Abstract: A main line cable and a backup line cable are laid in a land portion in different routes. A land terminal station includes a break detecting unit that detects a break of the main line cable, and a path switching unit that switches a transmission path to the backup line cable. The break detecting unit detects a break of the cables based on a received-light level of a main signal transmitted from an underwater cable, or based on a received-light level of a returned monitor signal that has been output by the break detecting unit and reflected by the beach manhole. The beach manhole includes optical couplers that couple and divide the main signal for the main line cable and the backup line cable, a fiber grating that reflects the monitor signal, and an optical director.

Abstract: A main line cable and a backup line cable are laid in a land portion in different routes. A land terminal station includes a break detecting unit that detects a break of the main line cable, and a path switching unit that switches a transmission path to the backup line cable. The break detecting unit detects a break of the cables based on a received-light level of a main signal transmitted from an underwater cable, or based on a received-light level of a returned monitor signal that has been output by the break detecting unit and reflected by the beach manhole. The beach manhole includes optical couplers that couple and divide the main signal for the main line cable and the backup line cable, a fiber grating that reflects the monitor signal, and an optical director.

Abstract: An internal unit is incorporated in a body of a submarine apparatus. The internal unit comprises a plurality of system units placed in a predetermined arrangement, and coupling bars fixed to coupling-bar fixing surfaces of the system units by screws so as to couple the system units in the predetermined arrangement. The system units include at least one electronic-circuit printed board having a part to be adjusted. The coupling-bar fixing surfaces are located at positions shifted from the electronic-circuit-printed board.

Abstract: A submarine apparatus is laid undersea by a submarine-cable laying device. The submarine apparatus comprises a cylindrical body performing a signal processing, a conical boot arranged at each of both ends of the body so as to fix an end of a submarine cable, and a gimbal joint provided on each of both ends of the body so as to support an end of an arm portion extending from the boot. The diameter of an end of the boot is smaller than a diameter of each of both ends of the body. A spacer mechanism is provided between the body and the boot so as to occupy a part of a space therebetween.

Abstract: In a submarine branching unit which comprises in a pressure-tight cylinder, a circuit board, at least one circuit unit and plural vacuum relays each having terminals and wirings, the circuit unit is mounted on one side of the circuit board; the vacuum relays are mounted on the other side of the circuit board; and insulator covers accommodate the respective vacuum relays, terminals and wirings to insulate the vacuum relays from each other. The submarine branching unit further comprises a pair of cables extending out of a cover of the pressure-tight cylinder, which cables are each spiraled and engaged with each other in an interleaved and overlapped fashion.

Abstract: A submarine apparatus is laid undersea by a submarine-cable laying device. The submarine apparatus comprises a cylindrical body performing a signal processing, a conical boot arranged at each of both ends of the body so as to fix an end of a submarine cable, and a gimbal joint provided on each of both ends of the body so as to support an end of an arm portion extending from the boot. The diameter of an end of the boot is smaller than a diameter of each of both ends of the body. A spacer mechanism is provided between the body and the boot so as to occupy a part of a space therebetween.

Abstract: An internal unit is incorporated in a body of a submarine apparatus. The internal unit comprises a plurality of system units placed in a predetermined arrangement, and coupling bars fixed to coupling-bar fixing surfaces of the system units by screws so as to couple the system units in the predetermined arrangement. The system units include at least one electronic-circuit printed board having a part to be adjusted. The coupling-bar fixing surfaces are located at positions shifted from the electronic-circuit-printed board.

Abstract: A gain equalizing device capable of realizing optimum gain equalization according to the amplification characteristic of a repeater and the transmission characteristic of a cable. The gain equalizing device includes a pressure-resistant housing consisting of a cylinder and first and second covers welded to the opposite ends of the cylinder. A plurality of optical fibers of a first tail cable are introduced into the pressure-resistant housing through a first feed through mounted to the first cover, and a plurality of optical fibers of a second tail cable are introduced into the pressure-resistant housing through a second feed through mounted to the second cover. A mounting plate is mounted on the first cover, and a plurality of optical equalizing modules are mounted on the mounting plate. A fiber accommodating structure accommodating a plurality of splice portions for respectively splicing the optical fibers of the first tail cable to the optical fibers of the second tail cable is mounted on the second cover.

Abstract: A submarine cable protecting device in which a plurality of pairs of half members are connected in series, includes a cylindrical portion which encloses a submarine cable. An outside spherical surface extending from one end of the cylindrical portion is provided at one end of each of the half members. An inside spherical surface extending from the other end of the cylindrical portion is provided at the other end of each of the half members, the inside spherical surface being shaped such that the inside spherical surface of one of the half members encompasses the outside spherical surface of another of the half members and the outside spherical surface cannot be detached from the inside spherical surface when the two half members are connected in series. The outside spherical surfaces of one pair of the half members has a reduced outside diameter when the outside spherical surfaces are contacted and the inside spherical surfaces are separated.

Abstract: An optical repeater having a first optical fiber extending from an input optical fiber cable, a light amplifying medium connected to the first optical fiber, a pumping light source for outputting pumping light, an optical coupling module for introducing the pumping light into the light amplifying medium, a drive circuit for driving the pumping light source, a power circuit for supplying electric power to the drive circuit, and a second optical fiber for sending signal light amplified. The optical repeater has a general-purpose common frame. The common frame has an inner space defined so as to accommodate the pumping light source and the optical coupling module, and has a bobbin portion for winding at least one of the first optical fiber and the second optical fiber. The drive circuit and the power circuit sometimes differing according to the kinds of products are mounted on an individual frame detachably fixed to the common frame.