| 摘要 |
PURPOSE:To correct the error generated by the variation in a wavelength caused by the change of the temp. in a light path, by catching the effect due to temp. as the change in the length of an optical fiber and using the same as a correction factor. CONSTITUTION:The expansion and contraction quantity of the optical fiber 9 arranged in the vicinity of the light path between an interferometer 3 and a reflecting mirror 4 is optically measured by an interferometer 8 and a receiver 10 and outputted as an electric signal by a fiber length operation circuit 11. On the basis of this signal, the average temp. distribution in this light path is calculated by an average temp. operation circuit 12 and the measured length value between the interferometer 3 and the reflecting mirror 4 is corrected on the basis of the output from said operation circuit 12 by a displacement quantity correction circuit 13. At this time, since the optical fiber 9 expands and contracts in proportion to temp. and a thermal time constant is small, by calculating the measured length value between the interferometer 3 and the reflecting mirror 4, the temp. distribution of the light path is calculated. On the basis of the temp. distribution thus obtained, the correction of the measured length value is performed to make it possible to perform highly accurate measurement.
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