Other

Showa Electric Wire & Cable Co., Ltd.

Shin-etsu Chemical Co., Ltd.

Nippon Telegraph and Telephone Corporation

Swcc Showa Cable Systems Co., Ltd.

Yuichi Morishita

Kenichi Muta

Masaru Kobayashi

Yuichi Murakami

Keiko Shiraishi

Ryo Nagase

Koichi Arishima

Seiko Mitachi

Dai Inoue

Hiroshi Oyamada

Shin Sumida

Yoshiaki Takeuchi

Eiji Matsuyama

Takashi Yoshida

Tomotaka Murase

Kenji Yagi

Kentaro Nouchi

Akira Kumagai

Yumi Ariga

Kazunari Sugi

Ken-ichi Muta

Masashi Saijo

Hen-Tai Shang

Jen-Hung Chu

Gen Tanimoto

Masamitsu Yamaguchi

Ken-Ichi Muta

An optical fiber includes a clad portion and a core portion surrounded by the clad portion. Here, the clad portion is formed by substantially pure quartz, and the core portion has a higher refractive index than the clad portion. The optical fiber is characterized in that a relative refractive index difference of a center of the core portion falls within a range from 0.15% to 0.30%, and a maximum relative refractive index difference of the core portion falls within a range from 0.4% to 0.6%. Here, it is preferable that an average relative refractive index difference of the core portion falls within a range from 0.30% to 0.40%. Here, a mode field diameter of the optical fiber falls within a range from 8.6 &#x3bc;m to 9.5 &#x3bc;m at 1310 nm, and a cable cutoff wavelength of the optical fiber is equal to or lower than 1260 nm. Note that, after the optical fiber is subjected to hydrogen aging, a loss of the optical fiber is preferably equal to or lower than 0.4 dB/km at 1383 nm.

Optical fiber

In order to supply the optical fiber for attenuating optical signal enable the attenuation amount to become flat in wide wavelength scope, simultaneously adding at least two kinds of dopants for attenuating optical signal over the core and the cladding of the optical fiber. Then, properly adjusting the kind and the concentration of dopants for manufacturing the optical fiberfor attenuating optical signal; simultaneously adding the dopant enabling the absorption of optical signal to increase with the wavelength become long and the dopant enabling the absorption of optical signal to decrease with the wavelength become long. As the dopant, it is desired to select at least two kinds of transitional metals from Co, Ni, Cr, V, Fe, Mn, Tb and Tm. Further, as the doped area, it is desired to dope the 6 times of the center portion of the core from the center of the core.

Optical fiber for attenuating optical signal

An optical fiber ribbon includes a plurality of optical fibers arranged in a row and an outer coating formed around the optical fibers. Each of the optical fibers has a core, a cladding, and a non-strippable thin coating made of synthetic resin with a Young's modulus of 50 kg/mm,to 250 kg/mm,at room temperature and coated around the cladding. The concentricity of the core to the diameter of the non-strippable thin coating is 1 &mgr;m or less.

Abnormal losses outside a reflection band attributable to a mismatch of core field diameters are suppressed. A photo-sensitive fiber comprising a core,and a cladding having a cladding inner layer and a cladding outer layer formed in this order around the core, in which at least the core is photo-sensitive to form a grating. The core and cladding inner layer include a photo-sensitive dopant for increasing the refractive index. The core additionally includes a first non-photo-sensitive dopant for increasing the refractive index and the cladding inner layer additionally includes a second non-photo-sensitive dopant for creasing the refractive index.

Photo-sensitive fiber

Disclosed are optical fibers for optical attenuation comprising a core and a cladding, wherein the cladding comprises two or more parts different from each other in their refractive indices and/or the attenuating dopant existence. By using the optical fibers for optical attenuation of the present invention, an optical attenuator which can effectively reduce the effect of cladding mode upon coupling of optical fibers and is excellent in characteristic stability can be manufactured at a low cost.

Optical fibers for optical attenuation

Growing community of inventors

Yokohama, Japan

Yuichi Morishita