Optical fiber non-reciprocal phase shifters and optical isolators using them
 In accordance with the invention, an optical fiber phase shifter comprises a length of asymmetrical optical fiber disposed perpendicular to a magnetic field for providing a non-reciprocal phase shift. Preferably the fiber is wound in a circular coil and exposed to an axial field as from a pancake magnet. In an isolator, the fiber length and magnet strength are chosen to provide non-reciprocal phase shifts of .+-.45.degree. or .+-.90.degree.. The isolator including the phase shifter can be any of several configurations. 
AT&T Corp.
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Kenneth L. David J. Raymond Weyl-Kuo
Walker DiGiovanni Wolfe Wang