DE102024119857B3 - Optical coupling module, test unit, method for producing an optical coupling module, method for optically testing a test element using a test unit and control unit - Google Patents

Abstract

The approach presented here creates an optical coupling module (100) with a module carrier (110) with a surface (125) and a waveguide (120) projecting obliquely from the surface (125) of the module carrier (110) at a connection point (115) for outputting optical test signals (143) to an element to be tested (135).

Description

The approach presented here relates to an optical coupling module, a test unit, a method for producing an optical coupling module, a method for optically testing a test element using a test unit, and a control unit according to the independent claims. Such a module and method are generically known from US 2011 / 0 279 812 A1 as well as from WO 2019 / 029 765 A1 known.

Out of WO 2021 / 078 318 A1 A wafer-level test method is known for testing optoelectronic chips arranged on a wafer, with electrical interfaces in the form of contact pads and fixed optical interfaces in the form of optical deflection elements. In three adjustment steps, the wafer with one of the chips is aligned to a contacting module such that the electrical interfaces of the chip and the contacting module are in contact with each other, and the optical interfaces of the chip and the contacting module (2) assume a maximum position for the optical coupling. The method is relatively complex and requires a high degree of positioning accuracy of the contacting module.

From the US 2006 / 0 109 015 A1 is an optoelectronic contacting module (probe module) for testing chips (object under test - DUT) with electrical and optical inputs and outputs. As described in the US 2006 / 0 109 015 A1 As described above, to optimize the coupling efficiency of the optical signal by collimating or focusing the optical beam, the entire contacting module must be adjusted with high precision in the sub-µm range, which is very complex.

The US 2011 / 0 279 812 A1 discloses a contacting module for testing chips with electrical and optical inputs and outputs. The chip is mounted on a movable carrier that allows it to be roughly aligned with the contacting module. Rough alignment is sensor-controlled based on the chip's position monitoring or alignment marks. This is complicated and prone to failure.

Out of US 7 412 138 B1 Optoelectronic alignment structures are known for wafer-level testing of optical and optoelectronic chips. The wafer-level test system uses optical and electronic probes to locate and align an optoelectronic alignment structure and includes alignment for maximum performance. The alignment process and the alignment structures are relatively complex.

For testing an optoelectronic device under test (DUT), a corresponding test unit is provided for wafer-level testing in volume production of, for example, photonic integrated circuits. A key feature of such a test unit is its plug-and-play capability with existing wafer-level test equipment and wafer probers used in volume production of conventional ICs. To achieve this, the insufficient positioning accuracy of conventional wafer probers for reproducible optical coupling should be compensated for by a suitable optical coupling principle that is insensitive to position tolerances. Currently, test units can be used to measure, for example, PICs, where the light is coupled via grating couplers (GCs) at the surface. For wafer-level testing of optoelectronic chips, only insufficient light coupling is achieved due to frequent misalignment.

Against this background, the present invention aims to provide a possibility for improved optical testing of an element to be tested.

This problem is solved by the subject matter of the subordinate patent claims.

• - einem Modulträger mit einer Oberfläche; und
• - einen an einer Verbindungsstelle schräg aus der Oberfläche des Modulträgers herausragenden Wellenleiter zur Ausgabe von optischen Prüfsignalen an ein zu prüfendes Element.

The approach presented here creates an optical coupling module with the following features:

• - a module carrier with a surface; and
• - a waveguide protruding obliquely from the surface of the module carrier at a connection point for outputting optical test signals to an element to be tested.

A module carrier can be understood, for example, as a one-piece or compact component on which the waveguide is arranged or protrudes. A surface can be understood, for example, as a main surface of the module carrier, which, for example, is directed towards an element to be tested or which is pressed onto the element to be tested. A connection point can be understood, in this case, as a point at which the waveguide is attached, so that an optical test signal from the module carrier can couple the waveguide into this point. A waveguide can be understood, in this case, as a light guide or a mode-guiding element, from which light, which has been coupled into the waveguide through the entry point, for example, is output as an optical test signal to an element to be tested arranged externally to the waveguide. The waveguide can have a core and a cladding. The core can have a higher refractive index than the cladding. The waveguide can also be cladding-free. In this case, the surrounding air with a refractive index close to 1 can ensure optical waveguiding in the core. The waveguide can be a single-mode waveguide with respect to the wavelength of the optical test signals. However, it can also be multi-mode. The optical test signals can be single-mode. Even single-mode test signals can be transmitted over short distances through a multi-mode waveguide, so a multi-mode waveguide can also be used in this case. A multi-mode waveguide can have the advantage over a single-mode waveguide in that the waveguide core can have a larger cross-section. This means that a lower alignment accuracy to the element under test can be sufficient to transmit the optical test signals. Alternatively, the test signals can be multi-mode. Single-mode test signals can be generated with a laser, while multi-mode test signals can also be generated with an LED (light-emitting diode).

The approach presented here is based on the realization that the use of a waveguide extending out of or away from the module carrier significantly improves the ability to output optical test signals to an element under test. Using such a waveguide can, for example, compensate for misplacement of the waveguide in relation to the element under test, for example at a connection point on the element under test, since the protruding waveguide usually enables a significantly larger coupling area than can be achieved with individual coupling pads or coupling regions on the element under test arranged on the surface of the module carrier. At the same time, the distance between the module carrier and the element under test can also be reduced, for example, by pressing the element under test against the module carrier, so that the waveguide is placed between the element under test and the surface and can efficiently couple the corresponding optical test signals to the element under test. At the same time, damage to the waveguide is usually not to be feared, since the movement paths from a waveguide to the element to be tested can be kept small during contacting, which requires only uncritical mechanical stress in the case of a flexible waveguide.

Another advantageous embodiment of the approach presented here is one in which the waveguide is designed as an optical fiber, and/or wherein a length of the waveguide corresponds to at least five times, advantageously at least ten times, a width of the waveguide and/or wherein the waveguide is designed as a glass fiber.

Such an embodiment offers the advantage of keeping the mechanical stress on this waveguide small due to the special design of the waveguide and/or of enabling the largest possible coupling area of optical test signals from the waveguide into the element to be tested.

According to a further embodiment of the approach proposed here, the module carrier and the waveguide can be formed as a single piece, or the waveguide can be attached, in particular glued, to the module carrier at the connection point. Such an embodiment offers the advantage of being able to manufacture the combination of module carrier and waveguide very flexibly and cost-effectively according to the desired optical and material specifications. It is also possible to attach the waveguide to the module carrier, for example, by splicing or by soldering using a glass solder. Splicing can be understood as a welding process in which the connection point can be locally melted.

In order to enable the most flexible contact between the waveguide and the element to be tested, the waveguide can extend in an arc over the surface.

Another conceivable embodiment of the approach proposed here is one in which the waveguide is at least partially aligned parallel to the surface and/or in which the waveguide is flexibly shaped. Such an embodiment offers the advantage of enabling the largest possible coupling area between the waveguide and a corresponding coupling region of the element under test.

Furthermore, according to another embodiment of the approach proposed here, the waveguide can contact the surface at an end opposite the connection point. Such an embodiment offers the advantage of being able to monitor or evaluate the coupling behavior of an optical test signal via the waveguide specifically at the end of the waveguide opposite the connection point, thus enabling a spatial separation of the output of the optical test signal and the monitoring of the coupling behavior.

Particularly robust against mechanical stress is an embodiment of the approach proposed here, in which the waveguide has a spring element that is located between a Area of the junction and an end opposite the junction supports the waveguide against the surface.

Very low optical losses in the output of the optical test signal are made possible by an embodiment of the approach proposed here, in which a module carrier waveguide is embedded in the module carrier, which is designed to guide the optical test signals to the connection point in the waveguide.

According to another embodiment of the approach proposed here, an additional waveguide protruding obliquely from the surface of the module carrier at a further connection point can also be used to output additional optical test signals to the element under test. Such an embodiment enables the testing of the element under test with a plurality of optical test signals, which can be coupled into the element under test at different positions, for example, and/or output independently of one another and, for example, simultaneously. In this way, an increase in flexibility in testing the element under test can be achieved.

• - einem optischen Koppelmodul gemäß einer Variante einer hier vorgestellten Ausführungsform; und
• - einer Analyseeinheit, die ausgebildet ist, um ein optisches Prüfsignal durch das optische Koppelmodul an das zu prüfende Element zu senden und ein vom zu prüfenden Element erhaltenes Testsignal auszuwerten.

Furthermore, an embodiment of the approach proposed here is advantageous as a test unit for optical testing of a test element, wherein the test unit has the following features:

• - an optical coupling module according to a variant of an embodiment presented here; and
• - an analysis unit designed to send an optical test signal through the optical coupling module to the element to be tested and to evaluate a test signal received from the element to be tested.

Such an embodiment allows the above-mentioned advantages to be realized quickly, cost-effectively and efficiently.

• - Bereitstellen eines Modulträgers, und
• - Ausbilden an einer Verbindungsstelle schräg aus der Oberfläche des Modulträgers herausragenden Wellenleiter zur Ausgabe von optischen Prüfsignalen an ein zu prüfendes Element.

Furthermore, an embodiment of the approach proposed here is advantageous as a method for producing an optical coupling module according to a variant of an embodiment presented here, wherein the method comprises the following steps:

• - Providing a module carrier, and
• - Forming a waveguide protruding obliquely from the surface of the module carrier at a connection point for outputting optical test signals to an element to be tested.

Such an embodiment allows the above-mentioned advantages to be realized quickly, cost-effectively and efficiently.

An optical coupling module can be manufactured particularly simply and cost-effectively if, according to one embodiment, the forming step involves exposing, in particular etching, the waveguide from a material of the module carrier and/or forming the waveguide using 3D printing and/or bonding the waveguide to the surface of the module carrier at the connection point. In this case, technically sophisticated and cost-effective methods can be used to manufacture such an optical coupling module.

• - Beaufschlagen des zu prüfenden Elements mit dem optischen Prüfsignal unter Verwendung des optischen Koppelmoduls; und
• - Auswerten eines vom zu prüfenden Element erhaltenen Testsignals oder Auswertesignals.

Furthermore, an embodiment of the approach proposed here is advantageous as a method for optically testing a test element using a variant of an embodiment of a test unit presented here, the method comprising the following steps:

• - applying the optical test signal to the element to be tested using the optical coupling module; and
• - Evaluating a test signal or evaluation signal received from the element under test.

Advantageously, the optical test signal can be transmitted from the waveguide to the element under test by means of evanescent coupling. For example, a cladding of the waveguide can be thinned or removed at a point on the waveguide intended for transmission. A core of the waveguide can also be flattened at the point intended for transmission to increase the degree of evanescent coupling.

The evanescent coupling between the waveguide and the element under test can be achieved by placing the waveguide on the element under test with the point intended for transmission in place. Alternatively, the evanescent coupling can also be achieved via a gap between the waveguide and the element under test, without the waveguide having to be placed on the element under test. The latter method can therefore be contactless and thus wear-free on the waveguide. On the other hand, the contactless method can provide a higher degree of coupling than the non-contact method.

In addition, the method for optically testing a test element may comprise reducing the distance between the test element and the coupling module before the test process and increasing the distance between the element to be tested and the coupling module after the test process. The reduction of the distance and the increase of the distance can occur in a normal direction to the surface of the element to be tested, which can be defined as a z-direction. The normal direction can be the normal to the wafer plane if the elements to be tested are arranged on the wafer. This wafer plane can be referred to as an xy plane, where xyz can form a Cartesian coordinate system. The reduction of the distance can occur, for example, by lowering the coupling module onto the element to be tested if the element to be tested is arranged in a plane below the coupling module. However, it can also occur by raising the element to be tested if the coupling module is arranged in a fixed plane above the element to be tested. The reduction of the distance can occur, for example, by raising the coupling module onto the element to be tested if the element to be tested is arranged in a plane above the coupling module. However, it can also be achieved by lowering the element to be tested if the coupling module is positioned in a fixed plane below the element to be tested. Increasing the distance can then be done in the opposite direction. The terms "above" and "below" can be considered in relation to the force of gravity.

If the element to be tested is positioned above the coupling module, it can be tested upside down. This can reduce the likelihood of contamination, for example, from falling particles. However, the likelihood of contamination of the coupling module may be increased compared to a non-upside-down test.

However, the test can also be carried out vertically. This means that the normal direction of the element to be tested is horizontal with respect to the force of gravity.

The above-mentioned methods can be implemented, for example, in software or hardware or in a mixed form of software and hardware, for example in a control unit.

The approach presented here further provides a control unit configured to perform, control, or implement the steps of a variant of a method presented here in corresponding devices. This embodiment of the invention in the form of a control unit also allows the problem underlying the invention to be solved quickly and efficiently.

For this purpose, the control unit can have at least one computing unit for processing signals or data, at least one memory unit for storing signals or data, at least one interface to a sensor or an actuator for reading in sensor signals from the sensor or for outputting data or control signals to the actuator, and/or at least one communication interface for reading in or outputting data embedded in a communication protocol. The computing unit can be, for example, a signal processor, a microcontroller, or the like, wherein the memory unit can be a flash memory or a magnetic storage unit. The communication interface can be designed to read in or output data wirelessly and/or via a wired connection, wherein a communication interface that can read in or output wired data can read this data, for example, electrically or optically from a corresponding data transmission line or output it to a corresponding data transmission line.

In this case, a control unit can be understood as an electrical device that processes sensor signals and outputs control and/or data signals depending on them. The control unit can have an interface that can be implemented in hardware and/or software. In a hardware implementation, the interfaces can, for example, be part of a so-called system ASIC, which contains a wide variety of functions of the control unit. However, it is also possible for the interfaces to be separate integrated circuits or to consist at least partially of discrete components. In a software implementation, the interfaces can be software modules that are present, for example, on a microcontroller alongside other software modules.

Also advantageous is a computer program product or computer program with program code that can be stored on a machine-readable carrier or storage medium such as a semiconductor memory, a hard disk memory or an optical memory and is used to carry out, implement and/or control the steps of the method according to one of the embodiments described above, in particular when the program product or program is executed on a computer, a control unit or generally a device.

• 1 eine schematische Darstellung eines Ausführungsbeispiels eines optischen Koppelmoduls;
• 2 eine Darstellung eines weiteren Ausführungsbeispiels eines optischen Koppelmoduls;
• 3 eine schematische Darstellung eines Ausführungsbeispiels eines optischen Koppelmoduls nun in einer Seitenansicht;
• 4 ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zur Herstellung eines optischen Koppelmoduls;
• 5 ein Ablaufdiagramm eines Ausführungsbeispiels eines Verfahrens zum optischen Testen von einem prüfenden Element;
• 6 ein Blockschaltbild eines Ausführungsbeispiels einer Steuereinheit zur Herstellung eines optischen Koppelmoduls;
• 7 ein Blockschaltbild eines Ausführungsbeispiels einer Steuereinheit zum optischen Testen von einem prüfenden Element; und
• 8 eine schematische Darstellung eines weiteren Ausführungsbeispiels eines optischen Koppelmoduls.

Examples of the approach presented here are shown in the drawings and explained in more detail in the following description. It shows:

• 1 a schematic representation of an embodiment of an optical coupling module;
• 2 a representation of a further embodiment of an optical coupling module;
• 3 a schematic representation of an embodiment of an optical coupling module now in a side view;
• 4 a flowchart of an embodiment of a method for producing an optical coupling module;
• 5 a flowchart of an embodiment of a method for optically testing a test element;
• 6 a block diagram of an embodiment of a control unit for producing an optical coupling module;
• 7 a block diagram of an embodiment of a control unit for optical testing of a test element; and
• 8 a schematic representation of another embodiment of an optical coupling module.

In the following description of advantageous embodiments of the present invention, the same or similar reference numerals are used for the elements shown in the various figures and having a similar effect, whereby a repeated description of these elements is omitted.

1 shows a schematic representation of an embodiment of an optical coupling module 100. The optical coupling module 100 comprises a module carrier 110, on which a waveguide 120 is arranged at a connection point 115. The waveguide 120 is arranged such that it emerges obliquely from a surface 125 of the module carrier 110 at the connection point 115 and is guided in an arc or as a curved web over the surface 124, so that it contacts the surface 125 again, for example, at an end 130 opposite the connection point 115. The surface 120 can be a main surface facing an element to be tested 135 (DuT = Device under Test). In order to be able to couple optical test signals into the waveguide 120, a module carrier waveguide 140 is formed in the module carrier 110, via which light signals are coupled from a light source 142 as optical test signals 143 to the connection point 115 in the waveguide 120. During a test process of the element 135 to be tested, the 1 For example, the distance shown is significantly reduced because, for a test mode, the optical coupling module 100 is pressed onto the surface of the element 135 to be tested, so that, for example, the waveguide 120 is pressed very close to a coupling region 145, so that by evanescent coupling at least part of the light of the optical test signals from the light guide 120 is coupled into the coupling region 145 and thereby enables a test of optical parameters or properties of the element 135 to be tested.

It is also conceivable that by reflecting part of the light of the optical test signal at the end 130 or by detecting it at a location, it can be detected which portion of the light power has been coupled from the waveguide 120 into the coupling region 145, so that a corresponding evaluation of the quality of the coupling can also be carried out here.

It is also conceivable that, in a return path, light from the coupling region 145 is coupled into the waveguide 120 and, for example, as evaluation signals 147 via the connection point 115, which then acts as an entry point, is coupled into the module carrier waveguide 140 and guided to an evaluation unit 150, which is arranged, for example, in the region of the light source 142. By evaluating the evaluation signals 147, the element 135 to be tested can then, for example, be tested for correct functionality. This can, for example, create a test unit 155 comprising the light source 142, the optical coupling module 100, and the evaluation unit 150.

It is also possible that several of the 1 illustrated waveguides 120 protrude from the module carrier 110 at different positions or protrude obliquely and thus different coupling areas 145 of the element 135 to be tested can be subjected to corresponding optical test signals 143.

The direction z shown can be the direction of gravity. In this case, the DUT is tested upside down. In a first variation of this example, the direction z can be opposite to gravity. In this case, the DUT is tested upside down, i.e., from above. In a second variation of this example, the direction z can be perpendicular to the direction of gravity. In this case, the DUT is tested vertically.

2 shows a representation of a further embodiment of an optical coupling module 100. In contrast to the 1 In the optical coupling module 100 constructed, the waveguide 120 is not stretched in an arc over the surface 125, but has a straight Section 200. In addition, the waveguide 120 is dropped over a spring element 210, which resiliently supports the waveguide 120 in the region of the end 130. If the optical coupling module 100 is now pressed downwards in a test direction 220 for a test mode, so that, for example, the straight section 200 of the waveguide 120 is pressed onto the coupling region 145, the optical test signal 143 can be coupled into a test object waveguide 230 by designing this coupling region 145 as an evanescent coupler, an optical signal coupled back from the coupling region 145 can be coupled back into the waveguide 120 via the coupling region 145, and in this way, an optical function of the element 135 under test can be tested by evaluating a received and retransmitted evaluation signal 147.

3 shows a schematic representation of an embodiment of an optical coupling module 100, now in a side view. Here, it can be seen that the module carrier waveguide 140 has a smaller cross-section than the waveguide 120. In this way, it can be ensured that the light power of the optical test signal 143 from the module carrier waveguide 140 is completely coupled into the waveguide 120 and can thus be emitted as efficiently as possible. For this purpose, the test object waveguide 230 in the coupling region 145 can also have a smaller width than the waveguide 120, so that here too the greatest possible overlap occurs between the test object waveguide 230 and the waveguide 120, thus enabling the most efficient coupling of light from the waveguide 120 into the test object waveguide 230.

An important aspect of the approach presented here can be seen in the fact that an already available UFO probe technology for testing PICs can be extended to systems in which the light is coupled evanescently. For this purpose, an optical coupling module 100 can be modified in such a way that one or more waveguides 120 are led out of the coupling module 100 and, for example, in the form of thin glass structures (thickness in the range of a few µm), guide the light under the coupling module 100, as shown in the 2 is shown. For the contact between the optical coupling module 100 and the element 135 to be tested (DuT), the module 100 is brought so close to the element 135 to be tested (DuT) that these structures or, in this case, the waveguide 120 press against the element 135 to be tested (DuT), thus enabling near-field coupling. Since the structures or, respectively, the waveguide 120 are relatively flexible due to their small size, a certain positional inaccuracy in the z-direction (i.e., axial) can be compensated. The lateral (x, y) position tolerance of the prober system can be compensated via the width of the projected waveguides 120, as shown in the 3 is shown schematically. The coupling efficiency can be adjusted by changing the length of the structures.

The removal of the waveguide(s) 120 from the optical chip as the optical coupling module 100 can be done additively or subtractively: In a first approach, structures for forming the waveguide 120 can be applied to the aforementioned structures or waveguides 120 or the optical chip or module carrier 110 (for example, by 3D printing or deposition). In a second approach, these structures or waveguides 120 can be removed from the glass block as the module carrier 110 of the optical coupling module 100. This is possible, for example, by laser-selective etching.

The structures or waveguides 120 themselves are available in different designs: They can be designed as a curved ridge (for example as shown in 1 ) can be implemented under the optical coupling module 100. This allows signals 143 and 147 to be fed back into the coupling module 100, which, for example, enables feedback measurement (regarding the coupled intensity). The disadvantage of this is that the actual coupling path is difficult to implement due to the bend.

A particularly suitable solution is the realization by a double flexure joint, as in the 2 This ensures that the coupling path between the coupling structure and the evanescent coupler remains constant. This can be achieved by providing the straight section 200 in the waveguide 120, which then enables or ensures a constant distance from the element 135 under test.

The approach presented here allows the UFO probe technology for wave-level tests to be extended to PICs, where the light can be coupled evanescently. Compared to the "classic" UFO, no grating couplers are required on the PICs. Furthermore, a significantly increased coupling efficiency can be expected, since less glare occurs during coupling (i.e., the transmission of the optical test signal 142 from the optical coupling module 100 to the element 135 or DuT under test), and no imaging of the emitted light into a waveguide 120 is necessary during coupling (i.e., the transmission of the evaluation signal 147 from the element 135 or DuT under test to the optical coupling module 100).

4 shows a flow diagram of an embodiment of a method 400 for producing an optical coupling module according to a variant presented here, wherein the method 400 comprises a step 410 of providing a module carrier 100 and a step 420 of forming a waveguide protruding obliquely from the surface of the module carrier at a connection point for outputting optical test signals to an element to be tested.

5 shows a flow diagram of an embodiment of a method 500 for optically testing a test element using a variant of a test unit presented here, wherein the method 500 comprises a step 510 of applying the optical test signal to the element to be tested using the optical coupling module and a step 520 of evaluating a test signal or evaluation signal received from the element to be tested.

6 shows a block diagram of an embodiment of a control unit 600 for producing an optical coupling module according to a variant presented here, wherein the control unit 600 comprises a provision unit 610 for providing a module carrier 100 and a formation unit 620 for forming a waveguide protruding obliquely from the surface of the module carrier at a connection point for outputting optical test signals to an element to be tested.

7 shows a block diagram of an embodiment of a control unit 700 for optically testing a test element using a variant of a test unit presented here, wherein the control unit 700 comprises an application unit for applying the optical test signal to the element to be tested using the optical coupling module and an evaluation unit 720 for evaluating a test signal or evaluation signal received from the element to be tested.

8 shows a schematic representation of another embodiment of an optical coupling module. During the testing process of the element 135 to be tested, in contrast to the 1 In the example shown, the waveguide 120 of the optical coupling module 100 is placed on the surface of the element 135 to be tested, so that the degree of coupling of the evanescent coupling of the optical test signals between the coupling region 145 and the waveguide 120 is optimized. Also in this 8 It can be seen that an offset in the placement of the waveguide 120 relative to the coupling region 145, here in the x direction, is tolerable within a certain tolerance range without impairing the coupling. In the illustration, the apex of the optical waveguide is not exactly in the center of the coupling region 145, but shifted slightly to the left. After the test procedure, the optical coupling module 100 can be lifted in the z direction, for example, to place it over another element 135 to be tested and to lower it for a subsequent test procedure.

Claims (15)

Optical coupling module (100) with the following features: - a module carrier (110) with a surface (125); and - a waveguide (120) protruding obliquely from the surface (125) of the module carrier (110) at a connection point (115) for outputting optical test signals (143) to an element to be tested (135). Optical coupling module (100) according to Claim 1 , in which the waveguide (120) is designed as an optical fiber, and/or wherein a length of the waveguide (120) corresponds to at least five times a width of the waveguide (120) and/or wherein the waveguide (120) is designed as a glass fiber. Optical coupling module (100) according to one of the preceding claims, in which the module carrier (110) and the waveguide (120) are formed in one piece or in which the waveguide (120) is fastened, in particular spliced, soldered or glued, to the module carrier (110) at the connection point (115). Optical coupling module (100) according to one of the preceding claims, wherein the waveguide (120) extends in an arc shape over the surface (125). Optical coupling module (100) according to one of the preceding claims, wherein the waveguide (120) is aligned at least partially parallel to the surface (125) and/or wherein the waveguide (120) is flexibly formed. Optical coupling module (100) according to one of the preceding claims, wherein the waveguide (120) contacts the surface (125) at an end (130) opposite the connection point (115). Optical coupling module (100) according to one of the preceding claims, in which the waveguide (120) has a spring element (210) which is arranged between a region of the connection point (115) and a region opposite the connection point (115) lying end (130) supports the waveguide (120) against the surface (125). Optical coupling module (100) according to one of the preceding claims, wherein a module carrier waveguide (140) is embedded in the module carrier (110), which is designed to guide the optical test signals (143) to the connection point (115) in the waveguide (120), in particular wherein the module carrier waveguide (140) has a smaller width than the waveguide (120). Optical coupling module (100) according to one of the preceding claims, with a further waveguide (120) projecting obliquely from the surface (125) of the module carrier (110) at a further connection point (115) for outputting further optical test signals (143) to the element to be tested (135). A test unit (155) for optically testing an element (135) under test, the test unit (155) having the following features: - an optical coupling module (100) according to one of the preceding claims; and - an analysis unit (142, 150) configured to send an optical test signal (143) through the optical coupling module (100) to the element (135) under test, in particular, wherein the optical test signal is transmittable from the waveguide (120) to the element (135) under test by means of evanescent coupling, and to evaluate a test signal or evaluation signal (147) received from the element (135) under test. Method (400) for producing an optical coupling module (100) according to one of the preceding Claims 1 until 9 , wherein the method (400) comprises the following steps: - providing (410) a module carrier (110), and - forming (420) a waveguide (120) projecting obliquely from the surface (125) of the module carrier (110) at a connection point (115) for outputting optical test signals (143) to an element to be tested (135). Procedure (400) according to Claim 11 , in which in the step (420) of forming, an exposure, in particular an etching-free of the waveguide (120) from a material of the module carrier (110) and/or a formation of the waveguide (120) by means of 3D printing and/or an adhesive bonding of the waveguide (120) at the connection point (115) to the surface (125) of the module carrier (110) takes place. Method (500) for optically testing a test element (135) using a test unit (155) according to Claim 10 , wherein the method (500) comprises the following steps: - applying (510) the optical test signal (143) to the element to be tested (135) using the optical coupling module (100); and - evaluating (520) a test signal or evaluation signal (147) received from the element to be tested (135). Control unit (600, 700) which is arranged to carry out the steps (410, 420; 510, 520) of one of the methods (400; 500) according to one of the preceding Claims 11 until 12 or 13 to be executed and/or controlled in corresponding units (610, 620; 710, 720). Computer program which is designed to carry out the steps (410, 420; 510, 520) of one of the methods (400; 500) according to one of the preceding Claims 11 until 12 or 13 to execute and/or control.