WO2024018566A1

WO2024018566A1 - Laser oscillator, failure sensing method, and optical fiber inspection method

Info

Publication number: WO2024018566A1
Application number: PCT/JP2022/028244
Authority: WO
Inventors: 哲也千葉
Original assignee: ファナック株式会社
Priority date: 2022-07-20
Filing date: 2022-07-20
Publication date: 2024-01-25

Abstract

A laser oscillator according to the present invention comprises a laser oscillation source, a drive power supply, an oscillation control device, and an optical fiber that transmits a laser beam oscillated from the laser oscillation source. The laser oscillator further comprises a photodetector that detects light from the peripheral surface of the optical fiber. A coating layer that reflects at least some of visible light is provided on the outer side of a cladding layer of the optical fiber. Further, a method according to the present invention for sensing failure of the laser oscillator determines that an optical fiber has a failure on the basis of a visible light detection value by the photodetector.

Description

Laser oscillator, failure detection method and optical fiber inspection method

The present invention relates to a technique for transmitting a laser beam through an optical fiber, and particularly relates to a laser oscillator that transmits a laser beam through an optical fiber, a failure detection method thereof, and an optical fiber inspection method.

In the technical fields of laser processing and optical communications, a technology is known in which a laser beam emitted from an oscillation source is transmitted through an optical fiber. A typical optical fiber has a structure with a cladding layer around the outer periphery of a core layer, and uses the difference in refractive index at the interface between the core layer and cladding layer to transmit light incident on the core layer. do.

When transmitting a laser beam through such an optical fiber, for example, if impurities get mixed into the core layer during the manufacturing of the optical fiber, or if multiple optical fibers are fused and connected, the above impurities and The bonding portion absorbs the laser beam and generates heat, which may cause destruction of the core layer. At this time, if the laser beam continues to be incident, a so-called "fiber fuse" occurs in which the core layer breaks down continuously toward the oscillation source.

When such a "fiber fuse" occurs, most of the optical fiber is destroyed, causing the problem that the transmission of the laser beam stops. Therefore, as a method to solve such problems, for example, Patent Document 1 describes the need to reliably detect when a fiber fuse occurs in an optical fiber, and the visible light from the fiber fuse has been developed to be monitored at a monitoring position. A technique has been disclosed for stopping the oscillation of a laser beam when the oscillation of the laser beam is detected.

Japanese Patent Application Publication No. 2012-127903

One aspect of conventional technology for detecting the fiber fuse phenomenon that occurs in optical fibers is that the occurrence of the fiber fuse itself cannot be detected until the fiber fuse has progressed from the origin to the position of the photodetector. For this reason, there is a time lag between when a fiber fuse occurs in the optical fiber and laser beam transmission is no longer possible, and when a defect in the optical fiber is detected and the oscillation source stops operating. There was a problem that efficiency and communication efficiency decreased.

Due to these circumstances, there is a need for a technology that can quickly detect defects caused by fiber fuses that occur when transmitting laser beams in optical fibers that transmit laser beams.

According to one aspect of the present invention, a laser oscillator including a laser oscillation source, a drive power source, an oscillation control device, and an optical fiber that transmits a laser beam emitted from the laser oscillation source includes The optical fiber further includes a photodetector that detects light, and is configured to have a coating layer that reflects at least a portion of visible light on the outside of the cladding layer of the optical fiber.

Further, according to another aspect of the present invention, there is provided an oscillation control device for a laser oscillator that includes a laser oscillation source, a drive power source, an oscillation control device, and an optical fiber that transmits a laser beam oscillated from the laser oscillation source. In the failure detection method to be carried out, the laser oscillator further includes a photodetector that detects light from the outer peripheral surface of the optical fiber, and the optical fiber has a coating layer that reflects at least a part of visible light on the outside of the cladding layer. Based on the detected value of visible light by the photodetector, it is determined that there is a failure in the optical fiber.

Further, according to still another aspect of the present invention, there is provided an optical fiber inspection method for determining defects in an optical fiber by making a laser beam enter the inside of the optical fiber. A device that forms a reflective coating layer, introduces a laser beam emitted from a laser oscillator into one end of the optical fiber, and determines whether the optical fiber is defective based on the detected value of light detected from the outer peripheral surface of the optical fiber. It is.

1 is a schematic diagram showing the configuration of a laser oscillator according to a first embodiment, which is a typical example of the present invention. 2 is a partial cross-sectional view showing the internal structure of the optical fiber shown in FIG. 1. FIG. 3 is a partial cross-sectional view showing behavior when a fiber fuse occurs in the optical fiber shown in FIG. 2. FIG. 3 is a flowchart illustrating an example of the operation of the failure detection method according to the first embodiment. FIG. 2 is a block diagram showing a state in which a laser beam is normally transmitted in the laser oscillator according to the first embodiment. FIG. 2 is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the first embodiment. It is a flowchart which shows an example of operation of the failure detection method by the 1st modification of a 1st embodiment. It is a flowchart which shows an example of operation of the failure detection method by the 2nd modification of a 1st embodiment. It is a graph which shows an example of the characteristic of the photodetector applied to the laser oscillator and failure detection method by 2nd Embodiment. FIG. 7 is a block diagram showing an outline of a photodetector applied to a laser oscillator according to a modification of the second embodiment. FIG. 7 is a block diagram showing a state in which a fiber fuse is generated during laser beam transmission in a laser oscillator according to a third embodiment. FIG. 7 is a block diagram showing a state in which a laser beam is transmitted to an optical fiber in a laser oscillator according to a modification of the third embodiment. FIG. 7 is a schematic diagram showing the configuration of a laser oscillator according to a fourth embodiment. FIG. 12 is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the fifth embodiment. FIG. 12 is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in a laser oscillator according to a first modification of the fifth embodiment. FIG. 12 is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in a laser oscillator according to a second modification of the fifth embodiment. FIG. 12C is a partial cross-sectional view schematically showing the vicinity of the stopper member shown in FIG. 12C. FIG. 12 is a block diagram showing an overview of a preparatory operation of an optical fiber inspection method according to a sixth embodiment. FIG. 12 is a block diagram showing an overview of the operation when the optical fiber is a non-defective item in the optical fiber inspection method according to the sixth embodiment. FIG. 12 is a block diagram showing an overview of the operation when the optical fiber is a defective product in the optical fiber inspection method according to the sixth embodiment.

Hereinafter, embodiments of a laser oscillator, a failure detection method, and an optical fiber inspection method related thereto according to a typical example of the present invention will be described with reference to the drawings.

<First embodiment>
FIG. 1 is a schematic diagram showing the configuration of a laser oscillator according to a first embodiment, which is a typical example of the present invention. Moreover, FIG. 2 is a partial cross-sectional view showing the internal structure of the optical fiber shown in FIG. Furthermore, FIG. 3 is a partial cross-sectional view showing behavior when a fiber fuse occurs in the optical fiber shown in FIG. 2.

As an example, the laser oscillator 100 according to the first embodiment includes a laser oscillation source 110, a drive power source 120, an oscillation control device 130, and an optical fiber 140 that transmits the laser beam LB oscillated from the laser oscillation source 110. , and a photodetector 150 that detects light (visible light VL) from the outer peripheral surface of the optical fiber 140. In the example shown in FIG. 1, the oscillation control device 130 of the laser oscillator 100 is configured to turn on and off in response to an oscillation command signal OS from the main control unit 20 of the control device 10 of the object that emits the laser beam LB. has been done.

As an example, the laser oscillation source 110 is a laser source with a wavelength that has high absorption efficiency and can be transmitted through an optical fiber, depending on the work to be irradiated with the laser beam LB used for processing or measurement. Ru. Examples of such a laser oscillation source 110 include a YAG laser, a YVO ₄ laser, a fiber laser, a disk laser, and a direct diode laser. Further, the laser beam LB emitted from the laser oscillation source 110 may be either a continuous wave or a pulse wave.

The drive power source 120 supplies or stops driving power to the laser oscillation source 110 based on control commands (drive command signal DS and stop command signal SS) from an oscillation control device 130, which will be described later. Note that although FIG. 1 illustrates a case where the drive power source 120 is provided inside the laser oscillator 100, the drive power source 120 may be provided outside the casing that constitutes the laser oscillator 100.

The oscillation control device 130 outputs a drive command signal DS or a stop command signal SS to the drive power source 120 based on the oscillation command signal OS from the main control unit 20 of the control device 10. Further, in the laser oscillator 100 according to the first embodiment, the oscillation control device 130 determines that a failure (fiber fuse: FF) has occurred in the optical fiber 140 based on a detected value by the photodetector 150, which will be described later. It also has functions.

As shown in FIG. 2 as an example, the optical fiber 140 includes a core layer 142 that transmits the laser beam LB emitted from the laser oscillation source 110, a cladding layer 144 surrounding the outside of the core layer 142, and a cladding layer 144. a covering layer 146 covering the outer surface of the holder. The laser beam LB is transmitted by being reflected at the interface IF1 between the core layer 142 and the cladding layer 144 due to the difference in refractive index between the core layer 142 and the cladding layer 144. In addition, examples of materials constituting the core layer 142 and cladding layer 144 of the optical fiber 140 include glasses such as quartz glass and fluoride glass, and transparent plastics.

In the first embodiment, the covering layer 146 is formed of a material that reflects at least a portion of visible light VL, which will be described later. An example of such a covering layer 146 is acrylic resin.

As shown in FIG. 3, when a fiber fuse occurs at the fault occurrence position FP of the core layer 142 of the optical fiber 140, strong light emission is generated by the fiber fuse and is visible in a radial direction centered at the fault occurrence position FP. Light VL is emitted. At this time, since the covering layer 146 is formed of a material that reflects at least a part of the visible light VL, the emitted visible light VL is reflected at the interface IF2 between the cladding layer 144 and the covering layer 146, and is reflected in the cladding layer 146. transmitted inside.

As shown in FIG. 1, a part of the visible light VL transmitted through the cladding layer 144 returns to the laser oscillation source 110 side, leaks out from the opening 146a of the cladding layer 146, and reaches the light receiving section 152 of the photodetector 150. The light is received by When the photodetector 150 receives the visible light VL, it outputs a detection signal LD corresponding to the detection level to the oscillation control device 130. Here, although FIG. 1 illustrates a case where the opening 146a is formed in a part of the optical fiber 140 located near the photodetector 150, the coating layer 146 is not formed without the opening 146a. The photodetector 150 may be configured to detect a portion of the visible light VL leaking from the sensor.

Next, an embodiment of the failure detection method executed by the laser oscillator according to the first embodiment will be described using FIGS. 4 to 7.

FIG. 4 is a flowchart illustrating an example of the operation of the failure detection method according to the first embodiment. Moreover, FIG. 5A is a block diagram showing a state in which a laser beam is normally transmitted in the laser oscillator according to the first embodiment. Further, FIG. 5B is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the first embodiment.

In the failure detection method according to the first embodiment, as shown in FIG. 4, first, the oscillation control device 130 receives an oscillation command signal OS from the main control unit 20 of the external control device 10 (step S101). Here, the laser oscillator 100 according to the first embodiment shown in FIG. 1 is configured to continue oscillating the laser beam LB while receiving the oscillation command signal OS.

The oscillation control device 130, which is receiving the oscillation command signal OS, outputs the drive command signal DS to the drive power supply 120 (step S102). The drive power supply 120 that has received the drive command signal DS supplies drive power to the laser oscillation source 110, and thereby, as shown in FIG. 5A, the laser beam LB is emitted from the laser oscillation source 110.

Next, the oscillation control device 130 determines whether the detection signal LD of visible light VL is received from the photodetector 150 (step S103). In step S103, if it is determined that the detection signal LD from the photodetector 150 has been received, the oscillation control device 130 determines that the photodetector 150 has detected the visible light VL, that is, the optical fiber 140 has detected the visible light VL, as shown in FIG. It is determined that a malfunction (fiber fuse) has occurred in the controller 10, and a stop command signal SS to stop the operation of the laser oscillator 100 is output to notify the main control unit 20 of the control device 10 (step S104).

Next, the oscillation control device 130 outputs a stop command signal SS to the drive power supply 120 to stop outputting the drive power to the laser oscillation source 110 (step 105), and ends the control operation of the laser oscillator 100. . At this time, the main control unit 20 that has received the stop command signal SS from the oscillation control device 130 sends a display command signal DC to the display unit 30 to indicate that a failure has occurred in the optical fiber 140. It may also be configured to output.

On the other hand, if it is determined in step S103 that the detection signal LD from the photodetector 150 is not received, the oscillation control device 130 determines whether the oscillation command signal OS is received from the main control unit 20 ( Step S106). If it is determined in step S106 that the oscillation command signal OS is still being received, the oscillation control device 130 returns to step S102, outputs the drive command signal DS to the drive power supply 120, and executes the subsequent steps. repeat.

On the other hand, if it is determined in step S106 that the oscillation command signal OS has not been received, the oscillation control device 130 determines that the laser oscillation operation command from the main control unit 20 has stopped, and proceeds to step S105. Then, the oscillation control device 130 outputs a stop command signal SS to the drive power supply 120 to stop outputting the drive power to the laser oscillation source 110, and ends the control operation of the laser oscillator 100.

By performing such an operation, when the oscillation control device 130 of the laser oscillator 100 receives the detection signal LD of visible light VL from the photodetector 150 while emitting the laser beam LB from the laser oscillation source 110, It is possible to determine and notify that a malfunction (fiber fuse) has occurred in the optical fiber 140. On the other hand, when the detection signal LD from the photodetector 150 is not received, the emission of the laser beam LB is continued until the oscillation command signal OS is no longer received.

Next, a modification of the first embodiment will be described using FIGS. 6 and 7. FIG. 6 is a flowchart illustrating an example of the operation of the failure detection method according to the first modification of the first embodiment. FIG. 7 is a flowchart illustrating an example of the operation of the failure detection method according to the second modification of the first embodiment.

In the failure detection method according to the first modification of the first embodiment, as shown in FIG. 6, when the oscillation control device 130 determines that the detection signal LD from the photodetector 150 has been received in step S103, Furthermore, it is determined whether the detected value of the intensity level of the visible light VL based on the detection signal LD is equal to or higher than a predetermined threshold (step S103a). At this time, the predetermined threshold value serving as an index of the strength level is set, for example, to the strength level actually measured in the past when a fiber fuse occurred.

If it is determined in step S103a that the detected value is equal to or greater than the threshold value, the oscillation control device 130 determines that a defect (fiber fuse) has definitely occurred in the optical fiber 140, and the main control unit of the control device 10 20, a stop command signal SS to stop the operation of the laser oscillator 100 is output and notified (step S104). On the other hand, if it is determined in step S103a that the detected value is lower than the threshold value, the oscillation control device 130 returns to step S102, outputs the drive command signal DS to the drive power source 120, and repeats the subsequent steps.

By performing such an operation, in the first modification of the first embodiment, the determination based on the detection signal LD from the photodetector 150 is made based on whether the detection signal LD is greater than or equal to a predetermined threshold. Erroneous detection due to a detection value (so-called noise) that is less than the threshold value at 150 can be avoided.

In the failure detection method according to the second modification of the first embodiment, as shown in FIG. 7, when the oscillation control device 130 determines that the detection signal LD from the photodetector 150 has been received in step S103, It is determined that a problem (fiber fuse) has occurred in the optical fiber 140, and an emergency stop command signal ES is output to the drive power source 120 (step S103b). Then, upon receiving the emergency stop command signal ES, the drive power supply 120 immediately stops supplying drive power to the laser oscillation source 110.

Next, the oscillation control device 130 outputs a stop command signal SS to notify the main control unit 20 of the control device 10 of stopping the operation of the laser oscillator 100 (step S104). On the other hand, if it is determined in step S103 that the detection signal LD from the photodetector 150 has not been received, the oscillation control device 130 executes the same operations from step S106 as described in FIG. 4.

By performing such an operation, in the second modified example of the first embodiment, the drive power to the laser oscillation source 110 is immediately applied to the laser oscillation source 110 when the fiber fuse is detected, prior to notifying the control device 10. Since the supply is stopped, it is possible to suppress the progress of a problem in the optical fiber 140 caused by continuing to emit the laser beam LB after detecting a problem in the optical fiber 140.

By having the above configuration, the laser oscillator and failure detection method according to the first embodiment provide a coating layer that reflects at least a part of visible light on the outside of the cladding layer of the optical fiber, and By arranging a photodetector that detects light from the outer peripheral surface of the fiber, it becomes possible to quickly detect a malfunction caused by the fiber fuse that occurs when transmitting the laser beam. Note that the flowcharts according to the modified examples shown in FIGS. 6 and 7 may be configured to be executed in combination.

<Second embodiment>
FIG. 8 is a graph showing an example of the characteristics of a photodetector applied to the laser oscillator and failure detection method according to the second embodiment of the present invention. Moreover, FIG. 9 is a block diagram showing an outline of a photodetector applied to a laser oscillator according to a modification of the second embodiment. In addition, in the second embodiment, in the schematic diagrams shown in FIGS. 1 to 7, parts that can have the same or common configurations as those in the first embodiment are denoted by the same reference numerals. The explanation of the repetition of is omitted.

In the laser oscillator 100 according to the second embodiment, the photodetector 250 is configured to measure light in a specific range of wavelengths. For example, as shown in FIG. 8, the photodetector 250 is configured to detect only the visible light wavelength range in order to selectively detect the visible light VL caused by the fiber fuse generated in the core layer 142 of the optical fiber 140. is configured to have a high sensitivity range of .

At this time, the high-sensitivity range of the sensor of the photodetector 250 is not a range where visible light has high intensity as shown in FIG. It may be set within the possible range. As a result, in the laser oscillator 100 according to the second embodiment, the photodetector 250 detects only the light caused by the fiber fuse, and it is possible to suppress erroneous detection due to, for example, fluctuation of the laser beam LB.

Furthermore, in the laser oscillator 100 according to the modification of the second embodiment, as shown in FIG. 9, the photodetector 250 further includes an optical filter 254 that covers the light-receiving surface of the light-receiving section 252. At this time, the optical filter 254 has optical filtering characteristics as shown in FIG. According to such a configuration, a special optical filtering function can be provided to a generally commercially available photodetector 250 by simply providing an additional optical filter 254 that transmits only light with wavelengths in a specific range. It can be applied without any problems.

By having the above configuration, the laser oscillator and failure detection method according to the second embodiment have the effect described in the first embodiment, and also allows the photodetector to select only light with wavelengths in a specific range. Since the optical fiber is configured so that it can be detected visually, it is possible to improve the accuracy of detecting defects in the optical fiber caused by the fiber fuse.

<Third embodiment>
FIG. 10A is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the third embodiment. FIG. 10B is a block diagram showing a state in which a laser beam is transmitted to an optical fiber in a laser oscillator according to a modification of the third embodiment. Note that in the third embodiment as well, in the schematic diagrams shown in FIGS. 1 to 9, the same or common configurations as those in the first embodiment and the second embodiment can be adopted. A description of these repetitions will be omitted by attaching reference numerals.

In the laser oscillator 300 according to the third embodiment, the optical fiber 340 has a bent section BS in at least a portion thereof, as shown in FIG. 10A. By having such a bent section BS, the reflection angle of the visible light VL generated by the fiber fuse generated at the fault occurrence position FP changes irregularly, so that the incident angle of the visible light VL guided into the core layer becomes large and easily migrates to the cladding layer side. Therefore, a large amount of the visible light VL that enters the photodetector 150 can also be made to enter from irregular angles.

Furthermore, in a laser oscillator 300 according to a modification of the third embodiment, as shown in FIG. 10B, the optical fiber 340 may include an annularly wound section as a bent section BS. As a result, the direction of transmission through the optical fiber 340 can be arbitrarily selected, improving the degree of freedom in the layout of the laser oscillator 300 and peripheral devices. Note that although FIG. 10B illustrates a case in which the optical fiber 340 is arranged in a ring shape with only one turn, the number of turns may be multiple times.

By having the above configuration, the laser oscillator and failure detection method according to the third embodiment have the advantage that, in addition to the effects described in the first embodiment, at least a part of the optical fiber is provided with a bent section. Therefore, among the visible light caused by the fiber fuse, the light that enters the core layer can be transferred to the cladding layer side, so that the amount detected by the photodetector can be increased.

<Fourth embodiment>
FIG. 11 is a schematic diagram showing the configuration of a laser oscillator according to the fourth embodiment. In addition, in the fourth embodiment as well, in the schematic diagrams shown in FIGS. 1 to 10B, the same or common configurations can be adopted as those in the first to third embodiments. A description of these repetitions will be omitted by attaching reference numerals.

In the laser oscillator 400 according to the fourth embodiment, as shown in FIG. 11, the optical fiber 440 can be exemplified as a fiber laser that is connected to the excitation light source 410 and forms part of the laser oscillation source. The excitation light source 410 emits excitation light that is input to the fiber laser by being supplied with drive power from the drive power supply 120 that has received the drive command signal DS from the oscillation control device 130 .

For example, the fiber laser constituting the optical fiber 440 has a core layer doped with a rare earth element and transmits a laser beam LB generated by excitation light from an excitation light source 410 inside an inner cladding layer formed in two layers. A double-clad fiber that emits light by reflecting it and amplifying it can be used. The optical fiber 440 further includes a coating layer (not shown) on the outer surface of the outer cladding layer that reflects at least a portion of visible light, and an opening 446a is formed near the photodetector 150. .

In the optical fiber 440, visible light VL caused by a fiber fuse generated in the core layer during amplification of the fiber laser is reflected between the outer cladding layer and the coating layer and transmitted within the outer cladding layer. The transmitted visible light VL then leaks from the opening 446a of the coating layer and is received by the light receiving section 152 of the photodetector 150.

By having the above-described configuration, the laser oscillator and failure detection method according to the fourth embodiment, in addition to the effects described in the first embodiment, allow the optical fiber to become at least a part of the laser oscillation source. Because of this configuration, the length of the optical fiber serving as the oscillation source can be increased, thereby making it possible to increase the maximum output of the laser oscillator.

<Fifth embodiment>
FIG. 12A is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the fifth embodiment. Further, FIG. 12B is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in the laser oscillator according to the first modification of the fifth embodiment. Further, FIG. 12C is a block diagram showing a state in which a fiber fuse occurs during laser beam transmission in a laser oscillator according to a second modification of the fifth embodiment. Moreover, FIG. 12D is a partial sectional view schematically showing the vicinity of the stopper member shown in FIG. 12C.

In addition, in the fifth embodiment as well, in the schematic diagrams shown in FIGS. 1 to 11, the same or common configurations can be adopted as those in the first to fourth embodiments. A description of these repetitions will be omitted by attaching reference numerals.

In the laser oscillator 500 according to the fifth embodiment, the optical fibers 540 have a structure in which a plurality of optical fibers are continuously connected via a fusion part 560. That is, as an example, as shown in FIG. 12A, the optical fiber 140 connected to the laser oscillation source 110 and another optical fiber 540 are optically connected via the fusion part 560 at the exposed part 546a. There is. Further, like the optical fiber 140, the optical fiber 540 includes a coating layer (not shown) outside the cladding layer that reflects at least a portion of the visible light VL.

The fused portion 560 is a portion where two fibers are fused using the same components as the core layer or cladding layer of the

optical fibers

140 and 540, and therefore transmits the transmitted laser beam LB with minimal loss. be able to. Further, an exposed portion 546a is formed at the connection portion of the fused portion 560 between the

optical fibers

140 and 540, and a photodetector 150 is disposed near the exposed portion 546a. This makes it possible to efficiently detect the transmitted visible light VL using the exposed portion 546a from which the coating has been removed in order to connect the plurality of optical fibers.

Further, as shown in FIG. 12B, in the laser oscillator 500 according to the first modification of the fifth embodiment, the optical fiber 140 from which the coating layer 146 has been removed is surrounded in the area of the exposed portion 546a shown in FIG. 12A. It further includes a cylindrical protection member 570. The protective member 570 is formed of a material that transmits at least the visible light VL propagating inside the optical fiber 140 while protecting the components such as the optical fiber 140 and the fused portion 560 that are exposed in the exposed portion 546a. Ru. As a material for such a protection member 570, a material having a higher refractive index than the cladding layer 144 of the optical fiber 140 can be exemplified.

In addition, in the laser oscillator 500 according to the second modification of the fifth embodiment, as shown in FIG. An annular stopper member 580 is further provided on the outer surface of the coating layer 146 at a position on the source 110 side. Here, the stopper member 580 is made of, for example, a material having a higher refractive index than the coating layer 146 of the optical fiber 140 in which the stopper member 580 is inscribed.

By providing the stopper member 580 as described above, in the area where the stopper member 580 is arranged, a part of the laser beam LB emitted from the laser oscillator 500 may unintentionally fall into the core, as shown in FIG. 12D, for example. In the case where the laser beam LB propagates through the coating layer 146 instead of the layer 142 or the cladding layer 144, the laser beam LB is transmitted into the stopper member 580 without being reflected at the interface IF3 between the coating layer 146 and the stopper member 580. Therefore, it is possible to suppress the interference light (noise light) caused by the unintended laser beam LB from entering the photodetector 150. Therefore, it is possible to improve the detection accuracy of the photodetector 150 and prevent false detection.

By having the above-described configuration, the laser oscillator and failure detection method according to the fifth embodiment provide the effects described in the first embodiment, as well as the exposure By arranging the photodetector near the portion, it becomes possible to efficiently detect visible light without providing an opening where the covering portion is removed at another location. Note that the configurations according to the first modification and the second modification of the fifth embodiment described above can also be applied in combination.

<Sixth embodiment>
Next, an optical fiber inspection method according to a sixth embodiment, which is another specific example of the present invention, will be explained using FIGS. 13A to 13C.

FIG. 13A is a block diagram showing an overview of the preparatory operation of the optical fiber inspection method according to the sixth embodiment. Moreover, FIG. 13B is a block diagram showing an outline of the operation when the optical fiber is a non-defective item in the optical fiber inspection method according to the sixth embodiment. Furthermore, FIG. 13C is a block diagram showing an overview of the operation when the optical fiber is a defective product in the optical fiber inspection method according to the sixth embodiment.

The optical fiber inspection method according to the sixth embodiment detects visible light caused by the fiber fuse generated in the core layer of the optical fiber, as described in the first to fifth embodiments. It applies technology that detects fiber defects as failures. That is, a laser beam is transmitted to the optical fiber to be inspected, and it is determined whether the optical fiber is a good product or a defective product based on whether visible light is detected by a photodetector.

In the preparatory operation of the optical fiber inspection method according to the sixth embodiment, as shown in FIG. optically connect one end of the At this time, as in the case of the first embodiment, the optical fiber 640 to be inspected is provided with a coating layer (not shown) that reflects at least a portion of the visible light VL caused by the fiber fuse on the outside of the cladding layer. ) are preformed.

Subsequently, an oscillation command signal OS is sent to the oscillation control device 130, and the laser beam LB is emitted from the laser oscillation source 110 to the optical fiber 640 via the optical fiber 140 and connector 680. At this time, if the optical fiber 640 to be inspected is non-defective, as shown in FIG. 13B, no fiber fuse is generated and the laser beam LB continues to be transmitted as is.

On the other hand, when the optical fiber 640 to be inspected is a defective product, as shown in FIG. The light is propagated inside the coating layer of the optical fiber 640 and returns to the optical fiber 140, and a portion thereof is detected by the photodetector 150. Then, the oscillation control device 130 that has received the detection signal LD from the photodetector 150 outputs a failure occurrence signal FS to the external control device 10 to notify it.

By having the above-described configuration, the optical fiber inspection method according to the sixth embodiment includes providing in advance a coating layer that reflects at least a portion of visible light on the outside of the cladding layer of the optical fiber to be inspected. When a laser beam is transmitted from a laser oscillator through this optical fiber, the quality of the optical fiber is determined by whether visible light is detected by a photodetector. It becomes possible to promptly detect malfunctions in optical fibers caused by fiber fuses. Note that the optical fiber inspection method according to the sixth embodiment may be configured to perform a combination of the operations performed in the flowcharts shown in FIGS. 6 and 7.

Note that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the spirit. Within the scope of the present invention, any component of the embodiments may be modified or any component of the embodiments may be omitted.

For example, in the above embodiment, the external control device that receives the stop command signal output from the oscillation control device of the laser oscillator displays the occurrence of a failure on the display section, but the laser oscillator itself has a display section. It may be configured such that when the oscillation control device detects a malfunction in the optical fiber, the malfunction is notified on the display section of the laser oscillator. Furthermore, the specific examples shown in the first to fifth embodiments can be applied in combination with their respective characteristics.

10 control device 20 main control section 30 display section 100 laser oscillator 110 laser oscillation source 120 drive power source 130 oscillation control device 140 optical fiber 142 core layer 144 cladding layer 146 coating layer 146a opening 150 photodetector 152 light receiving section 250 photodetector 252 Light receiving section 254 Optical filter 300 Laser oscillator 340 Optical fiber 400 Laser oscillator 410 Excitation light source 440 Optical fiber 446a Opening section 500 Laser oscillator 540 Optical fiber 546a Exposed section 560 Fusion section 570 Protective member 580 Stopper member 600 Laser Oscillator 640 Optical fiber 680 connector

Claims

A laser oscillator including a laser oscillation source, a driving power source, an oscillation control device, and an optical fiber that transmits a laser beam oscillated from the laser oscillation source,
further comprising a photodetector that detects light from the outer peripheral surface of the optical fiber,
A laser oscillator including a coating layer outside the cladding layer of the optical fiber that reflects at least a portion of visible light.
The laser oscillator according to claim 1, wherein the photodetector is configured to measure light in a specific range of wavelengths.
3. The laser oscillator according to claim 2, wherein the photodetector further includes an optical filter in the light receiving section that transmits light having a wavelength in the specific range.
The laser oscillator according to claim 1, wherein the optical fiber has a bent section in at least a portion thereof.
The laser oscillator according to claim 1, wherein the optical fiber constitutes at least a part of the laser oscillation source.
The optical fiber has a structure in which a plurality of optical fibers are continuously connected via a fusion part,
5. The optical detector according to claim 1, wherein the photodetector is arranged to detect light from an exposed portion of the optical fiber including the fused portion from which the coating layer has been removed. laser oscillator.
further comprising a cylindrical protection member surrounding the optical fiber from which the coating layer has been removed in the exposed portion region;
7. The laser oscillator according to claim 6, wherein the protection member is made of a material that transmits at least the visible light propagating inside the optical fiber.
The laser oscillator according to claim 6, wherein the optical fiber further includes an annular stopper member that transmits the laser beam on an outer surface of the coating layer at a position on the laser oscillation source side of the coating layer near the exposed portion. .
A failure detection method performed by the oscillation control device of a laser oscillator including a laser oscillation source, a drive power source, an oscillation control device, and an optical fiber that transmits a laser beam oscillated from the laser oscillation source, the method comprising:
The laser oscillator further includes a photodetector that detects light from the outer peripheral surface of the optical fiber,
The optical fiber has a coating layer outside the cladding layer that reflects at least a portion of visible light,
A failure detection method for determining that there is a failure in the optical fiber based on a detected value of visible light by the photodetector.
10. The failure detection method according to claim 9, wherein when the detected value of visible light by the photodetector exceeds a predetermined threshold value, it is determined that the optical fiber has failed.
11. The failure detection method according to claim 9, further comprising issuing an emergency stop command to the drive power source when it is determined that the optical fiber is at fault.
An optical fiber inspection method for determining defects in an optical fiber by injecting a laser beam into the interior, the method comprising:
forming a coating layer that reflects at least a portion of visible light on the outside of the cladding layer of the optical fiber;
Introducing the laser beam emitted from a laser oscillator into one end of the optical fiber,
An optical fiber inspection method for determining whether an optical fiber is defective based on a detected value of light detected from the outer peripheral surface of the optical fiber.
13. The optical fiber inspection method according to claim 12, wherein when the detected value exceeds a predetermined threshold value, it is determined that the optical fiber is defective.