JP7086922B2 - Fiber laser system and its control method - Google Patents

Description

The present invention relates to a fiber laser system including a plurality of fiber laser units. It also relates to a control method for such a fiber laser system.

As a laser device for processing, a fiber laser system including a plurality of fiber laser units is used. The power of the output light of the fiber laser system roughly matches the sum of the powers of the laser light generated by each fiber laser unit. The power of the laser beam generated by each fiber laser unit is determined according to the magnitude of the drive current that drives the excitation light source included in the fiber laser unit. Therefore, the control of the output light power in the fiber laser system is realized by changing the magnitude of the drive current that drives the excitation light source included in each fiber laser unit.

Patent Document 1 is, for example, a document that discloses a technique for controlling the power of output light of a fiber laser system. In the technique described in Patent Document 1, the integrated value of the drive time of the fiber laser unit weighted according to the magnitude of the drive current for driving the excitation light source included in each fiber laser unit is associated with the fiber laser unit. It will be remembered. Then, in the technique described in Patent Document 1, a number of fiber laser units corresponding to the target value of the power of the output light of the fiber laser system are selected in ascending order of the integrated value and emit light.

Japanese Unexamined Patent Publication No. 2017-89464 (published on May 18, 2017)

However, in a conventional fiber laser system, when an accidental failure of an excitation light source (hereinafter, also referred to as “death”) occurs in any of the fiber laser units, the power of the laser light generated by each fiber laser unit is increased. There will be variation. Then, when the power of the laser beam generated by each fiber laser unit varies, Stokes oscillation occurs due to induced Raman scattering starting from the fiber laser unit that generates the laser beam having a relatively large power. This can result in a failure of the fiber laser system.

In the fiber laser system described in Patent Document 1, it is not possible to suppress variations in the power of the laser beam generated by each fiber laser unit. Therefore, in the fiber laser system described in Patent Document 1, the possibility of failure due to Stokes oscillation cannot be reduced.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to realize a fiber laser system in which failure due to Stokes oscillation is unlikely to occur.

In order to solve the above-mentioned problems, the fiber laser system according to one aspect of the present invention includes a plurality of fiber laser units, a combiner that combines laser light generated by each fiber laser unit, and each fiber laser unit. It is provided with a control unit for controlling the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit so that the difference in the power of the laser light generated in the above is small.

Further, in order to solve the above-mentioned problems, the control method of the fiber laser system according to one aspect of the present invention includes a plurality of fiber laser units and a combiner that combines the laser light generated by each fiber laser unit. It is a control method of a fiber laser system including. The control method includes a control step of controlling the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit so that the difference in the power of the laser light generated by each fiber laser unit becomes small. ,including.

According to the above-described configuration, it is possible to suppress variations in the power of the laser beam generated by each fiber laser unit, and as a result, it is possible to realize a fiber laser system in which failure due to Stokes oscillation is unlikely to occur.

Further, in the fiber laser system according to one aspect of the present invention, the control unit has an output so that the difference in power of the laser light generated by each fiber laser unit becomes small and the output is generated by the combiner. It is preferable to control the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit so that the power of light approaches a target value set by the user.

Further, in the control method of the fiber laser system according to one aspect of the present invention, the control step is generated by the combiner so that the difference in the power of the laser light generated by each fiber laser unit becomes small. It is preferable to control the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit so that the power of the output light produced approaches the target value set by the user.

According to the above-described configuration, it is possible to suppress variations in the power of the laser light generated by each fiber laser unit while outputting the laser light having a power close to the target value set by the user.

Further, in the fiber laser system according to one aspect of the present invention, at least one of the survival number and the death number of the excitation light source included in the fiber laser unit is based on the power of the laser light generated by each fiber laser unit. Further including an estimation unit for estimating one, the control unit is a drive for supplying to each excitation light source included in each fiber laser unit according to at least one of the number of survivals and the number of deaths estimated by the estimation unit. It is preferable to control the magnitude of the current.

Further, the control method of the fiber laser system according to one aspect of the present invention is based on the power of the laser beam generated by each fiber laser unit, and the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit are determined. Further comprising an estimation step of estimating at least one, the control step is for each excitation light source included in each fiber laser unit, depending on at least one of the survival and death numbers estimated in the estimation step. It is preferable to control the magnitude of the drive current to be supplied.

When a drive current of the same magnitude is supplied to each fiber laser unit having a different number of excitation light sources (in other words, a fiber laser unit having a different survival number of excitation light sources), it is generated by each fiber laser unit. The power of the laser beam varies. According to the above-described configuration, the control unit controls the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit according to the number of survivors or the number of deaths, thereby being generated in each fiber laser unit. It is possible to surely suppress the variation in the power of the laser beam.

Further, in the fiber laser system according to one aspect of the present invention, at least one of the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit is based on the power of the laser beam generated by each fiber laser unit. Further includes an estimation unit for estimating one and a notification unit for notifying when at least one of the number of survivors and the number of deaths estimated in the estimation unit reaches a predetermined number. Is preferable.

Further, the control method of the fiber laser system according to one aspect of the present invention is based on the power of the laser beam generated by each fiber laser unit, and the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit are determined. An estimation step for estimating at least one, and a notification step for notifying when at least one of the number of survivors and the number of deaths estimated in the estimation step reaches a predetermined number. Further, it is preferable to include it.

According to the above configuration, when at least one of the number of survivors and the number of sudden deaths reaches a predetermined number, the user is notified to that effect, so that the user can use at least one of the number of survivors and the number of sudden deaths. It can be known that is a suitable time for replacement of the fiber laser unit which has reached a predetermined number.

Further, in the fiber laser system according to one aspect of the present invention, the estimation unit determines the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit and the laser generated by each fiber laser unit. It is preferable to estimate at least one of the number of survivors and the number of deaths of the excitation light source contained in the fiber laser unit based on the power of light.

Further, in the control method of the fiber laser system according to one aspect of the present invention, in the estimation step, the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit and the magnitude of the drive current supplied by each fiber laser unit are generated. It is preferable to estimate at least one of the survival number and the death number of the excitation light source contained in the fiber laser unit based on the power of the laser beam.

According to the above-mentioned configuration, at least one of the number of survivors and the number of sudden deaths can be estimated accurately.

Further, in the fiber laser system according to one aspect of the present invention, the control unit is a fiber laser unit in which the number of survivals estimated by the estimation unit is small, or the number of deaths estimated by the estimation unit is large. It is preferable to control the magnitude of the drive current so that the unit increases the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit.

Further, in the control method of the fiber laser system according to one aspect of the present invention, in the control step, the fiber laser unit having a smaller number of survivors estimated in the estimation step, or the number of deaths estimated in the estimation step is higher. It is preferable to control the magnitude of the drive current so that the larger the number of fiber laser units, the larger the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit.

According to the above-described configuration, it is possible to further suppress variations in the power of the laser beam generated by each fiber laser unit.

Further, the fiber laser system according to one aspect of the present invention has a coefficient corresponding to each fiber laser unit, and is a coefficient corresponding to at least one of the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit. It may be further provided with a storage unit for storing the above. The control unit includes (1) a basic current value calculation unit that calculates a basic current value based on a target value of the power of the output light generated by the combiner and is set by the user. (2) For each fiber laser unit, the fiber laser is based on the basic current value calculated by the basic current value calculation unit and the coefficient stored in the storage unit corresponding to the fiber laser unit. The individual current value calculation unit that calculates the individual current value corresponding to the unit, and (3) the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit for each fiber laser unit are determined by the individual current value. It is preferable to have a drive current setting unit that sets the individual current value corresponding to the fiber laser unit calculated by the calculation unit.

According to the above-mentioned configuration, even if at least one of the survival number and the death number of the excitation light sources included in each fiber laser unit is different, the variation in the power of the laser light generated by each fiber laser unit is suppressed. be able to.

Further, the fiber laser system according to one aspect of the present invention further includes a laser power measuring unit for measuring the power of the laser beam generated by each fiber laser unit, and the control unit is (4) each fiber laser unit. With respect to (5), an estimation unit that estimates at least one of the number of survivors and the number of deaths of the excitation light source contained in the fiber laser unit based on the power of the laser beam measured by the laser power measurement unit. For each fiber laser unit, the coefficient corresponding to the fiber laser unit stored in the storage unit is updated based on at least one of the survival number and the death rate of the excitation light source estimated by the estimation unit. It is preferable to further have a coefficient updating unit.

According to the above-described configuration, at least one of the survival number and the death rate of the excitation light source included in each fiber laser unit is accurately estimated based on the measured value, and at least one of the estimated survival number and the death rate is determined. , Can be reflected in the coefficient used to set the individual current value.

The fiber laser system according to one aspect of the present invention can realize a fiber laser system that is less likely to cause a failure due to Stokes oscillation.

It is a block diagram of the fiber laser system which concerns on embodiment of this invention. It is a functional block block diagram of the control part in embodiment of this invention. It is a figure explaining the relationship between the drive current and the power of a laser beam with respect to the fiber laser unit in embodiment of this invention. It is a flowchart explaining the control method of the fiber laser system which concerns on embodiment of this invention. It is a flowchart explaining another control method of the fiber laser system which concerns on embodiment of this invention.

(Structure of fiber laser system)
The configuration of the fiber laser system FLS according to the embodiment of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration of a fiber laser system FLS.

The fiber laser system FLS is a laser device for processing a work W, and as shown in FIG. 1, n fiber laser units FLU1 to FLUN, n laser delivery fibers LDF1 to LDFn, an output combiner OC, and an output. It includes a delivery fiber ODF, an output head OH, n laser power measurement units M1 to Mn, a control unit C, a storage unit ME, and a notification unit IN. The fiber laser units FLU1 to FLUN and the laser delivery fibers LDF1 to LDFn have a one-to-one correspondence with each other. Here, n is an arbitrary natural number of 2 or more, and represents the number of the fiber laser units FLU1 to FLUN and the laser delivery fibers LDF1 to LDFn. Note that FIG. 1 shows a configuration example of the fiber laser system FLS when n = 7.

The fiber laser unit FLUi (i is a natural number of 1 or more and n or less) generates a laser beam. In this embodiment, a forward-excited fiber laser is used as the fiber laser units FLU1 to FLUN. The fiber laser unit FLUi is connected to the input end of the corresponding laser delivery fiber LDFi. The laser light generated by the fiber laser unit FLUi is input to the laser delivery fiber LDFi.

The laser delivery fiber LDFi waveguides the laser light generated by the corresponding fiber laser unit FLUi. In this embodiment, single mode fiber or fumode fiber is used as the laser delivery fibers LDF1 to LDFn. The output end of the laser delivery fiber LDFi is connected to the input port of the output combiner OC. The laser light generated by the fiber laser unit FLUi and guided through the laser delivery fiber LDFi is input to the output combiner OC via this input port.

The output combiner OC is generated by each of the fiber laser units FLU1 to FLUN, and the laser light guided through each of the laser delivery fibers LDF1 to LDFn is combined. The output port of the output combiner OC is connected to the input end of the output delivery fiber ODF. The laser beam combined with the output combiner OC is input to this output delivery fiber ODF.

The output delivery fiber ODF guides the laser beam combined with the output combiner OC. In this embodiment, the multimode fiber is used as the output delivery fiber ODF. The output end of the output delivery fiber ODF is connected to the output head OH. The laser beam synthesized by the output combiner OC is applied to the work (workpiece) via the output head OH.

The laser power measuring unit Mi (i is a natural number of 1 or more and n or less) measures the power of the laser beam generated by the corresponding fiber laser unit FLUi. In the present embodiment, a photodiode is used as the laser power measuring unit Mi, and the laser light branched by the branching optical fiber is detected from the laser light generated by the fiber laser unit FLUi using this photodiode. Further, the laser power measurement unit Mi outputs a signal representing the measured value Pi to the control unit C described later.

The laser power measuring unit Mi is not limited to the configuration in which the power of the laser beam is measured via the branching optical fiber. For example, each laser power measuring unit Mi may be arranged at a position separated from the laser delivery fiber LDFi by a predetermined distance, and may be configured to detect Rayleigh scattered light of light propagating in the laser delivery fiber LDFi. The laser power measuring unit Mi configured in this way is a so-called Rayleigh monitor.

In the control unit C, the difference in the power of the laser light generated by the fiber laser units FLU1 to FLUN becomes small (preferably 0), and the power of the output light generated by the output combiner OC becomes small. The magnitude of the drive current Ii supplied to the excitation light sources PS1 to PSm is controlled in each fiber laser unit FLUi so as to approach (preferably match) the target value P0 set by the user. The details of the function of the control unit C will be described later instead of the reference drawings.

The storage unit ME stores the coefficient αi corresponding to each fiber laser unit FLUi. Each coefficient αi is a coefficient referred to by the control unit C in order to control the magnitude of the drive current Ii supplied to the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi. Each coefficient αi is set by the control unit C according to the number of sudden deaths of the excitation light sources PS1 to PSm included in the corresponding fiber laser unit FLUi. Here, the number of dead states of the excited light sources PS1 to PSm refers to the number of excited light sources that have already died (become unable to emit light due to an accidental failure) among the excited light sources PS1 to PSm. The specific definition of the coefficient αi will be described later. Further, the storage unit ME stores the threshold number of sudden deaths referred to by the control unit C as described later. The threshold number of sudden deaths is predetermined according to the specifications of the fiber laser unit FLUi and the like.

When the number of sudden deaths estimated by the number of sudden deaths estimation units C04_1 to C04_n included in the control unit C reaches the threshold number of sudden deaths, which is a predetermined number, the notification unit IN is controlled by the control unit C to that effect. To notify the user. The notification unit IN may be configured to (1) notify the user by emitting a voice (for example, by issuing an alarm), or (2) by displaying a character or an image. It may be configured to notify the user to that effect, or (3) it may be configured to notify the user by emitting a voice and displaying characters or images. In the case of a configuration for emitting voice, the notification unit IN may be provided with, for example, a speaker, and in the case of a configuration for displaying characters or images, the notification unit IN may be provided with, for example, a display device. An example of a display device is a liquid crystal display. The details of the functions of the sudden death number estimation units C04_1 to C04_n will be described later.

(Structure of fiber laser unit)
The configuration of the fiber laser unit FLU1 included in the fiber laser system FLS will be described with reference to FIG. The fiber laser units FLU2 to FLUN are also configured in the same manner as the fiber laser unit FLU1.

The fiber laser unit FLU1 is a forward-excited fiber laser, and as shown in FIG. 1, a current source CS1, m excitation light sources PS1 to PSm, m excitation delivery fibers PDF1 to PDFm, an excitation combiner PC, and the like. It is equipped with a high-reflection fiber Bragg grating FBG-HR, an amplification fiber AF, and a low-reflection fiber Bragg grating FBG-LR. The excitation light sources PS1 to PSm and the excitation delivery fibers PDF1 to PDFm have a one-to-one correspondence with each other. Here, m is an arbitrary natural number of 2 or more, and represents the number of excitation light sources PS1 to PSm and excitation delivery fibers PDF1 to PDFm. Note that FIG. 1 shows a configuration example of the fiber laser unit FLU1 when m = 6.

The current source CS1 supplies the drive current I1 to the excitation light sources PS1 to PSm. The magnitude of the drive current I1 is controlled by the control unit C. Each excitation light source PSj (j is a natural number of 1 or more and m or less) produces excitation light. The power of the excitation light generated by each excitation light source PSj is determined according to the magnitude of the drive current I1 supplied from the current source CS. In this embodiment, the laser diode is used as the excitation light source PS1 to PSm. The excitation light source PSj is connected to the input end of the corresponding excitation delivery fiber PDFj. The excitation light generated by the excitation light source PSj is input to the excitation delivery fiber PDFi.

The excitation delivery fiber PDFj waveguides the excitation light generated by the corresponding excitation light source PSj. The output end of the excitation delivery fiber PDFj is connected to the input port of the excitation combiner PC. The excitation light generated by the excitation light source PSj and waved through the excitation delivery fiber PDFj is input to the excitation combiner PC via this input port.

The excitation combiner PC is generated by each of the excitation light sources PS1 to PSm, and the excitation light waved through each of the excitation delivery fibers PDF1 to PDFm is combined. The output port of the excitation combiner PC is connected to the input end of the amplification fiber AF via a high reflection fiber Bragg grating FBG-HR. Of the excitation light combined with the excitation combiner PC, the excitation light transmitted through the highly reflective fiber Bragg grating FBG-HR is input to the amplification fiber AF.

The amplification fiber AF uses the excitation light transmitted through the highly reflective fiber Bragg grating FBG-HR to generate a laser beam. In this embodiment, a double clad fiber in which a rare earth element (for example, Yb) is added to the core is used as the amplification fiber AF. The excitation light transmitted through the highly reflective fiber Bragg grating FBG-HR is used to maintain this rare earth element in an inverted distribution state. The output end of the amplification fiber AF is connected to the input end of the laser delivery fiber LDF1 via a low reflection fiber Bragg grating FBG-LR. The high-reflection fiber Bragg grating FBG-HR functions as a mirror at a wavelength λ (eg, 1060 nm) (reflectance is, for example 99%), and the low-reflection fiber Bragg grating FBG-LR acts as a half mirror at that wavelength λ. It works (reflectance is, for example, 10%). Therefore, the amplification fiber AF, together with the high-reflection fiber Bragg grating FBG-HR and the low-reflection fiber Bragg grating FBG-LR, constitutes a resonator that oscillates a laser beam having a wavelength of λ. Of the laser light generated by the amplification fiber AF, the laser light transmitted through the low reflection fiber Bragg grating FBG-LR is input to the laser delivery fiber LDF1.

In the present embodiment, the forward-excited fiber laser is used as the fiber laser units FLU1 to FLUN, but the present invention is not limited to this. That is, in the present invention, the backward excitation type fiber laser can be used as the fiber laser units FLU1 to FLUN, or the bidirectional excitation type fiber laser can be used as the fiber laser units FLU1 to FLUN.

Further, in the present embodiment, the fiber laser system FLS includes a plurality of resonator type fiber laser units FLUi. However, the fiber laser system FLS according to one aspect of the present invention may further include a plurality of excitation light sources arranged after the output combiner OC and an amplification fiber. In this case, the portion including the plurality of fiber laser units FLUi and the output combiner OC functions as an MO (Master Oscillator) unit for generating seed light, and a plurality of excitation light sources and amplification fibers arranged after the output combiner OC. The part including is functioning as a PA (Power Amplifier) part. That is, one aspect of the present invention can also be suitably used for a MOPA type fiber laser system.

(Structure of control unit)
The function of the control unit C will be described with reference to FIG. FIG. 2 is a functional block diagram showing the function of the control unit C. In FIG. 2, the control unit C includes a basic current value calculation unit C01, an individual current value calculation unit C02_1 to C02_n, a drive current setting unit C03_1 to C03_n, a sudden death number estimation unit C04_1 to C04_n, and a coefficient updating unit C05_1 to. Includes C05_n. Note that FIG. 2 shows a configuration example of the control unit C when n = 7, as in FIG. 1. Further, the sudden death number estimation units C04_1 to C04_n are one aspect of the estimation units described in the claims.

The basic current calculation unit C01, the individual current value calculation units C02_1 to C02_n, and the drive current setting units C03_1 to C03_n refer to the drive currents Ii supplied to the excitation light sources PS1 to PSm in each fiber laser unit FLUi from the fiber laser units FLU1 to. The difference in the power of the laser beam generated by FLUN becomes small (preferably 0), and the power of the output light generated by the output combiner OC approaches the target value P0 set by the user. It is a configuration for controlling so as to (preferably match). The functions of the basic current calculation unit C01, the individual current value calculation units C02_1 to C02_n, and the drive current setting units C03_1 to C03_n are as follows.

The basic current value calculation unit C01 calculates the basic current value I0 based on the target value P0 set by the user. Here, the basic current value I0 means that the power of the output light generated by the output combiner OC is the target value P0 when the number of deaths of the excitation light sources PS1 to PSm is 0 in all the fiber laser units FLU1 to FLUN. Refers to the current value of the drive current to be supplied to the excitation light sources PS1 to PSm in each fiber laser unit FLUi in order to match.

For example, the basic current value calculation unit C01 calculates the basic current value I0 using a predetermined function Pm (I). This function Pm (I) is the relationship between the current value I of the drive current supplied to the m excitation light sources PS1 to PSm and the sum Pm of the powers of the excitation lights output from the m excitation light sources PS1 to PSm. Is a function that represents. In this case, the current value I satisfying Pm (I) = P0 is the basic current value I0. Alternatively, the basic current value calculation unit C01 calculates the basic current value I0 using a predetermined table Tm. This table Tm is a table in which the current value I of the drive current supplied to the m excitation light sources PS1 to PSm and the sum Pm of the powers of the excitation lights output from the m excitation light sources PS1 to PSm are associated with each other. Is. In this case, in the table Tm, the current value I associated with the power Pm closest to the target value P0 becomes the basic current value 0.

Each individual current value calculation unit C02_i is excited light sources PS1 to the corresponding fiber laser unit FLUi based on the basic current value I0 calculated by the basic current value calculation unit C01 and the coefficient αi stored in the storage unit ME. The individual current value supplied to PSm is calculated. More specifically, the individual current value calculation unit C02_i calculates the individual current value αi × I0 by multiplying the basic current value I0 by the coefficient αi. In each drive current setting unit C03_i, the drive current Ii supplied to the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi matches the individual current value αi × I0 calculated by the corresponding individual current value calculation unit C02_i. As such, the current source CS included in the corresponding fiber laser unit FLUi is controlled.

The number of deaths estimation unit C04_1 to C04_n and the coefficient update units C05_1 to C05_n set the coefficient αi referred to by each individual current value calculation unit C02_i according to the number of deaths of the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi. It is a configuration to do. The functions of the sudden death number estimation units C04_1 to C04_n and the coefficient update units C05_1 to C05_n are as follows.

Each dead number estimation unit C04_i refers to the excitation light sources PS1 to PSm in the fiber laser unit FLUi based on the measured value Pi of the laser light measured by the laser power measurement unit Mi for the corresponding fiber laser unit FLUi. Estimate the number of deaths.

For example, each sudden death number estimation unit C04_i estimates the number of sudden deaths of the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi by using m predetermined functions P1 (I) to Pm (I). Here, the function Pj (I) is the sum of the current values I of the drive currents supplied to the j excitation light sources PS1 to PSj and the powers of the excitation lights output from the j excitation light sources PS1 to PSj Pj. It is a function representing the relationship between (j = 1 to m). FIG. 3 is a graph illustrating these functions P1 (I) to Pm (I). In this case, the sudden death number estimation unit C04_i substitutes the drive current Ii (that is, the individual current value αi × I0 applied at the time when the measured value Pi is obtained) into each function Pj (I) to power Pj. (Ii) is calculated. Then, the sudden death number estimation unit C04_i identifies the power closest to the measured value Pi among the calculated powers P1 (Ii) to Pm (Ii). When the power closest to the measured value Pi is Pk (Ii), the dead number estimation unit C04_i has k survivors of the excitation light sources PS1 to PSm, that is, the deadness numbers of the excitation light sources PS1 to PSm are m-. It is estimated to be k. For example, when the power closest to the measured value Pi is P1 (Ii), the dead number estimation unit C04_i has one surviving number of the excitation light sources PS1 to PSm, that is, the dead number of the excitation light sources PS1 to PSm is one. It is estimated that there are m-1 pieces. Further, when the power closest to the measured value Pi is P2 (Ii), the dead number estimation unit C04_i has two surviving numbers of the excitation light sources PS1 to PSm, that is, the deadness numbers of the excitation light sources PS1 to PSm are two. It is estimated that there are m-2 pieces. Alternatively, each dead number estimation unit C04_i estimates the dead numbers of the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi using m predetermined tables T1 to Tm. Here, the table Tj is associated with the current value I of the drive current supplied to the j excitation light sources PS1 to PSj and the sum Pj of the powers of the excitation lights output from the j excitation light sources PS1 to PSj. It is a table (j = 1 to m). In this case, the sudden death number estimation unit C04_i selects the power Pj (Ii) associated with the current value I closest to the drive current Ii in each table Tj. Then, the sudden death number estimation unit C04_i identifies the power closest to the measured value Pi among the selected powers P1 (Ii) to Pm (Ii). When the power closest to the measured value Pi is Pk (Ii), the dead number estimation unit C04_i has k survivors of the excitation light sources PS1 to PSm, that is, the deadness numbers of the excitation light sources PS1 to PSm are m-. It is estimated to be k.

The control unit C controls the notification unit IN so as to notify when the number of sudden deaths estimated by the number of sudden deaths estimation unit C04_i reaches a predetermined threshold number of sudden deaths. At this time, the control unit C identifies (1) the fiber laser unit whose number of deaths has reached the threshold number of deaths among the fiber laser units FLU1 to FLU7, and (2) information for identifying the specified fiber laser unit. It is preferable to control the notification unit IN so as to notify when the number of deaths has reached a predetermined threshold number of deaths.

According to this configuration, the notification unit IN notifies that the number of sudden deaths has reached a predetermined number. Therefore, the user can know that the number of sudden deaths has reached a predetermined number in any of the fiber laser units FLU1 to FLU7. That is, the user can know that it is a suitable time to replace any one of the fiber laser units FLU1 to FLU7. Further, in addition to the fact that the number of sudden deaths has reached a predetermined number, the notification unit IN notifies the information for identifying the fiber laser unit whose number of sudden deaths has reached the threshold number of sudden deaths, so that the user can use the number of sudden deaths. Can easily identify the fiber laser unit that has reached the threshold number of sudden deaths.

The coefficient update unit C05_i updates the coefficient αi stored in the storage unit ME based on the number of deaths estimated by the death rate estimation unit C04_i for the corresponding fiber laser unit FLUi. For example, when the number of sudden deaths estimated by the sudden death number estimation unit C04_i is one, the coefficient updating unit C05_i sets the coefficient αi in the storage unit ME to αi = m / (m-1). Alternatively, when the number of sudden deaths estimated by the sudden death number estimation unit C04_i is two, the coefficient updating unit C05_i sets the coefficient αi in the storage unit ME to αi = m / (m-2). Generally, when the number of sudden deaths estimated by the sudden death number estimation unit C04_i is x, the coefficient updating unit C05_i sets the coefficient αi in the storage unit ME to αi = m / (mx).

When the number of sudden deaths estimated by the number of sudden deaths estimation unit C04_i reaches the threshold number of sudden deaths, the control unit C subsequently supplies a drive current Ii to be supplied to the fiber laser unit whose number of sudden deaths has reached the threshold number of sudden deaths. It is preferable to control the magnitude of the drive current Ii so that it becomes a constant value without changing. For example, the control unit C does not update the coefficient αi with respect to the coefficient update unit C05_i corresponding to the sudden death number estimation unit C04_i in which the number of sudden deaths reaches the threshold number of sudden deaths, so that the control unit C has a large drive current Ii. The coefficient can be controlled to a constant value.

In the present embodiment, the sudden death number estimation unit C04_i, which is one aspect of the estimation unit, estimates the number of survivors after estimating the survival number using m predetermined functions P1 (I) to Pm (I). It was explained as an estimate of the number of sudden deaths using the number of survivors. However, in one aspect of the present invention, the estimation unit may be configured to estimate either the number of survivors or the number of sudden deaths using a plurality of functions Pj (I) or a plurality of tables Tj.

In this case, when the estimation unit is configured to estimate either the number of survivors or the number of deaths, the control unit determines in advance either the number of survivals or the number of deaths estimated by the estimation unit. When the threshold number of survivors or the threshold number of deaths is reached, the notification unit may be controlled to notify the fact.

In this case, the control unit is a fiber laser unit with a small number of survivors estimated by the estimation unit, or a fiber laser unit with a large number of deaths estimated by the estimation unit, each excitation light source included in the fiber laser unit. It is preferable that the size of the drive current is controlled so as to increase the size of the drive current supplied to the light source.

Further, the fiber laser system according to one aspect of the present invention has a coefficient corresponding to each fiber laser unit, and is a coefficient corresponding to at least one of the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit. It is preferable to further include a storage unit for storing the above. Then, the control unit is (1) a basic current value calculation unit that calculates the basic current value based on the target value of the power of the output light generated by the combiner and is set by the user. , (2) For each fiber laser unit, the fiber is based on the basic current value calculated by the basic current value calculation unit and the coefficient stored in the storage unit corresponding to the fiber laser unit. The individual current value calculation unit that calculates the individual current value corresponding to the laser unit, and (3) the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit for each fiber laser unit are determined by the individual current. It is preferable to have a drive current setting unit that sets the individual current value corresponding to the fiber laser unit calculated by the value calculation unit.

Further, it is preferable that the fiber laser system according to one aspect of the present invention further includes a laser power measuring unit for measuring the power of the laser light generated by each fiber laser unit. Then, the control unit (4) for each fiber laser unit, at least the number of survivors and the number of deaths of the excitation light source contained in the fiber laser unit based on the power of the laser beam measured by the laser power measurement unit. The estimation unit that estimates either one and (5) each fiber laser unit are stored in the storage unit based on at least one of the number of survivors and the number of deaths of the excitation light source estimated by the estimation unit. Further, it is preferable to further have a coefficient updating unit for updating the coefficient corresponding to the fiber laser unit.

The control method of the fiber laser system FLS configured as described above has a short cycle control S1 that is repeatedly executed in a relatively short cycle (for example, executed once per second) and a relatively long cycle. It includes a long-period control S2 that is repeatedly executed (for example, executed once an hour). Hereinafter, these controls will be described with reference to FIGS. 4 to 5. It is assumed that 1 is stored in the storage unit ME as the initial value of the coefficients α1 to αn. Further, it is assumed that the above-mentioned functions P1 (I) to Pm (I) or tables T1 to Tm are stored in the storage unit ME.

FIG. 4 is a flowchart showing the flow of the short cycle control S1. The short cycle control S1 includes the following steps S101 to S104.

Step S101: The basic current value calculation unit C01 acquires the target value P. When the target value P is not input, a predetermined value may be used as the target value P.

Step S102: The basic current value calculation unit C01 calculates the basic current value I0 based on the target value P acquired in the step S101.

Step S103: Each individual current value calculation unit C02_i calculates the individual current value αi × I0 by using the basic current value I0 calculated in the step S102 and the coefficient αi stored in the storage unit ME.

Step S104: Each drive current setting unit C03_i sets the magnitude of the drive current Ii supplied to the excitation light sources PS1 to PSm in the corresponding fiber laser unit FLUi to the individual current value αi × I0 calculated in the step S103.

FIG. 5 is a flowchart showing the flow of the long period control S2. The long period control S2 includes the following steps S201 to S204.

Step S201: Each dead number estimation unit C04_i acquires the measured value Pi of the power of the laser beam generated by the corresponding fiber laser unit FLUi from the laser power measurement unit Mi.

Step S202: The dead number estimation unit C04_i estimates the dead number of the excitation light sources PS1 to PSm based on the measured value Pi acquired in step S201 and the individual current value αi × I0 for the corresponding fiber laser unit FLUi. do.

Step S203: The control unit C controls the notification IN so as to notify when the number of sudden deaths estimated by the number of sudden deaths estimation unit C04_i reaches the threshold number of sudden deaths. Further, the control unit C controls the magnitude of the drive current Ii so that the drive current Ii supplied to the fiber laser unit having reached the threshold number of sudden deaths becomes a constant value without changing thereafter. Is preferable.

Step S204: The coefficient updating unit C05_i calculates a new value of the coefficient αi based on the number of sudden deaths estimated in the step S202, and updates the value of the coefficient αi stored in the storage unit ME.

(Effect of this embodiment)
The control unit C described in the present embodiment calculates and stores the coefficient αi corresponding to the number of deaths of the excitation light sources PS1 to PSm included in each fiber laser unit FLUi at an arbitrary time point, and stores each fiber laser unit. The magnitude of the drive current Ii supplied to the FLUi is controlled according to the value of the coefficient αi. More specifically, the control unit C controls the fiber laser unit FLUi, which has a larger number of sudden deaths estimated by the number of sudden deaths estimation unit C04_i, so as to increase the magnitude of the drive current Ii. In other words, when comparing any two fiber laser units out of the seven fiber laser units FLU1 to FLU7, the control unit C supplies to each excitation light source included in the above-mentioned fiber laser unit having a large number of deaths. Drive to be supplied to each excitation light source included in each fiber laser unit so that the magnitude of the drive current to be driven exceeds the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit having a small number of deaths described above. Control the magnitude of the current. The same applies to the control method described in this embodiment.

As a result, even if the excitation light sources PS1 to PSm in each fiber laser unit FLUi have different numbers of deaths, it is possible to suppress variations in the power of the laser light generated in each fiber laser unit FLUi. As a result, the present embodiment can realize a fiber laser system in which failure due to Stokes oscillation is unlikely to occur.

(Modification example)
The fiber laser system FLS may include an output power measuring unit in addition to the configuration shown in FIG. The output power measuring unit measures the power of the output light synthesized by the output combiner OC. For example, the output power measuring unit M may perform measurement by detecting the laser beam branched from the laser beam waveguideed by the output delivery fiber ODF by using a photodiode. Further, the output power measuring unit outputs a signal representing the measured value P to the control unit C.

In this case, the basic current value calculation unit C01 in the control unit C obtains the basic current value I0 based on the measured value P measured by the output power measuring unit in addition to being based on the target value P0 set by the user. calculate. Specifically, when the basic current value calculation unit C01 determines that the measured value P is not equal to the target value P0, the value obtained by multiplying the basic current value I0 calculated as described above by P0 / P. May be calculated as a new basic current value I0.

[Example of implementation by software]
Each functional block of the control unit C in the fiber laser system FLS (particularly, the basic current value calculation unit C01, the individual current value calculation unit C02_i, the drive current setting unit C03_i, the dead number estimation unit C04_i, and the coefficient update unit C05_i) is an integrated circuit. It may be realized by a logic circuit (hardware) formed in (IC chip) or the like, or may be realized by software.

In the latter case, the fiber laser system FLS comprises a computer that executes the instructions of a program that is software that realizes each function. The computer includes, for example, one or more processors and a computer-readable recording medium that stores the program. Then, in the computer, the processor reads the program from the recording medium and executes it, thereby achieving the object of the present invention. As the processor, for example, a CPU (Central Processing Unit) can be used. The recording medium may be a "non-temporary tangible medium", for example, a ROM (
In addition to Read Only Memory), tapes, disks, cards, semiconductor memories, programmable logic circuits, etc. can be used. In addition, RAM (Random) that expands the above program
Access Memory) and the like may be further provided. Further, the program may be supplied to the computer via any transmission medium (communication network, broadcast wave, etc.) capable of transmitting the program. It should be noted that one aspect of the present invention can also be realized in the form of a data signal embedded in a carrier wave, in which the above program is embodied by electronic transmission.

(Additional notes)
The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and the embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

FLS Fiber Laser System FLU1 to FLUN Fiber Laser Unit LDF1 to LDFn Laser Delivery Fiber OC Output Combiner ODF Output Delivery Fiber OH Output Head M1 to M7 Laser Power Measuring Unit C Control Unit ME Storage Unit CS1 Current Source PS1 to PS6 Excitation Light Source PDF1 to PDF6 Excited delivery fiber PC Excitation combiner FBG-HR High reflection fiber Bragg grating AF Amplification fiber FBG-LR Low reflection fiber Bragg grating

Claims (9)

With multiple fiber laser units
A combiner that combines the laser light generated by each fiber laser unit,
Each fiber laser so that the difference in the power of the laser light generated by each fiber laser unit becomes small and the power of the output light generated by the combiner approaches the target value set by the user. A control unit that controls the magnitude of the drive current supplied to each excitation light source included in the unit,
A estimation unit for estimating at least one of the number of survivors and the number of deaths of the excitation light source contained in the fiber laser unit based on the power of the laser beam generated by each fiber laser unit is provided.
The control unit controls the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit according to at least one of the survival number and the sudden death number estimated by the estimation unit.
A fiber laser system characterized by this. Further including a notification unit for notifying when at least one of the number of survivors and the number of sudden deaths estimated in the estimation unit reaches a predetermined number.
The fiber laser system according to claim 1 . Further, the estimation unit is at least one of the number of survivors and the number of deaths of the excitation light sources included in the fiber laser unit , based on the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit. Estimate one,
The fiber laser system according to claim 1 or 2 . In the control unit, the more the fiber laser unit estimated by the estimation unit has a smaller survival number, or the more the fiber laser unit estimated by the estimation unit has a larger number of deaths, the more the excitation light source included in the fiber laser unit. Control the magnitude of the drive current so that the magnitude of the supplied drive current is increased.
The fiber laser system according to any one of claims 1 to 3 . Further, a storage unit is provided, which is a coefficient corresponding to each fiber laser unit and stores a coefficient corresponding to at least one of the number of survivors and the number of deaths of the excitation light source included in the fiber laser unit.
The control unit is (1 ) a basic current value calculation unit that calculates a basic current value based on the target value, and (2) a basic calculation unit that calculates each fiber laser unit by the basic current value calculation unit. An individual current value calculation unit that calculates an individual current value corresponding to the fiber laser unit based on the current value and the coefficient corresponding to the fiber laser unit stored in the storage unit, and (3) each. For the fiber laser unit, the magnitude of the drive current supplied to each excitation light source included in the fiber laser unit is set to the individual current value corresponding to the fiber laser unit calculated by the individual current value calculation unit. It has a drive current setting unit.
The fiber laser system according to claim 2 . It is a control method of a fiber laser system including a plurality of fiber laser units and a combiner that combines the laser beams generated by each fiber laser unit.
Each fiber laser so that the difference in the power of the laser light generated by each fiber laser unit becomes small and the power of the output light generated by the combiner approaches the target value set by the user. A control process that controls the magnitude of the drive current supplied to each excitation light source included in the unit,
Including an estimation step of estimating at least one of the number of survivors and the number of deaths of the excitation light source contained in the fiber laser unit based on the power of the laser beam generated by each fiber laser unit.
The control step controls the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit according to at least one of the survival number and the death number estimated in the estimation step.
A method for controlling a fiber laser system. Further including a notification step of notifying when at least one of the number of survivors and the number of sudden deaths estimated in the estimation step reaches a predetermined number.
The control method for a fiber laser system according to claim 6 , wherein the fiber laser system is controlled. In the estimation step, at least one of the number of survivors and the number of deaths of the excitation light sources included in the fiber laser unit is based on the magnitude of the drive current supplied to each excitation light source included in each fiber laser unit. Estimate one,
The control method for a fiber laser system according to claim 6 or 7 , wherein the fiber laser system is controlled. In the control step, a fiber laser unit with a small number of survivors estimated in the estimation step, or a fiber laser unit with a large number of deaths estimated in the estimation step, is used for each excitation light source included in the fiber laser unit. Control the magnitude of the drive current so that the magnitude of the supplied drive current is increased.
The control method for a fiber laser system according to any one of claims 6 to 8 , wherein the fiber laser system is controlled.

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