Fiber laser apparatus and method of detecting failure of fiber laser apparatus

Patent metadata

Field	Value
Publication number	US-2016359288-A1
Application number	US-201615240442-A
Country	US
Kind code	A1
Filing date	Aug 18, 2016
Priority date	Feb 25, 2014
Publication date	Dec 8, 2016
Grant date	—

Abstract

To provide a fiber laser apparatus capable of detecting a failure of an optical fiber within a wide range of the apparatus with an inexpensive configuration. The fiber laser apparatus 100 has a plurality of fiber laser units 110, a combiner 120 operable to optically combine output laser beams outputted from the fiber laser unit 110 to generate a combined laser beam, a laser emission portion 130 operable to emit the combined laser beam, output laser beam power detection parts 170 operable to detect a power of an output laser beam of each of the fiber laser units 110, a combined laser beam power detection part 140 operable to detect a power of the combined laser beam, and a failure detection part 160 operable to compare the total of detected powers of the output laser beams (total laser beam power) with the detected power of the combined laser beam and determine that a failure has occurred in the fiber laser unit 110 when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than a predetermined threshold T.

First claim

1 . A fiber laser apparatus comprising:
a plurality of fiber laser units each having an amplifying optical fiber operable to amplify a laser beam, a pumping light source operable to supply pumping light to the amplifying optical fiber, and an optical cavity operable to oscillate the laser beam; a combiner operable to optically combine output laser beams outputted from the plurality of fiber laser units to generate a combined laser beam; a laser emission portion operable to emit the combined laser beam generated by the combiner; a plurality of output laser beam power detection parts operable to detect a power of an output laser beam outputted from the optical cavity of each of the plurality of fiber laser units; a combined laser beam power detection part operable to detect a power of the combined laser beam generated by the combiner; and a failure detection part including an adder part operable to sum up the powers of the output laser beams detected by the output laser beam power detection parts of the plurality of fiber laser units to calculate a total laser beam power, a comparator part operable to compare the total laser beam power calculated by the adder part with a power of the combined laser beam detected by the combined laser beam power detection part, and a determination part operable to determine that a failure has occurred in at least one of the plurality of fiber laser units when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than a predetermined threshold T.

2 . The fiber laser apparatus as recited in claim 1 , wherein the predetermined threshold T is set to be (U−1)/U where U is the number of the plurality of fiber laser units and p1 the determination part of the failure detection part determines that a failure has occurred in one of the plurality of fiber laser units when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than the predetermined threshold T.

3 . The fiber laser apparatus as recited in claim 1 , wherein the predetermined threshold T is set to be (U−n)/U where U is the number of the plurality of fiber laser units, and n is an integer that is equal to or greater than l but equal to or smaller than U, and
the determination part of the failure detection part determines that a failure has occurred in n of the plurality of fiber laser units when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than the predetermined threshold T.

4 . The fiber laser apparatus as recited in claim 1 , Wherein the predetermined thresh is set so as to meet the following inequality:

(

1
+
α

)

·
T

<

1
-

β


(

1
-
α

)

·
T

≥

(

1
+
β

)



U
-
1

U

where U is the number of the plurality of fiber laser units, ±α is a detection accuracy of the power at the output laser beam power detection part, and ±β is a detection accuracy of the power at the combined laser beam power detection part, and
the determination part of the failure detection part determines that a failure has occurred in one of the plurality of fiber laser units when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than the predetermined threshold T.

5 . The fiber laser apparatus as recited in claim 1 , wherein the predetermined threshold T is set so as to meet the following inequality:

(

1
+
α

)

·
T

<

1
-

β


(

1
-
α

)

·
T

≥

(

1
+
β

)



U
-
n

U

where U is the number of the plurality of fiber laser units, n is an integer that is equal to or greater than I but equal to or smaller than U, ±α is a detection accuracy of the power at the output laser beam power detection part, and ±β is a detection accuracy of the power at the combined laser beam power detection part, and
the determination part of the failure detection part determines that a failure has occurred. in n of the plurality of fiber laser units when a ratio of the power of the combined laser beam to the total laser beam power becomes lower than the predetermined threshold T.

6 . The fiber laser apparatus as recited in claim 1 , wherein the failure detection part includes a drive control part operable to control a current to be supplied to pumping light sources of the plurality of fiber laser units so as to operate at least one of the plurality of fiber laser units in sequence, and
the determination part of the failure detection part specifies a fiber laser unit in which the failure has occurred from the at least one of the plurality of fiber laser units that is being driven by the drive control part, based on a difference between the total laser beam power calculated by the adder part and the power of the combined laser beam that is detected by the combined laser beam power detection part.

7 . The fiber laser apparatus as recited in claim 1 , wherein the combined laser beam power detection part includes a photodetector operable to receive leakage light from a fusion splicing portion provided on an optical fiber connecting between the combiner and the laser emission portion, the photodetector being disposed on a downstream side of the fusion splicing portion.

8 . A method of detecting a failure in a fiber laser apparatus operable to emit a combined laser beam into which output laser beams outputted from a plurality of fiber laser units are combined by a combiner, the plurality o

Assignees

• Fujikura Ltd

Inventors

• Matsuoka Yuji

Classifications

• H01S3/2383

  Parallel arrangements · CPC title

• H01S3/094011

  with bidirectional pumping, i.e. with injection of the pump light from both two ends of the fibre · CPC title

• H01S3/0675

  Resonators including a grating structure, e.g. distributed Bragg reflectors [DBR] or distributed feedback [DFB] fibre lasers · CPC title

• G02B6/4286

  Optical modules with optical power monitoring · CPC title

• H01S3/1305

  Feedback control systems · CPC title