JP6468867B2 - Optical power monitoring device, optical power monitoring method, and fiber laser device - Google Patents

Description

  The present invention relates to an optical power monitoring device, an optical power monitoring method, and a fiber laser device.

  In recent fiber laser devices, output light power exceeding 1 kW can be achieved by increasing the brightness of a pumping semiconductor laser or commercializing an amplification double-clad fiber. Such a high-power fiber laser can be applied to the field of material processing where a carbon dioxide laser has been mainly used. The fiber laser is excellent in beam quality and light condensing performance as compared with the carbon dioxide laser. Therefore, the high-power fiber laser has excellent features such as shortening the processing time, improving throughput, realizing processing characteristics equivalent to high power even at low power, and saving energy. Further, since no spatial optical component is required, there are advantages such as no problems such as durability and alignment of optical components, and no maintenance.

On the other hand, material processing using a fiber laser device has the following problems.
For example, when reflected light from the processing surface returns to the fiber laser during material processing, the oscillation state becomes unstable. As a result, the output light power fluctuates and the processing characteristics deteriorate. In the worst case, unstable oscillation becomes random pulse oscillation, which causes failure of the excitation light source, breakage of the fiber, etc., resulting in failure of the fiber laser. In order to cope with this type of problem, it is necessary to monitor the reflected light power and the output light power to prevent the oscillation state from becoming unstable.

  As one means for monitoring the reflected light power, the following Patent Document 1 discloses that reflected light (returned light) from a laser processing position of a workpiece is externally transmitted in an optical fiber that transmits high-power laser light for laser processing. There is disclosed a method in which a return light leakage portion for leaking is provided, and return light leaking from the return light leakage portion is detected by a sensor. In this document, the return light leakage portion is formed by processing a part of the outer core, which is normally in a mirror state, into a rough surface.

JP 2004-151667 A

  Although the point of monitoring the power of the output light is not described in Patent Document 1, there is a demand for monitoring the power of the output light using a photodetector or the like. In this case, if the emission side fiber is, for example, an amplifying double clad fiber, at least a part of the reflected light propagates in the inner clad. When the reflected light propagates through the inner cladding and reaches the fusion splice point, the reflected light leaks at the fusion splice point and is received as noise by the output light power detection monitor. As a result, it becomes difficult to accurately monitor the power of the output light.

  One aspect of the present invention is made to solve the above-described problem, and an object of the present invention is to provide an optical power monitoring apparatus and an optical power monitoring method capable of accurately monitoring the power of output light. . Another aspect of the present invention is to provide a fiber laser device having the above-described optical power monitor device and having excellent reliability.

  In order to achieve the above object, an optical power monitoring device according to one aspect of the present invention includes an incident side optical fiber, a core connected to the incident side optical fiber, and a first clad surrounding the outer side of the core. An output side optical fiber having a second clad surrounding the outside of the first clad, and an output leaked from the connection point provided near a connection point between the incident side optical fiber and the emission side optical fiber. A first photodetector for detecting light, wherein an interface between the first cladding and the second cladding of the emission side optical fiber is closer to the light emission side than a position of the first photodetector. In a part, in at least one of the cross sections parallel to the central axis of the emission-side optical fiber, a first inclination inclined in a direction approaching the central axis from the light emission side toward the connection point side Having a part And butterflies.

  For example, when a fiber laser device is used for laser processing or the like, the reflected light of the output light returns from the exit end of the exit side optical fiber toward the connection point. At this time, the reflected light travels toward the connection point while being reflected at the interface between the first cladding and the second cladding of the emission side optical fiber. When the reflected light returns to the connection point, there is a risk of leaking from the connection point to the outside and entering the first photodetector, and the incident reflected light becomes noise of the output light power monitor. On the other hand, in the optical power monitoring device according to one aspect of the present invention, the interface between the first cladding and the second cladding of the emission side optical fiber has the first inclined portion described above. Therefore, in the first inclined portion, the incident angle of the reflected light with respect to the interface between the first cladding and the second cladding is reduced. As a result, of the reflected light that propagates, light that leaks from the first inclined portion before reaching the connection point is generated, and the reflected light is incident on the first photodetector as compared with the case where there is no first inclined portion. The amount of light is reduced. Thereby, the precision of the power monitor of the output light by a 1st photodetector can be raised.

In the optical power monitoring device according to one aspect of the present invention, the interface is on the light emission side with respect to the position of the first photodetector and on the connection point side with respect to the first inclined portion. In a part, in at least one of the cross sections parallel to the central axis of the emission side optical fiber, a second inclination inclined in a direction away from the central axis from the light emission side toward the connection point side May have a part.
When the interface has the second inclined portion, the first inclined portion and the second inclined portion can be formed at the same time by, for example, a method such as stretching, so that it is easy to manufacture the emission side optical fiber suitable for the present invention. . In addition, when the second inclined portion is provided, the core and the cladding at the connection point can be secured at the connection point in order to expand again from the position where the outer diameter of the core and the cladding is minimized toward the connection point side. it can.

The optical power monitoring device according to one aspect of the present invention may further include a second photodetector that detects reflected light leaking from the first inclined portion.
According to this configuration, it is possible to monitor not only the output light power but also the reflected light power by the second photodetector.

  An optical power monitoring method according to one aspect of the present invention detects output light leaking from a connection point between an incident side optical fiber and an emission side optical fiber having a core, a first cladding, and a second cladding, The interface between the first cladding and the second cladding of the emission side optical fiber is parallel to the central axis of the emission side optical fiber at a part of the light emission side from the position of the first photodetector. At least one cross section of the first clad in the direction closer to the central axis from the light exit side toward the connection point side, so that the inside of the first clad is connected to the connection point side. At least a part of the reflected light propagating toward the outside is leaked out from the first inclined portion, and the output light is detected.

  According to this method, the output light is detected in a state where at least a part of the reflected light propagating in the first cladding toward the connection point side is leaked to the outside from the first inclined portion of the emission side optical fiber. Therefore, compared with the case where there is no first inclined portion, the reflected light incident on the first photodetector is reduced, and the accuracy of the power monitor of the output light by the first photodetector can be improved.

A fiber laser device according to one aspect of the present invention includes the optical power monitor device according to one aspect of the present invention.
According to this configuration, by including the optical power monitor device according to one aspect of the present invention, it is possible to provide a fiber laser device with excellent reliability.

  According to one aspect of the present invention, it is possible to provide an optical power monitoring device and an optical power monitoring method capable of accurately monitoring the amount of output light. Moreover, according to one aspect of the present invention, it is possible to provide a fiber laser device with excellent reliability.

It is a block diagram which shows schematic structure of the fiber laser apparatus of one Embodiment of this invention. It is sectional drawing of the optical power monitor apparatus of 1st Embodiment. It is a side view of an optical power monitor apparatus. It is sectional drawing of the optical power monitor apparatus of 2nd Embodiment. It is sectional drawing of the optical power monitor apparatus of 3rd Embodiment.

[Fiber laser equipment]
Hereinafter, a fiber laser device according to an embodiment of the present invention will be described with reference to FIG.
The fiber laser device of this embodiment is suitable for use in applications such as laser processing. However, the application is not limited to laser processing.
FIG. 1 is a block diagram showing a schematic configuration of the fiber laser apparatus of the present embodiment.
In the following drawings, in order to make each component easy to see, the scale of the size may be varied depending on the component.

  As shown in FIG. 1, the fiber laser device 1 includes a laser diode power source 2, a plurality of fiber laser units 3, a combiner unit 4, a fusion part storage case 5, a control unit 6, a control power source 7, a feed fiber 8, And an injection end 9. Although not shown, the fiber laser device 1 includes various sensors, an operation / display unit, an external interface, and the like in addition to the above-described components.

  The laser diode power supply 2 supplies power to the plurality of fiber laser units 3. The fiber laser unit 3 generates laser light by resonating and amplifying the excitation light. The combiner unit 4 combines a plurality of laser beams emitted from the plurality of fiber laser units 3 into one high output laser beam. The fusion part storage case 5 stores therein the fusion connection points of the optical fibers connecting the plurality of fiber laser units 3 and the combiner unit 4. The control unit 6 controls each unit in the apparatus including the plurality of fiber laser units 3 and the combiner unit 4. The control power supply 7 supplies power to the control unit 6. The laser light emitted from the combiner unit 4 is emitted from the emission end 9 through the feed fiber 8 toward, for example, the surface to be processed.

  The fiber laser unit 3 includes an excitation laser diode 11, a laser diode driver 12, an optical resonator 13, and an optical power monitor device 14. The excitation laser diode 11 emits excitation light. As the excitation laser diode 11, for example, a Fabry-Perot type semiconductor laser made of a GaAs semiconductor is used. The laser diode driver 12 receives a control signal from the control unit 6 and supplies predetermined power to the excitation laser diode 11. The optical resonator 13 resonates and amplifies the excitation light emitted from the excitation laser diode 11 and emits laser light. The optical power monitor device 14 measures the power of the output light in the optical resonator 13 and monitors the state of the output light such as the presence or absence of power fluctuation. As the optical power monitor device 14, any of the optical power monitor devices of the first to third embodiments described later may be used.

  The combiner unit 4 includes a combiner 16, an abnormality monitoring monitor 17, and a combiner unit control unit 18. The combiner 16 combines a plurality of laser beams emitted from the plurality of fiber laser units 3 into one laser beam. The abnormality monitoring monitor 17 monitors the presence or absence of an abnormality such as a change in optical power in the combiner unit 4. The combiner unit control unit 18 controls each unit in the combiner unit 4.

[Optical Power Monitor Device of First Embodiment]
Hereinafter, the optical power monitoring apparatus according to the first embodiment will be described with reference to FIGS.
FIG. 2 is a cross-sectional view of the optical power monitor apparatus according to the first embodiment. FIG. 3 is a side view of the optical power monitor device.

As shown in FIGS. 2 and 3, the optical power monitoring device 21 of the first embodiment includes an incident side optical fiber 22, an emission side optical fiber 23, a support member 24, a filler 25, and an output light monitor. A photodetector 26. The incident side optical fiber 22 and the emission side optical fiber 23 are fusion-bonded to each other. The reflected light LR travels from the incident side optical fiber 22 toward the emission side optical fiber 23. Hereinafter, the incident-side optical fiber 22 and the emission-side optical fiber 23 that are fused and connected together may be referred to as an optical fiber 27. Further, the end surface of the incident side optical fiber 22 and the end surface of the exit side optical fiber 23 which are in contact with each other and are fusion-bonded are referred to as a connection point J.
The output light monitoring photodetector 26 of the present embodiment corresponds to the first photodetector in the claims.

  The incident side optical fiber 22 is composed of a single clad fiber having a two-layer structure of a core 28 and a clad 29 surrounding the core 28. The outer side of the clad 29 is covered with a coating 30. The constituent materials of the core 28, the clad 29, and the coating 30 are those used for general optical fibers. The coating 30 is made of a material having a refractive index higher than that of the clad 29. Within a range of a predetermined distance from the connection point J, the coating 30 is peeled off, and the clad 29 is exposed.

  The emission side optical fiber 23 is composed of a double clad fiber having a three-layer structure of a core 31, a first clad 32 surrounding the core 31, and a second clad 33 surrounding the first clad 32. The refractive index of the first cladding 32 is lower than the refractive index of the core 31, and the refractive index of the second cladding 33 is lower than the refractive index of the first cladding 32. As a specific example, for example, the diameter of the core 31 is 30 μm, the diameter of the first cladding 32 is 420 μm, and the diameter of the second cladding 33 is 440 μm. The outside of the second cladding 33 is covered with a coating 34. Within a range of a predetermined distance from the connection point J, the coating 34 is peeled off and the second cladding 33 is exposed.

  The constituent material of the core 31 is, for example, quartz to which an element such as aluminum for increasing the refractive index of quartz is added, and is emitted from the excitation laser diode 11 into at least a partial region of the core 31. Ytterbium (Yb) which is an active element that is excited by excitation light is added. Examples of this type of active element include ytterbium (Yb) and rare earth elements such as neodymium (Nd) and erbium (Er). Furthermore, examples of the active element include rare earth elements, bismuth (Bi), chromium (Cr), and the like. As a constituent material of the first cladding 32, for example, quartz to which a dopant is not added can be cited. As a constituent material of the second cladding 33, for example, an ultraviolet curable resin can be cited.

  The support member 24 functions as a reinforcing material that supports the optical fiber 27 and particularly reinforces the strength near the connection point J. In the drawing, the support member 24 is shown as a member having a rectangular planar shape, but the planar shape of the support member 24 is not particularly limited to a rectangular shape. On the upper surface of the support member 24, a groove 24M large enough to accommodate the optical fiber 27 is provided. The optical fiber 27 is fixed to the support member 24 while being accommodated in the groove 24M. The support member 24 is made of, for example, aluminum that has been subjected to black alumite treatment. The shape and dimensions of the groove 24M are not particularly limited.

  The filler 25 is filled in the groove 24M so as to fill the periphery of the optical fiber 27. Since the coating 30 and the coating 34 are peeled off in the vicinity of the connection point J of the optical fiber 27, the filler 25 in the vicinity of the connection point J is in direct contact with the second cladding 33 in the emission side optical fiber 23. The incident side optical fiber 22 is in direct contact with the clad 29. The filler 25 is made of a material having a refractive index equal to that of the second clad 33 and the clad 29 or a refractive index higher than that of the second clad 33 and the clad 29. For the filler 25, for example, a resin material may be used, or glass may be used. When a resin material is used for the filler 25, the filler 25 can be formed by a method of curing after pouring the resin material into the groove 24M. In this case, the advantage that the filler 25 can be embedded in the groove 24M without a gap is obtained.

  As shown in FIG. 3, fine irregularities are provided on the inner wall surface of the groove 24M. Thereby, the light scattering property is provided to the inner wall surface of the groove 24M. However, the light scattering property may not be provided to all the inner wall surfaces of the groove 24M, and it is sufficient that the light scattering property is provided at least in the vicinity of the connection point J among the inner wall surfaces of the groove 24M. Alternatively, as a means for imparting light scattering properties to the inner wall surface of the groove 24M, for example, another member having light scattering properties, a so-called scatterer may be inserted into the groove 24M. As this type of member, for example, a scatterer made of crystallized glass having light scattering properties can be used.

  As shown in FIG. 2, the output light monitoring photodetector 26 is provided on the upper surface of the filler 25 above the emission side optical fiber 23. That is, the output light monitoring photodetector 26 is arranged at a predetermined distance from the connection point J at a position overlapping the emission side optical fiber 23 when viewed from above the support member 24. The light LA from the incident side optical fiber 22 toward the emission side optical fiber 23 slightly leaks outside the optical fiber 27 when passing through the connection point J. As shown in FIG. 3, the leaked light LA is scattered on the inner wall surface of the groove 24 </ b> M and enters the output light monitoring photodetector 26. As the output light monitoring photodetector 26, for example, an infrared photodiode can be used, but other photodetectors may be used.

  The emission side optical fiber 23 has a first inclined portion 36 and a second inclined portion 37 on the light emission side from the position of the output light monitoring photodetector 26. The first inclined portion 36 has a central axis from the light emission side toward the connection point J side in a cross section in which the interface between the first cladding 32 and the second cladding 33 is parallel to the central axis C of the emission side optical fiber 23. It is a portion inclined in a direction approaching C. In the second inclined portion 37, the interface F between the first cladding 32 and the second cladding 33 is connected to the light emission side from the position of the output light monitoring photodetector 26 and more than the first inclined portion 36. A part of the point J side is a portion inclined in a direction away from the central axis C from the light emission side toward the connection point J side in a cross section parallel to the central axis C of the emission side optical fiber 23.

  FIG. 2 is a cross-sectional view in a cross section parallel to the central axis C of the emission side optical fiber 23, and there are innumerable cross sections parallel to the central axis C of the emission side optical fiber 23. The exit side optical fiber 23 of the present embodiment has the same shape in any cross section, and has a first inclined portion 36 and a second inclined portion 37 in any cross section. That is, in the emission side optical fiber 23, the portion where the first inclined portion 36 and the second inclined portion 37 are provided has a rotationally symmetric shape about the central axis C of the emission side optical fiber 23. .

  In other words, the exit side optical fiber 23 includes a reduced diameter portion in which the diameter of the exit side optical fiber 23 decreases from the light exit side toward the connection point J side, and an exit side light from the light exit side toward the connection point J side. It has a constricted portion 38 including an enlarged diameter portion where the diameter of the fiber 23 is enlarged. The reduced diameter portion corresponds to the first inclined portion 36, and the enlarged diameter portion corresponds to the second inclined portion 37. That is, the constricted portion 38 has two inclined surfaces including the inclined surface 36K of the first inclined portion 36 and the inclined surface 37K of the second inclined portion 37. In the case of this embodiment, the outer shape of the core 31, the outer shape of the first cladding 32, and the outer shape of the second cladding 33 all have a constricted shape. Such a double clad fiber having the constricted portion 38 can be produced by, for example, drawing a heated fiber.

  As described above, when a fiber laser is used for laser processing, for example, when reflected light from the processing surface returns to the fiber laser during processing of the material, the output light power may fluctuate and processing characteristics may deteriorate. Therefore, an optical power monitoring device for monitoring the output optical power is required. However, if the exit side fiber is a double clad fiber, there is reflected light LR that propagates in the first clad 32 while being reflected at the interface between the first clad 32 and the second clad 33 as shown in FIG. To do. At this time, the incident angle θ1 of the reflected light LR with respect to the interface F between the first cladding 32 and the second cladding 33 is always constant no matter how many times it is reflected. When the reflected light LR propagates through the first cladding 32 and reaches the connection point J, the reflected light LR leaks out at the connection point J and is received by the output light monitoring photodetector 26 as noise. As a result, the power of the output light may not be monitored accurately.

  With respect to this problem, in the optical power monitoring device 21 of the present embodiment, the emission side optical fiber 23 is closer to the light emission side than the position of the output light monitoring photodetector 26 and the first clad 32 and the second clad. 33 has a first inclined portion 36 that is inclined in a direction approaching the central axis C of the emission side optical fiber 23 from the light emission side toward the connection point J side from the light emission side. Therefore, the incident angle θ <b> 2 of the reflected light LR reflected by the inclined surface 36 </ b> K of the first inclined portion 36 is smaller than the incident angle θ <b> 1 before reaching the first inclined portion 36. That is, θ1> θ2. As a result, part of the reflected light LR propagated toward the connection point J leaks from the inclined surface 36K before reaching the connection point J, and does not have the first inclined portion 36. Compared to the case, the amount of reflected light incident on the output light monitoring photodetector 26 is reduced. Thereby, the accuracy of the power monitoring of the output light by the output light monitoring photodetector 26 can be improved.

  When the exit-side optical fiber 23 has the constricted portion 38, the first inclined portion 36 and the second inclined portion 37 can be formed simultaneously by a method such as stretching, which is suitable for the optical power monitoring device 21 of the present embodiment. An exit side optical fiber having an inclined surface can be easily manufactured. In addition, when the second inclined portion 37 is provided in the emission side optical fiber 23, it expands again on the connection point J side from the position where the outer diameter of the core or the cladding is minimized. Dimensions can be secured.

  As a result of monitoring the power of the output light while using the fiber laser, for example, when the output light power exceeds an allowable value, the control unit 6 performs control such as reducing the drive current supplied to the excitation laser diode 11. May be. At this time, the control unit 6 may perform APC control. How to use the monitor result obtained by the optical power monitor device 14 is not particularly limited in the present invention.

[Optical Power Monitoring Device of Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG.
The basic configuration of the optical power monitoring apparatus of the second embodiment is the same as that of the first embodiment, and the configuration of the optical fiber is different from that of the first embodiment.
FIG. 4 is a cross-sectional view of the optical power monitoring device of the second embodiment.
4, the same code | symbol is attached | subjected to the same component as drawing used in 1st Embodiment, and the description is abbreviate | omitted.

  In the first embodiment, the exit side optical fiber has a constricted portion including a first inclined portion and a second inclined portion. On the other hand, as shown in FIG. 4, in the optical power monitor device 41 of the present embodiment, the exit side optical fiber 42 has a constricted portion including a first inclined portion and a second inclined portion. Absent. In the emission side optical fiber 42, the interface F between the first cladding 44 and the second cladding 45 is inclined in the direction approaching the central axis C of the emission side optical fiber 42 from the light emission side toward the connection point J side. Only the inclined portion 36 is provided.

In the emission-side optical fiber 42 of the present embodiment, the outer diameter of the core 43, the outer diameter of the first cladding 44, and the outer diameter of the second cladding 45 on the connection point J side with respect to the first inclined portion 36 are as follows. Smaller than the outer diameter of the core 43, the outer diameter of the first cladding 44, and the outer diameter of the second cladding 45 on the light emission side of the inclined portion 36. Correspondingly, the outer diameter of the core 47 of the incident side optical fiber 46 and the outer diameter of the cladding 48 are the outer diameter of the core 43 closer to the connection point J than the first inclined portion 36 of the emission side optical fiber 42 and The outer diameter of each of the second claddings 45 coincides with that of the second cladding 45.
Other configurations are the same as those of the first embodiment.

  Also in the present embodiment, the same effect as in the first embodiment that the accuracy of the power monitor of the output light can be improved by reducing the reflected light incident on the output light monitoring photodetector 26 is obtained.

[Optical Power Monitoring Device of Third Embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG.
The basic configuration of the optical power monitoring apparatus of the third embodiment is the same as that of the first embodiment, and is different from the first embodiment in that a reflected light monitoring photodetector is added.
FIG. 5 is a cross-sectional view of the optical power monitoring device of the third embodiment.
5, the same code | symbol is attached | subjected to the same component as drawing used in 1st Embodiment, and the description is abbreviate | omitted.

As shown in FIG. 5, the optical power monitoring device 51 of the third embodiment detects the reflected light LR leaking from the inclined surface 36K of the emission side optical fiber 23 in addition to the optical power monitoring device 21 of the first embodiment. Further, a reflected light monitoring photodetector 52 is provided. In this example, the reflected light monitoring photodetector 52 is disposed in the vicinity of the center of the constricted portion 38, but in a region where the reflected light LR that is reflected by the inclined surface 36 K of the emission side optical fiber 23 and leaks arrives. It suffices if they are arranged. Thereby, the reflected light monitoring photodetector 52 can detect the reflected light LR leaking from the inclined surface 36K of the emission side optical fiber 23.
Other configurations are the same as those of the first embodiment.
The reflected light monitoring photodetector 52 of the present embodiment corresponds to the second photodetector in the claims.

  Also in this embodiment, the same effect as the first and second embodiments can be obtained that the accuracy of the power monitor of the output light can be increased by reducing the reflected light incident on the output light monitoring photodetector 26. It is done. Further, in the case of the present embodiment, a further effect that the reflected light power can be monitored by the reflected light monitoring photodetector 52 is obtained. As a result of monitoring the power of the reflected light, for example, when the reflected light power exceeds an allowable value, the control unit 6 detects an abnormality and performs control such as reducing the drive current supplied to the excitation laser diode 11. Also good. According to this embodiment, it is possible to quickly cope with an abnormality in reflected light.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the said embodiment, the example in which the exit side optical fiber has the 1st inclination part was given in any cross section among the countless cross sections parallel to the central axis of the exit side optical fiber. Instead of this configuration, the exit-side optical fiber has a first inclined portion in one of a number of sections (specific sections) parallel to the central axis of the exit-side optical fiber, and in the other sections The output side optical fiber may not have the first inclined portion. That is, the portion of the emission side optical fiber provided with the first inclined portion does not necessarily have a rotationally symmetric shape around the central axis of the emission side optical fiber. Even with this configuration, the accuracy of the output optical power monitor can be improved as compared with the conventional configuration that does not have the first inclined portion.

The inclined surface of the exit side optical fiber is straight when viewed in the cross-sectional shape of FIG. 2 or the like, but may be curved. In addition, an example was shown in which the optical power monitoring device was applied to the fusion splice point between a single clad fiber and a double clad fiber, but instead of this configuration, it was applied to a fusion splice point between a double clad fiber and a double clad fiber. May be.
In addition, the specific description regarding the shape, size, arrangement, and material of each component of the optical power monitor device and the fiber laser device is not limited to the above embodiment, and can be changed as appropriate.

  The present invention can be used for, for example, a fiber laser device used for laser processing and an optical power monitor device.

  DESCRIPTION OF SYMBOLS 1 ... Fiber laser apparatus, 14, 21, 41, 51 ... Optical power monitor apparatus, 22, 46 ... Incident side optical fiber, 23, 42 ... Emission side optical fiber, 26 ... Output light monitoring photodetector (1st (Detector), 31, 43 ... core, 32, 44 ... first clad, 33, 45 ... second clad, 36 ... first inclined portion, 36K ... inclined surface, 37 ... second inclined portion, 38 ... Constriction, 52... Reflected light monitor photodetector (second photodetector), C... Central axis.

Claims (5)

An incident side optical fiber;
An emission-side optical fiber connected to the incident-side optical fiber and having a core, a first cladding surrounding the outside of the core, and a second cladding surrounding the outside of the first cladding;
A first photodetector that is provided in the vicinity of a connection point between the incident-side optical fiber and the emission-side optical fiber and detects output light leaking from the connection point;
With
The interface between the first clad and the second clad of the emission side optical fiber is parallel to the central axis of the emission side optical fiber in a part of the light emission side from the position of the first photodetector. An optical power monitor device comprising a first inclined portion inclined in a direction approaching the central axis from the light exit side toward the connection point side in at least one of the cross sections.   The interface is on the light exit side from the position of the first photodetector, and in the part of the connection point side from the first inclined portion, to the central axis of the exit side optical fiber. The at least one of the parallel cross sections includes a second inclined portion that is inclined in a direction away from the central axis from the light emission side toward the connection point side. Optical power monitor device.   The optical power monitoring apparatus according to claim 1, further comprising a second photodetector that detects reflected light leaking from the first inclined portion. Detecting output light leaking from the connection point between the incident side optical fiber and the exit side optical fiber having the core, the first cladding, and the second cladding;
The interface between the first clad and the second clad of the emission side optical fiber is parallel to the central axis of the emission side optical fiber at a part of the light emission side from the position of the first photodetector. In at least one of the cross-sections, a first inclined portion inclined in a direction approaching the central axis from the light emitting side toward the connection point side is provided, and the connection point is formed in the first cladding. An optical power monitoring method comprising detecting at least a part of reflected light propagating toward the outside from the vicinity of the first inclined portion and detecting the output light.   A fiber laser device comprising the optical power monitor device according to any one of claims 1 to 3.

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