Abstract: Disclosed is an optical switch for changing over the mode connecting two optical transmission lines comprising two optical fibers directly to each other and the mode connecting an optical communication device between the two transmission lines. In this optical switch, in order to reduce the insertion loss, first, second, third and fourth optical fibers, each having an optical connector attached to one end, are attached to a substrate so that at least parts of the respective optical fibers are fixed to the substrate, and the ends of the first and second fibers are arranged on the substrate movably so that the end face of the first optical fiber confronts the end faces of the second and third optical fibers and the end face of the second optical fiber confronts the end faces of the first and fourth optical fibers.

Abstract: An optical measurement system for eliminating the influences of time variations on light sources, transmission lines, photo detectors, etc. The system includes light sources which generate two pulse-shaped optical signals of different light wavelengths with a portion of the optical signals being transmitted to a measuring part in a distant place by a transmission line. In the measuring part, a change of a measured object is converted into a variation in the quantity of transmission of light, and the optical signal subjected to the variation is transmitted to a signal processing portion by a transmission line. The varied optical signal is converted into a first electric signal by a photo detector. Another portion of the optical signals from the light sources is converted into a second electric signal by another photo detector.

Abstract: A laser-to-fiber coupler is constructed by an optical waveguide arranged between a semiconductor laser and a transmitting optical fiber through which an optical beam emanating from the laser is transmitted in order to reduce the amount of a reflection beam from the optical fiber, which is injected into the active layer of the semiconductor laser.The waveguide is made by an optical fiber of which at least one of core radius or numerical aperture (N.A.) is smaller than those of the transmitting optical fiber.

Abstract: Iodinated compounds useful for photoscanning the adrenal glands.

Abstract: A mold for continuous casting made of a copper alloy having been subjected to 15 to 40% cold working, said alloy consisting of copper as main constituent and an addition of 0.18 to 0.85% by weight of tin, and, if desired, several other metal components, the alloy having a high softening temperature and high-temperature strength, whose numerical values are given by specific formulas in which the thermal conductivity .lambda. is a determining factor which, in itself, is dependent on the construction of the mold, operating conditions etc.