An optical transducer includes a light emitting unit, a light detecting unit, light radiating sensor heads and light receiving sensor heads; the light radiating sensor heads and light receiving sensor heads are alternately arranged at intervals, and moving objects pass through the intervals in such a manner as to intersect light beams between the sensor heads; since the light emitting unit and light detecting unit are remote from the sensor heads, the light emitting unit and light detecting units are optically coupled to the sensor heads through optical fibers; a bundle of optical fibers is clipped on a predetermined route, and the optical fibers swerve from predetermined points of the bundle so that the optical fibers are surely warped so as to exert the resilient force on the inner surfaces of the optical devices, thereby being kept stable during the adhesion therebetween.