Patent ID: 8854716

Claim:
A reflection type variable optical attenuator having an optical input/output portion, an optical attenuation mechanism having Faraday rotator, and a reflector arranged along an optical axis in order named, wherein: the optical attenuation mechanism includes a permanent magnet for applying a fixed magnetic field to the Faraday rotator in an in-plane direction to magnetically saturate the Faraday rotator and variable magnetic field generation means for applying a variable magnetic field to the Faraday rotator in a direction of the optical axis, the permanent magnet is arranged so as to face a side surface of the Faraday rotator in a direction intersecting the optical axis, and wherein the permanent magnet comprises a ferrite permanent magnet, the variable magnetic field generation means comprises an air-core coil, and the Faraday rotator and the permanent magnet are arranged within an internal space of the air-core coil.