| 摘要 |
An optical fiber amplifier suited for use in optical fiber transmission systems includes a plurality of optical passive components. The optical passive components are integrated into an assembly including a birefringent crystal, a first lens, a magneto-optic crystal, an optical filter, and a second lens, all of which are axially aligned in this order, with a half-wave plate interposed between the birefringent crystal and the first lens. The birefringent crystal is opposed to end faces of first and second optical fibers and separates incident light into two linearly polarized light beams having respective polarized light planes generally perpendicular to each other. The half-wave plate allows light emitted from the second optical fiber to pass therethrough and rotates a polarized light plane of incident light. The first lens converts incident light into a generally collimated ray, and the magneto-optic crystal rotates a polarized light plane of incident light by an angle of (pi)/8+Nn/4 (N=0, 1, 2, . . .) under the influence of a magnetic field. The optical filter reflects light having a specific wavelength and allows light having a wavelength other than this specific wavelength to pass therethrough, and the second lens are opposed to end faces of third and fourth optical fibers and converges a collimated ray introduced thereinto. By this construction, an optical coupling system is constituted between the first and second optical fibers and between the third and fourth optical fibers and one of the first and second optical fibers.
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