JP2011192670A - Apparatus and method of monitoring laser diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus of monitoring a laser diode capable of monitoring an output of an excitation laser diode with a simple structure at a low cost. <P>SOLUTION: Part of a coupling fiber coating 143 of a combiner output fiber 14 is removed to form a notch forming part 144 having a coupling fiber clad 142 exposed. A clad 222 of a monitoring double clad fiber 22 formed of a material having a refractive index same as or lower than that of the coupling fiber clad 142 of the combiner output fiber 14 is brought into contact with the notch forming part 144. Thus, part of output excitation light of laser diodes 12-1 to 12-n for transmitting the coupling fiber clad 142 of the combiner output fiber 14 is caused to leak and transmitted to the monitoring double clad fiber 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a technique for monitoring the output of an excitation laser diode in a fiber laser device composed of all fibers.

  Conventionally, for example, there is a remote sensing device using a fiber laser device. In this remote sensing device, the measurement object is extracted by irradiating the measurement object with laser light, receiving the laser reflected light from the measurement object, and analyzing the reflected light.

  In addition, a fiber laser device using an all-fiber fiber has a plurality of fiber-coupled laser diodes, a fiber Bragg grating, a combiner, and a rare-earth doped fiber connected to the output side of the combiner. The connection is established (for example, Patent Document 1 and Patent Document 2). Here, the combiner enters the laser light generated from the fiber Bragg grating and the excitation light of each of the plurality of laser diodes, and emits them to the rare earth doped fiber. The excitation light of each of the plurality of laser diodes is incident on the rare earth doped fiber to excite the rare earth doped fiber serving as the laser medium.

JP 2008-3116 A Japanese Patent Laid-Open No. 3-250674

  By the way, in the above fiber laser device, when the output of the laser diode is reduced for some reason or when the output is reduced due to the lifetime, it is difficult to monitor the output of the laser diode because all parts are connected by fusion. It is. For this reason, conventionally, when the output decreases, it is necessary to cut a part of the fiber of the laser diode and check the output of each laser diode.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a laser diode monitoring device and a laser diode monitoring method capable of monitoring the output of a laser diode for excitation with a simple configuration and at a low cost.

  In order to achieve the above object, a laser diode monitoring device according to the present invention includes a combiner that receives laser light and receives output light from each of a plurality of laser diodes, and is connected to the output side of the combiner. Of the output light, a core part that propagates the laser light, a clad part that covers the outer periphery of the core part and propagates the output light of each of the laser diodes, and a coating part that covers the outer periphery of the clad part Used in a fiber laser device including an optical fiber, and is formed in a notch formed in at least a part of a coating portion of a propagation optical fiber, and a notch forming portion that exposes a cladding portion to the outside, and one end portion in a notch forming portion The leakage of the output light of each of the plurality of laser diodes that are in contact and are propagating through the cladding of the propagation optical fiber The additional fiber that propagates the light, is connected to the other end of the additional fiber is a leakage light propagating through the additional fiber that is to include an optical detection section for receiving.

  The additional fiber is formed of a material having the same refractive index as that of the cladding portion of the propagation optical fiber or a lower refractive index than that of the cladding portion of the propagation optical fiber.

  According to this configuration, a part of the coating portion of the propagation optical fiber is notched, and the notch forming portion has the same refractive index as that of the cladding portion of the propagation optical fiber, or is compared with the cladding portion of the propagation optical fiber. By contacting one end of the additional fiber formed of a material having a low refractive index, a part of the output light of the laser diode propagating through the cladding of the optical fiber for propagation leaks to the additional fiber and propagates Will do.

  Therefore, it is possible to monitor the state of the output light of the laser diode by installing a light detector at the other end of the additional fiber.

  According to the above invention, it is possible to provide a laser diode monitoring apparatus and a laser diode monitoring method that can monitor the output of the laser diode for excitation with a simple configuration and at a low cost.

1 is a block diagram showing a configuration of a fiber laser device in which a laser diode monitor device according to the present invention is used. The perspective view which shows the structure of the combiner shown in FIG. 1, and a combiner output fiber. The figure which shows the structure of a laser diode monitor apparatus. The figure which shows the structure of the monitor apparatus used before. The block diagram which shows the other structure of the fiber laser apparatus in which the laser-diode monitor apparatus based on this invention is used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a configuration of a fiber laser device in which a laser diode monitor device according to the present invention is used. Here, for the sake of simplicity, consider the case where an all-fiber fiber laser amplifier is used as the fiber laser device.

  This fiber laser device includes a laser oscillator 11, a plurality of fiber coupled laser diodes 12-1 to 12-n, a combiner 13, a combiner output fiber 14 as a propagation optical fiber, and a rare earth doped fiber 15. Each is fusion spliced.

  The signal light (fiber laser output light) from the laser oscillator 11 and the pumping light from the laser diodes 12-1 to 12-n are incident on the rare earth doped fiber 15 through the combiner 13 and the combiner output fiber 14, and thereby the laser light. Is amplified and output.

  The combiner output fiber 14 is in contact with a monitoring double clad fiber 22 as an additional fiber via a monitoring fiber coupling portion 21. A photodetector 23 is connected to the other end of the monitoring double clad fiber 22.

  The structure of the combiner 13 and the combiner output fiber 14 is shown in FIG. The combiner 13 couples a signal light (fiber laser light) fiber 131 and pumping light fibers 132-1 to 132-n to a single combiner output fiber. The combiner output fiber 14 includes a coupling fiber core 141 that propagates laser light in a double clad structure, and a coupling fiber cladding 142 that covers the outer periphery of the coupling fiber core 141 and propagates the excitation light of each of the laser diodes 12-1 to 12-n. And a coupling fiber coating 143 covering the outer periphery of the coupling fiber clad 142. The fiber coating 143 is made of resin.

  FIG. 3 shows the configuration of the laser diode monitor device. The laser diode monitoring device is roughly divided into a monitoring fiber coupling portion 21, a monitoring double clad fiber 22, and a photodetector 23.

  In the monitoring fiber coupling portion 21, the coupling fiber coating 143 is removed from a part of the combiner output fiber 14, and a notch forming portion 144 is provided in which the coupling fiber cladding 142 is exposed. The monitoring double clad fiber 22 includes a clad 221 and a coating 222 covering the outer periphery of the clad 221. Further, a portion of the monitoring double clad fiber 22 that contacts the notch forming portion 144 is formed with a contact portion 223 that is removed from the coating 222 and contacts the coupling fiber clad 142.

  The clad 221 of the monitoring double clad fiber 22 is formed of a material having the same refractive index as that of the coupling fiber clad 142 of the combiner output fiber 14 or a lower refractive index than that of the coupling fiber clad 142 of the combiner output fiber 14. Is done.

  Then, a part of the excitation light of the laser diodes 12-1 to 12-n propagating through the coupling fiber clad 142 of the combiner output fiber 14 leaks and propagates to the clad 221 of the monitor double clad fiber 22, and is transmitted to the photodetector 23. Sent. Based on the light reception result, the photodetector 23 determines which laser diode 12-1 to 12-n output has decreased or which laser diode 12-1 to 12-n has decreased life and output. It is to detect.

Next, the operation in the above configuration will be described.
Previously, as described in Patent Document 2, a 2-input × 2-output optical splitter 31 was used as a monitor component. This monitor device is shown in FIG. 4, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this optical branching device 31, it is possible to monitor the light of the light emitting device and the light traveling backward from the outside. However, in the case of multimode, various core diameters (105 μm, 200 μm, 400 μm, etc.) are used for the combiner output fiber 14. It is not easy to manufacture an optical branching device 31 equivalent to these core diameters, and a high level of technology is required.

  Therefore, in this embodiment, when monitoring the outputs of the laser diodes 12-1 to 12-n, first, the coupling fiber coating 143 of the combiner output fiber 14 is partially removed to expose the coupling fiber cladding 142. It is only necessary to form the forming portion 144, remove the coating 222 at the tip of the monitoring double clad fiber 22 to be used, and bring the clad 221 into contact with the notch forming portion 144.

  After that, only by connecting the optical detector 23 to the other end of the monitoring double clad fiber 22, one of the excitation lights of the laser diodes 12-1 to 12 -n propagating through the coupling fiber clad 142 of the combiner output fiber 14. The portion leaks to the clad 221 of the monitoring double clad fiber 22 and is transmitted to the photodetector 23. Using the light reception result of the light detector 23, it can be determined which laser diodes 12-1 to 12-n have a reduced output or which laser diodes 12-1 to 12-n have a life reduced. It becomes possible to monitor.

  The monitoring double clad fiber 22 does not need to be a fiber composed of a core and a clad, and can be any material that has a refractive index equal to or lower than that of the combiner output fiber 14.

  As described above, in the above-described embodiment, the coupling fiber coating 143 of the combiner output fiber 14 is partially removed to form the notch forming portion 144 in which the coupling fiber cladding 142 is exposed, and the notch forming portion 144 is The clad 222 of the monitor double clad fiber 22 formed of a material having the same refractive index as the coupled fiber clad 142 of the combiner output fiber 14 or a low refractive index is brought into contact with the coupled fiber clad 142 of the combiner output fiber 14. A part of the output pumping light of the propagating laser diodes 12-1 to 12-n leaks to the monitoring double clad fiber 22 and propagates.

  Therefore, the state of the output light from the laser diodes 12-1 to 12-n can be monitored by installing the photodetector 23 at the other end of the monitoring double clad fiber 22.

  In the above embodiment, the example applied to the all-fiber type fiber laser amplifier has been described. However, as shown in FIG. 5, it may be used for a fiber laser oscillator using a fiber composed of all-fibers. . In this case, the laser beam resonates between the two gratings 41 and 42 and is output.

  In the implementation stage, the constituent elements can be modified and embodied without departing from the spirit of the invention. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment.

  DESCRIPTION OF SYMBOLS 11 ... Laser oscillator, 12-1 to 12-n ... Laser diode, 13 ... Combiner, 14 ... Combiner output fiber, 21 ... Monitor fiber coupling part, 22 ... Monitor double clad fiber, 23 ... Optical detector, 141 ... Coupling fiber core, 142 ... Coupling fiber cladding, 143 ... Coupling fiber coating.

Claims (4)

A combiner that injects laser light and the output light of each of a plurality of laser diodes;
A core portion that is connected to the output side of the combiner and propagates laser light out of the output light of the combiner, a cladding portion that covers an outer periphery of the core portion and propagates output light of each of the plurality of laser diodes, and the cladding Used in a fiber laser device comprising a propagation optical fiber having a coating portion covering the outer periphery of the portion,
A notch formed in at least a part of the coating portion of the optical fiber for propagation, and a notch forming portion exposing the clad portion to the outside;
One end of the additional fiber that is in contact with the notch forming portion and propagates leakage light of the output light of each of the plurality of laser diodes that is propagating through the cladding portion of the propagation optical fiber;
A laser diode monitor device comprising: a light detection unit connected to the other end of the additional fiber and receiving leakage light propagating through the additional fiber.   The additional fiber is formed of a material having the same refractive index as that of the cladding portion of the propagation optical fiber or a lower refractive index than that of the cladding portion of the propagation optical fiber. 1. The laser diode monitor device according to 1. When the additional fiber has a clad portion that propagates output light of each of the plurality of laser diodes and a coating portion that covers an outer periphery of the clad portion, a portion that contacts the notch forming portion of the propagation optical fiber 3. The laser diode monitor device according to claim 2, wherein the coating portion is removed and the clad portion is brought into contact with the clad portion of the propagation optical fiber. A combiner that injects laser light and the output light of each of a plurality of laser diodes;
A core portion that is connected to the output side of the combiner and propagates laser light out of the output light of the combiner, a cladding portion that covers an outer periphery of the core portion and propagates output light of each of the plurality of laser diodes, and the cladding In a laser diode monitoring method used in a fiber laser device comprising a propagation optical fiber having a coating portion covering the outer periphery of the portion,
At least a part of the coating portion of the propagation optical fiber is formed by notching a notch forming portion that exposes the cladding portion to the outside,
One end portion of the additional fiber is brought into contact with the notch forming portion, and leakage light of the output light of each of the plurality of laser diodes propagating through the cladding portion of the propagation optical fiber is propagated to the additional fiber,
A laser diode monitoring method characterized in that a light detector is connected to the other end of the additional fiber so that leak light propagating through the additional fiber is received by the light detector.

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