JP5865977B1 - FIBER LASER DEVICE, OPTICAL POWER MONITOR DEVICE, AND OPTICAL POWER MONITOR METHOD - Google Patents

Abstract

A fiber laser device and the like that can accurately monitor reflected light and prevent deterioration of processing characteristics. A fiber laser device includes an optical fiber F that functions as an amplification medium, an optical fiber F1 that functions as a transmission medium that transmits light output from the optical fiber F, and a fusion splicing point between the optical fibers F and F1. The light detector 26a is arranged on the output side of the output light from P and detects the output light leaking out at the fusion splice point P, and is arranged on the input side of the output light from the fusion splice point P. An optical power monitor device 12 having a photodetector 26b for detecting reflected light leaking at the connection point P, and photodetectors 26a and 26b obtained in advance from the optical power monitor device 12 in a situation where no reflected light is generated. And a calculation unit 31 that performs a calculation for eliminating the influence of the output light from the detection result of the photodetector 26b. [Selection] Figure 5

Description

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

In recent years, fiber laser devices have attracted attention as high-power laser devices used in the industrial field. This fiber laser device has excellent beam quality (BPP and M ² ) and high light condensing performance compared to conventional high-power laser devices (for example, carbon dioxide laser devices), so that the processing time can be shortened. , It has the advantage of being able to save energy. In addition, the fiber laser apparatus has an advantage that there is no need for maintenance such as alignment because there is no spatial optical component.

  In such a fiber laser device, for example, when reflected light generated on the work surface of the workpiece returns to the fiber laser device during processing of the workpiece, the oscillation state becomes unstable, and the power of the output light fluctuates. As a result, a phenomenon occurs in which the machining characteristics are deteriorated. In order to avoid such a phenomenon, it is necessary to monitor the power of the output light and the reflected light temporally to prevent the oscillation state from becoming unstable.

As a method for monitoring the power of output light and reflected light, the following two methods are mainly mentioned.
(1) A method in which an optical fiber coupler having a low branching ratio is connected to an output fiber, and the branched output light and reflected light are respectively detected and monitored by a photodetector such as a photodiode (PD). A method of detecting and monitoring output light and reflected light leaking from a connection point with an optical fiber by a photodetector (see Patent Document 1 below)

JP 2013-174583 A

  By the way, in the method (1) described above, there is a problem that the optical fiber coupler is damaged without being able to withstand the high output of the fiber laser device. Currently, there are optical fiber couplers that can be used with an output of several [W] to tens [W], but there are no optical fiber couplers that can be used with an output of several hundred [W] to several [kW]. Even if an optical fiber coupler capable of withstanding such a high output is developed, there may be a problem that the addition of the optical fiber coupler causes an increase in cost and a decrease in efficiency.

  On the other hand, in the method (2) described above, although it is possible to cope with a high output of several hundred [W] to several [kW], the output light leaked from the connection point monitors the output light. May be detected by both the photodetector for detecting the reflected light and the photodetector for monitoring the reflected light. For this reason, there is a problem that the reflected light is monitored even when there is no reflected light returning to the fiber laser device.

  Here, if the photodetector for monitoring the reflected light is moved away from the connection point, it is considered that the output light monitored by the photodetector can be reduced. However, if the photodetector for monitoring the reflected light is moved away from the connection point, the power of the reflected light to be monitored itself decreases, and the scattered light is detected to increase the noise. Then, the reflected light to be monitored is influenced by noise, and there is a problem that the reflected light cannot be monitored with high accuracy.

  The present invention has been made in view of the above circumstances, and a fiber laser device capable of accurately monitoring reflected light to prevent deterioration of processing characteristics, and optical power capable of accurately monitoring reflected light. It is an object of the present invention to provide a monitoring device and an optical power monitoring method.

In order to solve the above problems, a fiber laser device of the present invention includes a first optical fiber (F) that functions as an amplification medium and a second optical fiber that functions as a transmission medium that transmits light from the first optical fiber. In the fiber laser device (1) comprising (F1), the output light that is disposed on the output side of the output light (L1) from the connection point (P) in the second optical fiber and leaks at the connection point. A first detector (26a) for detecting, and a second detector (26b) that is disposed closer to the input side of the output light than the connection point and detects reflected light (L2) leaked at the connection point. And using the relationship between the detection results of the first detector and the second detector obtained in advance from the optical power monitor device in a situation where the reflected light does not occur, Detection result of 2 detectors It is characterized by comprising calculating unit for performing an operation to eliminate the influence of al the output light and (31).
Further, the fiber laser device of the present invention has a characteristic value indicating a ratio of detection results of the first detector and the second detector obtained in advance from the optical power monitor device in a situation where the reflected light is not generated. A storage unit (32) that stores the value obtained by multiplying the characteristic value stored in the storage unit by the detection result of the first detector, It is characterized by performing an operation of subtracting from the detection result of the detector.
In the fiber laser device of the present invention, the storage unit stores the characteristic value for each temperature of the optical power monitoring device, and the calculation unit includes the characteristic value stored in the storage unit. The characteristic value according to the measurement result of the temperature measuring device (40) provided in the optical power monitor device is multiplied by the detection result of the first detector.
Further, in the fiber laser device of the present invention, the storage unit stores the characteristic value every predetermined time elapsed, and the calculation unit includes the characteristic value stored in the storage unit. The characteristic value corresponding to the elapsed time measured by the timer unit (34) is multiplied by the detection result of the first detector.
In the fiber laser device of the present invention, the connection point is covered with a transparent material (27) in which absorption does not cause a substantial loss with respect to light having the same wavelength as the output light and the reflected light. It is characterized by that.
In the fiber laser device of the present invention, the connection point is covered with a material having higher thermal conductivity than the first optical fiber and the second optical fiber.
The fiber laser device of the present invention includes a light source device (11) that supplies pumping light to the first optical fiber, and the first detector and the second detector that are output from the optical power monitor device. The control device (13) that controls the light source device based on the detection result of the first detector and the calculation result of the calculation unit obtained using the detection result of the second detector. ).
The optical power monitoring device of the present invention is an optical power monitoring device that detects light leaking at a connection point (P) of an optical fiber and monitors the power of output light (L1) and reflected light (L2). A first detector (26a) for detecting the output light leaked at the connection point, disposed on the output side of the output light from the point, and disposed on the input side of the output light from the connection point; The second detector (26b) for detecting the reflected light leaking at the connection point, and the detection results of the first detector and the second detector obtained in advance under the condition where the reflected light does not occur. And a calculation unit (31) that performs a calculation that excludes the influence of the output light from the detection result of the second detector.
The optical power monitoring method of the present invention is an optical power monitoring method for detecting light leaking at a connection point (P) of an optical fiber and monitoring the power of output light (L1) and reflected light (L2), The output light leaking at the connection point is detected by the first detector (26a) disposed on the output side of the output light from the connection point, and the reflected light leaking at the connection point is detected by the connection point. Detection by the second detector (26b) disposed on the input side of the output light with respect to the point, and detection of the first detector and the second detector obtained in advance under the condition where the reflected light does not occur Using the result relationship, an operation for eliminating the influence of the output light from the detection result of the second detector is performed.

  According to the present invention, the relationship between the detection results of the first detector and the second detector obtained in advance from the optical power monitor device under the condition where no reflected light is generated is used to output light from the detection result of the second detector. Therefore, the reflected light can be monitored with high accuracy. As a result, it is possible to prevent a situation in which the oscillation state becomes unstable, so that it is possible to prevent deterioration of processing characteristics.

It is a block diagram which shows the principal part structure of the fiber laser apparatus by 1st Embodiment of this invention. It is a plane perspective view of the optical power monitor apparatus with which the fiber laser apparatus by 1st Embodiment of this invention is provided. It is a front view of the optical power monitor device. It is a cross-sectional arrow view of the AA line (BB line) in FIG. It is a block diagram which shows the principal part structure of the control apparatus with which the fiber laser apparatus by 1st Embodiment of this invention is provided. In 1st Embodiment of this invention, it is a figure which shows an example of the monitoring result of the optical power monitor apparatus in the condition where reflected light does not arise. It is a figure for demonstrating the effect of the correction | amendment performed with the fiber laser apparatus by 1st Embodiment of this invention. It is a block diagram which shows the principal part structure of the control apparatus with which the fiber laser apparatus by 2nd Embodiment of this invention is provided. It is a figure which shows an example of the temperature table used by 2nd Embodiment of this invention. It is a block diagram which shows the principal part structure of the control apparatus with which the fiber laser apparatus by 3rd Embodiment of this invention is provided. It is a figure which shows an example of the time table used in 3rd Embodiment of this invention.

  Hereinafter, a fiber laser device, an optical power monitoring device, and an optical power monitoring method according to embodiments of the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a block diagram showing a main configuration of the fiber laser device according to the first embodiment of the present invention. As shown in FIG. 1, a fiber laser device 1 includes an optical fiber F (first optical fiber) that functions as an amplification medium, an optical fiber F1 (second optical fiber) that functions as a transmission medium, a light source device 11, and an optical power monitor device. 12 and the control device 13, and outputs laser light (output light) L 1 from the output end X of the optical fiber F 1 under the control of the control device 13.

  The optical fiber F functioning as an amplifying medium is a single clad fiber including a core to which an active element is added and a clad surrounding the core. The optical fiber F amplifies the light propagating through the core of the optical fiber F by the active element excited by the excitation light supplied from the light source device 11. In this optical fiber F, fiber Bragg gratings G1 and G2 in which the refractive index of the core is periodically changed are formed. For this reason, the light propagating through the core of the optical fiber F is amplified while being repeatedly reflected by these two fiber Bragg gratings G1 and G2.

  The optical fiber F1 functioning as a transmission medium is a single clad fiber including a core and a clad surrounding the core. Note that the active fiber is not added to the core of the optical fiber F1 unlike the core of the optical fiber F. One end of the optical fiber F1 is an output end X of the output light L1, and the other end is fusion-connected to the optical fiber F in the optical power monitor device 12 (details will be described later).

  The light source device 11 includes, for example, a plurality of semiconductor lasers, and supplies excitation light to the optical fiber F under the control of the control device 13. The optical power monitoring device 12 includes the power of the output light L1 output from the output end X of the optical fiber F1 and the reflected light L2 input through the output end X (for example, on the processing surface of the workpiece during processing of the workpiece). Of the generated reflected light, the power of the reflected light input via the output terminal X is monitored. Details of the optical power monitor device 12 will be described later.

  The control device 13 refers to the power of the output light L1 and the reflected light L2 monitored by the optical power monitor device 12, and controls the light source device 11 so that the power of the output light L1 output from the output terminal X is constant. Control. In addition, the control device 13 emits light from the light source device 11 in order to protect the fiber laser device 1 when the power of the reflected light L2 monitored by the optical power monitor device 12 exceeds a predetermined threshold. Control to stop.

  FIG. 2 is a plan perspective view of the optical power monitor device provided in the fiber laser device according to the first embodiment of the present invention, and FIG. 3 is a front view of the optical power monitor device. 4 is a cross-sectional view taken along line AA (line BB) in FIG. As shown in FIGS. 2 to 4, the optical power monitoring device 12 includes a pedestal 21, a grooved plate 22, a scatterer 23, a cover plate 24, a fixed block 25, a photodetector 26 a (first detector), and light. A detector 26b (second detector) is provided, and the light leaked at the fusion splice point P (connection point) of the optical fibers F and F1 is detected to monitor the power of the output light L1 and the reflected light L2. . 2 and 4, the illustration of the cover plate 24 is omitted.

  The pedestal 21 is a plate-like member having a rectangular shape in plan view, and is formed of, for example, a metal such as aluminum whose surface is black anodized. Similar to the base 21, the grooved plate 22 is a plate-like member having a rectangular shape in plan view, and is formed of a metal such as aluminum whose surface is black anodized, for example, and is fixed on the base 21. . A groove G extending from the left end to the right end of the grooved plate 22 is formed on the upper surface of the grooved plate 22.

  The scatterer 23 is a rectangular parallelepiped member, which is made of crystallized glass such as Neoceram (registered trademark), and is disposed in the groove G and fixed to the bottom surface of the groove G as shown in FIG. Yes. The scatterer 23 randomizes the propagation direction of the light leaked at the fusion splicing point P of the optical fibers F and F1, so that the output light L1 and the reflected light obtained from the detection results of the photodetectors 26a and 26b. It is provided to reduce the fluctuation of the power of L2. Further, as shown in FIG. 2, a groove extending from the left end to the right end of the scatterer 23 is formed on the upper surface of the scatterer 23.

  In the groove formed on the upper surface of the scatterer 23, as shown in FIGS. 2 and 3, an optical fiber F and an optical fiber F1 whose end faces are fusion-connected are arranged. The optical fiber F is fixed near the left end of the scatterer 23 and the grooved plate 22 by adhesives A11 and A12. Similarly, the optical fiber F1 is fixed in the vicinity of the right end of the scatterer 23 and the grooved plate 22 by adhesives A21 and A22, respectively.

  The groove of the scatterer 23 in which the optical fibers F and F1 are arranged is filled with a high refractive index resin 27 (transparent material). The high refractive index resin 27 is a transparent resin having a higher refractive index than the clad of the optical fibers F and F1, and light leaking from the core to the clad at the fusion splice point P is not confined in the clad. This is for leaking out of the fibers F and F1. The optical fibers F and F1 have their coatings peeled off in the vicinity of the fusion splice point P in order to make the clad directly contact with the high refractive index resin 27.

  Here, the “transparent resin” is a resin in which the substantial loss factor is only scattering and reflection with respect to light having the same wavelength as the output light L1 and the reflected light L2, that is, absorption is a substantial loss factor. The resin that does not become. The reason why such a transparent resin is used is to prevent light leaking at the fusion splice point P from being absorbed by the high refractive index resin 27 and increasing the temperature around the fusion splice point P. is there. In addition, as the high refractive index resin 27, it is desirable to use a material having higher thermal conductivity than the optical fibers F and F1. This is because the light leaked at the fusion splice point P is absorbed by the high refractive index resin 27 to easily release the heat to the outside, thereby preventing the temperature around the fusion splice point P from rising. It is to do.

  The lid plate 24 is a plate-like member having a rectangular shape in plan view, like the pedestal 21, and is formed of a metal such as aluminum whose surface is black anodized, for example. The cover plate 24 is disposed on the grooved plate 22 so as to cover the groove G, and is fixed to the upper surface of the grooved plate 22 (part other than the groove G shown in FIG. 2). Thereby, external light incident on the groove G is blocked, and a dark room state is realized in the groove G.

  As shown in FIG. 4, the pedestal 21 and the grooved plate 22 are formed with openings H at portions where the photodetectors 26a and 26b are arranged. These openings H are for allowing the light leaked at the fusion splice point P of the optical fibers F and F1 to be guided to the photodetectors 26a and 26b. The opening H may be any shape as long as it is larger than the light receiving surfaces of the photodetectors 26a and 26b and smaller than the pedestal contact surface of the fixed block 25.

  As shown in FIGS. 3 and 4, photodetectors 26 a and 26 b are arranged on the bottom surface side of the base 21. The photodetectors 26a and 26b are, for example, infrared photodiodes, which are respectively disposed directly below the opening H, and detect light leaked at the fusion splice point P of the optical fibers F and F1. Specifically, the photodetector 26a is disposed on the output side of the output light L1 with respect to the fusion splice point P (right side in FIG. 3), and detects the output light L1 leaked at the fusion splice point P. Further, the photodetector 26b is arranged on the input side (left side in FIG. 3) of the output light L1 with respect to the fusion splice point P, and detects the reflected light L2 leaking at the fusion splice point P.

  Here, the propagation direction of the output light L1 is a direction from the optical fiber F toward the optical fiber F1, and the output light L1 leaked at the fusion splice point P is mainly a high refractive index resin from the side surface of the optical fiber F1. It leaks into 27. For this reason, the photodetector 26a for detecting the output light L1 is arranged on the output side of the output light L1 with respect to the fusion splice point P. On the other hand, the propagation direction of the reflected light L2 is a direction from the optical fiber F1 toward the optical fiber F, and the reflected light L2 leaked at the fusion splice point P is mainly a high refractive index from the side surface of the optical fiber F. It leaks into the resin 27. For this reason, the photodetector 26b for detecting the reflected light L2 is arranged on the input side of the output light L1 with respect to the fusion splice point P.

  As shown in FIGS. 3 and 4, the photodetectors 26 a and 26 b are fixed to the base 21 by the fixing block 25. The fixing block 25 is a rectangular parallelepiped member formed of, for example, a metal such as aluminum. The fixing block 25 fixes the photodetectors 26a and 26b and surrounds the space including the photodetectors 26a and 26b from four sides. This prevents light from entering the photodetectors 26a and 26b. A lens 28 is disposed on the front side of the light receiving surfaces of the photodetectors 26a and 26b.

  FIG. 5 is a block diagram showing a main configuration of the control device provided in the fiber laser device according to the first embodiment of the present invention. In FIG. 5, the optical power monitor device 12 is illustrated in a simplified manner, and the components corresponding to the components illustrated in FIGS. 2 to 4 are denoted by the same reference numerals. As shown in FIG. 5, the control device 13 of the fiber laser device 1 includes a calculation unit 31, a storage unit 32, and a control unit 33.

  The calculation unit 31 receives the detection results (monitor values) of the photodetectors 26a and 26b provided in the optical power monitor device 12, and uses these monitor values to perform calculations for increasing the accuracy of the reflected light L2. Do. Specifically, the calculation unit 31 is obtained from the optical power monitoring device 12 using the relationship between the monitor values of the photodetectors 26a and 26b obtained in advance from the optical power monitoring device 12 in a situation where the reflected light L2 is not generated. An operation for correcting the monitor value of the photodetector 26b is performed. This calculation is to eliminate the influence of the output light L1 leaking at the fusion splicing point P between the optical fiber F and the optical fiber F1 being received by the photodetector 26b that detects the reflected light L2. Is.

Here, it is assumed that the monitor value of the photodetector 26a obtained from the optical power monitor device 12 under the condition where the reflected light L2 is not generated is “α”, and the monitor value of the photodetector 26b is “β”. Also, assume that the monitor value of the photodetector 26a obtained from the optical power monitor device 12 in the actual use state (for example, during machining of the workpiece) is “P1”, and the monitor value of the photodetector 26b is “P2”. The calculation unit 31 calculates the monitor value “P2 ′” after the correction of the photodetector 26b by performing the calculation shown in the following equation (1).
P2 '= P2- (β / α) · P1 (1)

  FIG. 6 is a diagram illustrating an example of a monitoring result of the optical power monitoring device in a situation where no reflected light is generated in the first embodiment of the present invention. In FIG. 6, the actual power of the output light L1 is taken on the horizontal axis, and the monitor value obtained from the optical power monitor device 12 is taken on the vertical axis. In FIG. 6, the straight line to which the reference sign Q1 is attached is a straight line indicating the monitor value of the photodetector 26a, and the straight line to which the reference sign Q2 is attached is a straight line indicating the monitor value of the photodetector 26b.

  Referring to FIG. 6, the monitor values of the photodetectors 26a and 26b both increase in proportion to the power of the output light L1. For this reason, the monitor values of the photodetectors 26a and 26b under the condition where the reflected light L2 is not generated have a relationship in which the ratio (β / α) is constant regardless of the power of the output light L1. In the present embodiment, the output value L1 is received by the photodetector 26b by multiplying the monitor value “P1” of the photodetector 26a by the ratio (β / α) by using such a relationship. (See the second term on the right side of the above equation (1)). Then, the corrected monitor value “P2 ′” is obtained by subtracting the influence from the monitor value “P2” of the photodetector 26b.

  The storage unit 32 includes a non-volatile memory such as a flash memory, for example, and a ratio of monitoring values (β / α: characteristic value) of the photodetectors 26a and 26b obtained in advance under the condition where the reflected light L2 is not generated. Remember. The calculation unit 31 reads the ratio stored in the storage unit 32 and performs the calculation of the above formula (1). The storage unit 32 also stores a threshold value for stopping light emission of the light source device 11. This threshold is for protecting the fiber laser device 1.

  Here, the ratio (β / α) is stored in the storage unit 32 when the fiber laser device 1 is shipped from the factory, or when the shipped fiber laser device 1 is installed, for example. For example, it is stored through the following procedure. First, an absorber is installed in front of the output end X (the direction in which the output light L1 is output) to set the situation where no reflected light L2 is generated. Next, the output light L1 is output, and the monitor values of the photodetectors 26a and 26b obtained from the optical power monitoring device 12 are acquired. Then, the ratio (β / α) of these monitor values is obtained and stored in the storage unit 32. Such a procedure may be performed automatically or manually by the operator.

  The control unit 33 refers to the monitor value “P1” of the photodetector 26a obtained from the optical power monitoring device 12 and the monitor value “P2 ′” after correction of the photodetector 26b obtained by the calculation unit 31. The light source device 11 is controlled so that the power of the output light L1 output from the output terminal X is constant. In addition, the control unit 33 controls to stop the light emission of the light source device 11 in order to protect the fiber laser device 1 when the monitor value “P2 ′” exceeds the threshold value stored in the storage unit 32. I do.

  Next, the operation of the fiber laser device 1 having the above configuration will be briefly described. When the operation is started by an operation start instruction or the like to the control device 13, the light source device 11 is controlled by the control device 13 and excitation light is output from the light source device 11. When the excitation light output from the light source device 11 is incident on the optical fiber F, the active element added to the core of the optical fiber F is excited. The light propagating through the core of the optical fiber F is amplified by the active element that is excited while being reflected by the fiber Bragg gratings G1 and G2 formed in the optical fiber F, and laser oscillation occurs. The output light L1 is output.

  The output light L1 is output from the output end X through the optical power monitor device 12 and the optical fiber F1 in order. When a workpiece or the like is disposed in front of the output end X, a part of the reflected light generated on the processed surface of the workpiece is reflected in the fiber laser device 1 via the output end X as reflected light L2. Entered. At this time, in the optical power monitor device 12, the output light L1 leaked at the fusion splice point P is received by the photodetector 26a, received by the photodetector 26b, and leaked at the fusion splice point P. The reflected light L2 is received by the photodetector 26b. The detection results (monitor values) of these photodetectors 26 a and 26 b are output to the control device 13.

  When the monitor values of the photodetectors 26a and 26b are input to the calculation unit 31 of the control device 13, the calculation of the above-described equation (1) is performed. That is, a value obtained by multiplying the monitor value “P1” of the photodetector 26a by the ratio (β / α) stored in the storage unit 32 is subtracted from the monitor value “P2” of the photodetector 26b. Then, the calculation for obtaining the corrected monitor value “P2 ′” is performed. The monitor value “P1” of the photodetector 26a and the corrected monitor value “P2 ′” of the photodetector 26b are output to the control unit 33, and the power of the output light L1 output from the output terminal X is The light source device 11 is controlled to be constant. When the monitor value “P2 ′” exceeds the threshold value stored in the storage unit 32, control for stopping the light emission of the light source device 11 is performed.

  FIG. 7 is a diagram for explaining the effect of correction performed by the fiber laser device according to the first embodiment of the present invention. FIG. 7A is a diagram showing an example of a monitor value (output monitor value) of the photodetector 26a, and FIG. 7B is an example of a monitor value (reflection monitor value) of the photodetector 26b. FIG. 7C is a diagram illustrating an example of a monitor value after correction (corrected reflection monitor value) of the photodetector 26b. Here, in order to facilitate understanding, it is assumed that the output light L1 is output in a situation where the reflected light L2 is not generated.

  As shown in FIG. 7A, when the fiber laser device 1 pulsates, the output light L1 is intermittently output. Therefore, the monitor value of the photodetector 26a varies intermittently at a constant period. Become. Here, as shown in FIG. 7B, since the output light L1 is received by the photodetector 26b even in a situation where the reflected light L2 is not generated, the monitor value of the photodetector 26b is the light Although it is smaller than the monitor value of the detector 26a, it fluctuates intermittently at the same cycle as the monitor value of the photodetector 26a. On the other hand, as shown in FIG. 7C, the corrected monitor value of the light detector 26b is output by the light detector 26b by performing the calculation of the above-described equation (1). This eliminates the effects caused by this and becomes zero (or almost zero).

  As described above, in the present embodiment, the ratio (β / α) of the monitor values of the photodetectors 26a and 26b obtained from the optical power monitor device 12 under the condition where the reflected light L2 is not generated is obtained in advance. In the state of use, the above-described ratio (β / α) is used to perform an operation for eliminating the influence of the output light L1 from the monitor value of the photodetector 26b. For this reason, it is possible to monitor the reflected light L2 with high accuracy, thereby preventing deterioration of processing characteristics.

[Second Embodiment]
FIG. 8 is a block diagram showing a main configuration of a control device provided in the fiber laser device according to the second embodiment of the present invention. The overall configuration of the fiber laser device of this embodiment is the same as that of the fiber laser device shown in FIG. In FIG. 8, the same reference numerals are given to the components corresponding to those shown in FIG.

  As shown in FIG. 8, the fiber laser device of this embodiment includes a temperature measuring device 40 that measures the temperature of the optical power monitoring device 12, and the reflected light L <b> 2 in consideration of the temperature measured by the temperature measuring device 40. Is monitored with higher accuracy. That is, since the ratio (β / α) of the monitor values of the photodetectors 26a and 26b described above changes according to the temperature (internal temperature) of the optical power monitor device 12, the change in the ratio (β / α) is changed. In consideration of this, the reflected light L2 is monitored with higher accuracy by changing the correction amount of the monitor value of the photodetector 26b.

  The temperature measuring device 40 is attached to the optical power monitor device 12 and measures the temperature (internal temperature) of the optical power monitor device 12. As the temperature measuring device 40, for example, a temperature sensor including a thermocouple, a temperature sensor including a resistance temperature detector, a temperature sensor including a bimetal, or the like can be used. However, the temperature measuring device 40 is preferably small because it is necessary to measure the internal temperature of the optical power monitoring device 12.

  The temperature measuring device 40 can be installed at an arbitrary position of the optical power monitoring device 12, but the ratio (β / α) described above is the temperature at the fusion splice point P (or the fusion splice point P). It is desirable to install it at a position as close as possible to the fusion splice point P. However, the temperature measuring device 40 needs to be installed so as not to affect the detection of the photodetectors 26a and 26b.

  In the present embodiment, the temperature table illustrated in FIG. 9 is stored in the storage unit 32. FIG. 9 is a diagram showing an example of a temperature table used in the second embodiment of the present invention. As shown in FIG. 9, the temperature table is a table in which the ratio (β / α) of the monitor values of the photodetectors 26a and 26b is stored for each temperature. Note that the temperature table illustrated in FIG. 9 is in increments of 1 [° C.], but the temperature increment is arbitrary. This temperature table acquires the monitor values of the photodetectors 26a and 26b obtained from the optical power monitor device 12 while changing the temperature in a state where the reflected light L2 does not occur in advance, and the ratio of the acquired monitor values (β / α) is obtained for each temperature.

  The operation of the fiber laser device of this embodiment is substantially the same as that of the fiber laser device of the first embodiment. However, in the present embodiment, when the calculation of the above-described equation (1) is performed by the calculation unit 31, the ratio (β /?) Corresponding to the measurement result of the temperature measuring device 40 is calculated from the temperature table stored in the storage unit 32. α) is read out, and this ratio (β / α) is multiplied by the monitor value “P1” of the photodetector 26a. Thereby, the correction amount of the monitor value “P2” of the photodetector 26b (the second term on the right side of the above-described equation (1)) takes the temperature into consideration, and as a result, the reflected light L2 is monitored with higher accuracy. be able to.

[Third Embodiment]
FIG. 10 is a block diagram showing a main configuration of a control device provided in the fiber laser device according to the third embodiment of the present invention. The overall configuration of the fiber laser device according to the present embodiment is the same as that of the fiber laser device shown in FIG. 1, and in FIG. 10, the same reference numerals are given to the components corresponding to the configuration shown in FIG. .

  As shown in FIG. 10, the fiber laser device of the present embodiment is provided with a timer 34 in the control device 13, and monitors the reflected light L2 with higher accuracy in consideration of changes over time of the fiber laser device. is there. Here, the time-dependent change of the fiber laser device is mainly a time-dependent change of the optical fibers F and F1 (for example, changes in transmittance and refractive index of the optical fibers F and F1 that occur with time).

  The timer unit 34 includes a timer, and outputs information indicating the timing result to the calculator 31. For example, the timer 34 measures the elapsed time from the factory shipment of the fiber laser device, the elapsed time from the installation of the shipped fiber laser device, or the accumulated time in which the fiber laser device is in the operating state. Since the fiber laser device is considered to be used for a long period of time, it is desirable to use a timing unit that does not cause an error as much as possible.

  Further, in the present embodiment, the time table exemplified in FIG. 11 is stored in the storage unit 32. FIG. 11 is a diagram showing an example of a time table used in the third embodiment of the present invention. As shown in FIG. 11, the time-lapse table is a table in which the ratio (β / α) of the monitor values of the photodetectors 26a and 26b is stored every time the specified time elapses. In the time table illustrated in FIG. 11, the specified time is set to 1 [year], but the specified time can be arbitrarily set.

  The operation of the fiber laser device of this embodiment is also substantially the same as that of the fiber laser device of the first embodiment. However, in the present embodiment, when the calculation of the above-described equation (1) is performed by the calculation unit 31, the ratio (β / α) corresponding to the time measurement result of the time measurement unit 34 is determined from the time-lapse table stored in the storage unit 32. ) And is multiplied by the ratio (β / α) and the monitor value “P1” of the photodetector 26a. As a result, the amount of correction of the monitor value “P2” of the photodetector 26b (the second term on the right side of the above-described equation (1)) takes into account the change over time of the fiber laser device, and as a result, the reflected light L2 is more It is possible to monitor with high accuracy.

  As mentioned above, although embodiment of this invention was described, this invention is not restrict | limited to the said embodiment, It can change freely within the scope of the present invention. For example, in the above-described embodiment, the case where the optical fiber F is a single clad fiber including a core to which an active element is added and a clad surrounding the core has been described. However, the present invention can also be applied when the optical fiber F is a double-clad fiber including a core to which an active element is added, an inner cladding that surrounds the core, and an outer cladding that surrounds the inner cladding. .

  Here, the double-clad fiber has a lower absorption rate of pumping light per unit length (absorption rate by the active element added to the core) than the single-clad fiber. In the single clad fiber, the excitation light from the light source device 11 propagates through the core to which the active element is added, whereas in the double clad fiber, the excitation light from the light source device 11 propagates through the inner cladding. This is because it is absorbed by the active element added to the core.

  Therefore, when the optical fiber F is a double clad fiber, the excitation light propagating through the inner clad is not completely absorbed by the optical fiber F, enters the optical power monitor device 12 and is received by the photodetector 26b. It is possible. Even in such a case, if the ratio (β / α) of the monitor values of the photodetectors 26a and 26b obtained from the optical power monitor device 12 in a situation where the reflected light L2 is not generated is obtained in advance, (1 ), It is possible to eliminate both the influence when the output light L1 is received by the photodetector 26b and the influence when the excitation light is received by the photodetector 26b.

  In the above-described embodiment, the light leaked at the fusion splice point P between the optical fiber F functioning as an amplification medium and the optical fiber F1 functioning as a transmission medium is detected, and the power of the output light L1 and the reflected light L2 is detected. An example of monitoring the above has been described. However, for example, when the optical fiber F1 functioning as a transmission medium is formed by fusion splicing of two optical fibers, the light leaked at the fusion splicing point in the optical fiber F1 The power of the output light L1 and the reflected light L2 may be monitored by detection.

  In the above-described embodiment, the calculation unit 31 and the storage unit 32 that perform the calculation of the above-described expression (1) are provided in the control device 13, but these can also be provided in the optical power monitoring device 12. is there. By doing in this way, the monitoring precision of the reflected light L2 of the optical power monitor apparatus 12 can be improved.

DESCRIPTION OF SYMBOLS 1 ... Fiber laser apparatus, 11 ... Light source device, 12 ... Optical power monitor apparatus, 13 ... Control apparatus, 26a ... Photo detector, 26b ... Photo detector, 27 ... High refractive index resin, 31 ... Calculation part, 32 ... Memory | storage 34, timing unit, 40 ... temperature measuring device, F ... optical fiber, F1 ... optical fiber, L1 ... output light, L2 ... reflected light, P ... fusion splice point

Claims (9)

In a fiber laser device comprising: a first optical fiber that functions as an amplification medium; and a second optical fiber that functions as a transmission medium that transmits light from the first optical fiber.
The connection point between the first optical fiber and the second optical fiber or the output point of the output light from the connection point in the second optical fiber is detected, and the output light leaking at the connection point is detected. An optical power monitor device comprising: a first detector; and a second detector that is disposed on the input side of the output light with respect to the connection point and detects reflected light leaking at the connection point;
Using the relationship between the detection results of the first detector and the second detector obtained in advance from the optical power monitor device in a situation where the reflected light does not occur, the output light is calculated from the detection result of the second detector. A fiber laser device comprising: a calculation unit that performs a calculation that eliminates the influence of. A storage unit for storing a characteristic value indicating a ratio of detection results of the first detector and the second detector obtained in advance from the optical power monitor device in a state where the reflected light does not occur;
The arithmetic unit performs an operation of subtracting a value obtained by multiplying the characteristic value stored in the storage unit and the detection result of the first detector from the detection result of the second detector. 2. The fiber laser device according to claim 1, wherein: The storage unit stores the characteristic value for each temperature of the optical power monitoring device,
The computing unit includes the characteristic value according to the measurement result of the temperature measuring device provided in the optical power monitoring device, and the detection result of the first detector, among the characteristic values stored in the storage unit. The fiber laser device according to claim 2, wherein: The storage unit stores the characteristic value every predetermined time elapsed,
The calculation unit multiplies the characteristic value stored in the storage unit according to the elapsed time measured by the time measuring unit and the detection result of the first detector. The fiber laser device according to claim 2 or 3.   The said connection point is covered with the transparent material from which absorption does not become a substantial loss factor about the light which has the same wavelength as the said output light and the said reflected light. The fiber laser device according to any one of the above.   The fiber according to any one of claims 1 to 5, wherein the connection point is covered with a material having a higher thermal conductivity than the first optical fiber and the second optical fiber. Laser device. A light source device for supplying excitation light to the first optical fiber;
The detection results of the first detector and the second detector output from the optical power monitor device are input and obtained using the detection result of the first detector and the detection result of the second detector. The fiber laser device according to claim 1, further comprising: a control device that controls the light source device based on a calculation result of the calculation unit. Leaked at a connection point between the first optical fiber functioning as an amplification medium and a second optical fiber functioning as a transmission medium for transmitting light from the first optical fiber, or at a connection point in the second optical fiber In an optical power monitor device that detects light and monitors the power of output light and reflected light,
A first detector that is disposed on the output side of the output light with respect to the connection point and detects the output light leaking at the connection point;
A second detector that is disposed on the input side of the output light with respect to the connection point and detects the reflected light leaking at the connection point;
Calculation that eliminates the influence of the output light from the detection result of the second detector using the relationship between the detection results of the first detector and the second detector obtained in advance under the situation where the reflected light does not occur An optical power monitoring device comprising: an arithmetic unit that performs the following. Leaked at a connection point between the first optical fiber functioning as an amplification medium and a second optical fiber functioning as a transmission medium for transmitting light from the first optical fiber, or at a connection point in the second optical fiber An optical power monitoring method for detecting light and monitoring the power of output light and reflected light,
The output light leaking at the connection point is detected by a first detector disposed on the output side of the output light from the connection point,
The reflected light leaking at the connection point is detected by a second detector arranged on the input side of the output light from the connection point,
Calculation that eliminates the influence of the output light from the detection result of the second detector using the relationship between the detection results of the first detector and the second detector obtained in advance under the situation where the reflected light does not occur An optical power monitoring method characterized by:

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