Elliptically birefringent optical fiber architecture proposed for electric-current or magnetic-field sensing

The problem concerning excitation of an elliptically birefringent fiber is dealt with by the variably coupled mode theory under the slowly varying condition. A composite fiber element is structured in a one-step fabrication process, comprising an extra spun hi-bi section whose spin-pitch varies from zero to a value equal to the constant spin-pitch of the main spun hi-bi fiber section. Meanwhile, the magnetic field strength distribution along the tapered portion of the fiber is made to taper simultaneously. Theoretical analysis indicates that such a composite tapered fiber architecture is capable of supporting transmission of a single elliptical eigenmode, and moreover, responding analytically to an applied magnetic-field. practical aspects of the fiber architecture are discussed on the basis of a preliminary experimental investigation.