Mitsubishi Denki Kabushiki Kaisha

Other

Eiichi Nakagawa

Satoshi Kumayasu

Tadayoshi Kitayama

Takashi Mizuochi

Katsuhiro Shimizu

Kiwami Matsushita

Junichiro Yamashita

Nobuyuki Takemura

Shigeyuki Akiba

Masatoshi Suzuki

Koji Goto

Kazunori Sato

Kuniaki Motoshima

Kenichi Asakawa

Naoki Norimatsu

Haruo Abe

First to sixth optical switchestoare provided: in event of failure on the part of a third input/output port, only the first and second optical switchesandturn ON; in the event of failure on the part of a second input/output port, only the third and fourth optical switchesandturn ON; and in the event of failure on the part of a first input/output port, only the fifth and sixth optical switchesandturn ON.

Circuit for switching optical paths

An optical variable attenuator is provided including polarizers for extracting a predetermined polarized wave component from an input optical signal, an array of Faraday rotators formed of a ferromagnetic material and arranged in series for rotating the plane of polarization of the input signal, electromagnetic coils for supplying magnetic fields to the Faraday rotators, and current supply control circuits for setting the polarization-rotating angle of the array by controlling the intensity of the magnetic fields supplied to the Faraday rotators. The polarization-rotation angle of the array can be finely adjusted and maintained, even when the magnetic fields are not continuously supplied to the Faraday rotators.

Optical variable attenuator

A plurality of submarine cable transmission paths extending from a plurality of land-based terminal stations are connected with each other in a submarine branching apparatus, and an electric power feeding line is arranged between each land-based terminal station and an electric power feeding line switching unit of the submarine branching apparatus to supply electric power from the electric power feeding line to a communication signal of the corresponding submarine cable transmission path through repeaters. The electric power feeding lines are connected with each other in the electric power feeding line switching unit. A control signal superposed on the communication signal is sent to the electric power feeding line switching unit through one submarine cable transmission path, and the connection of the electric power feeding lines is switched according to the control signal. Because the switching is performed when the electric power feeding lines are electrically set to a stable state, no electric arc is generated in the switching. Also, each submarine cable transmission path is formed of an optical fiber, so that the electric power is supplied from one electric power feeding line to the control signal of the submarine cable transmission path. Therefore, the control signal is not attenuated, and the connection of the electric power feeding lines can be reliably switched.

Electric power feeding line switching method, electric power feeding line switching apparatus and electric power feeding line switching system

A feed line switching circuit includes a relay connected between feed lines, a normally close contact of the relay, and a resistor that constitutes a series circuit with the normally close contact, which series circuit is connected in parallel with the relay. The resistance of the coil of the relay and the resistance of the resistor are determined to satisfy the condition that the current flowing through the relay after energizing the relay can prevent the chattering of the relay. Thus, the feed line switching circuit can positively carry out the feed line switching.

Feed line switching circuit and branching unit

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

An optical-fiber light amplifier using rare-earth-doped optical fibers. The light amplifier combines first and second excitation light from first and second sources to form combined excitation light and divides the combined excitation light for inverted distribution to both two optical fibers. The light entered one optical fiber and that entered the other optical fiber are polarized so as to be perpendicular to each other so that fluctuation of output level is prevented without mutual interference. Alternatively the first excitation light and the second excitation light may have different wavelengths; also in this case, fluctuation of level is prevented without any interference.

Optical-fiber light amplifier

Optical amplifier

A novel optoelectronics package includes an optical semiconductor, an electronic cooling element carrying the optical semiconductor and electrically connected to one of the terminals thereof, a pair of transmission lines having distributed constant characteristics and an airtight vessel housing the optical semiconductor, cooling element and transmission lines. A grounding line of the transmission lines is connected between the terminal of the optical semiconductor and an external ground terminal fixed at the vessel. A signal line of the transmission line is connected between the other terminal of the optical semiconductor and an external signal terminal, whereby the stray capacitance of the cooling element is shorted by the distributed constant grounding line.

Growing community of inventors

Tokyo, Japan

Eiichi Nakagawa