FIELD: optics. SUBSTANCE: optical valve unit has optical splitter splitting optical signal coming through input hole, photodetector receiving split light beam and compensator of polarization mode dispersion. First lens in optical valve unit focuses incident optical signal. First birefringence unit is wedge- shaped, its input surface forms first preset angle with output surface from which polarized light is emitted. Coat for partial reflection of portion of incident optical signal is deposited on input surface of first birefringence unit. Faraday shifter turns polarized light through second preset angle. Second birefringent unit is also wedge-shaped and its input surface forms second preset angle with output surface. Optical axis of second birefringence unit turns in direction opposite to direction of turn of light beam by Faraday shifter with reference to optical axis of first birefringence unit. Photodetector receives light reflected from input surface of first birefringence unit. Second lens focuses light beam outgoing from second birefringence unit. EFFECT: simplified design of optical valve unit and low optical losses in it. 22 cl, 9 dwg
