To provide an optical attenuator which has extremely small polarization mode dispersion and polarization dependency loss and can be made small in sized and light in weight.
A polarization beam splitter 10 polarizes and separating an input light signal into light signals of two substantially orthogonal polarized components and outputs the light signal of one polarized component and the light signal of the other polarized component. A Faraday rotator 11 rotates the plane of polarization of the light signal of the one polarized component by a 1st Faraday rotational angle and outputs the light signal, and a reflecting mirror 12 reflects the light signal to put it back to the polarization beam splitter 10 through the Faraday rotator 11. A Faraday rotator 21 rotates the plane of polarization of the light signal of the other polarized component by a 2nd Faraday rotational angle and outputs the light signal and a reflecting mirror 22 reflects the light signal to put it back to the polarization beam splitter 10 through the Faraday rotator 21. The polarization beam splitter 10 puts together and outputs the light signals which are returned, and varies the Faraday rotational angles to vary the attenuation quantity of the composite light signal.
MATSUMOTO SADAYUKI
YOSHIARA KIICHI
Osamu Kawamiya
Masahiro Ishino