Abstract: An infrared optical fiber comprises a core preponderantly made of a halogenide and a trace quantity of a dopant formed of a halogenide and retains its infrared transmission property stably for a long time.

Abstract: A mechanism for cooling optical fibers which include optical fibers, metal netting wound around the fibers to conduct heat therefrom, and a sheath in which the fibers and netting are inserted. In accordance with one embodiment, the sheath and netting are spaced from each other so as to permit cooling air to flow therebetween to cool the fibers. In another embodiment, the netting is connected to a cooler by a heat connected element so that heat in the fibers is drawn to the cooler through the heat conductive element to cool the fibers.

Abstract: A construction for holding optical fibers, in which at least one of the ends of an optical fiber in a cable is a free end which is slidably and rotatively mounted to a hand piece at an end of the cable so as to prevent breakage of the optical fiber during bending of the cable.

Abstract: A laser surgical knife characterized by switches, which can adjust an output power within the safe scope from the output power preliminarily set for a laser oscillator, mounted on an attachment of said laser surgical knife which is held by an operating surgeon's hand in order to irradiate laser rays on the affected parts.The present invention can provide a laser surgical knife of which output power can be changed at one touch and in safe without interrupting surgical operations merely by a simple process in which an operating surgeon operates a handy switch for hinself.

Abstract: A focal point direct observation type laser scalpel device has a construction wherein laser beams generated by an infrared laser generator and transmitted through an optical fiber adapted for infrared laser beams and visible rays issued from a visible ray source and transmitted through optical fibers adapted for visible rays are passed through one common converging lens system so that recognition of the focal point of the laser beams is accomplished by visual observation of the focal point of the visible rays.

Abstract: A CO.sub.2 laser machining apparatus, has a CO.sub.2 laser oscillator connected with a condenser through a flexible cable including a fiber bundle for transmitting infrared rays of 10.6 micrometers therein.

Abstract: A safety device for a laser ray guide in which a laser ray-receiving element is installed on the input side of a lens of a laser ray guide including said lens, and troubles occurring in said laser ray guide can be detected by means of said laser ray-receiving element.

Abstract: A flexible cable suitably used as a jacket or cover for an inner conduit member such as a gas conduit or a liquid conduit, a signal transmission line, or an energy transmission line, or the like, which can provide safe use of the conduit inserted thereinto by limiting the bending radius thereof. The cable includes a plurality of axially symmetrical pipe members having large and small diameter ends which are assembled with the small ends of each pipe member fitted into the large end of an adjacent pipe member and loosely fitting flexible ring members fitted over the small ends of the pipe members.

Abstract: An optical fiber for infrared transmission constructed by winding a cladding around a core in the manner of a coil, the cladding having a refractive index lower than that of the core, a protective tube being employed to jacket the clad core.