Light intensity monitor capable of detecting light intensity and fiber breaking

摘要

A fiber laser system with a fiber laser device including a fiber laser; a laser output end part; and a delivery fiber. The delivery fiber is constituted by a double cladding fiber. An SFBG is provided on the output end side of the delivery fiber, which reflects part of laser light propagating in the core of the delivery fiber to thereby couple the part of the laser light with a backward-propagating cladding mode propagating in a first cladding in a backward direction. A backward-propagating cladding mode detecting section is provided on the input end side of the delivery fiber, which detects the intensity of backward-propagating light in a cladding mode, which light is the part of the laser light coupled by the SFBG with the backward-propagating cladding mode.