Optical coupling module, fibre-optic measuring or inspection device and method for ensuring reliable transmission of optical signals between a first optical fibre and a second optical fibre

Abstract

A coupling module comprises a first coupling element (3) having a first fibre end (5). The coupling element allows coupling to a second coupling element (9) having a second fibre end (11) in such a way that the second fibre end (11) is in an intended position in relation to the first fibre end (5). Located in a light path (17) between the first fibre end (5) and the second fibre end (11) is an adjustable adjusting device (15), which acts on the light path (17). A detector (19) detects the intensity of the reflection of an optical signal at the second fibre end, and a controller (21) determines on the basis of the intensity of the optical signal an actuating signal for the adjusting device that leads to an optimized intensity of the transmitted optical signal.

Description

[0001] Optical coupling module, fiber optic measuring or testing device and method for ensuring reliable transmission of optical signals between a first optical fiber and a second optical fiber

[0002] The present disclosure relates to an optical coupling module for establishing a coupling between a first fiber end and a second fiber end for the purpose of transmitting optical signals, and furthermore to a fiber-optic measuring or testing device and a method for ensuring reliable transmission of optical signals between a first optical fiber and a second optical fiber.

[0003] The coupling of optical fibers for the purpose of transmitting optical signals is necessary in many technical fields. For example, in the medical field, OCT systems are used, which employ disposable fibers for sterility reasons. Therefore, a new disposable fiber must be coupled to the OCT system for each examination.

[0004] Optical fiber coupling can be achieved with or without physical contact between the fiber ends. Coupling without physical contact is referred to as contactless coupling. In the case of contactless coupling, beam expansion can also be used, which reduces the sensitivity of the contactless coupling to lateral misalignment of the fiber ends relative to each other. Contactless coupling with beam expansion is also known as "expanded beam contact." However, contactless coupling with beam expansion requires very precise angular alignment of the two optical fibers relative to each other. Even very small angular deviations result in a significant loss of signal strength during the transmission of optical signals.In beam-expansion coupling, the fiber end of an optical fiber is therefore arranged in a coupling element that has a precisely shaped reference surface. This surface aligns with the reference surface of the fiber being coupled. To ensure that the optical fiber runs exactly parallel to the surface normal of the reference surface within the coupling element, the end of the optical fiber is fitted with a high-precision sleeve that is located in a high-precision receptacle within the coupling element. However, the manufacture of such a coupling element is complex and expensive, which makes contactless beam-expansion coupling unattractive for use with disposable fibers.While contactless coupling without beam expansion is cost-effective and less sensitive to angular deviations than contactless coupling with beam expansion, even a slight bilateral misalignment of the fibers relative to each other leads to a significant loss of signal strength when transmitting optical signals. Coupling with physical contact is advantageous and results in reliable signal strength when transmitting optical signals, but only if there is no contamination at the fiber ends. Even minor contamination in the fiber end area can lead to a significant loss of signal strength when transmitting optical signals. Therefore, before coupling with physical contact, the fiber ends must be inspected and, if necessary, cleaned, which makes handling coupling with physical contact complex if a reliable signal strength is desired.Unremoved contaminants can damage the fiber end faces, leading to signal loss or even complete signal failure. In particular, damage to the fiber end face of a fiber integrated into an optical device, such as an OCT system, can result in total device failure and significant repair costs. Therefore, a primary objective of the present invention is to provide an optical coupling module for establishing a coupling between a first fiber end of a first optical fiber and a second fiber end of a second optical fiber for the purpose of transmitting optical signals. This module should enable reliable signal transmission, facilitate coupling without significant effort, and be cost-effective.

[0005] A second object of the present invention is to provide a fiber optic measuring or testing device that enables easy coupling of cost-effective optical fibers, whereby the coupling can ensure reliable signal transmission.

[0006] A third object of the present invention is to provide a method for ensuring reliable transmission of optical signals between a first optical fiber with a first fiber end and a second optical fiber with a second fiber end.

[0007] The first problem is solved by an optical coupling module according to the invention, the second problem by a fiber-optic measuring or testing device according to the invention, and the third problem by a method according to the invention for ensuring reliable transmission of optical signals between a first optical fiber with a first fiber end and a second optical fiber with a second fiber end. The dependent claims contain advantageous embodiments of the invention.

[0008] According to the invention, an optical coupling module is provided with a first fiber end of a first optical fiber, which serves to establish a coupling between the first optical fiber and a second optical fiber to be coupled, with a second fiber end, for the purpose of transmitting optical signals between the first optical fiber and the second optical fiber. The optical coupling module comprises:

[0009] A first coupling element, in which the first fiber end is located. The first coupling element is designed such that it enables coupling with a second coupling element present on the second optical fiber to be coupled, in which the second fiber end is located, such that the second fiber end is in a predetermined position relative to the first fiber end. The first coupling element can be designed to be complementary to the second coupling element. For example, it can be designed as a receptacle for the second coupling element, or it can be designed so that it can be inserted into the second coupling element. However, an identical design of the coupling elements with contact surfaces on which they come into mutual contact is also possible.

[0010] A light path exists between the first fiber end and the second fiber end when the second fiber end is in its intended position. The light path can be considered the axis of the beam of light traveling between the first and second fiber ends. The beam of light can be collimated along at least part of the light path, meaning it can travel as parallel beams along at least part of the path, to the extent possible.

[0011] An adjustable device that acts on the path of light to change it. The device can act either on an endpoint of the path of light to change the initial position or direction of the light path emanating from the endpoint, or on another point along the path of light to deflect it.

[0012] A detector for detecting the intensity of an optical signal originating from the second fiber end and transmitted via the optical path to the first fiber end. The detector could be, for example, a simple photodiode. However, a CCD sensor or a CMOS sensor could also be used as a detector.

[0013] A control unit connected to the detector to receive a detection signal representing the detected intensity and to the adjustable adjustment device to output a control signal representing a setting of the adjustable adjustment device. The control unit is designed to determine an optimized control signal based on the received detection signal, which then prompts a setting of the adjustable adjustment device that results in an optimized intensity of the optical signal.

[0014] Due to tolerances in the arrangement of optical fibers within coupling elements and / or tolerances in the shape of the coupling elements, an offset of the second fiber end relative to the first fiber end and / or an angular deviation between the axes of the optical fibers in the region of their fiber ends can occur. This offset and / or angular deviation leads to a loss of signal strength when transmitting optical signals between the coupled fibers. Using the control system and the adjustable positioning device, this offset and / or angular deviation can be actively compensated for, thus mitigating signal loss due to tolerances in the positioning of the fiber ends and achieving optimized signal strength.Since the adjustment mechanism and the control system can be fully integrated into the coupling module, the fiber to be coupled can be equipped with a simple coupling element that does not require high-precision machining, making the fiber to be coupled cost-effective to manufacture. This is particularly advantageous in the case of single-use fibers, such as sterile disposable fibers in the medical field.

[0015] The control unit of the coupling module can be configured, in particular, to output a series of control signals to the adjustable adjustment device, each control signal representing a different value of at least one setting parameter of the adjustable adjustment device in order to bring about a series of different settings of the adjustable adjustment device. In this case, for each setting of the adjustable adjustment device brought about by one of the control signals, the control unit receives the corresponding detection signal from the detector and assigns the intensity represented by the received detector signal to the respective value of at least one setting parameter. The control unit then determines the optimized control signal from the assignment of the intensities to the values ​​of the at least one setting parameter.This makes it possible, for example, to adapt a function to the determined intensities, which describes the intensity as a function of the value of at least one setting parameter, to determine the value of the at least one setting parameter for which the function has a maximum, and to output as the optimized control signal that represents the value of the at least one setting parameter at which the intensity maximum of the function occurs. A gradient ascent method, for example, can be used to find the maximum of the function. In this way, for an intensity maximum that lies between two values ​​of the at least one setting parameter represented by control signals, the value of the setting parameter with which the intensity maximum is achieved can be interpolated.Based on the interpolated value of at least one setting parameter, the control signal suitable for achieving the maximum intensity can then be determined particularly precisely and output to the adjustment device.

[0016] In an advantageous embodiment of the invention, the detector is configured to use the reflection of a signal emanating from the first fiber end at the second fiber end as the optical signal whose intensity is detected. The signal reflected from the second fiber end is easily distinguishable, for example in an OCT system, from a signal that is reflected or scattered by the actual object being measured. This makes it possible, for instance, to compensate for a lateral offset and / or an angular deviation that changes during a measurement with the OCT system by means of a continuously adjusted control signal for the adjustment device.

[0017] In one embodiment of the optical coupling module according to the invention, the first coupling element can comprise a lens associated with the first fiber end. The adjustment device is then configured, for example, to displace the lens in a plane extending perpendicular to its optical axis. For this purpose, the adjustment device can have controllable actuators with which the first lens can be displaced in a plane extending perpendicular to the optical axis of the lens. By displacing the lens, for example, the focal point of the beam represented by the light path can be laterally displaced in the region of the second fiber end. Additionally, the adjustment device can be configured to displace the lens along its optical axis. For this purpose, the adjustment device can have at least one controllable actuator with which the lens can be displaced along its optical axis.This allows, for example, the focal point to be moved along the path of light.

[0018] In one embodiment of the optical coupling module according to the invention, the light path can be folded by means of a reflective element such as a mirror or a prism such that a first light path segment is present at the first fiber end and a second light path segment is present at the second fiber end, wherein the first light path segment forms an angle > 0°, in particular > 10°, and more specifically > 30° with the second light path segment. The axis of the beam present at the respective fiber end can be considered the light path segment. The adjustment device is then configured to rotate the reflective element independently of each other about two non-parallel axes. For this purpose, controllable actuators can be provided with the aid of which the reflective element can be rotated independently of each other about two non-parallel axes.The reflective element can be, for example, a galvanometer mirror or a MEMS mirror (MEMS: microelectromechanical systems). MEMS and galvanometer mirrors can have compact forms and are easy to control.

[0019] In one embodiment of the optical coupling module according to the invention, the adjustment device can be configured to displace the first fiber end in a plane extending perpendicular to the light path. For this purpose, the adjustment device can have controllable actuators with the aid of which the first fiber end can be displaced in a plane extending perpendicular to the light path.

[0020] Even in the case of a light path folded with the aid of a reflective element, or in the case of a fiber end that can be displaced in a plane extending perpendicular to the light path, the first coupling element can comprise a lens associated with the first fiber end, whose optical axis can in particular run parallel to the light path, as well as a displacement device designed to displace the lens along its optical axis.

[0021] The invention also provides a fiber-optic measuring or examination device. This device comprises an internal optical fiber and a coupling module according to the invention for coupling an external measuring or examination fiber to the internal optical fiber. The fiber-optic measuring or examination device can, in particular, be an OCT system or a laser scanning microscope. The use of the coupling module according to the invention enables a simple coupling of cost-effective optical fibers to the fiber-optic measuring or examination device, whereby the coupling ensures reliable signal transmission.

[0022] Furthermore, the invention provides a method for ensuring reliable transmission of optical signals between a first optical fiber with a first fiber end and a second optical fiber with a second fiber end, which is positioned relative to the first fiber end in a predetermined position, along a light path. The method comprises the following steps:

[0023] Detecting the intensity of an optical signal emanating from the second fiber end and transmitted to the first fiber end along the light path, whereby the light path can be influenced to change it by means of an adjustable adjustment device.

[0024] Determining an optimized setting of the adjustable adjustment device leading to an optimized intensity of the optical signal, based on the received detection signal.

[0025] The optical signal whose intensity is detected can, for example, be the reflection of a signal emanating from the first fiber end at the second fiber end. In an OCT system, the signal reflected from the second fiber end is easily distinguishable from a signal reflected or scattered by the actual object being measured. This makes it possible, for instance, to compensate for a changing lateral offset and / or angular deviation during a measurement with the OCT system by means of a continuously adjusted control signal for the adjustment mechanism.

[0026] Due to tolerances in the arrangement of optical fibers in coupling elements and / or tolerances in the shape of the coupling elements, an offset of the second fiber end relative to the first fiber end and / or an angular deviation between the axes of the optical fibers in the region of their fiber ends can occur. An offset and / or an angular deviation leads to a loss of signal strength when transmitting optical signals between the coupled fibers. The optimized setting actively determined by the method according to the invention compensates for an offset and / or an angular deviation and thus ensures optimized signal strength despite the tolerances that occur.To determine the optimized setting, a series of settings of the adjustable adjustment device can be brought about within the framework of the method according to the invention, wherein each setting is characterized by a different value of at least one setting parameter of the adjustable adjustment device, the associated intensity of the optical signal is determined for each brought about setting of the adjustable adjustment device and assigned to the respective value of the at least one setting parameter, and the optimized setting is determined from the assignment of the determined intensities to the respective values ​​of the at least one setting parameter.

[0027] This allows for the determination of an optimized setting, which is not part of the range of settings of the adjustable adjustment device, by means of interpolation based on the settings made and the intensities recorded for them. One possible approach to performing the interpolation is to fit a function to the determined intensities, which describes the intensity as a function of the value of at least one adjustment parameter, to determine the value of the at least one adjustment parameter at which the function exhibits a maximum, and to define as the optimized setting the setting characterized by the value of the at least one adjustment parameter at which the function exhibits a maximum.The value of at least one setting parameter can be determined very precisely, allowing for a highly accurate determination of an interpolated value for that parameter. Based on this interpolated value, the adjustment setting required for the optimized intensity of the optical signal can then be precisely calibrated.

[0028] To find the maximum of the function, a gradient ascent method can be used, for example.

[0029] Further features, properties and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the accompanying figures.

[0030] Figure 1 shows a highly schematic representation of a fiber optic measuring or testing device with an optical coupling module.

[0031] Figure 2 shows a signal as it may be in the case of an OCT system as a fiber optic measuring or examination device.

[0032] Figure 3 shows a first exemplary embodiment of an optical coupling module.

[0033] Figure 4 shows a second exemplary embodiment of an optical coupling module.

[0034] The invention is described below with reference to the accompanying figures using an exemplary embodiment of a fiber optic measuring or testing device with an optical coupling module and using exemplary embodiments of optical coupling modules.

[0035] Figure 1 shows an exemplary embodiment of a fiber optic measuring or testing device 1, which includes an exemplary embodiment of an optical coupling module. The coupling module of the fiber optic measuring or testing device 1 comprises a coupling element 3, hereinafter referred to as the first coupling element, into which a fiber end 5 of an optical fiber 7 is integrated. The fiber end 5 and the optical fiber 7 are hereinafter referred to as the first fiber end 5 and the first optical fiber 7, respectively.

[0036] The first coupling element 3 is designed to be coupled to a second coupling element 9, into which a second fiber end 11 of a second optical fiber 13 is integrated. The second optical fiber 13 is an optical fiber to be coupled to the first optical fiber 7 of the fiber-optic measuring or testing device 1 for the purpose of transmitting optical signals. In the present exemplary embodiment, the first coupling element 3 is designed as a receptacle into which the second coupling element 9, which is designed to be complementary to the first coupling element 3, can be inserted.

[0037] The first coupling element 3 is equipped with a controlled, adjustable adjustment device 15, which allows the optical path 17 between the first fiber end 5 and the second fiber end 11 to be changed. The adjustable adjustment device 15 can be implemented, for example, by at least one adjustable mirror, at least one adjustable lens, or at least one adjustable diffraction grating, etc. However, a device that allows the position of the first fiber end 5, and thus an endpoint of the optical path 17, to be changed is also suitable as an adjustment device 15. In principle, any type of adjustable optical element that can influence the direction of the optical path 17 or the position of one of its endpoints can be used in the adjustable adjustment device 15.

[0038] The fiber optic measuring or testing device 1 comprises a detector 19 with which the signal strength of the signal transmitted from the second optical fiber 13 to the first optical fiber 7, i.e., the intensity of the transmitted signal, can be determined. In the present exemplary embodiment, the fiber optic measuring or testing device 1 is configured as an OCT system. In an OCT system, a signal is split into a reference signal and a measurement signal. The measurement signal, which in this exemplary embodiment consists of polychromatic light, is transmitted via the first optical fiber 7, which is part of the OCT system, to the second optical fiber 13, which is an external optical fiber coupled to the OCT system, and directed onto a sample by means of the second optical fiber 13. The measurement signal is reflected from the sample.The reflected measurement signal is then received by the second optical fiber 13 and transmitted to the OCT system, where it is coupled into the first optical fiber 7. From the first optical fiber 7, it is directed to a detector 19, where the reflected measurement signal is superimposed on the reference signal. Differences in the path lengths traveled by the reflected measurement signal and the reference signal, which in this exemplary embodiment travels a constant optical path length, lead to interference. This interference is constructive if and only if the path length difference between the measurement signal and the reference signal corresponds to the wavelength of the light or a multiple thereof. In the case of polychromatic light, the path length differences between the measurement signal and the reference signal at which constructive interference occurs differ for the individual wavelength components of the light.In this case, the reflected measurement light and the reference light can be split into their components, and the different wavelengths can be directed to different positions on a line detector. Since each wavelength interferes constructively at a different path length difference, the individual wavelengths represent different path lengths of the measurement signal. The intensities detected for the different wavelengths thus represent intensities for reflections from different depths of the sample. A depth profile of the intensities reflected from the sample is therefore displayed on the line sensor. In alternative implementations of the OCT system, monochromatic light can be used instead of polychromatic light. In this case, the depth profile can be created by changing the position of a reflector located in the path of the reference branch, thereby changing the optical path length of the reference signal.By adjusting the reflector, constructive interferences are sequentially induced for measurement light reflected from different depths within the sample. In this way, a depth profile of the intensities reflected from the sample can be created even when using monochromatic light. Besides the aforementioned types of OCT systems, the OCT system can also be configured as a so-called swept-source OCT system in further alternative configurations. In a swept-source OCT system, instead of a polychromatic light source, a light source is used that can be tuned across a specific wavelength range. Typically, the light source is a tunable laser. The tuning of the light source, referred to as a "sweep," can be performed very quickly, so that a "sweep" can be carried out for each scan point of the OCT system.As with the use of a polychromatic light source, each wavelength interferes constructively at a different path length difference, allowing a depth profile of the object at the scan point to be created with a single "sweep".

[0039] The optical coupling module 3 comprises a controller 21, which is connected to the detector 19 for receiving a detection signal. The detection signal represents the intensity detected by the detector 19 of an optical signal emanating from the second fiber end 11 of the second optical fiber 13 and transmitted to the first optical fiber 7. The controller 21 is also connected to the adjustable adjustment device 15 for outputting control signals representing the settings of the adjustable adjustment device 15. The controller 21 includes a control routine that, based on the received detection signal, optimizes the setting of the adjustable adjustment device 15 such that the intensity represented by the detection signal reaches a maximum. It then outputs a control signal to the adjustable adjustment device 15, which represents the setting of the adjustable adjustment device 15 that results in the maximum intensity.With the help of this control signal, the adjustable adjustment device 15 is brought into the setting with which the intensity of an optical signal transmitted from the second fiber end 11 to the first fiber end 5 and thus the transmitted signal strength is maximized.

[0040] In this exemplary embodiment, the optical signal whose intensity is maximized by the control routing is light reflected from the second fiber end 11 of the second optical fiber 13. Such a reflection occurs when the measurement light is transmitted from the first optical fiber 7 to the second optical fiber 13 to direct it to the sample. Using the reflection of the measurement light at the second fiber end 11 offers the advantage that, on the one hand, it provides a higher intensity than measurement light reflected from the sample, and on the other hand, it can be easily distinguished from optical signals that are based on reflection within the sample. This is illustrated in Figure 2, which plots the intensity detected at the detector as a function of the distance from which the measurement light is reflected. An intensity peak 23 can be seen, which is based on a reflection occurring at a relatively small distance.This intensity peak 23 is due to the measurement light reflected at the second fiber end 11. That it is indeed the light reflected at the fiber end 11 can be seen from the fact that the distance from which the signal originates is considerably smaller than the distance between the signals 25 reflected in the sample. The optical signal reflected at the second fiber end 11 of the second optical fiber 7 is therefore particularly well suited for determining the setting of the adjustable adjustment device 15, which enables signal transmission optimized with respect to signal strength.

[0041] The settings of the adjustable adjustment device 15 can each be characterized by the value of at least one setting parameter. In the present exemplary embodiment, the control routine of the controller 21 is designed such that it successively outputs control signals to the adjustable adjustment device 15, which represent different values ​​of the at least one setting parameter. Each different value of the at least one setting parameter leads to a different setting of the adjustable adjustment device 15. For each of these settings of the adjustable adjustment device 15, the control routine then receives a detection signal, which represents the intensity of the signal reflected from the second fiber end 11 achieved with the respective setting.The control routine then assigns each intensity represented by a received detection signal to the value of the at least one setting parameter that resulted in the setting for which the intensity was detected. In other words, the control routine creates a mapping that represents the detected intensity as a function of the value of the at least one setting parameter. The control routine then adapts a parameterized function to this mapping, which represents the intensity as a function of the value of the at least one setting parameter. The adaptation is achieved by optimizing the function's parameters in such a way as to minimize a measure of the deviation of the function values ​​from the measured intensities. The parameterized function can, for example, be a polynomial, in particular an even-order polynomial.After the parameterized function has been adapted to the determined intensity values, the control routine determines at which value of the setting parameter the adapted function reaches its maximum. In this exemplary embodiment, a gradient ascent method is used to find the maximum. Since the adapted function represents the intensity as a function of the value of the at least one setting parameter, the maximum of the adapted function also corresponds to a maximum of the intensity. In the next step, the control routine generates a control signal representing the value of the at least one setting parameter at which the adapted function exhibits its maximum. The controller 21 then outputs this control signal to the adjustable adjustment device 15 to make the adjustment characterized by the value of the at least one setting parameter.This setting ensures optimized signal transmission between the two optical fibers, i.e., transmission in which the intensity of the transmitted signal is maximized and thus signal losses during transmission are minimized.

[0042] Particularly in OCT systems for medical applications, sterile, disposable fibers are frequently used as the second optical fiber 13, making the second optical fiber 13 a disposable product. Therefore, efforts are made to keep the design of the second optical fiber 13 simple in order to produce it cost-effectively. This would not be possible if the second optical fibers had to be manufactured with very tight tolerances. The present invention allows for relatively large tolerances, which then also lead to relatively large tolerances in the positioning of the second fiber end 11 relative to the first fiber end 5. However, by means of the controlled adjustable adjustment device 15 and the control unit 21, the present invention ensures a high signal strength for the transmission of optical signals between the two coupled optical fibers 7, 13, even with relatively large tolerances.The invention achieves this by having the control unit 21, after connecting the second coupling element 9 to the first coupling element 3, execute the described method to determine and then adjust an optimized setting for the controlled adjustable adjustment device 15. A high signal strength is then ensured. Achieving the optimized setting can be triggered manually by entering a keyboard command, a voice command, etc. However, it is also possible to trigger the optimized setting automatically. For this purpose, a sensor can be arranged in the first coupling element 3 that detects the presence of a second coupling element 9 and automatically starts the optimization of the setting upon detection of a second coupling element 9.Furthermore, it is possible to re-optimize the signal strength at regular intervals during a measurement carried out with the fiber optic measurement or investigation system 1, or to monitor and re-optimize the signal strength of the signal received from the first optical fiber 7 if a drop in signal strength is detected that exceeds a predetermined limit.

[0043] Another exemplary embodiment of an optical coupling module, which can be used in the fiber optic measuring or testing device from Figure 1 instead of the coupling module described with reference to Figure 1, is shown in Figure 3. This fiber optic coupling module comprises a first coupling element 103 in which a first fiber end 105 of a first optical fiber 107 is arranged. The first optical coupling element 103 has a receiving section 112 into which a second coupling element 109 can be inserted. In the second coupling element 113, a second fiber end 111 of a second optical fiber 113, which is to be coupled to the first optical fiber 107, is arranged. Furthermore, a converging lens 114 is provided in the second coupling element 109, with which a parallel beam of light is focused onto the second fiber end 111.A divergent beam of light emanating from the second fiber end 111 is transformed into a collimated beam of light, i.e., a beam with parallel light rays. The first coupling element 103 also contains a converging lens 116, which focuses a parallel beam of light onto the first fiber end 105 or transforms a divergent beam of light emanating from the first fiber end 105 into a collimated beam. Thus, a largely collimated beam of light propagates along the light path 117 between these two converging lenses 114 and 116. Between the lenses and the respective fiber ends, however, the beam of light is divergent or convergent.

[0044] In the present exemplary embodiment, the first coupling element is designed such that the longitudinal axis of the second optical fiber 113 runs at an angle of 90° to the longitudinal axis of the first optical fiber 107 in the region of the first fiber end 105 when the second coupling element 109 is folded by 90° into the receptacle 112 of the first coupling element by means of a deflecting mirror 115 or another suitable reflective element. In this way, a beam exiting one of the two fiber ends would enter the other fiber end precisely if the fiber ends could be positioned relative to each other without tolerance. However, due to tolerances, a tilting of the longitudinal axes relative to each other can occur in the region of the fiber ends of the two optical fibers 107 and 113.Furthermore, a lateral displacement relative to the intended position of the fiber end can occur. Both of these factors lead to a reduction in the signal strength of the transmitted signal.

[0045] To ensure optimized signal strength, the deflection mirror 115 arranged in the first coupling element 103 is rotatably mounted about two axes that are not parallel to each other, preferably about two axes that are perpendicular to each other. A controlled rotation of the deflection mirror 115 about one or both axes can be effected by means of one or more actuators 120. A rotatable deflection mirror can, for example, be implemented in the form of a galvanometer mirror or a MEMS mirror. The deflection mirror 115 is controlled by a controller (not shown in Figure 3) that essentially corresponds to the controller from the exemplary embodiment described with reference to Figure 1. The at least one setting parameter is the rotational position of the deflection mirror 115, and the value of the at least one setting parameter is the angle of rotation.Typically, in this example, at least two setting parameters are available, namely the two rotation angles, and thus at least two values ​​are available, namely the angle values ​​of the two rotation angles. The controller then determines optimized angle values ​​of the two rotation angles as the optimized values ​​of the setting parameters. The at least one actuator 120 thus forms an adjustment device with the aid of which the deflection mirror 115 can act on the light path 117 in such a way that the signal strength is optimized during the transmission of optical signals between the two optical fibers 107, 113.

[0046] In addition to the rotatably mounted deflecting mirror 115, the lens 116 arranged in the first coupling element 103 can be designed to be displaceable along the light path 117. This allows tolerances in the longitudinal positioning of the optical fibers 107 and 113 relative to each other, which can, for example, lead to insufficient focus at one fiber end, to be compensated for. The optimization is then performed by the control system not only to determine an optimized rotational position, but also to determine an optimized combination of the rotational position of the deflecting mirror 115 and the displacement of the lens 116. The previously described function of the intensity as a function of at least one setting parameter is then a function that depends on at least two setting parameters, namely the rotational angle of the deflecting mirror 115 and the displacement position of the lens 116.In the general case, it will even depend on three setting parameters, namely two rotation angles of the deflecting mirror 115 and the displacement position of the lens 116.

[0047] Another exemplary embodiment of an optical coupling module, which can be used in the fiber optic measuring or testing device from Figure 1 instead of the coupling module described with reference to Figure 1, is shown in Figure 4. In this exemplary embodiment, the first coupling element 203 and the second coupling element 209 each have a planar surface 204, 210 as buttress surfaces at which the coupling elements 203, 209 abut each other during coupling. The second

[0048] Coupling element 209, which is arranged, for example, on a single-use fiber, has a flange 212 on which suitable fastening means are provided for holding the second coupling element 209 in a defined position relative to the first coupling element 203, such that the second fiber end 211 of the second optical fiber 213 is in a designated position relative to the first fiber end 205 of the first optical fiber 207. Suitable fastening means include, for example, screws 215 arranged in the flange 212, which can be screwed into threads 218 embedded in the wall of the first coupling element 203. Alternatively, clamping springs arranged on the first coupling element 203, which can engage the flange 212 and press the second coupling element 209 against the first coupling element, are also suitable.To ensure lateral fixation, such clamping springs should be present at at least three locations distributed around the circumference of the coupling elements 203, 209. Alternatively, a locking nut can be provided, for example, on the second coupling element 209, which can be screwed onto a thread on the first coupling element 203, thereby pressing the flange 212 against the flat surface 204.

[0049] As in the exemplary embodiment shown in Figure 3, the exemplary embodiment shown in Figure 4 also includes a converging lens 214, 216 in both the first coupling element 203 and the second coupling element 203. These lenses focus a collimated beam of light onto the respective fiber end 205, 211, or convert a divergent beam of light emanating from the respective fiber end 205, 211 into a collimated beam. In this exemplary embodiment, the two lenses 214, 216 are achromatic lenses, each composed of two lenses linked together.

[0050] In contrast to the exemplary embodiment shown in Figure 3, the light path 217 in the present exemplary embodiment is not folded. To compensate for lateral misalignments of the lateral positions of the fiber ends 205, 211 of the two optical fibers 207, 213, the lens 216 arranged in the first coupling element 203 is mounted in a lens holder 220, which can be moved in two non-parallel directions, in particular in two mutually perpendicular directions, by means of actuators 222, for example, by means of piezoelectric elements. The actuators 222, with which a displacement in the x-direction of the coordinate system shown in Figure 4 is possible, can be seen in the figure. Those actuators that can bring about a displacement in the y-direction, on the other hand, are not shown. Furthermore, the lens 216 can be arranged to be displaceable along the z-direction.This can be achieved, for example, by dividing the lens holder 220 into a first part facing the lens 216 and a second part facing the actuators 222, with the two parts of the lens holder 220 being displaceable relative to each other along the optical axis of the lens 216. In this way, the lens 216 can be moved back and forth along its optical axis. This back-and-forth movement can be accomplished, for example, by means of piezoelectric elements arranged between the two parts of the lens holder 220, forming a stepping motor or an inchworm motor. Misalignments of the lateral positions of the fiber ends 205, 211 of the two optical fibers 207, 213 can be compensated for by means of displacement within the xy-plane. Misalignments along the light path 217, on the other hand, can be compensated for by displacement in the z-direction.In the present embodiment, the movable lens holder 220 thus forms the controlled, adjustable adjustment device, which can be set to achieve an optimized intensity of the optical signal. The parameters for which the control unit (not shown in Figure 4) determines optimized values ​​in order to optimize the signal strength represent the positions of the lens 216 in the xy-plane and, if a displacement along the z-direction is possible, the position of the lens 216 in the z-direction. The positions in the xy-plane can be specified in the form of x and y coordinates. However, it is also possible to specify the position in the form of polar coordinates, i.e., in the form of an angle and a radius. Otherwise, the procedure of the control routine corresponds to the procedures described with reference to the first exemplary embodiment.The present invention has been described in detail using exemplary embodiments for illustrative purposes. However, a person skilled in the art will recognize that they can deviate from the described details without departing from the subject matter of the invention. For example, in the exemplary embodiments, the coupling module was depicted as part of a fiber-optic measuring or testing instrument. This is not strictly necessary, however. In alternative embodiments of the invention, the coupling module can also be integrated into any other device in which optical fibers are coupled. In further alternative embodiments of the coupling module, the control unit can be integrated into the first coupling element. The control unit can, for example, be implemented in the form of a microchip on which the control routine is implemented. Such microchips are space-saving and can be integrated into the first coupling element without significant effort.To detect the intensity of the transmitted signal, the first coupling element can also include a detector. If this detector is designed as a photodiode, it can be implemented very compactly. A branch in the first optical fiber allows a portion of the signal received by the first optical fiber to be diverted towards the detector, generating a detection signal representing the intensity of the received signal. In particular, when the goal is to detect the reflection at the fiber end of the coupled fiber, which produces a strong signal, it is sufficient to divert a small portion of the signal so that the signal strength is not significantly affected by the branch. In this case, the coupling module can function as a standalone device.It is advantageous if a sensor is also integrated into the first coupling element, which detects the presence of a second coupling element coupled to the first coupling element and automatically performs the optimization upon detection of the second coupling element. Due to the possibility of deviations from the exemplary embodiment, the present invention is not to be limited by details of the exemplary embodiment, but only by the appended claims. List of reference numerals.

[0051] I fiber optic measuring or testing device

[0052] 3 first coupling element

[0053] 5 first fiber end

[0054] 7 first optical fiber

[0055] 9 second coupling element

[0056] II second fiber end

[0057] 13 second optical fiber

[0058] 15 Adjustment device

[0059] 17 Light Path

[0060] 19 Detector

[0061] 21 Control

[0062] 23 peak intensity

[0063] 25 Measurement signal

[0064] 103 first coupling element

[0065] 105 first fiber end

[0066] 107 first optical fiber

[0067] 109 second coupling element

[0068] III second fiber end

[0069] 112 Recording section

[0070] 113 second optical fiber

[0071] 114 lens

[0072] 115 Adjustment device

[0073] 116 lens

[0074] 117 Light Path

[0075] 117A Light Path Section

[0076] 117B Light Path Section

[0077] 120 actuator

[0078] 203 first coupling element

[0079] 204 Plan area

[0080] 205 first fiber end

[0081] 207 first optical fiber 209 second coupling element

[0082] 210 plan area

[0083] 211 second fiber end

[0084] 212 Flange 213 Second optical fiber

[0085] 214 lens

[0086] 215 Write

[0087] 216 lens

[0088] 217 Light path 218 Thread

[0089] 220 lens mount

[0090] 222 Actuator

[0091] Axis 1

[0092] A2 Axis 2

Claims

Patent claims 1. Optical coupling module with a first fiber end (5, 105, 205) of a first optical fiber (7, 107, 207), which serves to establish a coupling between the first optical fiber (7, 107, 207) and a second optical fiber (13, 113, 213) to be coupled with a second fiber end (11, 111, 211) for the purpose of transmitting optical signals between the first optical fiber (7, 107, 207) and the second optical fiber (13, 113, 213), wherein the optical coupling module comprises: a first coupling element (3, 103, 203) in which the first fiber end (5, 105, 205) is located and which couples with a second coupling element present on the second optical fiber (13, 113, 213) to be coupled. (9, 109, 209), in which the second fiber end is located (11, 111, 211), such that the second fiber end (11, 111, 211) is in a designated position relative to the first fiber end (5, 105, 205), a light path (167, 117,217) between the first fiber end (5, 105, 205) and the second fiber end (11, 111, 211), when the second fiber end (11, 111, 211) is in the intended position, a controlled adjustable adjustment device 815, 115, 216 acting on the light path (17, 117, 217) to change it, a detector (19) for detecting the intensity of an optical signal emanating from the second fiber end (11, 111, 211) and transmitted via the light path (17, 117, 217) to the first fiber end (5, 105, 205), and a control unit (21) connected to the detector (19) for receiving a detection signal representing the detected intensity and with the adjustable The adjusting device (15, 120, 220) is connected to output a control signal representing a setting of the adjustable adjusting device (15, 120, 220), wherein the control (21) is designed toBased on the received detection signal, an optimized control signal is generated. determine which causes an adjustment of the adjustable adjustment device (15, 120, 220) that leads to an optimized intensity of the optical signal, characterized in that the detector (19) is designed to use as the optical signal whose intensity is detected the reflection of a signal emanating from the first fiber end (5, 105, 205) at the second fiber end (11, 111, 211).

2. Optical coupling module according to claim 1, in which the control unit (21) is configured to output a series of control signals to the adjustable adjustment device (15, 120, 220), wherein each control signal represents a different value of at least one setting parameter of the adjustable adjustment device (15, 120, 220) in order to bring about a series of settings of the adjustable adjustment device (15, 120, 220), to receive the corresponding detection signal from the detector (19) for each setting of the adjustable adjustment device (15, 120, 220) brought about by one of the control signals, and to assign the intensity represented by the received detector signal to the respective value of at least one setting parameter, and to determine the optimized control signal from the assignment of the intensities to the values ​​of the at least one setting parameter.

3. Optical coupling module according to claim 2, in which the control is configured to adapt a function to the determined intensities, which describes the intensity as a function of the value of at least one setting parameter, to determine the value of at least one setting parameter for the adapted function at which a maximum of the function exists, and to output as the optimized control signal that control signal which represents the value of at least one setting parameter at which the maximum of the function exists.

4. Optical coupling module according to one of claims 1 to 3, in which the first coupling element (3, 103, 203) comprises a lens (116, 216) associated with the first fiber end (5, 105, 205) and the adjustment device (220) is configured to displace the lens (116, 216) in a plane extending perpendicular to its optical axis.

5. Optical coupling module according to claim 4, in which the adjustment device (220) is further configured to displace the lens (216) along its optical axis.

6. Optical coupling module according to one of claims 1 to 3, in which the light path (117) is folded by means of a reflective element (115) such that a first light path section (117A) is present at the first fiber end (105) and a second light path section (117B) is present at the second fiber end (111), wherein the first light path section (117A) forms an angle > 0° with the second light path section (117B) and the adjustment device (120) is configured to rotate the reflective element (115) independently of each other about two axes that are not parallel to each other.

7. Optical coupling module according to one of claims 1 to 3, in which the adjustment device is configured to displace the first fiber end in a plane extending perpendicular to the light path.

8. Optical coupling module according to claim 6 or claim 7, in which the first coupling element (203) comprises a lens (206) associated with the first fiber end and a displacement device (220) is provided which is configured to displace the lens (206) along its optical axis.

9. Fiber optic measuring or testing device (1 ) with an internal first optical fiber (7) and a coupling module according to one of claims 1 to 8 for coupling a second external fiber (13) as a measuring or testing fiber to the first internal optical fiber (7).

10. Method for ensuring reliable transmission of optical signals between a first optical fiber (7, 107, 207) with a first fiber end (5, 105, 205) and a second optical fiber (13, 113, 213) with a second fiber end (11, 111, 211) which is positioned relative to the first fiber end (5, 105, 205) in a provided position, along a light path (17, 117, 217), comprising the steps: Detecting the intensity of an optical signal originating from the second fiber end (11, 111, 211) and transmitted to the first fiber end (5, 105, 205) along the light path (17, 117, 217), wherein the light path (17, 117, 217) can be influenced to change it by means of an adjustable adjustment device (15, 120, 220), Determining an optimized setting of the adjustable adjustment device (15, 120, 220) leading to an optimized intensity of the optical signal on the basis of the received detection signal, characterized in that the optical signal whose intensity is detected is the reflection of a signal emanating from the first fiber end (5, 105, 205) at the second fiber end (11, 111, 211).

11. Method according to claim 10, in which a series of settings of the adjustable adjustment device is brought about, wherein each setting is characterized by a different value of at least one setting parameter of the adjustable adjustment device, for each brought about setting of the adjustable adjustment device the associated intensity of the optical signal is determined and assigned to the respective value of the at least one setting parameter, and the optimized setting is determined from the assignment of the determined intensities to the respective values ​​of the at least one setting parameter.

12. Method according to claim 11, in which a function is adapted to the determined intensities which describes the intensity as a function of the value of the at least one setting parameter, for the adapted function the value of the at least one setting parameter at which a maximum of the function is present is determined, and the setting characterized by the value of the at least one setting parameter at which the maximum of the function is present is defined as the optimized setting.

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