A casting die assembly which does not produce any burrs includes a stationary die and a movable die that are clamped in a condition in which a slide core is caused to move toward a center of a movable die, and a back surface of a protrusion of the slide core contacts a stopper section provided on a frame section. In an all-fiber Mach-Zehnder interferometer, the method involves using a photosensitive fiber as one of the arms of the interferometer and exposing this photosensitive fiber to UV radiation so as to adjust the thermal dependence of the interferometer. The MSs measure CQI with respect to their channels in response to the request from the BS, compute average CQI from the measured CQI, and transmit the average CQI to the BS.