Abstract: A semiconductor light amplifier having an active layer performing a light amplification function, in which the light amplification is performed intermittently by a stable clock timing synchronized with the clock timing of an input light pulse train to the active layer.

Abstract: A submarine optical fiber cable using a low-loss optical fiber as a transmission medium, which is provided with a cylindrical pressure resisting layer composed of an assembly of three equally divided long pressure resisting segments of fan-shaped sections with flat contact planes and having at least one optical fiber in an optical fiber housing space formed in the center of the assembly so as to protect the optical fiber from a high water pressure.

Abstract: An optical fiber submarine cable comprising at least one optical fiber. A pipe-like pressure resisting layer is produced by forming a tape-like pressure resisting material into a pipe-like configuration with the optical fiber inserted therein. The pressure resisting layer has butt ends in its cross section, and a waterproof insulator layer is disposed closely around the pipe-like pressure resisting layer for maintaining the pipe-like configuration of the pipe-like pressure resisting layer and for preventing seawater from entering into a gap between the butt ends.

Abstract: A system for converting the number of lines of a television signal having interlaced frames each formed by signals of two adjacent fields, in which signal of each field of each frame are formed by sequentially weighting and combining line signals of the former and the latter of the two fields under the conditions, that the order of lines is not reversed in the output frame, that the lines are not repeated in the same field, and that stational picture areas and moving picture areas of each frame are separately and suitably handled.

Abstract: A system for converting the number of lines of a television signal having interlaced frames each formed by signals of two adjacent fields, in which signals of each field of each frame are formed by sequentially weighting and combining line signals of the former and the latter of the two fields under the conditions that the order of lines is not reversed in the output frame and that the lines are not repeated in the same field.

Abstract: A picture signal transmission system for transmitting after coding a picture signal obtained by scanning at least one picture to be transmitted, in which a difference between a representative level value of each picture element unit formed by at least one picture element and a forecast value obtained in accordance with a predetermined rule and based on a representative level value of adjacent ones of said picture element units is detected, and in which first level information and second level information are transmitted. The first level information indicates, for each picture element by a bit of binary information, whether or not the difference exceeds a predetermined threshold value for a group of picture elements corresponding to a predetermined area of the picture. The second level information indicates level information of particular picture elements on each of which said difference exceeds the threshold value.