Abstract: An optical current transformer includes a sensor arranged adjacent to a conductor through which an electric current is to be measured flows, a light source for generating a measuring light, a detector for detecting the measuring light emitted from the sensor, a coupling optical system for optically connecting the sensor, the light source and the detector, and a signal processing system for processing a signal transmitted from the detector so as to calculate the electric current flowed through the conductor by using a Faraday effect of light which passes through the sensor. The sensor is formed by an optical fiber, the optical fiber being wound around the conductor, and the two ends of the optical fiber being arranged to form a closed loop of the optical fiber.

Abstract: An optical measurement device that can be made of small size and weight without impairing accuracy under ambient temperature variations. An optical system accommodating box, includes a polarizing unit in which incoming light from a light source is converted to linearly polarized light, and an analyzing unit that resolves into orthogonal components linearly polarized light that has been rotated. A casing is constituted by three identical members 41, 42, and 43, the members being mutually stuck together with polarizer 34, analyzers 35 and reflective mirrors 36, in the form of thin sheets, interposed therebetween.

Abstract: An optical fiber has a core structure and a first coating layer covering the core structure. The optical fiber, after being twisted, is covered at its outer side with a second coating layer. The second coating layer is higher in Young's modulus than the first coating layer. As a result, the twisting of the optical fiber is stably retained by the second coating layer. Further, an outer force coming from the second coating layer is absorbed by a soft first coating layer, so that no compressive force acts on a core and cladding in the optical fiber.

Abstract: A device for optically measuring a physical quantity in power equipment includes an optical fiber associated with the power equipment, an optical part for transmitting/receiving light to/from the optical fiber, calculation unit for calculating a physical quantity in the power equipment by detecting the polarized state of light polarized by the power equipment on the basis of the output from the optical part, a housing box for housing the optical part, and a fixing member to which the optical part is mounted and which is fixed to the housing box by laser welding.