Fujikura Limited

Tomio Abiru

Shoichiro Matsuo

Ryozo Yamauchi

Fumio Suzuki

Shoji Tanigawa

Koichi Harada

Itaru Ishida

Shigefumi Yamasaki

Koichi Takahashi

Hideki Sasaki

Shigeru Emori

The present invention relates to an optical fiber having improved hydrogen-resistance properties. The optical fiber includes a high concentration germanium layer and a low concentration germanium layer. The high concentration germanium layer is disposed at a central position of the optical fiber and contains germanium oxide in a concentration of 0.1% by weight or more, relative to the total weight of the high concentration germanium layer. The low concentration germanium layer is disposed around the high concentration germanium layer and contains germanium oxide in a concentration of less than 0.1% by weight, relative to the total weight of the low concentration germanium layer. The ratio of optical power leaking from the high concentration germanium layer to the low concentration germanium layer in an employed wavelength band is 0.4% or less, relative to the total optical power propagating through the optical fiber.

Optical fiber having improved hydrogen resistance

In the present invention, by forming a dispersion shifted optical fiber that has a refractive index profile comprising: a central core portion ; a step core portion provided at an outer periphery of the central core portion and having a refractive index lower than that of the central core portion ; and cladding provided at an outer periphery of the step core portion and having a refractive index lower than that of the step core portion , and which dispersion shifted optical fiber has, in a used wavelength band that is selected from between 1490 and 1625 nm, chromatic dispersion values of 7 to 15 ps/km/nm, an Aeff of 60 to 150 &mgr;m , a dispersion slope of 0.09 ps/km/nm or less, a bending loss of 100 dB/m or less, and a cutoff wavelength that provides essentially single mode transmission, it is possible to reduce the cost of the system and to achieve n improvement in the transmission characteristics.

Dispersion shifted optical fiber

The present invention's multimode optical fiber is characterized in that the propagating modes include a mode the lowest and second or higher order modes; and the difference between the propagation constants of the lowest order mode and the second order mode is 2-fold or more than the difference between the propagation constants of adjacent modes that are second order or higher order modes. Due to this design, single mode propagation becomes possible once the modes have propagated over a specific distance. As a result, it is possible to relax the conventional single mode conditions, enabling the fiber parameters to be set relatively freely.

Multimode optical fiber with a higher order mode removing function

In an optical-fiber coupler formed by disposing two single-mode optical fibers 1 and 2 in parallel, and fusing and elongating the optical fibers at one position in the longitudinal extent of the optical fibers 1 and 2, variation of insertion loss dependent on the polarization can be eliminated in its manufacturing by imparting a twist to the optical coupling part 3' of the fused-elongated portion 3 so that with respect to the direction of a line on a plane orthogonally intersecting the longitudinal direction of the optical fibers 1 and 2, the line linking the centers of the two optical fibers 1 and 2, the direction of the line on a plane at one end of the optical coupling part 3' of the fused-elongated portion 3 makes an angle of 90 degrees with the direction of the line on a plane at the other end of the optical coupling part 3'.

Optical-fiber coupler and manufacturing process therefor

Growing community of inventors

Sakura, Japan

Tomio Abiru