DE102022107948B4 - Fiber optic cable decoupling plug with holding element - Google Patents

Abstract

Optical cable decoupling plug (1) with a light exit opening (50) for coupling out light from an end piece (12) of an optical fiber cable (10), comprising a holding element (2 ') for holding the end piece (12) of the optical fiber cable (10), the end piece ( 12) of the light guide cable (10) is accommodated in the holding element (2'), characterized in that the holding element (2') comprises a scattering element (2) or is designed as a scattering element (2), the scattering element (2) being adapted for this purpose is to scatter reflected laser light into the light exit opening (50).

Description

Technical area

The present invention relates to an optical fiber cable decoupling plug with a light exit opening for coupling out light from an end piece of an optical fiber cable.

State of the art

To implement a laser processing process, it is known to guide laser light from a stationary beam source to a desired location using an optical fiber cable. The laser light is fed there by means of a coupling plug from the optical fiber cable to a processing optics, which ultimately shapes and/or focuses the laser beam, applies the laser beam to a workpiece and thereby processes it.

In such laser processing processes, laser light can be reflected from the workpiece depending on the focus position and the angular position of the processing optics to the workpiece, but also depending on the surface quality and the degree of reflection of the workpiece. These back reflections then reach the output connector, for example through the processing optics. Some of these back reflections are coupled into the optical fiber cable in the output connector and returned to the beam source. However, another part does not hit the optical fiber cable, but rather hits surface areas in the coupling plug, which can cause damage to the coupling plug if the processing threshold of the respective material of the coupling plug is exceeded by the back reflections.

Such unintentional processing of the material of the coupling plug leads to smoke and particles, which, for example, contaminates the light exit surface of the optical fiber cable as well as the protective glass of the coupling plug. Due to the increased absorption on these surfaces, the direct introduction of the laser light can destroy the optical components.

Previously, the coupling plug was gold-plated in the area of the light exit surface in order to guide the back reflections out of the coupling plug by reflecting them again. However, gold has a low melting point, so such a coupling plug cannot be used universally.
The US 8724945 B2 describes a high-performance fiber laser system with a fiber end piece in which coupling of the back-reflected laser beams by means of total reflection is to be avoided.

The DE 10 2017 210 350 B3 describes a device for coupling out radiation from an optical fiber, in which the coupling of the back-reflected laser beams is to be avoided by means of a diaphragm.

Presentation of the invention

Based on the known prior art, it is an object of the present invention to provide an improved optical fiber cable decoupling plug.

The task is solved by an optical fiber cable decoupling plug with the features of claim 1. Advantageous further developments result from the subclaims, the description and the figures.

Accordingly, a light guide cable decoupling plug with a light exit opening for decoupling light from an end piece of a light guide cable is proposed, comprising a holding element for holding the end piece of the light guide cable, the end piece of the light guide cable being accommodated in the holding element. According to the invention, the holding element comprises a scattering element, wherein the scattering element is designed to scatter laser light reflected back into the light exit opening.

The holding element can also be designed entirely as a scattering element and is preferably made of a correspondingly scattering material.

Preferably, the power density of the back-reflected, scattered laser light after passing through the scattering element is smaller than the processing threshold of material of the optical fiber cable decoupling plug. In other words, the power density of the back-reflected laser light is reduced or scattered over a larger area by the scattering element to such an extent that processing of the material of the optical fiber cable coupling plug is avoided and thus damage to the optical fiber cable coupling plug is also avoided.

The optical fiber cable is designed to guide the laser light of a laser, for example the laser light of an ultra-short pulse laser and/or a high-power laser, to the optical fiber cable decoupling plug. Such an optical fiber cable can, for example, comprise a glass fiber or another suitable fiber. The laser light is released from the light in the fiber optic cable decoupling plug conductor cable is guided into a so-called end piece, which is essentially an optical element melted and/or spliced and/or welded onto the end of the optical fiber cable.

Such an end piece is used because, for example, the maximum power that can be transported through the optical fiber cable is limited by the power density on the end surface of the optical fiber cable. Due to the small diameter of optical fiber cables, high laser powers can result in extremely high power densities and thus damage to the end surface of the optical fiber cable. By means of an end piece applied to the optical fiber cable, the diameter of the optical fiber cable can be artificially increased to a certain extent, so that the laser light can be coupled out via the so-called end surface of the end piece without causing damage.

Typically, a fiber optic cable coupling connector is used to guide the laser light from the beam source, the aforementioned laser, to processing optics. For example, such processing optics can be set up to apply laser light to a workpiece and thereby process the workpiece.

By impinging on a workpiece, the laser beam interacts in particular with the material of the workpiece. This can result in the laser beam being partially reflected on the material of the workpiece and being guided back to the optical fiber cable coupling connector via the processing optics.

In order to hold the end piece of the optical fiber cable in the optical fiber cable decoupling plug, for example always in the middle of the cross section of the optical fiber cable decoupling plug, the end piece is held in the holding element. The holding element can, for example, be arranged around the end piece and/or the holding element can surround the end piece and/or the holding piece can radially enclose the end piece. In a particularly preferred embodiment, a through hole is provided in the holding element, into which the end piece of the optical fiber cable is inserted in order to be held in the holding element.

This prevents or minimizes, in particular, an offset of the end piece perpendicular to the beam propagation direction, or perpendicular to the length axis of the optical fiber cable, in the optical fiber cable decoupling plug. In order to avoid damage to the material of the optical fiber cable decoupling plug, the holding element includes a scattering element.

The end piece can be held in the holding element so that it is flush with the holding element, or can protrude from it or be drawn into it.

The scattering element scatters the laser light that was reflected back into the fiber optic cable coupling connector. For example, the scattering element can have a large number of scattering centers for this purpose. For example, air inclusions, in particular air bubbles, can be scattering centers of the scattering element. In general, the scattering element can be porous, for example, so that it has a particularly large number of scattering centers.

By scattering the back-reflected laser light, the power of the laser light is distributed over a larger area, so that the power density decreases. In particular, this means that no laser power peaks occur on the affected surface, which means that damage to the material of the optical fiber cable decoupling plug is avoided. If the power density is lower than the processing threshold of the respective material of the optical fiber cable decoupling plug on which the back-reflected, scattered light hits, the optical fiber cable decoupling plug is merely heated or warmed by the back-reflected and scattered laser light. Damage (or unwanted processing) therefore does not occur.

The material of the optical fiber cable decoupling plug can be understood to mean any material that is installed in the optical fiber cable decoupling plug, for example the material of the housing, but in particular also the material of the optical fiber cable, the material of the end piece, the material of the cooling element described below and the protective glass.

The scattering element can have a transmission of at least 30%, preferably more than 90%. The transmission is specified here in particular for the wavelength of the back-reflected laser light.

The higher the transmission, the lower the absorption in the scattering element. Lower absorption can, for example, prevent the scattering element itself from being heated and destroyed by the back-reflected laser light. In particular, the back-reflected laser light can be scattered particularly frequently. At the same time, with higher absorption, the laser energy deposited in the remaining material of the optical fiber cable decoupling plug can also be reduced.

The scattering element can comprise a ceramic or consist of a ceramic or a glass include or consist of a glass, in particular include a quartz glass or consist of quartz glass, or include an opaque glass or consist of an opaque glass.

A ceramic is a porous material that provides a large number of scattering centers for the laser light. This makes it well suited for use in a scattering element. In particular, ceramics can be used, for example, at laser wavelengths where glasses cannot be used.

Glasses, in particular quartz glass or opaque glass, can be clouded by air inclusions during the manufacturing process, for example, so that they have a sufficiently high density of scattering centers for use in the scattering element. However, it is also possible for the glasses to have particularly good scattering properties for the laser light wavelength used due to a dye or another additive in the manufacturing process. Glasses typically have high transmission, making them particularly suitable for applications in which the laser light has to be scattered frequently.

The scattering element can be shaped axially symmetrically.

The scattering element can therefore be round in particular in cross section and have openings on the front and back that are connected to one another with a bore or a through hole.

Axis-symmetrical optical elements, for example, are particularly easy and cost-effective to manufacture. Thanks to the axially symmetrical shape, the back-reflected laser light is evenly scattered, so that there is no increase in the power density at any point.

For example, the end piece of the optical fiber cable can be inserted into the opening at the rear of the diffuser and arranged in the through hole. The end piece is preferably arranged in the scattering element in such a way that the laser light emerging from the end piece is not emitted into the scattering element. For example, the end piece can therefore be arranged in the entire through hole, so that the end surface of the end piece ends with the opening of the scattering element at the front.

The end piece can be arranged fixed or movable in the scattering element.

A fixed attachment of the end piece has the advantage that the end piece has a well-defined position in the optical fiber cable decoupling plug. For example, a fixed attachment can be achieved by gluing or clamping the end piece in or with the scattering element.

A movable attachment of the end piece has the advantage that no tensions occur in the optical fiber cable, for example when subjected to tensile load, so that the optical fiber cable decoupling plug is not damaged. For example, the end piece can move freely in the through hole in the axial direction, so that in the event of a tensile load, the end piece is pulled into the scattering element, for example.

The scattering element can have a conical opening, in the center of which the end piece lies or ends.

The opening of the front side of the scattering element and/or the opening of the rear side of the scattering element can be conical, for example.

A conical opening at the front has the advantage that cleaning the end piece is particularly easy. A conical opening at the rear has the advantage that the end piece can be inserted into the scattering element with particularly low tension.

The cone is designed in such a way that the base of the cone coincides with the opening on the front or rear side. In particular, the cone axis and the symmetry axis of the scattering element thus coincide.

The scattering element can be covered by a protective glass in the beam propagation direction, with the protective glass preferably covering the light exit opening.

As a result, the elements installed in the optical fiber cable decoupling plug, in particular the scattering element, as well as the end piece and the optical fiber cable, can be protected from external influences, in particular from mechanical influences. The protective glass is preferably highly transmissive for the wavelength of the laser light used.

The optical fiber cable decoupling plug can have a cooling element, with the scattering element being arranged between the end piece and the cooling element and with the cooling element being designed to dissipate the thermal energy of the scattered light.

The cooling element can be arranged around the scattering element so that it spatially encloses both the end piece and the scattering element. The back-reflected and scattered laser light is preferably directed to the cooling element, where it heats the cooling element and thus the energy of the scattered laser light can be dissipated with the cooling element.

This has the advantage that the optical fiber cable decoupling plug is well-tempered and the temperature of the optical fiber cable decoupling plug remains below the destruction threshold, in particular the melting temperature of the optical fiber cable decoupling plug.

The cooling element can include cooling fins.

Cooling fins are heat-conducting, flat elements that increase the surface area of the cooling element. For example, the cooling fins can be metallic disks arranged parallel to one another, which can be connected to the cooling element. For example, the cooling fins can be welded or soldered to the cooling element. The cooling element can also be designed in one piece with the cooling fins.

Due to the larger surface area, the thermal energy that is deposited in the cooling element by the scattered laser light can be dissipated particularly effectively.

The cooling element can comprise liquid cooling and the cooling element can be a liquid guide, preferably a metallic liquid guide, with a cooling liquid flowing through the liquid guide.

A liquid guide can in particular be a pipe. For example, the liquid guide can be a double-walled pipe, which consists of two pipes guided one into the other and a cooling liquid is carried in the space between the pipes.

The scattering element can be arranged in the inner tube of the liquid guide. If the scattering element scatters the reflected laser light onto the inner tube of the cooling element, then the cooling element can release the thermal energy to cooling liquid in the liquid guide.

The liquid can be actively pumped through the liquid guide and discharged at a suitable location, for example outside the optical fiber cable decoupling plug, for example with a radiator or by means of cooling fins. By pumping, the thermal energy is actively led out of the fiber optic cable decoupling plug, so that a particularly high level of protection for the materials installed in the fiber optic cable decoupling plug is guaranteed.

An absorption layer can be arranged between the scattering element and the cooling element, the absorption layer being designed to absorb the scattered, back-reflected laser light and/or to conduct the heat deposited in the absorption layer by the scattered, back-reflected laser light to the cooling element.

In particular, an absorbing absorption layer between the scattering element and the cooling element can prevent further reflection into the scattering element. Through a heat-conducting absorption layer, the scattered laser light can be supplied to the cooling element particularly effectively, so that the thermal energy can be led particularly effectively from the optical fiber cable decoupling plug.

Short description of the characters

• 1 eine schematische perspektivische Darstellung des Lichtleiterkabelauskoppelsteckers; und
• 2A, B weitere schematische Darstellungen des Lichtleiterkabelauskoppelsteckers.

Preferred further embodiments of the invention are explained in more detail by the following description of the figures. Show:

• 1 a schematic perspective view of the optical fiber cable decoupling plug; and
• 2A , B further schematic representations of the optical fiber cable decoupling plug.

Detailed description of preferred embodiments

Preferred exemplary embodiments are described below with reference to the figures. The same, similar or identical elements in the different figures are given identical reference numbers, and a repeated description of these elements is partly omitted in order to avoid redundancies.

In 1 and 2A , B, a possible embodiment of the optical fiber cable decoupling plug 1 is shown schematically.

In the present embodiment, the optical fiber cable decoupling plug 1 comprises an optical fiber cable 10, at the end of which a so-called end piece 12 is attached. The diameter of the optical fiber cable 10 is increased by the end piece 12, so that the laser light from the laser can be coupled out of the optical fiber cable 10 and made available, for example, for a material processing process.

To hold the end piece 12, the optical fiber cable decoupling plug 1 has a holding element 2', the holding element 2' being arranged around the end piece 12 of the optical fiber cable 10. The end piece 12 can be held fixedly or movably in the holding element 2' and, for example, can be inserted into a through hole in the holding element 2'.

The laser light thus emerges from the end surface 120 of the end piece 12 and enters a processing optics (not shown here) through a light exit opening 50, which is covered with a protective glass 5. The processing optics are ultimately used to guide the laser light into or onto a workpiece, where the laser light impinges on the workpiece and thereby processes it. Part of the laser light can get back into the processing optics through back reflection of the workpiece, so that the laser light is ultimately reflected through the light exit opening 50 back into the optical fiber cable coupling plug 1.

In order to avoid damage to the optical fiber cable decoupling plug 1 due to the back reflections of the laser light, the holding element 2' has a scattering element 2. The scattering element 2 is designed to scatter the back-reflected laser light. As a result, the laser light reflected back through the light exit opening 50 is distributed over a larger area, so that the power density of the laser light reflected back decreases. The power density of the scattered, back-reflected laser light is in particular smaller than the processing threshold of material of the optical fiber cable decoupling plug 1, i.e. in particular smaller than the components installed in the optical fiber cable decoupling plug 1. In other words, the scattering element 2 serves to protect the components installed in the optical fiber cable output connector 1 from damage.

The scattering element 2 has a transmission of at least 30%, preferably more than 90%, and can be made of or include a ceramic, for example. In the present embodiment, however, the scattering element is made of glass, for example quartz glass. By specifically introducing air bubbles during the manufacturing process, the glass can have a large number of scattering centers for the laser light. Such glass is also known as opaque glass. It should be emphasized at this point that the transmission of the scattering element 2 can be around 95%, but the laser light no longer emerges from the scattering element 2 in a directed manner due to the large number of scattering centers.

The scattering element 2 is in 1 and 2A , B axially symmetrical. In particular, the scattering element 2 is designed to be rotationally symmetrical about a longitudinal axis. The scattering element 2 further has an opening at the front 20 and an opening at the rear 22. The end piece 12 of the optical fiber cable 10 is inserted into the opening on the rear side 22 of the scattering element 2 and arranged there. The openings 20, 22 are particularly conically shaped. This has the advantage that the end piece 12 can be inserted particularly easily into the opening on the back 22. A conical opening on the front has the advantage that the end piece 12 can be cleaned particularly easily.

The end piece 12 is movably arranged in the scattering element 2, so that a tensile stress on the optical fiber cable can cause an axial movement of the end piece 12 to be accommodated by the scattering element 2. This has the advantage that tensile stress cannot damage the optical fiber cable decoupling plug 1. However, the end piece 12 can also be arranged fixedly in the scattering element 2, for example glued or clamped.

For example, the comparison of 2A and 2 B that the end piece 12 can be axially displaced in the scattering element 2.

A cooling element 30 of a cooling system 3 (not shown) is arranged around the scattering element 2 in the optical fiber cable decoupling plug 1. The cooling element 30 comprises a double-walled tube, wherein a cooling liquid can circulate between the walls of the double-walled tube or can be pumped through between them. The scattered, back-reflected laser light can, for example, hit the inner wall of the double-walled tube and be absorbed there. This heats the inner wall of the double wall pipe. The resulting heat can be dissipated by the circulating coolant, so that overall the thermal energy of the scattered, back-reflected laser light can be dissipated from the optical fiber cable decoupling plug.

An absorption layer (not shown) can also be arranged between the scattering element 2 and the cooling element 30, which, for example, absorbs the scattered, back-reflected laser light and, due to its heat-conducting properties, leads the thermal energy to the cooling element 30 particularly quickly.

To the extent applicable, all individual features shown in the exemplary embodiments can be combined and/or exchanged with one another without departing from the scope of the invention.

Reference symbol list

1

Fiber optic cable decoupling plug

10

fiber optic cable

12

End piece

120

end face

2

Scatter element

2'

Holding element

20

Opening on the front

22

Opening at the back

3

Cooling system

30

Cooling element

5

Protective glass

50

Light exit opening

Claims (13)

Optical cable decoupling plug (1) with a light exit opening (50) for coupling out light from an end piece (12) of an optical fiber cable (10), comprising a holding element (2 ') for holding the end piece (12) of the optical fiber cable (10), the end piece ( 12) of the light guide cable (10) is accommodated in the holding element (2'), characterized in that the holding element (2') comprises a scattering element (2) or is designed as a scattering element (2), the scattering element (2) being adapted for this purpose is to scatter reflected laser light into the light exit opening (50). Fiber optic cable decoupling plug (1). Claim 1 , characterized in that the holding element (2') is arranged around the end piece (12) and/or surrounds the end piece (12) and/or radially encloses the end piece (12). fiber optic decoupling plug (1). Claim 1 or 2 , characterized in that the scattering element (2) is designed such that the power density of the back-reflected, scattered laser light after passing through the scattering element (2) is smaller than a processing threshold of material of the optical fiber cable decoupling plug (1). Optical fiber decoupling plug (1) according to one of the preceding claims, characterized in that the scattering element (2) has a transmission of at least 30%, preferably of more than 90%. Optical cable decoupling plug (1) according to one of the preceding claims, characterized in that the scattering element (2) comprises a ceramic or consists of a ceramic or comprises a glass or consists of a glass, in particular comprises a quartz glass or consists of quartz glass, or comprises an opaque glass or consists of an opaque glass. Optical fiber cable decoupling plug (1) according to one of the preceding claims, characterized in that the scattering element (2) is shaped axially symmetrically. Optical cable decoupling plug (1) according to one of the preceding claims, characterized in that the scattering element (2) has at least one conical opening (20), in the center of which the end piece (12) is arranged or runs and or ends. Optical fiber cable decoupling plug (1) according to one of the preceding claims, characterized in that the end piece (12) is arranged in a fixed or movable manner in the scattering element (2). Optical cable decoupling plug (1) according to one of the preceding claims, characterized in that a cooling element (30) is provided, the scattering element (2) being arranged between the end piece (12) and the cooling element (30) and the cooling element (30) being thereto is set up to dissipate the thermal energy of scattered laser light. Fiber optic cable decoupling plug (1). Claim 9 , characterized in that the cooling element (30) comprises cooling fins. Fiber optic cable decoupling plug (1). Claim 9 or 10 , characterized in that the cooling element (30) comprises a liquid guide (300), preferably a metallic liquid guide, wherein the liquid guide (300) has a cooling liquid flowing through it. Fiber optic cable decoupling plug (1) according to one of the Claims 9 until 11 , characterized in that an absorption layer (4) is arranged between the scattering element (2) and the cooling element (30), which is designed to absorb the scattered laser light and / or which is deposited in the absorption layer (4) by the scattered laser light Conduct heat to the cooling element (30). Optical cable decoupling plug (1) according to one of the preceding claims, characterized in that the scattering element (2) is covered by a protective glass (5) in the direction of beam propagation, the protective glass (5) preferably covering the light exit opening (50).