Optical nonreciprocal device

An optical nonreciprocal device adapted to optically couple together two opposed optical fibers, said device comprising:

• light focusing and transmitting means located in an optical path between said two optical fibers on a side of either one of said optical fibers for converging and diverging light propagating through said optical path;
• a plurality of anisotropic crystal members interposed between said light focusing and transmitting means and the other optical fiber, while the thicknesses of said anisotropic crystal members being set to predetermined values such that the light is separated into ordinary ray and extraordinary ray and then said ordinary ray and said extraordinary ray are synthesized again to be transmitted to the other optical fiber while said ordinary ray and said extraordinary ray propagate in a forward direction, and that said ordinary ray and said extraordinary ray propagating from said other optical fiber in a reverse direction would not superpose each other at an excitation end of said one optical fiber;
• and
• magneto-optical members having a predetermined polarization rotating angle and interposed between any two of said plurality of anisotropic crystal members for imparting a predetermined polarization rotation to said separated ordinary and extraordinary rays while they propagate through said optical path.