| 摘要 |
PURPOSE:To reduce the influence of amplitude variations of signal light and reference light by monitoring the intensity values of the reference light and signal light, providing a light quantity adjusting mechanism to the incidence end of an optical fiber, and making the reference light and signal light constant in intensity. CONSTITUTION:The homogeneous light from a light source 1 is split by a beam splitter into two, which are made incident on signal and reference optical fibers 2 and 3. Light quantity adjusting mechanisms 6 and 15 are provided at the incidence terminals of the fibers 2 and 3. A sensing coil 4 is provided in the middle of the fiber 2. The signal light R and reference light R are propagated in the fibers 2 and 3 and part of the signal light S is incident as monitor light U on a photodetector 8. Further, part of the reference light R is incident as monitor light W on a photodetector 7. The intensity signals of the light beams U and W are amplified and supplied to the mechanisms 6 and 15. When the light beams U and W become larger than a normal value, the mechanisms 6 and 15 reduce the quantity of incident light. When the light beams U and W become smaller than the normal value, on the other hand, the mechanisms 6 and 15 increase the quantity of incident light. Thus, the amplitudes of the light beams S and R are held constant.
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