Patent Description:
Because fiber laser devices can obtain light with excellent light-condensing properties, high power density, and a small beam spot, fiber laser devices are being used in a variety of fields such as the laser processing field and the medical field. Consequently, fiber laser devices are sometimes used in combination with a processing machine.

In a fiber laser device, a plurality of laser diodes (LDs) are typically used as a source of pumping light. In some cases, laser diodes may malfunction or exhibit weakened output for various reasons. If one or some of the laser diodes in a fiber laser device malfunction or exhibit reduced output, the pumping light source may still continue to be used in some cases through means such as increasing the power of the light emitted from the other laser diodes. However, in some cases the power of the light from the pumping light source falls by a certain ratio or greater, in other cases the pumping light source must be replaced, and in still other cases the fiber laser device itself reaches a use limit and must be replaced. Consequently, there is demand for a way to estimate the degree of deterioration of a pumping light source.

Patent Literature <NUM> below describes an optical amplifier capable of determining the degree of deterioration of a pumping light source. In the optical amplifier, the relationship between the driving current of a pumping light source element, such as a laser diode, and the power of the emitted pumping light in an initial state is compared to the relationship between the driving current of the pumping light source element and the power of the emitted pumping light in a state after a certain duration of use. From the comparison result, the degree of deterioration of the pumping light source element is determined.

[Patent Literature <NUM>] <CIT>
Additionally, <CIT>, as it is stated in its abstract, relates to a laser diode driver, and driving method, for driving a laser diode in an optical recording/reproducing apparatus, having an auto laser power control (APC) operation, an optical pickup device, and an optical recording/reproducing apparatus, and method therefore, using the laser diode driver. Then, <CIT>, as it is stated in its abstract, relates to a method for predicting the lifetime of a photo-semiconductor device that has a maximum light output value restricted by thermal saturation, the maximum light output value is extracted by measuring the characteristic of light output from the photo-semiconductor device with respect to drive current. The decrease tendency of the maximum output values with respect to drive time is predicted to predict the lifetime of the photo-semiconductor. Further, the predicted lifetime is updated as time passes.

In Patent Literature <NUM>, the relationship between the driving current of a pumping light source element, such as a laser diode, and the power of the emitted pumping light is used to determine the degree of deterioration of each pumping light source element. However, the timing when the driving current applied to a laser diode and the timing when light is emitted from the laser diode may not match each other in some cases. Consequently, at the timing when a large driving current is applied to a laser diode, it is not necessarily always the case that high-power light will be emitted from the pumping light source, and sometimes high-power light may be emitted from the pumping light source at a timing when a small driving current is applied to the laser diode, or low-power light may be emitted from the pumping light source at a timing when a large driving current is applied to the laser diode. Consequently, simply comparing the relationship between the magnitude of the driving current input into a laser diode to the power of light emitted from the pumping light source may result in a determination that the pumping light source is deteriorated or that the pumping light source is not deteriorated much, depending on the timing when the degree of deterioration is determined. In this way, the estimation of the degree of deterioration of the pumping light source becomes inconsistent, and there are concerns about being unable to appropriately estimate the degree of deterioration. Such concerns may also extend to laser devices other than fiber lasers, insofar as the laser device uses a laser diode.

Accordingly, an object of the present invention is to provide a laser device capable of appropriately estimating a state of deterioration of a light source using laser diodes and a method for estimating the degree of deterioration of a light source of a laser device.

To solve the issues described above, the present invention provides a laser device as defined in claim <NUM>.

As described above, the timing when the driving current applied to a laser diode and the timing when light is emitted from the laser diode may not match each other in some cases. Consequently, in some cases, the timing when the magnitude of the driving current applied to a laser diode reaches a maximum may not match the timing when the power of the light emitted from a light source including a plurality of laser diodes reaches a maximum. In other words, in some cases, the maximum driving current is applied to a laser diode, and after predetermined amount of time elapses, light of maximum power according to the maximum driving current is emitted. For this reason, even in cases where the timing when the magnitude of the driving current reaches a maximum does not match the timing when the power of the light reaches a maximum, the maximum value of the magnitude of the driving current and the maximum value of the power of the light emitted from the light source correspond with each other for the most part. Consequently, by estimating the degree of deterioration of the light source from the maximum value of the driving current and the maximum value of the power of the light within a predetermined period like in the present invention, the state of deterioration of the light source can be estimated appropriately. Note that the maximum value of the driving current and the maximum value of the power of the light do not include phenomena such as a large current that flows momentarily because of spike noise or the like, or light having a high peak value that is emitted momentarily because of unintentional oscillations or the like.

Further, the memory additionally stores a relationship between the degree of deterioration and a time until the light source reaches a predetermined use limit, the laser device preferably further includes: a use-limit time estimation unit that refers to the memory to additionally estimate the time until the light source reaches the use limit from the estimated degree of deterioration.

Even when the state of deterioration of the light source is estimated appropriately, it is still difficult for a user to grasp the amount of time left until the use limit of the laser device is reached on the basis of the estimated degree of deterioration. However, as above, by estimating the time until a predetermined use limit is reached from the degree of deterioration of the light source, the user of the laser device can easily grasp the amount of time left until the light source reaches the use limit, and make appropriate preparations, such as readying a spare light source, in a timely manner.

Further, the laser device preferably further includes: a driving power source unit that applies a current to the plurality of laser diodes; and an optical power monitor that monitors the power of the light emitted from the light source, in which in a case where a signal indicating a drop in the power of the light is input from the optical power monitor, the controller controls the driving power source unit to increase the driving current in a range in which the power of the light emitted from the light source does not exceed the power of the light before the signal indicating the drop in the power of the light was input from the optical power monitor.

In this case, even if several of the plurality of laser diodes in the light source become deteriorated and the power of the light emitted from the light source drops, by controlling the driving power source unit to increase the driving current, an insufficiency in the power of the light emitted from the laser device can be suppressed. Also, by increasing the driving current, the maximum value of the driving current held in the driving current peak hold unit is updated. On the other hand, the maximum value of the power of the light held in the optical power peak hold unit remains the same value from before the signal indicating a drop in the power of the light was input from the optical power monitor. In the case where the light source has deteriorated, the driving current increases even if the power of the emitted light is constant. Consequently, according to the laser device, the state of deterioration of the light source can be estimated more appropriately.

Further, the laser device preferably further includes: a controller; a driving power source unit that applies a current to the plurality of laser diodes; and an optical power monitor that monitors the power of the light emitted from the light source, in which in a case where a signal indicating a drop in the power of the light is input from the optical power monitor, the controller controls the driving power source unit to make the power of the light emitted from the light source equal to the power of the light before the signal indicating the drop in the power of the light was input from the optical power monitor.

Through such control, an insufficiency in the power of the light emitted from the laser device can be suppressed further. Also, by increasing the driving current such that the power of the emitted light becomes the same as the power before the signal indicating a drop in the power of the light was input, the maximum value of the driving current held in the driving current peak hold unit is updated. Consequently, the state of deterioration of the light source can be estimated appropriately.

Further, according to the present invention, the driving current peak hold unit erases the maximum value of the driving current stored within the predetermined period after the predetermined period elapses, and the optical power peak hold unit erases the maximum value of the power of the light stored within the predetermined period after the predetermined period elapses.

By erasing the maximum value of the driving current and the maximum value of the power of the light after a predetermined period elapses in this way, the capacity of the temporary storage unit inside the driving current peak hold unit and the optical power peak hold unit can be reduced. Also, even in cases where the user switches to low-output operation for long-term use, a memory-full state can be suppressed and the present degree of laser diode deterioration can be diagnosed.

Further, it is preferable that the light source additionally include amplification optical fiber doped with an active element that is pumped by light emitted from the plurality of laser diodes.

In this case, the light source is formed from a fiber laser device, and the plurality of laser diodes acts as the pumping light source unit that emits pumping light. With such a light source, the light emitted from the plurality of laser diodes pumps the active element, and light emitted from the pumped active element is emitted from the amplification optical fiber. In this case, compared to the case where the light emitted from the laser diodes is emitted directly from the light source, the timing when the current is applied to the laser diodes and the timing when the light is emitted from the light source tend to separate further. However, according to the laser device according to the present invention in which the degree of deterioration of the light source is estimated from the maximum value of the driving current and the maximum value of the power of the light, even in cases that include amplification optical fiber as above, the state of deterioration of the light source can be estimated appropriately.

Further, the laser device may further include amplification optical fiber doped with an active element that is pumped by light emitted from the light source, in which the driving current peak hold unit holds the maximum value of the power of the light before the light enters the amplification optical fiber.

In this case, because the light emitted from the light source pumps the active element of the amplification optical fiber, the light source can be understood to be a pumping light source, and a fiber laser device is formed as the overall laser device. Even in such a case, the state of deterioration of the light source can be estimated appropriately. Also, in this case, by combining the above with another monitor, it becomes possible to better estimate the malfunctioning location in the overall fiber laser.

Further, to solve the issue described above, the present invention provides a method for estimating a degree of deterioration of a light source of a laser device, as defined in claim <NUM>.

According to such a method for estimating the degree of deterioration of a light source of a laser device, by estimating the degree of deterioration of the light source from the maximum value of the driving current and the maximum value of the power of the light within a predetermined period, the state of deterioration of the light source can be estimated appropriately.

Preferably, the memory additionally stores a relationship between the degree of deterioration and the amount of time until the light source reaches a predetermined use limit, and the method for estimating the degree of deterioration of a light source of a laser device additionally includes a use-limit time estimating step that additionally estimates the amount of time until the light source reaches the use limit from the estimated degree of deterioration.

According to such a method for estimating the degree of deterioration of a light source of a laser device, a user of the laser device can easily grasp the amount of time left until the light source reaches the use limit, and make appropriate preparations, such as readying a spare light source, in a timely manner.

As described above, according to the present invention, a laser device capable of appropriately estimating a state of deterioration of a light source using laser diodes and a method for estimating the degree of deterioration of a light source of a laser device are provided.

Hereinafter, preferred embodiments of the laser device and the method for estimating the degree of deterioration of a light source of a laser device according to the present invention will be described in detail with reference to the drawings.

<FIG> is a diagram illustrating a laser device according to the present embodiment. As illustrated in <FIG>, the laser device <NUM> according to the present embodiment is provided with a light source <NUM>, an optical power monitor <NUM>, a driving power source unit <NUM>, a driving current monitor <NUM>, a processor <NUM>, and a memory <NUM> as a major configuration.

The light source <NUM> is provided with a pumping light source unit <NUM> that emits pumping light, amplification optical fiber <NUM> doped with an active element that is pumped by the pumping light emitted from the pumping light source unit <NUM>, optical fiber <NUM> connected to one end of the amplification optical fiber <NUM>, a high-reflectivity FBG <NUM> provided in the optical fiber <NUM>, a combiner <NUM> for entering pumping light into the optical fiber <NUM>, optical fiber <NUM> connected to the other end of the amplification optical fiber <NUM>, and a low-reflectivity FBG <NUM> provided in the optical fiber <NUM> as a major configuration. The amplification optical fiber <NUM>, the high-reflectivity FBG <NUM>, and the low-reflectivity FBG <NUM> together form a resonator, and the light source <NUM> can be understood as including a fiber laser device.

The pumping light source unit <NUM> includes a plurality of laser diodes <NUM>, and emits pumping light of a wavelength that pumps the active element used to dope the amplification optical fiber <NUM>. Each laser diode <NUM> of the pumping light source unit <NUM> is connected to pumping optical fiber <NUM>, and light emitted from each laser diode <NUM> is propagated through the pumping optical fiber <NUM> optically connected to each laser diode <NUM>. The pumping optical fiber <NUM> may be multi-mode fiber, for example, and in this case, the pumping light is propagated through the pumping optical fiber <NUM> as multi-mode light. Note that in the case where the active element used to dope the amplification optical fiber <NUM> is ytterbium as described later, the wavelength of the pumping light is set to <NUM>, for example.

The amplification optical fiber <NUM> includes a core, an inner cladding that gaplessly surrounds the outer circumferential surface of the core, an outer cladding that covers the outer circumferential surface of the inner cladding, and a covering layer that covers the outer circumferential surface of the outer cladding. The material used to form the core of the amplification optical fiber <NUM> may be, for example, quartz doped with an element such as germanium that raises the refractive index and an active element such as ytterbium (Yb) that is pumped by the light emitted from the pumping light source unit <NUM>. Such an active element may be one of the rare-earth elements. Besides ytterbium mentioned above, the rare-earth elements include elements such as thulium (Tm), cerium (Ce), neodymium (Nd), europium (Eu), and erbium (Er). Furthermore, besides the rare-earth elements, an element such as bismuth (Bi) may also be used as the active element. Also, the material used to form the inner cladding of the amplification optical fiber <NUM> may be, for example, pure quartz not doped with any dopant. Note that in the case where the core is not doped with an element that raises the refractive index, the cladding is quartz doped with an element that lowers the refractive index, such as fluorine for example. Also, the material used to form the outer cladding of the amplification optical fiber <NUM> may be a resin having a lower refractive index than the inner cladding, for example, and the material used to form the covering layer of the amplification optical fiber <NUM> may be a UV-cured resin different from the resin used to form the outer cladding. The amplification optical fiber <NUM> is taken to be a single-mode fiber that propagates light mainly in a basic mode, but to enable the core of the amplification optical fiber to propagate high-power signal light, the diameter of the core may be made similar to the core of multi-mode fiber while still propagating light mainly in a basic mode. Alternatively, the amplification optical fiber <NUM> may be taken to be few-mode fiber that propagates light in a few modes while maintaining the beam quality of the light propagating through the core, or in cases where the beam quality is not a concern, the amplification optical fiber <NUM> may be taken to be multi-mode fiber.

The optical fiber <NUM> has the same configuration as the amplification optical fiber <NUM>, except that the core is not doped with an active element. The optical fiber <NUM> is connected to one end of the amplification optical fiber <NUM>, with the central axis of the core aligned with the central axis of the core of the amplification optical fiber <NUM>. Consequently, the core of the amplification optical fiber <NUM> and the core of the optical fiber <NUM> are optically coupled, and the inner cladding of the amplification optical fiber <NUM> and the inner cladding of the optical fiber <NUM> are optically coupled.

Also, the high-reflectivity FBG <NUM> is provided in the core of the optical fiber <NUM>. With this arrangement, the high-reflectivity FBG <NUM> is provided on one side of the amplification optical fiber <NUM>. In the high-reflectivity FBG <NUM>, a portion of higher refractive index is repeated on a fixed period along the lengthwise direction of the optical fiber <NUM>. By adjusting the period, the high-reflectivity FBG <NUM> reflects light of a specific wavelength from among the light emitted by the active element of the amplification optical fiber <NUM> in the pumped state. In the case where the active element used to dope the amplification optical fiber <NUM> is ytterbium as described above, the high-reflectivity FBG <NUM> reflects light having a wavelength of <NUM> for example with a reflectivity of <NUM>% or greater, for example.

Also, in the combiner <NUM>, the cores of the pumping optical fibers <NUM> are connected to the inner cladding of the optical fiber <NUM>. With this arrangement, the pumping optical fibers <NUM> connected to the pumping light source unit <NUM> are optically coupled with the inner cladding of the amplification optical fiber <NUM> via the inner cladding of the optical fiber <NUM>.

The optical fiber <NUM> includes a core similar to the core of the amplification optical fiber <NUM> except that the core is not doped with an active element, a cladding of similar configuration to the inner cladding of the amplification optical fiber <NUM> that gaplessly surrounds the outer circumferential surface of the core, and a covering layer that covers the outer circumferential surface of the cladding. The optical fiber <NUM> is connected to the other end of the amplification optical fiber <NUM>, and the core of the amplification optical fiber <NUM> and the core of the optical fiber <NUM> are optically coupled.

Also, the low-reflectivity FBG <NUM> is provided in the core of the optical fiber <NUM>. With this arrangement, the low-reflectivity FBG <NUM> is provided on the other side of the amplification optical fiber <NUM>. In the low-reflectivity FBG <NUM>, a portion of higher refractive index is repeated on a fixed period along the lengthwise direction of the optical fiber <NUM>, such that light of at least a portion of the wavelength(s) of the light reflected by the high-reflectivity FBG <NUM> is reflected at a lower reflectivity than the high-reflectivity FBG <NUM>. For example, the low-reflectivity FBG <NUM> is configured to reflect light of the same wavelength as the light reflected by the high-reflectivity FBG <NUM>, at a reflectivity of <NUM>%. Consequently, in the case where the high-reflectivity FBG <NUM> reflects light having a wavelength of <NUM> as above, the low-reflectivity FBG <NUM> transmits a portion of the light having that wavelength, and the transmitted light is emitted from the optical fiber <NUM>.

Consequently, in the present embodiment, the optical fiber <NUM> up to at least the portion containing the low-reflectivity FBG <NUM> is considered part of the light source <NUM>.

Also, on the side of the optical fiber <NUM> opposite from the amplification optical fiber <NUM>, a coupler <NUM> is provided. In the coupler <NUM>, optical fiber <NUM> acting as delivery fiber and optical fiber <NUM> acting as monitor fiber are connected to the optical fiber <NUM>. Note that the optical fiber <NUM> and the optical fiber <NUM> may also be a single unitary optical fiber. The majority of the light propagated through the optical fiber <NUM> is propagated to the optical fiber <NUM> in the coupler <NUM>, while a fixed ratio of the light propagated through the optical fiber <NUM> is split at the coupler <NUM> and directed into the optical fiber <NUM>.

The optical power monitor <NUM> is connected to the optical fiber <NUM>. The optical power monitor <NUM> includes a photodetector <NUM> and an A/D converter <NUM>. The photodetector <NUM> includes a photodiode or the like, and outputs a voltage corresponding to the power of the light emitted from the optical fiber <NUM>. Also, the A/D converter <NUM> is electrically connected to the photodetector <NUM>, and outputs a signal based on the input voltage. Consequently, a signal based on the power of the light propagated through the optical fiber <NUM> is output from the optical power monitor <NUM>. Because the light propagated through the optical fiber <NUM> is a fixed ratio of the light propagated through the optical fiber <NUM> as described above, a signal based on the power of the light propagated through the optical fiber <NUM> is output from the optical power monitor <NUM>. For this reason, the optical power monitor <NUM> can be understood as a component that monitors the power of the light emitted from the light source <NUM>. Note that the optical power monitor <NUM> is not limited to the above configuration insofar as the optical power monitor <NUM> monitors the power of the light emitted from the light source <NUM>.

Note that in the present embodiment, a portion of the light propagated through the optical fiber <NUM> is split by the coupler <NUM>, and the power of the light is monitored by the optical power monitor <NUM>. However, the power of the light propagated through the optical fiber <NUM> may also be monitored with a Rayleigh monitor that monitors the Rayleigh light propagated through the optical fiber <NUM> without using the coupler <NUM>.

The processor <NUM> is electrically connected to the optical power monitor <NUM>. The driving power source unit <NUM> is electrically connected to the processor <NUM>. The driving power source unit <NUM> applies a predetermined current to the plurality of laser diodes <NUM> in the pumping light source unit <NUM> of the light source <NUM>, on the basis of a signal received from the processor <NUM>.

Also, the driving current monitor <NUM> is electrically connected on the electrical path leading from the driving power source unit <NUM> to the pumping light source unit <NUM> of the light source <NUM>. The driving current monitor <NUM> monitors the magnitude of the current that the driving power source unit <NUM> applies to the plurality of laser diodes <NUM>. The driving current monitor <NUM> is electrically connected to the processor <NUM>, and inputs into the processor <NUM> a signal based on the magnitude of the current that the driving power source unit <NUM> applies to the plurality of laser diodes <NUM>.

The processor <NUM> includes a controller <NUM>, a driving current peak hold unit <NUM>, an optical power peak hold unit <NUM>, a degree-of-deterioration estimation unit <NUM>, and a use-limit time estimation unit <NUM>. Also, the memory <NUM> is electrically connected to the processor <NUM>.

The controller <NUM> controls the driving power source unit <NUM> and blocks other than the controller <NUM> inside the processor <NUM>.

The driving current peak hold unit <NUM> includes internal memory and a comparator, for example, and holds a maximum value of the current value of the driving current input from the driving current monitor <NUM>. Note that the internal memory may also be substituted by a portion of the memory <NUM>. In the present embodiment, the driving current peak hold unit <NUM> is reset on a predetermined period, and every time the predetermined period elapses, the held maximum value of the driving current is erased. Consequently, the driving current peak hold unit <NUM> holds the maximum value within the predetermined period of the driving current applied to the plurality of laser diodes <NUM>. The driving current peak hold unit <NUM> may perform the erasure every predetermined period, or the controller <NUM> may control the driving current peak hold unit <NUM> to perform the erasure every predetermined period. Also, the predetermined period is not particularly limited, and is set from <NUM> hour to <NUM> hours, for example.

The optical power peak hold unit <NUM> includes internal memory and a comparator, for example, and holds a maximum value of the optical power input from the optical power monitor <NUM>. Note that the internal memory may also be substituted by a portion of the memory <NUM>. As above, because the optical power monitor <NUM> can be understood as a component that monitors the power of the light emitted from the light source <NUM>, the optical power peak hold unit <NUM> that stores the maximum value of the optical power input from the optical power monitor <NUM> can be understood as holding the maximum value of the power of the light emitted from the light source <NUM>. In the present embodiment, the optical power peak hold unit <NUM> is reset on the above predetermined period that is reset by the driving current peak hold unit <NUM>, and every time the predetermined period elapses, the held maximum value of the power of the light is erased. Consequently, the optical power peak hold unit <NUM> holds the maximum value within the predetermined period of the power of the light emitted from the light source <NUM>. The optical power peak hold unit <NUM> may perform the erasure every predetermined period, or the controller <NUM> may control the optical power peak hold unit <NUM> to perform the erasure every predetermined period. Also, the predetermined period reset by the optical power peak hold unit <NUM> is taken to be the same as the predetermined period reset by the driving current peak hold unit <NUM>.

The degree-of-deterioration estimation unit <NUM> refers to the memory <NUM> to estimate the degree of deterioration of the light source <NUM> from the maximum value of the driving current held in the driving current peak hold unit <NUM> and the maximum value of the power of the light held in the optical power peak hold unit <NUM>.

Consequently, a relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source is stored in the memory <NUM>. <FIG> is a graph that schematically illustrates a relationship, stored in the memory <NUM>, between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM>. In <FIG> the horizontal axis represents the magnitude of the driving current applied to the plurality of laser diodes <NUM> of the pumping light source unit <NUM>, while the vertical axis represents the power of the light emitted from the light source <NUM>. In <FIG>, the solid line indicates the magnitude of the driving current and the magnitude of the power of the light in a state in which the efficiency of the plurality of laser diodes <NUM> of the pumping light source unit <NUM> is not reduced, while the dashed line indicates the magnitude of the driving current and the magnitude of the power of the light in a state in which the plurality of laser diodes <NUM> of the pumping light source unit <NUM> have a <NUM>% degree of deterioration. The degree of deterioration indicates the ratio of the drop in the power of the light emitted from the light source <NUM> in the case where the driving current that should be applied to the plurality of laser diodes <NUM> in the state in which each laser diode <NUM> is not deteriorated is applied to the plurality of laser diodes <NUM> in a deteriorated light source <NUM>. Consequently, the degree of deterioration exists in a predetermined relationship with the reduction in the efficiency of the light source <NUM>. For example, assuming that the pumping light source unit <NUM> of the light source <NUM> is provided with <NUM> laser diodes <NUM>, in the case where the power of the light from one of the laser diodes <NUM> falls to <NUM>% while the other laser diodes continue to emit light at <NUM>% power without being deteriorated, the degree of deterioration of the light source <NUM> is <NUM>%. In this case, the degree of deterioration is equal to the ratio of malfunctioning laser diodes <NUM> among the plurality of laser diodes <NUM>, or in other words the malfunction ratio. As another example, given a state in which the initial driving current is being applied to the plurality of laser diodes <NUM> in the light source <NUM>, in the case where the power of the light from each of the plurality of laser diodes <NUM> falls <NUM>%, the degree of deterioration of the light source <NUM> is <NUM>%. As <FIG> demonstrates, in the case of emitting light of fixed power from the light source <NUM>, the driving current to be applied to the plurality of laser diodes <NUM> of the pumping light source unit <NUM> is greater when the light source <NUM> is in a deteriorated state compared to when the light source <NUM> is in a non-deteriorated state. Note that in <FIG>, only the case of a <NUM>% degree of deterioration is illustrated as an example of deterioration of the light source <NUM>, but the memory <NUM> may store the relationship between the magnitude of the driving current and the magnitude of the power of the light for the cases of <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, and <NUM>% degree of deterioration of the light source <NUM>, for example.

The degree-of-deterioration estimation unit <NUM> reads out the maximum value of the driving current held in the driving current peak hold unit <NUM> and the maximum value of the power of the light held in the optical power peak hold unit <NUM>. Subsequently, a degree of deterioration stored in the memory <NUM> that is close to the relationship between the read-out maximum values of the driving current and the power of the light is determined. For example, in the case where the power of the light emitted from the light source <NUM> is <NUM> kW and the driving current is <NUM> A, from <FIG> the degree-of-deterioration estimation unit <NUM> estimates that all of the laser diodes <NUM> are operating without deterioration, and outputs a result indicating the same. As another example, in the case where the power of the light emitted from the light source <NUM> is <NUM> kW and the driving current is <NUM> A, from <FIG> the degree-of-deterioration estimation unit <NUM> estimates that the light source <NUM> has a <NUM>% degree of deterioration, and outputs a result indicating the same.

Also, the use-limit time estimation unit <NUM> refers to the memory <NUM> to estimate the time until the light source <NUM> reaches a predetermined use limit from the degree of deterioration of the light source <NUM> estimated by the degree-of-deterioration estimation unit <NUM>.

Consequently, a relationship between the degree of deterioration of the light source <NUM> and the time until the light source <NUM> reaches a predetermined use limit is stored in the memory <NUM>. <FIG> is a graph that schematically illustrates a relationship, stored in the memory <NUM>, between the degree of deterioration and the time until the light source reaches a predetermined use limit. In <FIG>, the horizontal axis represents the degree of deterioration of the light source <NUM>, while the vertical axis represents the remaining lifetime of the light source <NUM>. As illustrated in <FIG>, in the present embodiment, the light source <NUM> reaches the use limit after <NUM>,<NUM> hours in the case where all of the laser diodes <NUM> operate without deteriorating, but in the case where the degree of deterioration of the light source <NUM> is <NUM>%, the use limit is reached after <NUM>,<NUM> hours, and in the case where the degree of deterioration of the light source <NUM> is <NUM>%, the use limit is reached after <NUM>,<NUM> hours. Furthermore, in the case where the degree of deterioration of the light source <NUM> is <NUM>%, the light source <NUM> has reached the use limit.

The use-limit time estimation unit <NUM> reads the signal related to the degree of deterioration of the light source <NUM> output by the degree-of-deterioration estimation unit <NUM>, and if the estimation result from the degree-of-deterioration estimation unit <NUM> indicates that the degree of deterioration of the light source <NUM> is <NUM>%, the use-limit time estimation unit <NUM> estimates that the time until the use limit of the light source <NUM> is <NUM>,<NUM> hours, whereas if the estimation result from the degree-of-deterioration estimation unit <NUM> indicates that the degree of deterioration of the light source <NUM> is <NUM>% or higher, the use-limit time estimation unit <NUM> outputs a result indicating that the light source <NUM> has reached the use limit.

Note that, although not particularly illustrated in the diagrams, the degree of deterioration of the light source <NUM> estimated by the degree-of-deterioration estimation unit <NUM> and the time until the use limit of the light source <NUM> estimated by the use-limit time estimation unit <NUM> are preferably output to an output unit such as a monitor for visualization.

Next, the operations of the laser device <NUM> will be described.

First, the controller <NUM> controls the driving power source unit <NUM> such that the driving power source unit <NUM> applies a predetermined driving current to each laser diode <NUM> of the pumping light source unit <NUM>. Subsequently, pumping light is emitted from each laser diode <NUM>. The pumping light emitted from the pumping light source unit <NUM> proceeds from the pumping optical fiber <NUM> through the inner cladding of the optical fiber <NUM> and enters the inner cladding of the amplification optical fiber <NUM>. The pumping light entering the inner cladding of the amplification optical fiber <NUM> mainly propagates through the inner cladding, and when passing through the core of the amplification optical fiber <NUM>, pumps the active element used to dope the core. The pumped active element emits light of a specific wavelength by spontaneous emission. This spontaneously emitted light propagates through the core of the amplification optical fiber <NUM>, and the light of a portion of the wavelength(s) is reflected by the high-reflectivity FBG <NUM>. Of the reflected light, light of the wavelength that the low-reflectivity FBG <NUM> reflects is reflected by the low-reflectivity FBG <NUM> and travels back-and-forth between the high-reflectivity FBG <NUM> and the low-reflectivity FBG <NUM>, or in other words inside the resonator. This light is amplified by stimulated emission when propagating through the core of the amplification optical fiber <NUM>, and enters a laser oscillation state. Additionally, a portion of the amplified light is transmitted through the low-reflectivity FBG <NUM> and emitted from the optical fiber <NUM>. Almost all of the light emitted from the optical fiber <NUM> is propagated to the optical fiber <NUM> in the coupler <NUM>, and is emitted from the optical fiber <NUM>. With this arrangement, light is emitted from the laser device <NUM>.

Next, a method for estimating the degree of deterioration of the light source <NUM> of the laser device <NUM> and a method for estimating the use-limit time of the light source <NUM> will be described.

<FIG> is a flowchart illustrating a method for estimating the degree of deterioration of the light source <NUM> and a method for estimating the use-limit time of the light source <NUM>.

As above, when a predetermined driving current from the driving power source unit <NUM> is applied to each laser diode <NUM> of the pumping light source unit <NUM>, the driving current monitor <NUM> detects the driving current and inputs a signal corresponding to the magnitude of the driving current into the processor <NUM>. When the signal corresponding to the magnitude of the driving current is input into the processor <NUM>, the controller <NUM> controls the driving current peak hold unit <NUM> in a driving current peak holding step ST1. The driving current peak hold unit <NUM> controlled by the controller <NUM> compares the maximum value of the driving current already held within the predetermined period by the driving current peak hold unit <NUM> to the magnitude of the driving current input from the driving current monitor <NUM>. If the comparison result is that the magnitude of the driving current input from the driving current monitor <NUM> is greater than the maximum value of the driving current already held by the driving current peak hold unit <NUM>, the driving current peak hold unit <NUM> newly holds the magnitude of the driving current input from the driving current monitor <NUM> as the maximum value of the driving current. On the other hand, if the comparison result is that the maximum value of the driving current already held by the driving current peak hold unit <NUM> is greater than the magnitude of the driving current input from the driving current monitor <NUM>, the driving current peak hold unit <NUM> keeps holding the currently held maximum value of the driving current. Note that to eliminate phenomena such as spike noise, the driving current monitor <NUM> preferably includes a low-pass filter and is configured not to detect peaks in the driving current with a duration of <NUM> or less, for example. Alternatively, in cases where the duration over which the driving current reaches a maximum value is a predetermined time such as <NUM> or less, for example, the driving current peak hold unit <NUM> may be controlled to treat such values as spike noise and not handle such values as a maximum value of the driving current.

Also, when light is emitted from the light source <NUM> as above, most of the light propagated through the optical fiber <NUM> is propagated to the delivery fiber, namely the optical fiber <NUM>, in the coupler <NUM>, but a fixed ratio of the light propagated through the optical fiber <NUM> is propagated to the optical fiber <NUM>. The light propagated to the optical fiber <NUM> is received by the photodetector <NUM>. The photodetector <NUM> outputs a voltage based on the power of the received light, and the voltage is input into the A/D converter <NUM>. The A/D converter <NUM> outputs a signal based on the input voltage, and the signal is input into the processor <NUM>. Consequently, a signal based on the power of the light propagated through the optical fiber <NUM> is output from the optical power monitor <NUM> that includes the A/D converter <NUM> as above. As described earlier, the signal is also a signal based on the power of the light propagated through the optical fiber <NUM>. When a signal based on the power of the light propagated through the optical fiber <NUM> is input into the processor <NUM>, the controller <NUM> controls the optical power peak hold unit <NUM> in an optical power peak holding step ST2. The optical power peak hold unit <NUM> controlled by the controller <NUM> compares the maximum value of the optical power already held within the predetermined period by the optical power peak hold unit <NUM> to the magnitude of the optical power input from the optical power monitor <NUM>. If the comparison result is that the magnitude of the optical power input from the optical power monitor <NUM> is greater than the maximum value of the optical power already held by the optical power peak hold unit <NUM>, the optical power peak hold unit <NUM> newly holds the magnitude of the optical power input from the optical power monitor <NUM> as the maximum value of the optical power. On the other hand, if the comparison result is that the maximum value of the optical power already held by the optical power peak hold unit <NUM> is greater than the magnitude of the optical power input from the optical power monitor <NUM>, the optical power peak hold unit <NUM> keeps holding the currently held maximum value of the optical power. Note that to eliminate phenomena such as unintentional light having a high peak value, the optical power monitor <NUM> preferably includes a low-pass filter and is configured not to detect peaks in the light with a duration of <NUM> or less, for example. Alternatively, in cases where the duration over which the optical power reaches a maximum value is a predetermined time such as <NUM> or less, for example, the optical power peak hold unit <NUM> may be controlled to treat such values as unintentional light and not handle such values as a maximum value of the optical power.

Next, in a degree-of-deterioration estimating step ST3, the controller <NUM> controls the degree-of-deterioration estimation unit <NUM>. The degree-of-deterioration estimation unit <NUM> controlled by the controller <NUM> refers to the memory <NUM> to estimate the degree of deterioration of the light source <NUM> as above from the maximum value of the driving current within the predetermined period held in the driving current peak hold unit <NUM> and the maximum value of the power of the light within the predetermined period held in the optical power peak hold unit <NUM>. Note that in the case where an output unit is provided as above, the estimated degree of deterioration of the light source <NUM> is output from the output unit.

Next, in a use-limit time estimating step ST4, the controller <NUM> controls the use-limit time estimation unit <NUM>. The use-limit time estimation unit <NUM> controlled by the controller <NUM> refers to the memory <NUM> to estimate the time until the light source <NUM> reaches a predetermined use limit from the degree of deterioration of the light source <NUM> estimated by the degree-of-deterioration estimation unit <NUM> as above. Note that in the case where an output unit is provided as above, the estimated time until the use limit of the light source <NUM> is output from the output unit.

With this arrangement, according to the laser device <NUM> according to the present embodiment, the degree of deterioration of the light source <NUM> and the time until the use limit of the light source <NUM> are estimated.

The degree of deterioration of the light source <NUM> and the time until the light source <NUM> reaches the use limit estimated in this way are not updated within the predetermined period unless the maximum value of the driving current held by the driving current peak hold unit <NUM> or the maximum value of the power of the light held by the optical power peak hold unit <NUM> is updated. Also, because the driving current peak hold unit <NUM> and the optical power peak hold unit <NUM> are reset every predetermined period as above, after a reset, the maximum value of the driving current is again held in the driving current peak hold unit <NUM>, while in addition, the maximum value of the power of the light is again held in the optical power peak hold unit <NUM>. Consequently, after a reset, the degree of deterioration of the light source <NUM> and the time until the light source <NUM> reaches the use limit are estimated.

Next, the operations of the laser device <NUM> in the case where the power of the light emitted from the light source <NUM> drops because of deterioration of the light source <NUM>, a method for estimating the degree of deterioration of the light source <NUM> of the laser device <NUM>, and a method for estimating the use-limit time of the light source <NUM> will be described.

In the case where the plurality of laser diodes <NUM> in the pumping light source unit <NUM> of the light source <NUM> become deteriorated, the power of the light emitted from the light source <NUM> drops. Subsequently, a signal indicating the drop in the power of the light is input into the processor <NUM> from the optical power monitor <NUM>. In the present embodiment, when a signal indicating a drop in the power of the light is input into the processor <NUM> from the optical power monitor <NUM>, the controller <NUM> controls the driving power source unit <NUM> to increase the driving current in a range in which the power of the light emitted from the light source <NUM> does not exceed the power of the light before the signal indicating the drop in the power of the light was input from the optical power monitor <NUM>.

<FIG> is a diagram that schematically illustrates a relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM> in a case where the controller <NUM> controls the driving power source unit <NUM> to increase the driving current in a case where the light source <NUM> has deteriorated. Note that <FIG> illustrates an example of a case where the light source <NUM> has deteriorated <NUM>% from a non-deteriorated state. In a state in which the driving power source unit <NUM> is controlled as above, the driving power source unit <NUM> increases the value of the current as indicated by the dashed arrow in <FIG>. In this case, the power of the light emitted from the light source <NUM> increases compared to the case where the driving current is not increased at all as indicated by the dotted arrow in <FIG>. However, in the case of the present example, the power of the light emitted from the light source <NUM> is smaller compared to the state before the light source <NUM> became deteriorated, that is, before the signal indicating a drop in the power of the light was input into the processor from the optical power monitor <NUM>. Consequently, the maximum value of the driving current held in the driving current peak hold unit <NUM> is updated, but the maximum value of the power of the light held in the optical power peak hold unit <NUM> remains the same as before the signal indicating a drop in the power of the light was input from the optical power monitor <NUM>. However, because the maximum value of the driving current held in the driving current peak hold unit <NUM> is updated, compared to the case where the driving current is not increased at all as indicated by the dotted arrow in <FIG>, the degree-of-deterioration estimation unit <NUM> can appropriately estimate the degree of deterioration of the light source <NUM> in the degree-of-deterioration estimating step ST3, and the use-limit time estimation unit <NUM> can accurately estimate the time until the light source <NUM> reaches the use limit in the use-limit time estimating step ST4.

Also, in the case where the plurality of laser diodes <NUM> in the pumping light source unit <NUM> of the light source <NUM> become deteriorated, and a signal indicating a drop in the power of the light is input into the processor <NUM> from the optical power monitor <NUM>, the driving power source unit <NUM> is preferably controlled such that the power of the light emitted from the light source <NUM> becomes the same as the power of the light before the signal indicating a drop in the power of the light was input from the optical power monitor <NUM>. In other words, by increasing the current output from the driving power source unit <NUM> when a signal indicating a drop in the power of the light is input into the processor <NUM>, the controller <NUM> performs a feedback control causing the state of reduced power of the light emitted from the light source <NUM> to be temporary. In this case, the driving power source unit <NUM> increases the value of the current as indicated by the solid arrow in <FIG>. By controlling the current in this way, the maximum value of the power of the light held in the optical power peak hold unit <NUM> does not change, but the maximum value of the driving current held in the driving current peak hold unit <NUM> is updated. Consequently, in the degree-of-deterioration estimating step ST3, the degree-of-deterioration estimation unit <NUM> can estimate the degree of deterioration of the light source <NUM> more appropriately. For this reason, in the use-limit time estimating step ST4, the use-limit time estimation unit <NUM> can estimate the time until the light source <NUM> reaches the use limit more accurately.

As described above, the laser device <NUM> according to the present embodiment includes a light source <NUM> including a plurality of laser diodes <NUM>; a driving current peak hold unit <NUM> that holds a maximum value within a predetermined period of a driving current applied to the plurality of laser diodes <NUM>; an optical power peak hold unit <NUM> that holds a maximum value within the predetermined period of a power of light emitted from the light source <NUM>; memory <NUM> that stores a relationship between a magnitude of the driving current, a magnitude of the power of the light, and a degree of deterioration of the light source <NUM>; and a degree-of-deterioration estimation unit <NUM> that refers to the memory <NUM> to estimate the degree of deterioration from the maximum value within the predetermined period of the driving current held in the driving current peak hold unit <NUM> and the maximum value within the predetermined period of the power of the light held in the optical power peak hold unit <NUM>.

Further, a method for estimating the degree of deterioration of the light source <NUM> of the laser device <NUM> according to the present embodiment includes a driving current peak holding step ST1 that holds a maximum value within a predetermined period of a driving current applied to the plurality of laser diodes <NUM>; an optical power peak holding step ST2 that holds a maximum value within the predetermined period of a power of light emitted from the light source <NUM>; and a degree-of-deterioration estimating step ST3 that refers to the memory <NUM> that stores a relationship between a magnitude of the driving current, a magnitude of the power of the light, and a degree of deterioration of the light source <NUM> to estimate the degree of deterioration from the maximum value within the predetermined period of the driving current held in the driving current peak holding step ST1 and the maximum value within the predetermined period of the power of the light held in the optical power peak holding step ST2.

According to such a laser device <NUM> according to the present embodiment and such a method for estimating the degree of deterioration of the light source <NUM> of the laser device <NUM>, even in cases where the timing when the magnitude of the driving current applied to the laser diodes reaches a maximum does not match the timing when the power of the light emitted from the light source including the plurality of laser diodes becomes a maximum, the state of deterioration of the light source can be estimated appropriately by estimating the degree of deterioration of the light source from the maximum value of the driving current and the maximum value of the power of the light within a predetermined period.

Also, in the laser device <NUM> according to the present embodiment, the memory <NUM> additionally stores the relationship between the degree of deterioration and the time until the light source <NUM> reaches a predetermined use limit, and the laser device <NUM> is additionally provided with the use-limit time estimation unit <NUM> that refers to the memory <NUM> to additionally estimate the time until the use limit from the estimated degree of deterioration. Also, the method for estimating the degree of deterioration of the light source <NUM> of the laser device <NUM> according to the present embodiment additionally includes a use-limit time estimating step ST4 that additionally estimates the time until the light source <NUM> reaches a predetermined use limit from the estimated degree of deterioration.

Even when the state of deterioration of the light source <NUM> is estimated appropriately, it is still difficult for a user to grasp the amount of time left until the use limit of the laser device <NUM> is reached on the basis of the estimated degree of deterioration. However, as the present embodiment, by estimating the time until a use limit from the degree of deterioration of the light source <NUM>, the user of the laser device <NUM> can easily grasp the amount of time left until the use limit, and make appropriate preparations, such as readying a spare light source, in a timely manner.

Next, a second embodiment of the present invention will be described in detail and with reference to <FIG>. Note that, unless specifically described otherwise, structural elements which are the same or substantially the same as the first embodiment will be denoted with the same reference signs, and duplicate description will be omitted.

<FIG> is a diagram illustrating a laser device <NUM> according to the present embodiment. As illustrated in <FIG>, in the laser device <NUM> according to the present embodiment, the amplification optical fiber <NUM> is disposed on the outside of the light source <NUM>, and the light source <NUM> has a configuration similar to the pumping light source unit <NUM> of the first embodiment.

The laser diodes <NUM> of the light source <NUM> are respectively connected to the pumping optical fiber <NUM>, similarly to the pumping light source unit <NUM> of the first embodiment. Like the first embodiment, each pumping optical fiber <NUM> is connected in the combiner <NUM> to the optical fiber <NUM> in which the high-reflectivity FBG <NUM> is formed. Like the first embodiment, the end of the optical fiber <NUM> on the opposite side from the combiner <NUM> is connected to the amplification optical fiber <NUM>. Like the first embodiment, the end of the amplification optical fiber <NUM> on the opposite side from the optical fiber <NUM> is connected to the optical fiber <NUM> in which the low-reflectivity FBG <NUM> is formed. The side of the optical fiber <NUM> opposite from the amplification optical fiber <NUM> is connected to the delivery fiber, that is, the optical fiber <NUM>.

In the present embodiment, the coupler <NUM> is provided on the optical fiber <NUM> between the combiner <NUM> and the high-reflectivity FBG <NUM>. The majority of the light propagated through the optical fiber <NUM> continues to be propagated through the optical fiber <NUM> in the coupler <NUM>, while a fixed ratio of the light propagated through the optical fiber <NUM> is split at the coupler <NUM> and directed into the optical fiber <NUM>.

The laser device <NUM> according to the present embodiment forms a fiber laser device including the light source <NUM> and the amplification optical fiber <NUM>. In other words, in the laser device <NUM> according to the first embodiment, the power of the light emitted from the amplification optical fiber <NUM> is monitored by the optical power monitor <NUM>, whereas in the laser device <NUM> according to the present embodiment, the optical power monitor <NUM> monitors the power of the light before the light enters the amplification optical fiber <NUM>, and the optical power peak hold unit <NUM> holds the maximum value within the predetermined period of the power of the light before the light enters the amplification optical fiber <NUM>. For this reason, the relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM> stored in the memory <NUM> referenced by the degree-of-deterioration estimation unit <NUM> is different from the relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM> stored in the memory <NUM> in the first embodiment. Note that likewise in the present embodiment, the power of the light propagated through the optical fiber <NUM> may also be monitored with a Rayleigh monitor that monitors the Rayleigh light propagated through the optical fiber <NUM> without using the coupler <NUM>.

In such a laser device <NUM> according to the present embodiment, the degree of deterioration of the light source <NUM> and the time until the light source <NUM> reaches the use limit may be estimated in a similar manner as the method for estimating the degree of deterioration of the light source <NUM> and the method for estimating the use-limit time of the light source <NUM> in the laser device <NUM> according to the first embodiment.

According to the laser device <NUM> according to the present embodiment, the degree of deterioration and the use-limit time of the light source <NUM> acting as a pumping light source unit can be estimated.

Next, a third embodiment of the present invention will be described in detail and with reference to <FIG>. Note that, unless specifically described otherwise, structural elements which are the same or substantially the same as the first embodiment will be denoted with the same reference signs, and duplicate description will be omitted.

<FIG> is a diagram illustrating the laser device <NUM> according to the present embodiment. As illustrated in <FIG>, in the laser device <NUM> according to the present embodiment, the light source <NUM> is provided with a plurality of laser units 2a. Each laser unit 2a has a configuration similar to the light source <NUM> according to the first embodiment. In other words, the light source <NUM> in the laser device <NUM> according to the present embodiment is configured to include a plurality of the light source <NUM> according to the first embodiment. However, in each laser unit 2a according to the present embodiment, it is sufficient for the pumping light source unit <NUM> to include one or more laser diodes <NUM>. Each optical fiber <NUM> that emits the light from each light source <NUM> is connected to the delivery fiber, namely the optical fiber <NUM>, in a combiner <NUM>.

In the present embodiment, the coupler <NUM> is provided in the middle of the optical fiber <NUM>. Therefore, the majority of the light propagated through the optical fiber <NUM> continues to be propagated through the optical fiber <NUM> in the coupler <NUM>, while a fixed ratio of the light propagated through the optical fiber <NUM> is split at the coupler <NUM> and directed into the optical fiber <NUM>.

As above, because each laser unit 2a has a configuration similar to the light source <NUM> according to the first embodiment, the laser device <NUM> according to the first embodiment can be understood as monitoring the power of the light emitted from a single laser unit with the optical power monitor <NUM>, whereas in the laser device <NUM> according to the present embodiment, the power of the light emitted from a plurality of laser units 2a is monitored with the optical power monitor <NUM>. However, the laser device <NUM> according to the first embodiment and the laser device <NUM> according to the present embodiment are similar in that the power of the light emitted from the light source <NUM> including the plurality of laser diodes <NUM> is monitored with the optical power monitor <NUM>. Note that likewise in the present embodiment, the power of the light propagated through the optical fiber <NUM> may also be monitored with a Rayleigh monitor that monitors the Rayleigh light propagated through the optical fiber <NUM> without using the coupler <NUM>. The optical power peak hold unit <NUM> holds the maximum value within the predetermined period of the power of the light emitted from the plurality of laser units 2a. For this reason, the relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM> stored in the memory <NUM> referenced by the degree-of-deterioration estimation unit <NUM> is different from the relationship between the magnitude of the driving current, the magnitude of the power of the light, and the degree of deterioration of the light source <NUM> stored in the memory <NUM> in the first embodiment.

Even in the case where the light source <NUM> includes a plurality of laser units 2a in this way, the degree of deterioration of the light source <NUM> and the time until the light source <NUM> reaches the predetermined use limit may be estimated in a similar manner as the method for estimating the degree of deterioration of the light source <NUM> and the method for estimating the use-limit time of the light source <NUM> in the laser device <NUM> according to the first embodiment.

The above describes the present invention by taking the foregoing embodiments as examples, but the present invention is not limited to these examples, and appropriate modifications are possible.

For example, in the first and second embodiments, the amplification optical fiber <NUM>, the high-reflectivity FBG <NUM>, and the low-reflectivity FBG <NUM> are not strictly necessary. In the case where these components are omitted, the laser device <NUM> according to the first embodiment and the laser device according to the second embodiment have substantially the same configuration. Also, each laser unit 2a according to the third embodiment may have a configuration similar to the light source <NUM> according to the second embodiment.

Also, in the foregoing embodiments, even in cases where the amplification optical fiber <NUM> is used, the high-reflectivity FBG <NUM> and the low-reflectivity FBG <NUM> are not strictly necessary. For example, the light source <NUM> according to the first embodiment, the laser device <NUM> according to the second embodiment, or each laser unit 2a according to the third embodiment may also be configured as a master oscillator - power amplifier (MO-PA) fiber laser device including a different type of light source unit than a pumping light source unit.

Also, in the foregoing embodiments, the laser device <NUM> includes the driving current monitor <NUM>, and the driving current peak hold unit <NUM> holds the maximum value of the current value of the driving current input from the driving current monitor <NUM> according to a signal from the driving current monitor <NUM>. However, the driving current monitor <NUM> is not strictly necessary, and the driving current peak hold unit <NUM> may also hold the maximum value of the driving current on the basis of a signal by which the controller <NUM> controls the driving power source unit <NUM>, for example.

Claim 1:
A laser device (<NUM>) comprising:
a light source (<NUM>) including a plurality of laser diodes (<NUM>); and
a processor (<NUM>) comprising a driving current peak hold unit (<NUM>), an optical power peak hold unit (<NUM>) and a degree-of-deterioration estimation unit (<NUM>);
wherein the driving current peak hold unit (<NUM>) is configured to hold a maximum value within a predetermined period of a driving current applied to the plurality of laser diodes (<NUM>);
wherein the optical power peak hold unit (<NUM>) is configured to hold a maximum value within the predetermined period of a power of light emitted from the light source (<NUM>) when the light is emitted from each laser diode (<NUM>);
wherein a memory (<NUM>) is electrically connected to the processor (<NUM>) and stores a relationship between a magnitude of the driving current, a magnitude of the power of the light, and a degree of deterioration of the light source (<NUM>) for different cases corresponding to different degrees of deterioration;
wherein the degree-of-deterioration estimation unit (<NUM>) is configured to determine a degree of deterioration among the different degrees of deterioration that are stored in the memory (<NUM>) that is close to the relationship between the maximum value within the predetermined period of a power of light and the maximum value within the predetermined period of the driving current;
wherein the driving current peak hold unit (<NUM>) is configured to erase the maximum value of the driving current stored within the predetermined period after the predetermined period elapses, and
the optical power peak hold unit (<NUM>) is configured to erase the maximum value of the power of the light stored within the predetermined period after the predetermined period elapses.