Patent ID: 8811434

Claim:
A fiber laser apparatus in which pump light is introduced into an optical fiber to generate laser light, the fiber laser apparatus comprising: a detecting section that detects signal light leaking out from a core of the optical fiber as leakage signal light; a determining section that determines that, in a case where there is a decrease in an intensity of the leakage signal light detected in the detecting section, a failure of the fiber has occurred; a stopping section that stops, in a case where the determining section has determined that a failure of the fiber has occurred, the introduction of the pump light into the optical fiber; and a forward pumping light-multiplexer that multiplexes the laser light for pumping, the detecting section detecting the leakage signal light leaking out of a High Reflectivity Fiber Bragg Grating (FBG) that is provided on a side opposite to an output side of the laser light and the leakage signal light leaks out nearer a terminal side of the forward pumping light-multiplexer, wherein, in a case where an intensity of the leakage signal light has become smaller than a predetermined threshold, it is determined that a failure of the fiber has occurred nearer a terminal side beyond the forward pumping light-multiplexer, and stops the pump light.