| 摘要 |
PURPOSE:To make it possible to accurately measure power by excluding loss by light transmission, by allowing same light output to be incident to a polarizer and a light detector so as to allow the same to advance through a light path to mutually opposite directions and calculating the difference of mutual light receiving outputs in opposite directions. CONSTITUTION:Light from a light emitting diode 11 is incident to a polarizer through a half mirror 12 and an optical fiber 13 and receives the rotation in a polarization direction by the Faraday effect of a magneto-optical effect element 4 and further receives the change in a phase proportional to applied valtage V by an electrooptical effect element 5 to be converted to an oval polarized wave. This light passes through an 1/4 wavelength plate 6, a light detector 7, an optical fiber 14 and a half mirror 15 to be received by a photodiode 16. The light from the light emitting diode 17 is incident to the half mirror 15 and the reflected light of the half mirror 12 is received by a photodiode 18. Then, outputs of the photodiodes 16, 18 are inputted to a differential amplifier 20 and difference voltage is outputted as a power signal.
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