Light guide cable with cladding light sensor and associated adjustment, inspection and monitoring device

Abstract

The invention relates to a light guide cable (1), comprising an optical fiber (2), which has an optical fiber core (3) and an optical fiber cladding (4), and an outcoupling plug (6), which is arranged at an outcoupling-side optical fiber end (2b) of the optical fiber (2), comprising at least one cladding light sensor (8), which is arranged behind the outcoupling-side optical fiber end (2b), the device is used for measuring cladding light (9) which exits from the end face of the fiber cladding (4) at the coupling-out side fiber end (2b).

Description

[0001] This is a divisional application of patent application No. 201980043210.X, filed on June 6, 2019, with the title "Optical fiber cable with cladding light sensor and associated calibration, inspection and monitoring devices". TECHNICAL FIELD

[0002] The present invention relates to an optical fiber cable, for example a laser optical fiber cable, having an optical fiber with an optical fiber core and an optical fiber cladding and a coupling-out plug at a coupling-out side optical fiber end of the optical fiber, and to associated calibration, inspection and monitoring devices. BACKGROUND

[0003] An optical fiber cable of this kind is known, for example, from WO 2013 / 095272 A1 and EP 2 805 790 A1.

[0004] The main objective of the transmission of laser light through an optical waveguide is to transmit the radiation as well as possible with low losses. Decisive here is the coupling-in of the laser power into the optical waveguide as well as possible in order to transmit as much radiation component as possible through the optical waveguide. Also decisive is the focal surface which the beam to be coupled in has on the coupling-in plane. The radiation distribution is often a Gaussian distribution, so not all edge beams can be coupled in into the optical fiber core. These edge components are located in the coupling-in plane outside the optical fiber core diameter used, so these components are coupled in into the optical fiber cladding surrounding the optical fiber core. These radiation components are mostly coupled out by a mode stripper in the coupling-in plug and the coupling-out plug. The remaining radiation components are guided through the optical waveguide in the cladding with a larger divergence angle and exit at the end of the optical waveguide with the same manner with a larger divergence angle. In order to achieve a good, efficient fiber coupling, the components remain in the cladding as little as possible.

[0005] It is known that immediately after the coupling-in plane, the radiation components coupled in into the cladding are coupled out of the cladding on the cladding side or in the radial direction by means of a mode stripper and are detected by means of a photodiode. However, in the case of a calibration laser optical fiber cable, the photodiode can only be placed immediately adjacent to the mode stripper, because the coupled-out power must be cooled in this area.

[0006] The WO 2013 / 095272 A1 mentioned at the beginning discloses an output plug with a sensor for measuring laser light reflected from a machining point back into the optical fiber cladding and then exiting in the radial direction from the optical fiber cladding in order to control the machining process.

[0007] Also mentioned at the beginning, EP2805790A1 discloses an output plug with a sensor for measuring laser light emitted from the fiber cladding in the radial direction, thereby controlling the laser power.

[0008] According to WO2017 / 139630A1, a separate measuring device connected to an optical fiber is also known. This measuring device has an aperture and a detector for measuring the light scattered at that aperture. The measurement signal is used as a calibration signal for the coupling input. Summary of the Invention

[0009] The objective of this invention is to optimize the type of optical fiber cable mentioned at the outset in terms of calibration, inspection, and monitoring measures. Furthermore, the objective of this invention is to describe the corresponding calibration, inspection, and monitoring equipment.

[0010] According to the present invention, this task is solved by having a coupling output plug having at least one cladding optical sensor disposed behind the end of the coupling output optical fiber, the cladding optical sensor being used to measure cladding light emitted from the fiber cladding at the end face of the coupling output optical fiber.

[0011] According to the present invention, the coupling output plug has an integrated cladding light sensor for measuring the cladding light emitted from the end face, thus eliminating the need for a separate measuring device and enabling measurements to be performed at any time, especially during continuous operation. The sensor signal thus obtained can be used, for example, as a reference for the optical cable itself, or for coaxial alignment of the coupling input optics relative to the fiber core.

[0012] Preferably, the coupling output plug has a deflection optics, particularly a reflective aperture (far-field aperture), disposed between the end of the optical fiber on the coupling output side and the cladding optical sensor. This deflection optics deflects at least a portion of the emitted cladding light onto at least one cladding optical sensor. On the emission side of the optical cable, the reflective aperture deflects the edge portion of the coupled-input laser radiation guided in the fiber cladding, and said edge portion is detected by means of a cladding optical sensor (photodiode).

[0013] Particularly preferably, the optical fiber cable—especially the coupling output connector and / or the coupling input connector located at the end of the optical fiber on the coupling input side—has a data storage device for storing cable-specific data. Here, the data may be, for example, reference data of the optical fiber cable in a good / new condition, or data measured at a predetermined power value after a defined radiation duration. The stored data enables determinations such as whether the optical fiber cable can be used, and whether continuous, dynamic monitoring / inspection of the optical fiber cable is necessary during continuous operation.

[0014] Furthermore, the coupling output plug may have at least one scattered light sensor for measuring scattered light scattered on the fiber end face of the coupling output side or on other components of the coupling output plug, and / or, the coupling input plug located at the fiber end face of the coupling input side may have at least one scattered light sensor for measuring scattered light scattered on the fiber end face of the coupling input side. Scattered light measurement does not require a separate measuring device and can be performed at any time, especially during continuous operation.

[0015] The present invention also relates to a calibration device comprising: an optical fiber cable having an optical fiber core and an optical fiber cladding; at least one cladding photosensor disposed behind the end of the coupled output-side optical fiber for measuring cladding light emitted from the optical fiber cladding at the end face of the coupled output-side optical fiber end; means for moving the coupled input-side optical fiber end and / or a coupled input optics relative to each other in a direction perpendicular to the optical fiber axis according to a sensor signal from the at least one cladding photosensor, the coupled input optics being disposed in front of the coupled input-side optical fiber end for coupling light into the optical fiber core. The coupled input optics may be mounted either on the laser optical fiber cable itself or be a separately fixed component.

[0016] According to the present invention, fiber coupling can be optimized very sensitively by minimizing cladding light, and the coupled input optics can be tuned to minimize divergence and loss.

[0017] Preferably, the at least one cladding optical sensor is disposed on the coupling output plug of the optical fiber or on a laser processing head in which the coupling output plug is inserted. In the first case, the cladding optical sensor is integrated into the coupling output plug, thereby enabling the measurement and associated simple calibration of the fiber coupling in the optical cable without the need for additional measurement equipment or measurement analysis processing. Therefore, the calibration can be checked at any time and optimized as necessary. Alternatively, a closed-loop adjustment circuit can be used, whereby the fiber coupling input can be readjusted to maintain its optimal state by actively adjusting according to the cladding optical signal.

[0018] The present invention also relates to an inspection device comprising: an optical fiber cable having an optical fiber core and an optical fiber cladding; at least one cladding photosensor disposed behind the end of the optical fiber on the coupling output side, for measuring cladding light emitted from the optical fiber cladding at the end face of the optical fiber on the coupling output side; and an analysis processing apparatus for analyzing and processing the sensor signal of the cladding photosensor. Particularly preferably, the optical fiber cable has a data storage unit and at least one scattered light sensor, the data storage unit storing cable-specific data of the analysis processing unit, and the scattered light sensor measuring scattered light scattered at the end face of the optical fiber.

[0019] A key advantage of the inspection device according to the invention is that a detailed inspection of the optical cable is performed when it is first used on the laser device. The determination of whether the optical cable can be used on the laser device can be undertaken and executed independently and automatically. Furthermore, during continuous operation, continuous and dynamic monitoring / inspection can be performed based on the initial condition. When the optical cable is first connected / inserted, the laser device recognizes the new optical cable and requests a reference. Here, the optical cable is checked for necessary parameters through self-testing; if the limit values ​​are met, operation is permitted. Inspection can also be performed during continuous operation.

[0020] When first deploying an optical fiber cable on a laser device, several steps must be taken to ensure the most efficient and low-loss transmission of laser radiation through the cable. First, the optical fiber cable is assigned to the appropriate optical path of the laser device's beam steering mechanism. Then, the fiber coupling is checked, i.e., the alignment of the coupling input optics relative to the fiber core. For this, the cladding light in the coupling output connector and the scattered light in the coupling input can be used as a standard. If the cladding and scattered light are within device-specific limits stored within the laser device itself, reference can begin. The purpose of reference is to determine the cladding / scattered light reference values ​​in the optical fiber cable, which can be used for subsequent signal monitoring. These reference values ​​must be determined in good / new condition without any material processing. After a defined beam duration and at a predetermined power value, the signal is stored in the optical fiber cable's integrated data memory. However, this is only done if the detected signal is within predetermined limits also stored in the laser device.

[0021] The present invention also relates to a monitoring device comprising: an optical fiber cable having an optical fiber core and an optical fiber cladding; at least one cladding photosensor disposed behind the end of the coupled output-side optical fiber for measuring cladding light emitted from the optical fiber cladding at the end face of the coupled output-side optical fiber; at least one optical element (e.g., a protective glass) located in the beam path of the light emitted from the optical fiber core at the end face of the coupled output-side optical fiber; at least one scattered light sensor for measuring scattered light scattered on the at least one optical element; and an analysis processing apparatus for analyzing and processing the sensor signals of the cladding photosensor and the scattered light sensor. Advantageously, two optical elements, such as two protective glasses, are arranged sequentially in the beam path of the light emitted from the optical fiber core at the end face of the coupled output-side optical fiber, wherein each of the protective glasses is assigned a scattered light sensor.

[0022] If scattered light sensors are also used to monitor optical components in optical cables—for example, to monitor scattered light on protective glass or fiber end faces—contamination and damage can be identified early. Reflected laser or process radiation can also be detected using a suitable arrangement of optical components and at least one scattered light sensor. By using multiple scattered light sensors, contamination of optical components can be distinguished from reflected laser / process radiation, allowing contamination of optical components to be identified even during processing despite reflected laser / process radiation. Furthermore, it is possible to perform inspection quickly and easily, for example, during brief intervals between two processing runs, without processing. Here, the time required for changing processed parts can be used to transport the optical cable with processed optics to a designated location where the cladding light value and scattered light value in the unprocessed state can be inspected relative to the original values ​​(reference values) in a good / new state, using the same method as for the reference. If the sensor signal changes compared to the start (reference value), the operator can be informed of operational recommendations regarding laser control early, thus preventing unexpected downtime. The replacement of optical components, such as protective glass, can also be signaled early, allowing for planning.

[0023] Each sensor is assigned a reference value recorded during operation without processing. Subsequently, if the measured value deviates significantly from the corresponding reference value, the analysis and processing unit detects this and shuts down the laser equipment. If only one measured value deviates, this can be used for error determination. This allows it to determine whether the deviation is caused by process radiation, contamination of the protective glass, or misalignment of the fiber-optic coupling input.

[0024] Preferably, the optical fiber's coupling output plug has at least one cladding optical sensor, and the laser processing head into which the coupling output plug is inserted has at least one optical element.

[0025] Finally, the present invention also relates to a method for monitoring an optical fiber cable in continuous operation, the optical fiber cable having an optical fiber core and an optical fiber cladding, the method comprising the following steps: The cladding light emitted from the fiber cladding at the end face of the fiber at the coupling output side is measured. The scattered light scattered at least one optical element is measured, said optical element being arranged at the end face of the coupled output side optical fiber in the beam path of the light emitted from the fiber core, and The measured cladding light and scattered light are analyzed and processed.

[0026] If the measured value deviates too much from the pre-given reference value, the analysis process will identify this and shut down the laser.

[0027] Preferably, the scattered light scattered on the fiber end face of the optical fiber or on other components is also measured and analyzed together with the measured cladding light and scattered light. Attached Figure Description

[0028] Other advantages and advantageous configurations of the subject matter of this invention are apparent from the specification, claims, and drawings. Similarly, the features mentioned above and further enumerated can each be used individually or in any combination in multiple forms. The illustrated and described embodiments should not be construed as exhaustive, but rather as having exemplary features relevant to the narrative of this invention. The drawings show: Figure 1 A laser optical guide cable with a cladding optical sensor according to the present invention is shown; Figure 2 A calibration apparatus having a laser optical guide cable according to the present invention is shown; Figure 3 An inspection apparatus having a laser optical guide cable according to the invention is shown; and Figure 4 A monitoring device having a laser optical guide cable according to the present invention is shown. Detailed Implementation

[0029] Figure 1 The laser optical fiber cable 1 shown includes an optical fiber 2, a coupling input plug 5, and a coupling output plug 6. The optical fiber has an optical fiber core 3 and an optical fiber cladding 4 surrounding the optical fiber core 3. The coupling input plug is located at the coupling input side optical fiber end 2a of the optical fiber 2, and the coupling output plug is located at the coupling output side optical fiber end 2b. The laser 7 is coupled into the optical fiber core 3 at the coupling input side optical fiber end 2a and coupled out from the optical fiber core 3 at the coupling output side optical fiber end 2b.

[0030] The coupling output connector 6 has a cladding optical sensor (e.g., a photodiode) 8 disposed behind the fiber end 2b on the coupling output side. This cladding optical sensor measures the cladding light 9 emitted from the fiber cladding 4 at the end face of the fiber end 2b on the coupling output side. Between the fiber end 2b on the coupling output side and the cladding optical sensor 8, a deflecting optics device 10, for example configured as a reflective far-field aperture, is present in the coupling output connector 6. This deflecting optics device deflects a portion of the emitted cladding light 9 onto the cladding optical sensor 8.

[0031] The coupling output connector 6 may optionally include a scattered light sensor 11 for measuring reflected laser light and process radiation 12 generated at the processing location, which fall in opposite directions onto the fiber end face of the coupling output side and are scattered there (scattered light 13), or fall directly onto the scattered light sensor 11. Correspondingly, the coupling input connector 5 may also optionally include a scattered light sensor 14 for measuring laser light 7 scattered at the fiber end face of the coupling input side (scattered light 15). Furthermore, a data memory 16 may optionally be provided in the coupling input connector 5 or the coupling output connector 6 to store the measurement data provided by the cladding light sensor and the scattered light sensors 8, 11, 14 as cable-specific data. The two connectors 5, 6 may be electrically connected to each other via wiring not shown here so that the sensor data of one connector is stored in the data memory 16 of the other connector.

[0032] Figure 2 The calibration device 20 shown includes a laser optical cable 1 and a device 22: the laser optical cable has a coupling input plug 5 and a coupling output plug 6; the coupling input plug has a coupling input optics (coupling input lens) 21 arranged in front of the fiber end 2a on the coupling input side for coupling laser 7 into the fiber core 3; the coupling output plug has a cladding optical sensor 8; the device is used to move the coupling input lens 21 perpendicularly to the fiber axis A in the direction of the double arrow 23 relative to the coupling input plug 5. To calibrate the coupling input lens 21, laser 7 is coupled into the fiber core 3 through the coupling input lens 21, and the resulting cladding light 9 is measured using the cladding optical sensor 8. The coupling input lens 21 is moved according to the sensor signal of the cladding optical sensor 8 until the cladding light 9 is minimized. The coupling input lens 21 is then adjusted to minimize divergence and loss. Alternatively, a closed-loop adjustment circuit can be used, whereby the fiber coupling input can be readjusted to maintain its optimal state by actively adjusting according to the sensor signal of the cladding optical sensor 8. Alternatively, the cladding optical sensor 8 can be arranged on the laser processing head 41 into which the coupling output plug 6 is inserted. Figure 4 Instead of being arranged in the coupling output plug 6 as shown, it is located in the coupling output plug 6.

[0033] Figure 3 The inspection device 30 shown includes a laser optical cable 1 and an external analysis and processing device 31: the optical cable has a coupling input plug 5 with a coupling input lens 21, a scattered light sensor 14, a data storage 16, and a coupling output plug 6 with a cladding light sensor 8; the analysis and processing device analyzes and processes the sensor signals of the cladding light sensor and the scattered light sensors 8 and 14, and stores the sensor signals as cable-specific data in the data storage 16 of the coupling input plug 5.

[0034] When the laser fiber optic cable 1 is first put into operation on the laser device (laser beam generator) 32, several actions must be performed sequentially to ensure that the transmission of the laser 7 through the laser fiber optic cable 1 is as efficient and loss-free as possible. First, the laser fiber optic cable 1 is assigned to the corresponding optical path of the beam guiding device of the laser device 32, thereby connecting the cladding light sensor and scattered light sensor 8, 14, and the data storage 16 to the analysis and processing unit 31 associated with the laser device 32. Then, the fiber coupling, i.e., the correct alignment of the coupling input lens 21 relative to the fiber core 3, is checked. For this purpose, the cladding light 9 in the coupling output plug 6 and the scattered light 15 in the coupling input can be used as a standard. If the cladding light and scattered light 9, 15 are within device-type-specific limit values ​​stored in the analysis and processing unit 31 of the laser device 32, reference can begin. The purpose of the reference is to obtain the cladding light / scattered light value, based on which subsequent signal monitoring can be performed. The reference value must be obtained in good / new condition and without any material processing. After a defined beam duration, at a predetermined power value, the sensor measurements from the analysis and processing unit 31 are stored in the integrated data memory 16. However, this only occurs if the detected signal is within a predetermined limit value also stored in the analysis and processing unit 31.

[0035] Figure 4 The monitoring device 40 shown includes a laser optical cable 1 and a laser processing head 41. The optical cable has a coupling input plug 5 with a coupling input lens 21, a scattered light sensor 14, a coupling output plug 6 with a cladding light sensor 8, and a scattered light sensor 11. The laser processing head has two protective glasses 42 located in the beam path of the laser 7 emitted from the fiber core 3. The coupling output plug 6 is inserted into the laser processing head 41. Each of the two protective glasses 42 is assigned a scattered light sensor 43 to measure the scattered light 44 scattered on the respective protective glass 42.

[0036] Each sensor 8, 11, 14, 43 is assigned a reference value recorded when the laser light guide cable 1 is in operation without processing; this reference value is stored in the data memory 16. Subsequently, if the sensor measurement deviates excessively from the corresponding reference value, the analysis and processing unit 31 identifies this and shuts down the laser equipment 32. If only one sensor measurement shows a deviation, this can be used for error determination. Thus, the analysis and processing unit 31 can determine whether the deviation is caused by the laser reflected from the workpiece 45 and the process beam 12, by contamination of the protective glass, or by misalignment of the fiber-coupled input. By using multiple scattered light sensors 43 on the protective glass 42, contamination of the protective glass 42 and the reflected laser / process beam 12 can be distinguished, thereby identifying contamination of the protective glass during processing.

[0037] Furthermore, it is possible to perform inspections quickly and easily during brief intervals between two processing runs, without processing. Here, the time required for changing the processed part can be used to transport the laser processing head 41 to a designated location where the cladding light value and scattered light value in the unprocessed state can be inspected relative to the original values ​​(reference values) in a good / new state, using the same method as for the reference. If the sensor signal changes compared to the start (reference value), the operator can be informed of operational recommendations regarding laser control in advance, thereby preventing unexpected downtime. Replacement of the protective glass 42 can also be planned and notified in advance via signaling.

Claims

1. A calibration device (20), which has An optical cable (1) having an optical fiber (2), wherein the optical fiber has an optical fiber core (3) and an optical fiber cladding (4), wherein, The optical cable (1) has a coupling output plug located at the coupling output side fiber end (2b) of the optical fiber (2), wherein the coupling output plug has at least one cladding optical sensor (8) arranged behind the coupling output side fiber end (2b), the cladding optical sensor being used to measure cladding light (9) emitted from the fiber cladding (4) at the end face of the coupling output side fiber end (2b), wherein the coupling output plug (6) has a deflection optics (10) arranged between the coupling output side fiber end (2b) and the cladding optical sensor (8), the deflection optics deflecting at least a portion of the emitted cladding light (9) onto the at least one cladding optical sensor (8), and A means (22) for moving the coupled input side fiber end (2a) or the coupled input optics (21) of the optical fiber (2) relative to each other in a direction (23) perpendicular to the optical fiber axis (A) according to the sensor signal of the at least one cladding optical sensor (8), the coupled input optics being arranged in front of the coupled input side fiber end (2a) in order to couple light (7) into the optical fiber core (3).

2. A monitoring device (40), comprising: An optical cable (1) having an optical fiber (2), wherein the optical fiber has an optical fiber core (3) and an optical fiber cladding (4), wherein, The optical cable (1) has a coupling output plug located at the coupling output side fiber end (2b) of the optical fiber (2), wherein the coupling output plug has at least one cladding optical sensor (8) arranged behind the coupling output side fiber end (2b), the cladding optical sensor being used to measure cladding light (9) emitted from the fiber cladding (4) at the end face of the coupling output side fiber end (2b), wherein the coupling output plug (6) has a deflection optics (10) arranged between the coupling output side fiber end (2b) and the cladding optical sensor (8), the deflection optics deflecting at least a portion of the emitted cladding light (9) onto the at least one cladding optical sensor (8). At least one optical element (42) is located at the end face of the optical fiber end (2b) on the coupling output side in the beam path of the light ray (7) emitted from the fiber core (3). At least one light-scattering sensor (43) is used to measure the scattered light (44) scattered on the at least one optical element (42), and Analysis and processing device (31) analyzes and processes the sensor signals of the cladding light sensor and the scattered light sensor (8, 43).

3. The monitoring device according to claim 2, characterized in that, At least two optical elements (42) are arranged sequentially in the beam path of the light (7) emitted from the fiber core (3) at the end face of the coupled output side fiber end (2b), and each of the optical elements (42) is assigned a scattered light sensor (43).

4. The monitoring device according to claim 2 or 3, characterized in that, The at least one cladding optical sensor (8) is arranged on the coupling output plug (6) of the optical fiber (2).

5. The monitoring device according to claim 2 or 3, characterized in that, The at least one optical element (42) is arranged on the laser processing head (41) in which the coupling output plug (6) is inserted.

6. The monitoring device according to claim 2 or 3, characterized in that, At least one scattered light sensor (11, 14) is provided, which is used to measure scattered light (13, 15) scattered on the fiber end face of the optical fiber (2) or on other components.

7. A method for monitoring an optical fiber cable (1) during continuous operation, the optical fiber cable having an optical fiber (2) having an optical fiber core (3) and an optical fiber cladding (4), the method comprising the following steps: Cladding light (9) emitted from the fiber cladding (4) at the end face of the fiber end (2b) on the coupled output side is measured using at least one cladding light sensor (8), wherein, A deflection optics device (10) arranged between the end of the optical fiber (2b) on the coupling output side and the cladding photosensor (8) deflects at least a portion of the emitted cladding light (9) onto the at least one cladding photosensor (8). The scattered light (44) scattered on at least one optical element (42) is measured in the beam path of the light ray (7) emitted from the fiber core (3) at the end face of the fiber at the end (2b) on the coupling output side. The measured cladding light and scattered light (9, 43) were analyzed and processed.

8. The method according to claim 7, characterized in that, The scattered light (13, 15) scattered on the fiber end face of the optical fiber (2) or on other components is measured and analyzed together with the measured cladding light and scattered light (9, 43).

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