| 摘要 |
<p>PURPOSE:To measure voltage with a high degree of sensitivity by employing a branch interference type photomodulator which can modulate the intensity of light with a low applied voltage. CONSTITUTION:Light from a laser diode 60 enters from a light admitting section 21 via an optical fiber cable 61 and sent to a photomodulator section 30 and after divided into two with a branch section 31, to a phase modulator section 32. A phase difference proportional to a measuring voltage is given between divided lights with electrodes 401 and 402 for measuring voltage and interfered with each other with a connection section 33 to modulate the intensity of the light. Then, the light is converted into an electronic signal with a photodiode 71 with a lambda/4 plate 50 and amplified with an amplifier 72 to determine the measuring voltage applied to the electrodes 401 and 402. A part of light admitted from the light admitting section 21 is guided with a feedback waveguide 81 and converted into an electrical signal with a photodiode 83. The signal is fed back to a laser diode 60 through an amplifier 85 to maintain the intensity of light entering the light admitting section 21 thereby minimizing measuring errors.</p> |
