Sumitomo Electric Industries, Limited

Yoshio Yokoyama

Masaaki Hirano

Masashi Onishi

Akira Urano

Eisuke Sasaoka

Takatoshi Kato

Yuichi Ohga

Motonori Nakamura

Toshihiro Ooishi

Toshio Danzuka

A method for producing an optical fiber preform is provided in which the variation of the outer diameter in the longitudinal direction is minimized and a target quantity of glass is accumulated as a whole. Based on a predetermined relationship between three variables: the outer diameter of a starting rod being a first variable, the outer diameter of an optical fiber preform a second variable, and the timing for ending the glass particles depositing process a third variable, the starting rod and burners are subjected to relative reciprocating movement so as to deposit glass particles on the starting rod until the timing for ending the depositing process, and then the resulting deposit body is vitrified. The third variable may be the traverse velocity, the glass particles deposition time, or the weight of a soot glass deposit body.

Method of manufacturing optical fiber preform

A plurality of glass particle synthesizing burners are disposed opposite to a rotating starting rod. The starting rod and the glass particle synthesizing burners are relatively reciprocally moved to each other in parallel to the axial direction, so that glass particles synthesized by the burners are sequentially deposited on the surface of the starting rod. The movement is stopped and restarted repeatedly once or more than once during one reciprocal movement.

Method of producing glass particles deposit

An optical fiber is composed of silica glass and comprises a center core region doped with F element, a ring core region doped with GeO , and an inner cladding region doped with F element; wherein a buffer layer composed of undoped SiO or SiO doped with one or both of P and Cl or a concentration gradient region in which GeO concentration radially decreases toward the boundary is provided between the center core region and the ring core region.

Optical fiber and method of making the same

In an optical fiber of this invention, the MFD is increased to effectively suppress the influence of nonlinear optical effects. A method of manufacturing the optical fiber effectively prevents bubble occurrence in a transparent preform, deformation of the preform, and flaws on the preform surface during the manufacture. The optical fiber has, from its center to the peripheral portion, a first core having a first refractive index n , a second core having a second refractive index n (<n ), a first cladding having a third refractive index n (<n ), and a second cladding having a fourth refractive index n (>n , <n ). The outer diameter of the second core is set to be 25 to 40 &mgr;m. Specifically, the refractive indices of the first and second claddings of the optical fiber preferably increase in the radial direction from the inner side thereof to the peripheral side thereof. This structure is obtained by adjusting the supply amount of a fluorine material in the manufacturing process of preform regions corresponding to first and second claddings such that the contents of fluorine decreases in the radial direction.

Optical fiber and method of manufacturing the same

A tube-shaped, GeO -doped silica glass pipe having a high refractive index is prepared (step S ), a cylindrical silica glass rod doped with F element is inserted inside the GeO -doped silica glass pipe (step S ), and the GeO -doped silica glass pipe and silica glass rod in thus inserted state are heated so as to be unified (step S ). Further, thus formed assembly is inserted inside the a pure silica glass pipe (step S ), and they are heated so as to be unified (step S ), whereby an optical fiber preform is manufactured.

Fiber preform method with a hot drill-in step for a Ge-doped tube and an F-doped rod

The present invention relates to a dispersion-shifted optical fiber which comprises a structure for effectively eliminating the causes of deterioration in characteristics at the making stage thereof and is suitable for wavelength division multiplexing transmission. In the dispersion-shifted optical fiber according to the present invention, impurities to be added and the contents thereof are adjusted so as to reduce viscosity difference at each interface between individual glass regions. As a consequence of this structure, occurrence of structural irregularity and glass defect are effectively restrained in the vicinity of the interfaces between the regions.

Dispersion-shifted optical fiber

A dispersion-shifted fiber includes structure configured to effectively reduce nonlinear optical effects and transmission loss caused by structural mismatching. A core region in the dispersion-shifted fiber includes an inner core and an outer core, which are both glass areas. The inner core is doped with a predetermined amount of fluorine, having an average relative refractive index difference &Dgr;n,. The outer core is disposed between the inner core and the cladding region and is doped with a predetermined amount of germanium dioxide, having an average relative refractive index difference &Dgr;n,(&Dgr;n,>&Dgr;n,), such that the viscosity ratio between the inner core and the outer core at a drawing temperature is set within a predetermined range, thereby effectively restraining structural mismatching from occurring at the boundary between these glass regions.

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Yokohama, Japan

Yoshio Yokoyama