Kokusai Denshin Denwa Co., Ltd.

Kokusai Denshin Denwa Kabushiki Kaisha

Duo-fast Corporation

Yoshinao Iwamoto

Kenichi Asakawa

Kazuomi Yamamura

Yuichi Shirasaki

Kiyofumi Mochizuki

Shizuo Suzuki

Hideo Ishihara

Masayuki Fujise

Noboru Edagawa

Yuichi Sirasaki

Shu Yamamoto

Norio Seki

Haruo Sakaguchi

Toshio Izawa

Hifumi Sakaguchi

Hitoshi Yamamoto

Masao Morita

Hiroharu Wakabayashi

Makoto Nunokawa

Yoshinori Namihira

Teruji Watanabe

Takasuke Fukui

An optical fiber cable in which at least those metallic members of the optical fiber cable which are of high chemical reactivity and electrochemical reactivity are each precoated with a film for preventing them from making direct contact with water when it diffuses into the cable. The film may be a nonmetallic film or a metallic film of low chemical reactivity and electrochemical reactivity.

Optical fiber cable

A multi-point optical amplification repeating system is disclosed in which an output of a unidirectional amplifier inserted in a unidirectional repeating optical transmission system is branched and coupled to an input of a unidirectional amplifier inserted in another unidirectional repeating optical transmission system, so that bidirectional optical communication can be performed between many points connected to a plurality of first optical transmission lines. If a bidirectional amplifier is employed in a bidirectional repeating optical transmission system, the above bidirectional optical communication can be also realized by fed back the first port of the bidirectional amplifier to the second port thereof through an optical isolator.

Multi-point optical amplification repeating system

An optical privacy communication system in optical fiber communications between many points is disclosed in which, each station is provided with a privacy circuit. Each privacy circuit comprises a first optical branch for connecting the station to first and second optical branches, a second optical branch for connecting the first and second optical branches to the optical fiber transmission line, an optical isolator inserted in the first optical branch, for passing only a signal of a direction from the first optical branch to the second optical branch, and an optical filter inserted in the second optical branch, for passing only an optical signal of a frequency assigned to the station, so that an optical privacy communication is carried out between the stations.

Optical privacy communication system in two-way optical transmission

An optical amplification method or system for an optical communication system which transmits signal light from the transmitting side to the receiving side via an optical transmission medium formed by an optical fiber or space. In accordance with the present invention, the signal light entered a certain state of polarization in at least one part of the transmitting side, the receiving side and the optical transmission medium is separated into two orthogonal polarized waves by a polarizing beam coupler/splitter. The two polarized waves are amplified by optical amplifiers disposed in correspondence to their state of polarization, respectively. The amplified orthogonal polarized waves are combined together by another polarizing beam coupler/splitter.

Optical amplification

A core alignment system for aligning a pair of optical fibers to be spliced, in which core alignment is accomplished by applying a pair of aligned beams of light emitted in opposite directions by a semiconductor laser to the butt joint ends of a pair of optical fibers to be spliced, detecting a leakage beam leaking from a side surface of each optical fiber close to the laser, and adjusting the positioning of the optical fibers so that the leakage beams are minimized.

Core alignment system for optical fibers

A fault monitoring system for optical fiber communication system having a bidirectional optical amplifier between first and second optical fiber transmission lines. An optical monitoring signal of a first frequency different from frequencies of communication signal light of the optical fiber communication system is applied to the first input/output port of the bidirectional optical amplifier through the first optical fiber transmission line and then branched through a first optical filter passing therethrough of the first frequency to apply the branched optical monitoring signal of the first frequency to the second input/output port of the bidirectional amplifier. Another optical monitoring signal of a second frequency different from the first frequency and frequencies of the communication signal light is applied to the second input/output port of the bidirectional optical amplifier through the second optical transmission line and then branched through a second optical filter passing therethrough of the second frequency to apply the branched optical monitoring signal of the second frequency to the first input/output port of the bidirectional amplifier. A fault of the bidirectional amplifier can be detected by monitoring the optical monitoring signals of the first frequency and of the second frequency at respective ends of the first optical fiber transmission line and the second optical fiber transmission line.

Fault monitoring system for optical fiber communication systems

Delay time variation in an optical fiber digital communication system which includes optical regenerative repeaters is measured at one of terminal ends having reference clock signal. A monitor signal which depends upon the delay time variation is provided at the farthest repeater in an area where delay time is subject to secular change by dividing reference clock signal from said terminal end, and said monitor signal is returned to the terminal end from said farthest repeater, and the terminal end compares the returned monitor signal with the divided reference signal by using a phase comparator to provide measure of delay time variation.

System for measuring delay time variation in optical fiber digital

A signal coupler couples more than three transmitter-receivers through optical fiber cables and at least one repeater on a bit-multiplex system, by exchanging or reallocating each time slot according to a transmission station and the related destination. The coupler has a means to release the bit-multiplexing (or demultiplex) the signals from each transmitter by deriving the control clock signals from the information signals themselves. The coupler also has a means for multiplexing the bit signals for each destination by automatically adjusting the phase relationships among the released signals (demultiplexed signals) for bit-synchronization using a delay circuit.

Signal coupling system for optical repeater system

A device for burying a submarine cable under water by easily and accurately detecting the cable position and a method for guiding the same by utilizing the characteristics unique to submarine cables, by supplying an AC only to the portion of the cable between two arbitrary repeaters through a so-called transformer-coupling system to generate an AC magnetic field, and by detecting the magnetic field with a magnetic field detector.

Burying device for submarine cables and method for guiding the same

A rotary joint for optical fibers consists of two rotary members which enable efficient transmission of optical signals without the need of converting the same into electric signals by attaching rod lenses having a refractive index in the second order distribution relative to its center axis, to respective tips of the optical fibers capable of relative rotation so that an optical signal emitted from the tip of one optical fiber is transmitted from the end of one rod lens in the form of parallel rays to the other rod lens, and as a converged beam to the tip of the other optical fiber. The joint further includes a mechanism for imparting pressure to the rotary members, and a mechanism for finely setting the angle between the two rod lenses.

Rotary joint for optical fibers

This invention aims to provide an optical fiber which is capable of sufficiently dissipating the leaky mode in the cladding thereof characterizing in those particulate substances such as minute hollow glass beads having different refractive indices are sealed in the primary buffer layer or on the boundary between the primary buffer layer and the cladding, or between the primary and secondary buffer layers of the optical fiber, whereby nucleous elements for scattering or absorption can be formed uniformly.

Optical fiber with light reflecting particles dispersed through buffer

A device for burying a submarine cable under water by easily and accurately directing the cable position and a method for guiding the same by utilizing the characteristics unique to submarine cables, by supplying an AC only to the portion of the cable between two arbitrary repeaters through a so-called transformer-coupling system to generate an AC magnetic field, and by detecting the magnetic field with a magnetic field detector.

Apparatus for supplying AC current to an underwater cable

A connector for connecting together in a water-tight housing various optical instruments of an underwater or submarine arrangement having optical fiber cables. The connector is constructed in a manner such that a plug containing the terminals of optical fiber cables is connected in an easily attachable/detachable fashion to a receptacle which is mounted on the water-tight housing. Sealing material is interposed between the water-tight housing and the receptacle and between the receptacle and the plug for preventing the infiltration of water or sea water into the water-tight housing.

Underwater optical fiber connector

A device for burying a submarine cable under the water by easily and accurately detecting the cable position and a method for guiding the same by utilizing the characteristics unique to submarine cables, by supplying an AC only to the portion of the cable between two arbitrary repeaters through a so-called transformer-coupling system to generate an AC magnetic field, and by detecting the magnetic field with a magnetic field detector.

Alternating current induction method using an annular magnetic coupling

The present invention aims at providing a method and a device therefor which can effectively as well as accurately bury a cable under marine beds not only when a cable is newly laid and buried but also when a cable has to be reburied. The method and the device according to the present invention are characterized in that a burying device is guided to approach the cable by using a travelling member provided on said burying device, a travelling control mechanism thereof being controlled by a receiving output from a transmitter which is mounted on the cable in advance by a receiver provided on the burying device, that the cable is caught and held by a cable engaging member of said burying device while the burying device is detecting the buried cable track and travelling therealong, and that at the same time an excavation member of said burying device digs and forms a groove while the burying device guides and buries the cable within the excavated groove. The method according to the present invention is further characterized in that the burying device is provided with a travelling device which is controlled by the output from a receiver which receives the output from a transmitter on the cable, that said device body is provided at the middle portion thereof with a cable engaging member having a cable engaging mechanism as well as a buried cable route detection mechanism and an excavation member.

Growing community of inventors

Fujimi, Japan

Yoshinao Iwamoto