PURPOSE: To form a one corresponding to a fiber coil with one base, integrate optical members and reduce cost by forming a plurality of circular optical paths different in diameter so that those having larger diameters include those having smaller diameters, and adjacent optical paths are not concentric but partly situated in positions close to each other.

CONSTITUTION: A circular optical path II is provided on the inside of the most outside optical path I, an optical path III on the inside thereof, and an optical path IV further on the inside thereof, whereby an optical wave guide is formed to be an aggregate of a number of eccentric optical paths. The optical paths I, II or the optical paths II, III have an evanescent coupling part A or B, respectively. For example, a right-handed light CW advances in the optical path I from an end part (a), enters the optical path II from the evanescent coupling part A, further enters the optical path III in the evanescent coupling part B. Since the coupling efficiency is 100%, the light is perfectly exchanged in two optical paths, turned clockwise in the optical path III, returned again to the optical path II, and returned to the optical path I in the point A through the optical path II, reaching an end part (b). Since the light reaching the inside goes out to the outside again, thus, no intersection is present.