| 摘要 |
PROBLEM TO BE SOLVED: To provide a group delay time difference measuring method and its device for shortening a measuring time, by eliminating measurement of an initial position and simplifying polarization mode dispersion measurement of an optical fiber which is a measuring object. SOLUTION: Light is incident by a light incident means 6 so that directions of two straight line polarizations are made to coincide with the birefringence axes of the measuring object 7. Interference fringe forming means (8 and 9) form an interference fringe, by interfering the straight line polarization emitted from the measuring object. When optical path length regulation means (3, 4 and 6) fix an optical path length of an optical path of the straight line polarization, propagating one of the birefringence axes of the measuring object into prescribed length and regulate the length of the optical path of the straight line polarization propagating the other, the optical path length in which visibility is maximum and the optical path length of the optical path of the straight line polarization propagating the other birefringence axis are fixed. When regulating the length of the optical path of the straight line polarization propagating one birefringence, the optical path length, in which visibility is maximum and the optical path length of the optical path for measuring respectively are regulated. A group delay time difference is measured, on the basis of the obtained optical path length. COPYRIGHT: (C)2005,JPO&NCIPI
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