PROBLEM TO BE SOLVED: To provide a polarization retention photonic crystal fiber that can easily discriminate a polarization surface by observation using a microscope.;SOLUTION: Since a pair of pores 4b that oppose each other by sandwiching a core 1 in six pores 4a and 4b adjacent to the core 1 has a diameter larger than the other four pores 4a, a polarization retention photonic crystal fiber 10 has a polarization-retaining function. The section of a cladding section 2 comprising a number of pores 4a and 4b at the periphery of the core 1 is in a diamond shape. Therefore, the maximum width of the cladding section 2 observed from the side of the fiber 10 appears each time when the fiber 10 is rotated by 180°, and the minimum width also appears in the similar manner. Since the width directions of the maximum and minimum widths coincide with the polarization direction of the polarization surface, the direction of the polarization surface of the polarization retention photonic crystal fiber 10 can be discriminated by microscope observation from the side of the fiber 10.;COPYRIGHT: (C)2003,JPO
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