Mitsubishi Denki Kabushiki Kaisha

Kokusai Denshin Denwa Kabushiki Kaisha

Kakusai Denshin Denwa Kabushiki Kaisha Et Al.

Naoki Norimatsu

Masatoshi Suzuki

Shigeyuki Akiba

Koji Goto

Tadayoshi Kitayama

Yukio Noda

Kuniaki Motoshima

Yoshinori Mimura

Kenichi Asakawa

Eiichi Nakagawa

Junichi Kojima

Hideharu Tokiwa

Osamu Shinbori

Hitoshi Nishikawa

Junichiro Yamashita

Haruo Abe

When a trouble occurs in a cable, a feeding pass for another cable is ensured. In a feeding pass switching circuit, optical fibers are respectively connected to the terminals A, B and C. When a negative current is applied to the system in a state where a BRANCH2 is put in an open circuit and a TRUNK is grounded, a relay K1 is activated, and then a relay K2 is activated. Successively, when a positive current is supplied from the TRUNK, a cable connected to the TRUNK and a BRANCH1 is fed from both terminals. When the positive current is supplied from the BRANCH1 in a state where the TRUNK is put in a open circuit and the BRANCH2 is grounded, a relay K3 is activated. Successively, when the negative current is supplied to the BRANCH2, a relay K5 is activated. In such a manner, the power is fed to each feeding pass from one terminal.

Feeding pass switching circuit

A light amplifying apparatus adopting a redundant structure. Optical isolators 13, 14 are inserted between pump light sources 1, 2 and a photocoupler 4 so as to prevent injection locking, thereby preventing fluctuation of pump power. In another embodiment, optical fibers 15 adequately longer than the coherence length of the excitation light waves output from the pump light sources are provided. In still another embodiment, the frequency of the driving current for the pump light sources is modulated. In a further embodiment, wave plates 20, 21 are provided so as to circularly polarize the light waves output from the pump light sources clockwise and counterclockwise.

Light amplifying apparatus

A method and an apparatus for manufacturing a fluoride glass fiber preform are disclosed which preclude the step of pouring a glass melt into a mold from a crucible, and hence permit the fabrication of a long, homogeneous fluoride glass fiber preform free from foreign substances and air bubbles leading to scattering and which also allow ease in the fabrication of a preform having an elliptic core portion for drawing a polarized wave retaining fiber.

Method and apparatus for manufacturing preform for fluoride glass fiber

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Tokyo, Japan

Naoki Norimatsu