DE19960564A1 - Method for assembling an optical fiber with a connector - Google Patents

Abstract

The invention relates to a method for manufacturing an optical waveguide comprising a connector plug. According to said method, the front face (SS) of the optical waveguide (LW) is melted onto the plug using thermal radiation (WS) from a thermal source (LA). Said thermal radiation can be focussed onto a predetermined heating zone (HZ), which is a maximum 50 times greater than the surface of the front face of the optical waveguide, in particular onto a zone corresponding approximately to the surface area of the front face of the optical waveguide (LW).

Description

The invention relates to methods for assembling a Optical fiber with a plug.

The assembly of z. B. plastic optical fibers with one connector each, in particular according to the so-called called "hot plate process" 'performed. For this, the ever because of the connector from the front of its connector head protruding fiber optic end on a heated plate pressed. The plastic material of the Lichtwel melts lenleiters on the face and fills a cavity in the plug head out. In this known packaging method the whole with the help of electric heating elements Heated surface of the plate. Only when the entire plate after Turning off the heating elements has cooled and that is art Material of the deformed fiber optic end is sufficient is solidified, this can be flawless from the plate be removed. In particular, these waiting times to heat up zen and for cooling the plate are in practice long and affect mass production. Plastic- Optical waveguide is only around after its hardens molded plastic material, d. H. only after sufficient Cooling, removed from the plate. Would that Plastic optical fiber in the hot state from the Plate would be peeled off, so would be made viscous Glue plastic material partially to the plate and in uncontrollably elongated, so that the ge desired deformation of the optical fiber end affected or could not be reached at all. Cooling the plate is only done by convection through the circulating air such as B. by a blower or the like.

The invention has for its object to provide a way like a plastic optical fiber in simple and efficiently assembled with one connector each can be. This task is done in a process of a gangs mentioned solved in that the front of the Optical fiber with the help of heat radiation from the heat source is melted on a predeterminable heating zone (HZ) of at most 50 times the area of the face, in particular of approximately the surface shape of the end face of the Optical fiber is focusable.

The fact that through heat radiation in a targeted manner Heating zone is irradiated, at most 50 times the size ß corresponds to the end face of the optical waveguide an efficient heating of the fiber optic end enables light. By focusing or concentrating the heat Radiation to the localized heating zone is energy losses largely avoided. After switching off the heat measurement radiation is due to the locally limited or limited Heating zone also ensures that the optical fiber can cool down on the face immediately. Because through the Be delimitation of the heating zone will result in an undesirable heating of the Plate environment around the face of the Lichtwellenlei largely avoided. This increases the Cycle times in the assembly of optical fibers with one connector each compared to the conventional "hot Plate process "enables.

Due to the heat conduction of the plate material from the cal th plate areas are impermissibly long dead times, i. H. Waiting times until the plate in the loading area has cooled sufficiently range of the heating zone HZ and the one pressed against it by opening melt deformed optical fiber largely avoided the. This allows the plug with the integrated light world already after a very short cooling phase be removed from the plate with little liability. Through the Reduction of cooling phases compared to conventional hot  Plate process, in which the entire plate is heated the manufacturing speed for the mass confection nation of plastic optical fibers with one each Plugs increased in an advantageous manner.

It is particularly useful if the heat radiation on a such a heating zone is concentrated, the area shape of which Face shape of the optical fiber to be assembled corresponds. This is a particularly efficient way of melting tion and shaping of the respective optical fiber end in Plug head and after switching off the heat radiation a be particularly fast cooling of the formed optical fiber in the end.

Other developments of the invention are in the Unteran given sayings.

The invention and its developments are described below hand explained in more detail by drawings.

Show it:

Fig. 1 with 3 different schematic representation of three each Ver method steps for carrying out the invention Ver proceedings for assembling a plastic optical fiber with a connector,

Fig. 4 in a schematic front view of the pressure plate when performing the method steps according to Fig. 1 with 3, and

Fig. 5 shows a schematic representation of a modification of the procedural step according to Fig. 1 for performing a further variant of the assembly method according to the invention.

Elements with the same function and mode of operation are given the same reference numerals in FIG. 1 by 5.

FIGS. 1 3 show in time series various process steps of a first variant of the inventive SEN making-up of a plastic optical fiber with a connector LW ST. First of all, the plastic optical waveguide LW to be assembled is expediently preprepared by detaching from its optical fiber LF any existing plastic protective cover or coating layer CO along a predefinable final length. Such a coating layer usually serves to mechanically protect the optical fiber. Then the optical fiber LF is brought to a desired final length EL by cutting accordingly. The bare optical fiber LF of the optical waveguide LW is thus exposed along this end length EL. The light guide fiber LF is preferably made of plastic, in particular plexiglass or PMMA with the usual layer structure of light-guiding core and cladding layer applied over it to produce total reflections for the light guided in the core.

The optical waveguide LW prepared in this way at the end is then inserted into the shaft SH of the plug ST. It is pushed through its plug head SK so far that it protrudes from the plug head SK with a definable end length EL. In order to mechanically fix the optical waveguide LW in the connector ST along its axial longitudinal extent, a hot-melt adhesive or another adhesive is expediently applied to its outer coating layer CO and / or to the outer surface of the optical fiber LF. As a result, the plastic protective cover CO of the optical waveguide LW adheres mechanically permanently to the inner wall of the bushing SH and / or the plug head SK. The plug head SK has on its end face an externally freely accessible cavity CA, ie a free, still empty cavity, which is later filled with the melted plastic material of the optical fiber end LF who is to. The cavity CA is formed in the connector SK of FIG. 1 by the fact that the bushing or through bore DB widens in the radial direction towards the outside in the region of the end face of the connector head SK. Expressed in other words, the through hole for the optical waveguide in the connector ST in the region of the end face of the connector head SK widens outward in relation to its circular cylindrical shape. In particular, the Durchgangssboh tion DB is funnel-shaped or flared in the region of the end face of the plug head SK.

If necessary, the plastic optical fiber LW additionally or independently of adhesives also by means of common eng mechanical locking means in connector ST in axial Direction can be pre-fixed. So the respective light world cable can also be crimped into the connector, for example.

The bare exposed optical fiber expediently hangs LF from the plug head SK with such an end length ELV from that their protruding plastic material after late sufficient melting, the CA cavity in the plug head SK to fill out.

Subsequently, the plug ST which is assigned in this way, with its optical fiber LF pre-fixed in the axial direction, which protrudes on the face side along the end length ELV, is pressed against a flat plate PL under contact pressure. This pressing is marked in Fig. 1 with an arrow AP in the fiber longitudinal direction. The plate PL is shown schematically in FIG. 4 in a front view. For example, it has an approximately rectangular pressure surface. Its front side VS, on which the front side SS of the optical fiber LF is pressed or pressed, is designated VS in FIG. 1. This plate PL is preferably formed in FIG. 1 by a metal foil or metal plate.

In order to be able to melt the plastic material of the end length of the optical fiber LF protruding from the plug head SK, the plate PL is heated on the rear side RS by the heat radiation WS from a heat source LA. The heat radiation WS is concentrated on a predeterminable heating zone HZ of the plate PL, which lies opposite the contacting zone of the end face of the optical fiber LF. The Heizzo ne HZ is therefore axially symmetrical with respect to the plate PL, that is, corresponding to the local position of the optical fiber end face SS, in which it is pressed onto the front side VS of the plate PL. The heating zone HZ on the rear wall RS of the plate PL preferably has a surface shape which corresponds approximately to the surface shape of the end face of the optical fiber LF. The heating zone HZ is also included in the front view in FIG. 4. For example, it lies approximately at the intersection of the corner diagonals of the rectangular plate PL. The heat radiation WS is focused in such a way that the heating zone HZ is approximately circular. In the area of the heating zone HZ, the wall thickness of the plate PL is expediently reduced relative to its remaining area in order to achieve the most effective possible heating of the pressed optical fiber LF on the opposite front side VS of the plate PL. This reduction in wall thickness is indicated by dash-dotted lines in FIG. 1 and is marked with RW. By concentrating the heat radiation WS on a locally limited area of the plate PL, it is largely ensured that heating of the plate PL takes place only where on the opposite side the optical fiber LF contacts the plate PL with its end face. An inadmissibly strong heating of the other areas of the plate PL is avoided. In this way, a particularly effective heat transfer of the heat radiation WS from the plate rear side RS to the plate front side VS is brought about for heating the optical fiber end face contacting there. This largely avoids active heating of the entire surface of the plate PL, that is to say the remaining surface of the plate PL remains largely cool.

The heat radiation WS is preferably from a laser LA dispensed without contact on the plate PL. Of course is also suitable for other high-energy light or the like. The generated heat radiation WS has in particular the advantage of being targeted, d. H. dosed on a pre feasible spot of the plate PL focused, d. H. concentrated can be. In addition, it is largely ver in a simple manner can be switched on and off without delay. A predeterminable stain such as B. HZ on the plate PL will only be active then heats when the heat radiation WS is switched on, so that an unwanted reheating of the plate after switching off the Thermal radiation is largely avoided. The plate PL can largely after switching off the heat radiation WS Cool down with little delay in the area of the heating zone HZ. Because the Plate PL remains largely cold outside the heating zone HZ. Due to the heat convection of the plate PL, the previously heated spot HZ after switching off the heat radiation WS cooled down in a short time. Because the heat measurement radiation WS only on a spot HZ of the plate PL is concentrated, which is much smaller than the rest Remaining surface of the plate is PL, can be largely delayed smooth transfer of heat radiation WS to the forehead surface of the optical fiber LF and at the same time after switching off heat radiation a largely delay-free replay cooling of the fiber end can be achieved. Conveniently the plate PL is only in the heat radiation WS Area of the heating zone HZ heated in such a way that the heat capacity act of the remaining, cooling area of the plate PL larger than which is the heating zone HZ. For a quick heating process and subsequent rapid cooling process of the front face SS the optical fiber LF may already be sufficient  be appropriate that the heat radiation WS of the heat source LA on a specifiable heating zone HZ of at most 50 times, ins especially at most 2 times the size of the face the optical fiber LF is concentrated. This also allows sufficiently short cycle times for heating up and how cooling of the optical fiber can be achieved.

The heat source LA is preferably pulsed, ie it emits heat radiation WS in the form of a short temporal pulse. This heats the heating zone HZ on the rear side RS of the plate PL. The metered amount of heat is passed on to the contacting surface on the front side VS of the plate PL and the end face of the optical fiber LF contacting there is melted. In the meantime, the optical fiber LF is pressed or pressed onto the plate PL. As a result, the melted plastic material of the optical fiber LF flows into the cavity CA in the plug head SK. The melted plastic material then largely fills the cavity CA in the plug head SK completely. By melting the plastic material on the end face SS of the optical fiber LF and simultaneously pressing it onto the plate PL, the end face of the fiber is reshaped, in particular broadly pressed. The viscous plastic material flows into the cavity CA and forms a rivet-shaped end for the optical fiber LF. Fig. 2 shows this state of the optical fiber LF flattened on the end face. The end face of the formed optical fiber LF is designated SF *. The cavity is now filled with the plastic material of the optical fiber LF from FIG. 1 which previously protrudes along the end length ELV, ie the optical fiber LF no longer protrudes from the plug head SK after the shaping of its end face. The fact that the optical fiber LF is widened radially outward after its end-face shaping in the plug head on the face opposite the otherwise circular-cylindrical shape, in simple terms a locking in the axial direction of the optical fiber LF is brought about. So if ge pulled on the connector ST along the axial longitudinal extension of the optical waveguide LW, this anchoring of the optical fiber LF in the connector head largely prevents relative movements between the optical fiber LF and its outer protective layer CO. In the event of any tensile forces acting on the connector ST, a force transmission to the largely tensile optical fiber LF is thus achieved, while its outer shell CO is largely decoupled from it. As a result, shear movements between the outer shell CO and the optical fiber LF are largely avoided.

After this shaping process of the end face of the optical fiber LF, the heat source LA is switched off. This is indicated in FIG. 3 by the fact that the heat radiation WS is crossed out by a cross OU. Since the heat radiation WS for the forming process of the optical fiber end face has only been heated on a limited partial area of the plate PL, while the other areas of the plate PL have remained largely cool, the heated zone HZ can also be cooled again in a relatively short time by heat conduction . As a result, the melted plastic material of the optical fiber LF, which is pressed into the cavity CA, solidifies very quickly. The plug ST with the rivet-shaped end face SS * can then be pulled away from the plate PL with almost no liability. This is indicated in FIG. 3 by an arrow WZ, which is directed away from the plate PL in the direction of the longitudinal extension of the optical waveguide LW. If necessary, the corresponding method steps can also be transferred in an analogous manner for the assembly of glass optical fibers, each with a connector.

Furthermore, it may already be sufficient the respective optical fiber without stripping its coa Insert the ting layer in the connector, correspond at the end chend the process steps according to the invention, let cool and then peel off the plate.  

It may be particularly expedient to choose a material for the plate PL with a specific heat capacity C that is as small as possible. Such a material is e.g. B. glass. This enables a particularly efficient cooling of the plate PL after local heating. In particular, a concave curvature can also be provided in the glass plate PL in the area of the predetermined heating zone HZ when looking in the direction of the contact area of the optical fiber LF. This makes it easy to focus and focus the heat rays WS. FIG. 6 shows such a curvature KW in the surface of the plate PL for collecting the energetic radiation WS. Fig. 6 veran the outer contour of the plate PL illustrates this on its rear side RS in a section through the heating zone HZ perpendicular to the plane of right of Fig. 1,.

1 and 2, it may also be appropriate, in a modification of the method steps according to FIGS. 1 and 2, to heat and melt the end face SS of the optical fiber LF protruding from the plug head SK with the help of the thermal radiation WS before pressing it onto the plate PL. This is illustrated in FIG. 5. The heat radiation WS is directly focused on the end face SS of the optical fiber LF without the plate PL being arranged between the heat source LA and the plug ST. The heat radiation WS of the heat source LA is therefore concentrated directly on the fiber end face SS. Only then is the plate PL moved laterally to the longitudinal extent of the fiber LF in the beam path of the heat rays WS. This is indicated in FIG. 5 by a movement arrow LP transversely, in particular perpendicularly, to the longitudinal extension of the optical waveguide. Before or after the lateral displacement of the plate PL, the thermal radiation WS is switched off. The connector ST with the optical fiber LF melted on the end is then pressed onto the plate PL, which is illustrated by the arrow AP in the axial longitudinal direction of the fiber. By pressing, the reshaping of the end face of the fiber LF is again effected in accordance with the method steps according to FIG . This modification has the particular advantage that the plate PL is not heated directly by the heat radiation WS, but remains constantly cool.

In summary, the invention is therefore "Hot plate process" based in particular on the principle, Wär meergy onto the pressure plate in a very confined space stamp. For this, z. B. a laser, high-energy Light or other energetic radiation. The goal is to get ahead preferably only to heat a local area of the plate. A heating zone is preferably approximately circular in shape at most 500 µm in diameter, in particular 2 mm in diameter heated. Especially on the other side of the pressure plate the optical fiber is heated against the one heated from behind Plate pressed. After switching off the radiation energy due to the heat conduction of the plate within a very short time Time the temperature is lowered so far that a decrease of the finished connector with high quality is enabled. Consequently are advantageously cycle times of less than one Second possible. Long service life of the system, in particular those of the heat source are guaranteed.

Claims (12)

1. A method for assembling an optical fiber (LW) with a connector (ST), with the optical fiber (LW) being inserted into the connector (ST) in a first step such that it comes out of its connector head (SK) with a predefinable final length (EL) protrudes, in a subsequent, second step the optical waveguide (LW) at its protruding end is melted on the end face with the aid of a heat source (LA) and with this softened end face (SS) is pressed onto a plate (PL) , whereby it is placed on the end face in a predeterminable shape (SS *), characterized in that the end face (SS) of the optical waveguide (LW) is melted with the help of heat radiation (WS) from the heat source (LA), which is predefinable Heating zone (HZ) of at most 50 times the area of the end face, in particular of approximately the area shape of the end face of the optical waveguide (LW) can be focused. 2. The method according to claim 1, characterized, that the optical fiber (LW) in the first step in the plug (ST) is inserted so that it comes out of the plug head (ST) with such a final length that his mate hangs out sufficient after melting, a cavity (CA) in the Fill in the plug head (SK). 3. The method according to any one of the preceding claims, characterized, that the connector (ST) with the inserted optical fiber (LW) before it is melted on the front side by heat radiation the front of the plate (PL). 4. The method according to claim 3, characterized,  that after pressing the optical fiber (LW) the plat te (PL) on the back with the help of heat radiation le diglich locally in the area of the contact zone of the end face of the Optical fiber (LW) with the plate (PL) is heated. 5. The method according to any one of the preceding claims, characterized, that heat radiation (WS) from a laser (LA), energy rich light or the like is generated. 6. The method according to any one of the preceding claims, characterized, that the plate (PL) only by the heat radiation (WS) in the area of the heating zone (HZ) is heated such that the Heat capacity of the rest of the cooling area of the plate (PL) is larger than that of the heating zone (HZ). 7. The method according to any one of the preceding claims, characterized in that the wall thickness of the plate (PL) in the area of the heating zone (HZ) less than in the remaining area of the plate (PL) is selected. 8. The method according to any one of the preceding claims, characterized, that a metal foil is used as the plate (PL). 9. The method according to any one of claims 1 to 7, characterized, that for the plate (PL) one for heat radiation (WS) energetically transparent material is used. 10. The method according to any one of the preceding claims, characterized, that the end face (SS) of the optical fiber (LW) directly with the help of heat radiation (WS) before pressing on the plate (PL) is heated and melted.   11. The method according to claim 10, characterized, that the plastic optical fiber (LW) only after the end melting onto the plate (PL) for forming its face is pressed. 12. The method according to any one of the preceding claims, characterized, that as an optical fiber, a plastic optical fiber (LW) is inserted into the connector (ST).