| 摘要 |
PROBLEM TO BE SOLVED: To solve such a problem that the polarization dependence which means the propagation loss in a light beam entering an optical waveguide depends on a polarization plane is decreased in a light beam propagating in an upper side of the core, however, a conventional variable optical attenuator blocks a light beam propagating in an upper side of the core where influences of polarization dependence are less but transmits a lower part of the light much propagating the core strongly influenced by the polarization dependence. SOLUTION: The variable optical attenuator has an attenuation plate having an aperture formed, with the aperture diameter smaller than a diameter of a light beam propagating the core. COPYRIGHT: (C)2007,JPO&INPIT
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