Fdk Corporation

Shusuke Wada

Hiroaki Ono

Shohei Abe

Hidenori Nakada

Hideo Takeshita

Keisuke Ikeda

Yuko Ota

Tsugio Tokumasu

Ikuo Maeda

Tomokazu Imura

Mototsugu Goto

A low-cost compact optical attenuator structure has an input port and an output port for optical signals arranged side by side; a reflecting member arranged to face both ports to reverse light from the input side on an optical path folded 180&#xb0;; a birefringence crystal splits incident light into two polarization components, a converging lens converges the incident light, a fixed Faraday rotator having a variable rotation angle arranged in that order in the optical path. The partial reflecting member that transmits a portion of incident light to the rear side thereof, an optical sensor at the rear side of the reflecting member, optical guide means guide only the transmitted light from the input port side to the optical sensor, and optical detection signals of the optical sensor are used as optical input monitoring signals.

Optical attenuator

A first separating/combining birefringent element, first and second optical-path controlling birefringent elements, and a second separating/combining birefringent elementare spaced apart. Between the first separating/combining birefringent element and the first optical-path controlling birefringent element, a first polarization rotating meansis arranged for changing a polarization direction from an orthogonal relationship to a parallel relationship, or from a parallel relationship to an orthogonal relationship. Also, between the second optical-path controlling birefringent element and the second separating/combining birefringent element, a second polarization rotating meansis arranged. The first and second optical-path controlling birefringent elements are oppositely arranged symmetrically on optical axis about an arrangement center thereof, between which is arranged a &#xbd;-wavelength plate for rotating a polarization direction of a light on a central optical path 90 degrees, thereby structuring an optical circulator. With a similar structure, an optical switch can be structured by using a &#xb1;45-degree variable Faraday rotator in the first and second polarization rotation switch means.

Optical circulator and optical switch

A variable optical gain equalizer in accordance with one embodiment of the present invention comprises a variable branching ratio beam splitter having a variable polarization rotator, the variable branching ratio beam splitter branching an input light beam into two light beams at an arbitrary power ratio, through control of the rotation angle of the polarization direction by the variable polarization rotator; an optical filter presenting different filter characteristics to the two branched output light beams; and a polarization coupler for polarization coupling the two light beams that have passed through the optical filter, wherein the rotation angle of the polarization direction is controlled by the variable polarization rotator so as to vary the spectra of the output light beams.

Variable optical gain equalizer and variable branching ratio beam splitter

A beam shutter is provided which comprises a plane-parallel birefringent element for separation arranged to separate input light beams having orthogonal polarization directions on the same optical path; a plane-parallel birefringent element for synthesis arranged to synthesize light beams having orthogonal polarization directions on different optical paths, for output; the birefringent element for separation and the birefringent element for synthesis being disposed in a spaced apart relationship; and polarization rotating means having a variable Faraday rotator, the polarization rotating means interposed between the birefringent element for separation and the birefringent element for synthesis, for magneto-optically controlling the polarization directions; wherein transmission and interruption of output light beams are controlled by switching the polarization directions by means of the variable Faraday rotator.

Beam shutter

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Shizuoka, Japan

Shusuke Wada