OPTICAL ISOLATOR AND OPTICAL AMPLIFIER ADOPTING THE SAME

摘要

PURPOSE: An optical isolator is provided which is constructed in a manner that a tap and a wavelength division multiplexing filter are united to realize a small-sized optical amplifier. CONSTITUTION: An optical isolator is located on an optical path between the first and second optical fibers(41,51) to transmit beams emitted from the first optical fiber to the second fiber according to the polarization mode of an input beam and to block beams reversely emitted from the second optical fiber. The first polarizer(31) double-refracts most of the beam transmitted through the first optical fiber into the first beam that is a normal beam and the second beam that is an abnormal beam according to the decision optic axis. A tap(33) is placed opposite to the first optical fiber to reflect a part of the beam transmitted through the first optical fiber. A Faraday rotator(35) rotates the first and second beams in one direction. The second polarizer(37) converts the first beam and second beam that passed the Faraday rotator into an abnormal beam and normal beam, respectively. A wavelength division multiplexing filter(39) passes beams in the wavelength region transmitted through the first optical fiber but reflects beams in other wavelength regions.