Fdk Corporation

Hidenori Nakata

Hirotaka Kawai

Isao Kojima

Hiromitsu Umezawa

Teruhisa Sahashi

Kenji Sahara

Yuko Ohta

Teruhisa Nakamura

A variable optical attenuator comprising a separation/combination birefringent element, fixed polarization rotation means, a convex lens, variable polarization rotation means, and a mirror which are arranged in that order. The fixed polarization rotation means has a compensation film Faraday element placed in a cylindrical permanent magnet, and the variable polarization rotation means has a base film Faraday element that is placed outside the cylindrical permanent magnet, and an electromagnet applying a variable magnetic field thereto. Thereby, both the Faraday elements are magnetized in directions different from each other.

Variable optical attenuator

An optical attenuator with increased dynamic range and reduced temperature-dependence over the dynamic range. The optical attenuator has a Faraday rotational angle variable device which applies an external magnetic field to light polarized by a garnet crystal, and a polarizer and an analyzer disposed at the front and rear of the optical axis of the device. There is an angle x formed between the plane of polarization of the light incident to the garnet crystal and the magnetic field orthogonal to the optical axis, where an angle y is formed between the polarizer and the analyzer, and the angle x is set to satisfy {(&#x2212;z/2)+90&#xd7;n}&#x2212;12&#x3c;x&#x3c;{(&#x2212;z/2)+90&#xd7;n}+12 (n=0, 1, 2 or 3), where z=y&#xb1;90; z is the angle of rotation of the plane of polarization caused by the Faraday rotational angle variable device.

Optical attenuator

Growing community of inventors

Aichi, Japan

Hidenori Nakata