| 摘要 |
PROBLEM TO BE SOLVED: To especially enhance a reserve insertion loss in the case of a cancel type polarization independent type. SOLUTION: This isolator is constituted by overlapping a first 1/2 wavelength board 3 at a part and one side of a Faraday rotator 4 and overlapping a second 1/2 wavelength board 5 at the part, which the first 1/2 wavelength board 3 does not overlap, on the other side of the Faraday rotator 4. In this case, the accuracy of overlapping in the case of perpendicularly viewing a straight line side partitioning the parallel beams of the respective first and second 1/2 wavelength boards 3 and 5 by half from the incident direction of light is made lower than±5μm within the range irradiated with the beams.
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