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The present invention is characterized by the following : a plurality of cores 10 and a cladding 15 that surrounds the plurality of cores 10 are provided; each of the cores 10 has an inner core 11 and an outer core 12, which surrounds the inner core 11 with no gap therebetween, and which has a refractive index higher than that of the inner core 11 and the cladding 15; no rare earth elements are added to the cores 10; and light of two or more LP modes and having a prescribed wavelength is propagated through the cores 10 with a loss of 0.3 dB/km or less.