VARIABLE OPTICAL ATTENUATOR

摘要

A variable optical attenuator in which problems related to temperature is wiped off principally and attenuation of a light beam passing through an optical waveguide can be controlled to constant regardless of temperature variation. A positional variation detecting mechanism for detecting the inserting position of an inserting plate into the core of the waveguide is provided and the position of the inserting plate is subjected to drive control depending on the position of the inserting plate detected by the positional variation detecting mechanism. Based on a variation in the electrical capacity or the reactance between an electrode provided in the inserting plate driving mechanism and an electrode provided on an inserting plate driving mechanism supporting board or a waveguide holding board, a detecting circuit detects the inserting position of the inserting plate into a slit. Based on the detected position, a feedback control circuit performs drive control of the inserting plate driving mechanism such that the inserting plate is moved to a position where attenuation of the light beam becomes constant.