Eichverfahren für ein optisches Dämpfungsglied

The invention is designed to calibrate a low-level optical power by a substitution method using a pulse generating section (4) in which a light-shielding disk (4a) having a sectorial opening (4c), as a component capable of accurate optical attenuation, is rotated in a light beam to generate an intermittent pulse signal having a duty ratio corresponding to the size of the opening (4c), and the pulse signal is averaged to obtain an optical attenuation equal to the duty ratio. More specifically, while an object (2) to be calibrated is set in a given standard state, a first pulse train having a duty ratio d1 = Tw1/Tf1 is input to the object (2), and an average optical power value A of an output from the object (2) is measured and stored. Subsequently, a second pulse train having a duty ratio d2 = Tw2/Tf2 is input to the object (2), and the object (2) is adjusted such that an average optical power value of an output from the object (2) becomes the value A. Proper calibration can be performed by assigning the optical attenuation of the adjusted object to d1/d2.