Abstract: A transmission line between terminals of a three-terminal station is branched by a branching unit and power is transmitted between the terminals of the three-terminal station and a power feed system in the transmission line including: a switch for switching a power feed line feeding power to a repeater between a both-end power feed mode and a single-end power feed mode; and connection holding means for holding a power feed connection state without change upon an occurrence of a failure.

Abstract: Elongation distortion at any location of an optical fiber cable is measured by using the principle of the stimulated Raman effect in which a stokes beam with a little frequency difference from that of a pumping beam is generated when a pumping beam and a seed beam with the same frequency as that of the stokes beam meet in a Raman material like an optical fiber cable. Due to the fact that the group refractive index of an optical fiber cable for a pumping beam is different from that for a stokes beam, elongation of a cable is measured by observing time difference of the arrival of pumping beam and stokes beam. The location that the pumping beam meets with the stokes beam can be adjusted merely by shifting the pumping pulse, then, elongation distortion at any location can be measured. According to the invention, the pumping pulse is applied to the cable to be tested from both the ends of the cable with one of the pumping pulse delayed according to the desired location for meeting of two pulses.

Abstract: In the connection of the opposed ends of two optical fibers, a method and apparatus for core alignment of the optical fibers, comprises placing the two optical fibers being connected so that their ends face each other, and illuminating at least the facing ends with a beam of ultraviolet light thereby causing the illuminated ends of the cores of the optical fibers which are doped with germanium (Ge) to emit light of a wavelength in the visible region and enabling the core alignment to be directly monitored visually with the aid of the visible light so emitted from the cores during the course of the core alignment.

Abstract: A spliced portion housing structure for an optical fiber in an optical submerged repeater, characterized in that, in order to splice together in a joint ring an optical fiber and a power-supplying feeder from the optical submerged repeater to an optical fiber and a power-supplying feeder of a tail cable from a cable coupling of an optical submarine cable, respectively, a joint chamber is provided on an end plate of a housing of the optical submerged repeater in such a manner that the end plate forms a part of the joint chamber; the optical fiber and the power-supplying feeder from the submerged repeater are introduced into the joint chamber through a first feedthrough provided in the end plate for hermetically introducing the optical fiber and the power-supplying feeder; the tail cable from the cable coupling is hermetically introduced into the joint chamber through a second feedthrough provided in the wall of the joint chamber so that the tail cable is insulated from the joint chamber, the optical fibers and