Optical waveguide having diffraction grating area and method of

Abstract

The present invention is to provide a method for identifying an optical line easily and accurately regardless of the optical line length. A plurality of reflecting parts is placed on the optical line, and a combination of relative positions of the reflecting parts is changed for every optical line to form an identification code, and the relative positions of the reflecting parts are detected based on reflected lights when a detecting light is inputted to the optical line, so that the optical line is identified based on a result. Concretely, when the detecting light is inputted to one end of the optical line, the light is reflected at the plurality of the reflecting parts which form the identification code and comes back the input end. A combination of the relative positions etc. of the reflecting parts is changed for every optical line. To detect the relative positions of the reflecting parts which form the identification code, either the optical path difference of the reflected lights from the reflecting parts is measured or the time difference between the reflected lights come back from the reflecting parts is measured. Then, based on the result, the optical line can be identified.