Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: There is disclosed a method and apparatus for producing an optical fiber which is capable of producing the optical fiber having a high reliability by directly wiping the surface of the optical fiber with cleaning means for positively removing foreign materials adhered to or precipitated on the surface of the optical fiber and in which its facility is simple in structure and easy to maintain it. A cleaning member (11) is disposed on an optical fiber moving path. The surface of moving optical fiber (20) is cleaned by bringing the optical fiber (20) into a physical contact with the cleaning member (11). The cleaning member (11) can be formed of a porous or mesh member. The mesh member is formed of fiber sheets which are formed by knitting fiber threads. A plurality of the fiber sheets are laminated to provide a given lamination thickness for the cleaning length of the optical fiber (20).

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: A method of forming a silica soot preform comprising: forming a primary soot preform on an outer periphery of a glass rod by a primary burner; and forming a secondary soot preform by a secondary burner on an outer periphery the primary soot preform, wherein a diameter of the primary soot preform is set to be ranged from twice to five times of a diameter of the glass rod, a thickness of the secondary soot preform is set to be range from 1.5 times to seven times of that of the primary soot preform. Consequently, the deposition rate with respect to the introduction of the raw material gas is considerably increased. Further, it is possible to maximize a performance of depositing the primary soot preform.

Abstract: A concentric multi-tubular burner for synthesizing glass particles having a center port group constituted by a combination of jet ports of raw material gas, combustible gas and oxygen gas, wherein an outer wall of the oxygen gas jet port in the center port group protrudes more toward a burner head than an inner wall of the oxygen gas jet port. The flow rate of oxygen gas jetted from the oxygen gas jet port of the center port group is controlled to be in a proper range.

Abstract: An apparatus for producing a glass preform by VAD, includes a rotational drive device for rotating soot material, a detection device for detecting vibrations of the soot material, and a control device for controlling rotational speed of the rotational drive device. The control drive device changes the rotational speed of the rotational drive device on the basis of a detection output of the detection device.