Variable light attenuator

摘要

A lens array ( 38 ) is mounted on the front surface of an optical fiber array ( 32 ) holding optical fibers ( 35, 36 ) for input and emission. The lens array ( 38 ) includes: an input lens ( 40 a) for converting a signal light ( 45 ) emitted from the optical fiber ( 35 ) into parallel light or converged light; and an output lens ( 40 b) for converging the returned parallel light and connecting it to the optical fiber ( 36 ). A rectangular prism ( 34 ) having a form of a rectangular equilateral triangle is arranged in front of the optical fiber array ( 32 ) having the lens array ( 38 ). The signal light ( 45 ) emitted from the optical fiber ( 35 ) is totally reflected twice by the rectangular prism ( 34 ) and comes into the optical fiber ( 36 ). A transparent rectangular rotary block ( 33 ) is arranged between the lens array ( 38 ) and the rectangular prism ( 34 ). The outgoing signal light ( 45 ) and the returning signal light ( 45 ) have optical axis shifted by the rotary block ( 33 ) where the signal light passes. With this structure, it is possible to obtain a small-size variable light attenuator having a high control accuracy of the attenuation quantity of the signal light and a high resolution.