Fdk Corporation

Teruhisa Sahashi

Isao Kojima

Hirotaka Kawai

Hidenori Nakada

Tsugio Tokumasu

Keisuke Ikeda

Hiromitsu Umezawa

Shohei Abe

Hidenori Nakata

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

A reflection-type variable optical attenuator comprises: a main attenuator unit including a first birefringent crystal plate, a Faraday rotational angle varying unit, and a second birefringent crystal plate arranged in this order; an input port and an output port that are arranged on a side of one end of the main attenuator unit; and a two-point reflection-type optical path varying reflector that is arranged on a side of the other end of the main attenuator unit. Light that comes in from the input port makes a round trip in the main attenuator unit and goes out through the output port.

Reflective variable light attenuator

Optical devices including a Faraday rotation devices improved in wavelength and temperature characteristics and an optical attenuator reduced in wavelength dependence and temperature-dependent loss. The Faraday rotation device has permanent magnets magnetized in an axial direction of through-holes, and Faraday elements having a same Faraday rotation direction with respect to a same magnetization direction. The permanent magnets are directed in the same magnetization direction along an optical path, where part of the Faraday elements are accommodated in the through-hole of the permanent magnet, and the remaining Faraday elements are arranged between the magnets, whereby the Faraday elements are to be applied by magnetic fields in opposite directions. For a device variable in Faraday rotation angle, an electromagnet is provided. An input fiber collimator and polarizer are provided on an input side of with the Faraday elements while an analyzer and output fiber collimator are on an output side.

Faraday rotation device and optical device using same

Farady rotation device and optical device comprising it

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Minato-ku, Japan

Teruhisa Sahashi