Patent ID: 6978076

Claim:
A variable optical attenuator comprising: an input/output optical system to which are connected an input optical fiber and an output optical fiber and which has an input lens for taking light having entered by way of said input optical fiber as input light and an output lens for gathering output light to be coupled to said output optical fiber, to thereby couple said output light to said output optical fiber; a birefringent device provided on an output side of said input/output optical system; a liquid crystal device capable of changing polarizing states of said input light exiting said birefringent device; and a reflection device which reflects light passing through said liquid-crystal device so that the light returns to said output lens of said input/output optical system by way of said liquid-crystal device and said birefringent device, wherein said input/output optical system, said birefringent device, said liquid-crystal device, and said reflection device are integrated together.