Nec Corporation

Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology

Mitsubishi Denki Kabushiki Kaisha

Mitsubishi Electric Corporation

Japan Agency for Marine-Earth Science and Technology

Japan Marine Science and Technology Center

Independent Administrative Intitiution, Japan Agency for Marine-Earth Science and Technology

Katsuyoshi Kawaguchi

Kenichi Asakawa

Jun Muramatsu

Hitoshi Mikada

Toshiyuki Tokura

Tasuku Fujieda

Junichi Nakagawa

Katsuhiro Shimizu

Hideki Goto

Ken'ichi Asakawa

Hiroaki Munehira

A Raman amplifier includes a pumping light source, an optical coupler, and a Raman amplifier medium. The pumping light source outputs a pumping light that is intensity-modulated with a frequency equal to or higher than 100 megahertz. The optical coupler couples the pumping light with a carrier light. The Raman amplification medium is pumped by the pumping light to amplify the carrier light. The Raman amplification medium has characteristics of a low dispersion and a small difference between propagation times of the carrier light and the pumping light.

Raman amplifier and optical communication system

The present invention discloses a submarine observation system in which a plurality of carrier lights assigned to each submarine observation equipment is transmitted from a land terminal apparatus to an optical submarine cable (down-going) by using a WDM transmission. In the submarine observation equipment, only a prescribed carrier light is demultiplexed by an optical demultiplexer, an observation signal indicating an observation result is generated by an observation device, intensity of the carrier light demultiplexed by the optical demultiplexer is modulated by an optical amplifier based on an observation signal, and the modulated carrier light is multiplexed by an optical multiplexer. The multiplexed carrier light is output to the optical submarine cable (up-going) to be returned to the land terminal apparatus being the transmission station. The land terminal apparatus is able to obtain an observation signal of each observation point by separating carrier lights based on each wavelength and receiving a separated carrier light of each wavelength. Accordingly, the system can be structured with one optical fiber and can be extendable by increasing or decreasing carrier lights, and either one of the land terminal apparatuses can receive an observation signal even when the optical submarine cable is cut off.

Observation apparatus and observation system

In each of a plurality of submarine observation apparatus (to n), a branching unit () branches fixed-wavelength light (&#x3bb;) from an incoming wavelength-multiplexed light signal. An observation signal modulating unit () modulates the intensity of the branched fixed-wavelength light (&#x3bb;) with observation information multiplexed by an observation signal multiplex unit (). A combining unit () combines light signals (&#x3bb;) to (&#x3bb;n) passing through the branching unit () and the fixed-wavelength light (&#x3bb;a) modulated by the observation signal modulating unit () into a composite light signal, and outputs it to an optical fiber (). Therefore, in each of the plurality of submarine observation apparatus (to n), there is no necessity for providing a wavelength-division-multiplexing-transmission optical transmitter which requires high wavelength stability.

Submarine observation apparatus and submarine observation system

A submarine power feeding branching device comprises a constant current-constant current converter which isolates an input side for a trunk submarine cable from an output side for a branch submarine cable. The converter receives a first constant current and produces a second constant current by using the first constant current. The second constant current is supplied to the output side while the first constant current is returned to the input side. Because the input side and the output side are isolated, it is easy to add/remove the device to/from a submarine power feeding system. Intensity of the second constant current can be controlled by controlling duty ratios of switches included in the converter. Thus, it is possible that the intensity of the second constant current is equal to that of the first constant current. Therefore, a submarine repeater can be provided along either the trunk cable or the branch cable.

Submarine power feeding system having submarine feeding cables and power feeding branching devices

Submarine power feeding branching device for submarine power feeding system having submarine feeding cables arranged in mesh pattern

A submarine cable power feeding system includes N (N is an integer of 2 or larger) main submarine cables extending from the land in the offshore direction, N-stage (N is an integer of 2 or larger) submarine feed branching devices, and first to Nth (N is an integer of 2 or larger) sub submarine cables. Each submarine feed branching device is connected to the main submarine cable to receive constant-voltage power from a constant-voltage feed unit. Each sub submarine cable connects the Nth-stage submarine feed branching device, connected to the Nth main submarine cable, to the adjacent submarine feed branching device through submarine repeaters, thereby receiving power from a constant-current feed unit. Each constant-current feed unit is built in the submarine feed branching device. The submarine feed branching devices and the submarine repeaters are arranged in a matrix on a plane.

Submarine cable power feeding system

Growing community of inventors

Kanagawa, Japan

Katsuyoshi Kawaguchi