bottom surface always has a portion most adjacent to the surface of the substrate which is substantially a straight line, the straight line being substantially perpendicular to the direction of the fiber fed from the collet nozzle. 8. A method of applying an optical fiber to a substrate, the method comprising the steps of: - providing a substrate having a substrate surface, to which an optical fiber to be applied thereto, adheres, - providing a supply of the optical fiber, from which it can be drawn as required, - feeding the optical fiber from the supply through a collet or nozzle to contact a bottom surface of a hold-down means in order to make the optical fiber adhere to the substrate surface, characterized in - that in feeding the optical fiber from the supply to a bottom surface of a hold-down means it is fed at an angle to the substrate surface in order that it will deflected by only by substantially the same angle when coming in contact with the bottom surface, the angle being selected to be so small that the collet or nozzle will not contact optical fibers placed earlier on the substrate surface. 9. A device for applying an optical fiber to a substrate surface of a substrate, to which the optical fiber adheres, the device comprising: - a supply of the optical fiber, from which it can be drawn as required, - feeding means for feeding the optical fiber from the supply, - a hold-down means having a bottom surface, - guiding means arranged in a path of the optical fiber from the supply to the bottom surface, - moving means for moving the bottom surface to make the portion of the optical fiber at the bottom surface contact the substrate surface and be adhered to the substrate surface and then moving the bottom surface along a pattern at the substrate surface keeping successively new portions of the optical fiber at the pressing surface and in contact with the substrate surface so that the successively new portions adhere to the substrate surface and so that the optical fiber is drawn from the supply, characterized in - that the guiding means are arranged to all the time control the direction of the optical fiber at an outlet portion of the optical fiber located at a predetermined distance before the portion of the optical fiber which is located at the bottom surface, so that the direction is towards the pressing surface, - that the guiding means are so located in relation to the bottom surface that a free portion of the optical fiber between the outlet portion and the portion of the optical fiber which is located at the bottom surface passes through a distance without contacting the substrate surface being only guided as to its direction by its connection to the outlet portion owing to the rigidity of the optical fiber, and - that the moving means, when moving the bottom surface, are arranged to keep successively new portions of the optical fiber at the bottom surface and in contact with the substrate surface, the successively new portions of the optical fiber located after the distance and at the pressing surface against the substrate surface being only guided along the bottom surface in lateral directions by the connection of the successively new portions to the free portion owing to the rigidity of the optical fiber. 10. A device according to claim 9, characterized in that the guiding means, in making the free portion of the optical fiber pass through a distance without contacting the s substrate surface, are arranged to make the free portion form a small angle to the substrate surface, in particular an angle of 5 - 15°, preferably an angle of 5 - 10°. 11. A device according to any of claims 9 - 10, characterized in that the guiding means, in controlling all the time the direction of the optical fiber at the outlet portion of the optical fiber, are arranged to make the outlet portion have a small distance from the o substrate surface, in particular a distance of less than 0.5 mm, preferably in the range of 0.2 - 0.5 mm. 12. A device according to any of claims 9 - 11 , characterized in that the guiding means include a collet, through which the optical fiber is fed, the collet being placed at a smallest possible height over the substrate surface, the smallest possible height being 5 selected so that the collet will not contact optical fibers possibly earher placed on the substrate surface. 13. A device for applying an optical fiber to a surface of a substrate, to which the optical fiber adheres, the device comprising: - a supply of the optical fiber, from which it can be drawn as required, 0 - feeding means for feeding the optical fiber from the supply, - a hold-down means having a bottom surface, - guiding means arranged in a path of the optical fiber from the supply to the bottom surface, - moving means for moving the bottom surface at the surface of the substrate and at a 5 distance from d e surface of the substrate along a path, along which the optical fiber is applied to the surface of the substrate, characterized in - that the guiding means include a collet or nozzle receiving the optical fiber fed from the supply and letting the fiber pass through the collet or nozzle for defining the direction of 0 the fiber, - that the bottom surface of the hold-down means is a fixed portion of the hold-down means and is arranged in such a way that the part of the fiber which has passed through the collet or nozzle contacts, with a top side portion of the fiber, the bottom surface of the hold-down means, 5 - the moving means being arranged to move the bottom surface as such a distance that a bottom side portion of the fiber, which is opposite the top side portion, contacts the surface of the substrate. 14. A device according to claim 13, characterized in that the bottom surface has a portion most adjacent to the surface of the substrate which is substantially a straight line, the straight Une being substantially perpendicular to the direction of the optical fiber fed from the collet or nozzle. 15. A device according to any of claims 13 - 14, characterized in that the bottom surface comprises a partly cylindrical surface. 16. A device for applying an optical fiber to a substrate surface of a substrate, to which the optical fiber adheres, the device comprising: - a supply of the optical fiber, from which it can be drawn as required, - feeding means for feeding the optical fiber from the supply, - a hold-down means having a bottom surface, - guiding means arranged in a path of the optical fiber from the supply to the bottom surface, - moving means for moving the bottom surface at the substrate surface and at a distance from the substrate surface along a path, along which the optical fiber is applied to the substrate surface, characterized in that the guiding means are arranged to guide the optical fiber at an angle to the substrate surface in order that the optical fiber will be deflected by only substantially the same angle when coming in contact with the bottom surface, the angle being selected to be so small that the guiding means will not contact optical fibers placed earher on the substrate surface. 17. A method of applying an optical fiber to a substrate, the method comprising the steps of: - providing a substrate having a substrate surface, to which an optical fiber to be applied thereto, adheres, - providing a supply of the optical fiber, from which it can be drawn as required, - feeding the optical fiber from the supply to contact the substrate surface at a contact point and moving the contact point all the time along a desired path over the substrate surface to make the optical fiber adhere to the substrate surface, characterized by the additional steps of: - cutting, when a predetermined length of the optical fiber has been applied, the optical fiber at a cutting position located at a predetermined distance from the contact point, and - moving the contact point along a desired path to make the portion of the optical fiber, which is after cutting located from the contact point to the cutting position, to the substrate surface. 18. A device for applying a piece of an optical fiber to a substrate, to which the optical fiber adheres, comprising - a supply of the optical fiber, from which it can be drawn as required, - feeding and contacting means for feeding the optical fiber from the supply to contact a substrate surface of the substrate at a contact point, - moving means controlling the feeding and contacting means for moving the contact point all the time over the substrate surface along a desired path, so that die optical fiber is applied along d e desired path to the substrate, characterized by cutting means for cutting, when the moving means have controlled die feeding and contacting means for moving the contact point so that a predetermined lengtii of the optical fiber has been applied, the optical fiber at a cutting position located at a predetermined distance from the contact point, and the moving means being arranged to control die feeding and contacting means for thereupon moving the contact point so that the portion of the optical fiber between the contact point and the cutting position is applied to the substrate surface, whereby a whole piece of the optical fiber has been applied. 19. A device according to claim 18, characterized in that the feeding and contacting means comprise a feeder device arranged at the cutting means for feeding a cut-off end of die optical fiber from the supply to the contact point. 20. A method of applying an optical fiber to a substrate, comprising the steps of: - providing a substrate having a substrate surface, to which an optical fiber to be applied thereto, adheres, - providing a supply of the optical fiber, from which it can be drawn as required, - feeding die optical fiber from the supply to contact the substrate surface at a contact point and moving the contact point all the time along a desired patii over die substrate surface to make the optical fiber adhere to die substrate surface, characterized by die additional steps of: - arranging a portion of d e optical fiber between d e supply and die contact point as a loosely hanging or suspended or extending portion having a curvature, this portion of die optical fiber acting as an intermediate magazine of optical fiber to be applied, allowing a rapid feeding of die optical fiber at die contact point. 21. A method according to claim 20, characterized by d e additional steps of: - sensing d e position of d e portion of the optical fiber between d e supply and d e contact point, - feeding optical fiber from die supply when the sensed position indicates tiiat d e curvature of d e portion is smaller tiian a predetermined value or die position of its lowest point is higher than a predetermined value, so tiiat d e portion always has a sufficient lengtii for allowing die rapid feeding. 22. A device for applying a piece of an optical fiber to a substrate, to which d e optical fiber adheres, comprising: - a supply of die optical fiber, from which it can be drawn as required, - feeding and contacting means for feeding d e optical fiber from the supply to contact a substrate surface of d e substrate at a contact point, - moving means controlling the feeding and contacting means for moving d e contact point all d e time over die substrate surface along a desired patii, so that the optical fiber is applied along die desired path to d e substrate, characterized by guiding means for guiding d e optical fiber from d e supply to the feeding and contacting means, so tiiat a magazine portion of the optical fiber between the supply and d e contact point is formed and is loosely hanging or suspended having a curvature and/or a lower portion between higher end portions, tiiis magazine portion of the optical fiber acting as an intermediate magazine of d e optical fiber to applied, allowing a rapid feeding of die optical fiber at die contact point. 23. A device according to claim 22, characterized by - sensing means for sensing d e position of die magazine portion of d e optical fiber between the supply and die contact point, - supply control means coupled to die sensing means for feeding optical fiber from die supply when die sensed position indicates that die curvature of the magazine portion is smaller tiian a predetermined value or die position of its lowest point is higher than a predetermined value, so tiiat d e magazine portion always has a sufficient lengtii for allowing the rapid feeding.

Inventors: ENGBERG KRISTIAN, HESSELBOM HJALMAR, ENGBERG, KRISTIAN, HESSELBOM, HJALMAR
Applicants: ERICSSON TELEFON AB L M, TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)
Application year: 1998
Main classification: G02B6
IPC codes: G02B6