Fiber laser apparatus

A fiber laser apparatus, comprising:

• amplification optical fibers including a first amplification optical fiber and a second amplification optical fiber, each of the amplification optical fibers having different amplification characteristics and comprising a core to which an active element is doped;
• one or more cooling plates having a first cooling surface that thermally contacts and cools the first amplification optical fiber and a second cooling surface that thermally contacts and cools the second amplification optical fiber;
• one or more module boxes including a gain module box that houses the amplification optical fibers and the one or more cooling plates;
• and
• an enclosure housing the one or module boxes, wherein
• the first cooling surface and the second cooling surface are disposed at different heights in a height direction in the gain module box,
• at least a portion of the first cooling surface overlaps at least a portion of the second cooling surface as viewed along the height direction,
• a first cooling plate of the one or more cooling plates has the first cooling surface,
• a second cooling plate of the one or more cooling plates has the second cooling surface, and
• the first cooling plate and the second cooling plate are different in size.