Abstract: Passively biased fiber-optic Sagnac interferometric sensor architecture, for gyroscope and current sensor in particular, is disclosed. One embodiment uses a 3×3 coupler entirely made of circular polarization maintaining fiber that serves as a beam splitter and meanwhile a passive bias. An alternative is to use a 3×3 hybrid coupler consisting of two linear polarization maintaining fibers and one conventional single-mode fiber, with the former two connected in a common interferometric sensor circuitry, and with the latter one cut short at both ends to form matched terminations. Still another alternative is an integral unit of Faraday rotator, whose central part is a fiber-optic magneto-optic 45° rotator, with a “zero to fast” fiber-optic quarter wave plate attached to one side, and a “fast to zero” fiber-optic quarter wave plate to the other. Advantages of passive bias are simplicity in construction, no need of manual adjustment and operational stability.

Abstract: Passively biased fiber-optic Sagnac interferometric sensor architecture, for gyroscope and current sensor in particular, is disclosed. One embodiment uses a 3×3 coupler entirely made of circular polarization maintaining fiber that serves as a beam splitter and meanwhile a passive bias. An alternative is to use a 3×3 hybrid coupler consisting of two linear polarization maintaining fibers and one conventional single-mode fiber, with the former two connected in a common interferometric sensor circuitry, and with the latter one cut short at both ends to form matched terminations. Still another alternative is an integral unit of Faraday rotator, whose central part is a fine-optic magneto-optic 450 rotator, with a “zero to fast” fiber-optic quarter wave plate attached to one side, and a “fast to zero” fiber-optic quarter wave plate to the other. Advantages of passive bias are simplicity in construction, no need of manual adjustment and operational stability.

Abstract: A section of birefringent optical fiber spun at a slowly varying spin-rate from zero to a high value, or vice versa, behaves as a fiber-optic quarter wave plate in polarization transforms. Despite this similarity in SOP transforms with its bulk-optic counterpart which is narrow-band, this invention works on an entirely different mechanism that favorably makes the invention broad-band. Using different spin-rate functions, the invention is extended to include broad-band fiber-optic half wave, full wave, and fractional wave plates, capable of performing polarization transforms like the respective bulk-optic counterparts. Fabrication of the invented broad-band fiber-optic wave plates can be performed in the conventional way by using a birefringent preform drawn by a fiber-drawing tower incorporated with a variable-speed spinner on top of the setup. A nonconventional way is to use the moving microheater technique, devised by the same inventor, using a length of birefringent fiber as the starting material.

Abstract: A section of birefringent optical fiber spun at a slowly varying spin-rate from zero to a high value, or vice versa, behaves as a fiber-optic quarter wave plate in polarization transforms. Despite this similarity in SOP transforms with its bulk-optic counterpart which is narrow-band, this invention works on an entirely different mechanism that favorably makes the invention broad-band. Using different spin-rate functions, the invention is extended to include broad-band fiber-optic half wave, full wave, and fractional wave plates, capable of performing polarization transforms like the respective bulk-optic counterparts. Fabrication of the invented broad-band fiber-optic wave plates can be performed in the conventional way by using a birefringent preform drawn by a fiber-drawing tower incorporated with a variable-speed spinner on top of the setup. A nonconventional way is to use the moving microheater technique, devised by the same inventor, using a length of birefringent fiber as the starting material.

Abstract: A section of birefringent optical fiber spun at a slowly varying spin-rate from zero to a high value, or vice versa, behaves as a fiber-optic quarter wave plate in polarization transforms. Despite this similarity in SOP transforms with its bulk-optic counterpart which is narrow-band, this invention works on an entirely different mechanism that favorably makes the invention broad-band. Using different spin-rate functions, the invention is extended to include broad-band fiber-optic half wave, full wave, and fractional wave plates, capable of performing polarization transforms like the respective bulk-optic counterparts. Fabrication of the invented broad-band fiber-optic wave plates can be performed in the conventional way by using a birefringent preform drawn by a fiber-drawing tower incorporated with a variable-speed spinner on top of the setup. A nonconventional way is to use the moving microheater technique, devised by the same inventor, using a length of birefringent fiber as the starting material.

Abstract: A section of birefringent optical fiber spun at a slowly varying spin-rate from zero to a high value, or vice versa, behaves as a fiber-optic quarter wave plate in polarization transforms. Despite this similarity in SOP transforms with its bulk-optic counterpart which is narrow-band, this invention works on an entirely different mechanism that favorably makes the invention broad-band. Using different spin-rate functions, the invention is extended to include broad-band fiber-optic half wave, full wave, and fractional wave plates, capable of performing polarization transforms like the respective bulk-optic counterparts. Fabrication of the invented broad-band fiber-optic wave plates can be performed in the conventional way by using a birefringent preform drawn by a fiber-drawing tower incorporated with a variable-speed spinner on top of the setup. A nonconventional way is to use the moving microheater technique, devised by the same inventor, using a length of birefringent fiber as the starting material.

Abstract: The present invention is directed to a circular-polarization maintaining fiber structure, containing a stress-applying filament whirling around a central core. The fiber is fabricable by any of the existing fiber-making methods. The fiber is capable of maintaining circular polarizations of light, segments of such fiber can be easily spliced by lining up the cores only, and the fiber tolerates well bending and random perturbations likely to occur in practice. The invention is immediately applicable to fiber gyroscope and other interferometric architectures, to a variety of sensors, and to coherent optical transmission.

Abstract: A fiber-optic fabrication method is used for making the passive fiber-optic polarization control element capable of transforming an arbitrarily oriented linear polarization of light to a desired specific orientation, as so predicted by the super-mode theory. Central to this method is to locally heat and spin an anisotropic optical fiber with a variable spinning speed which is sufficiently high initially and which, as the micro-heater moves along the length of the fiber, drops slowly and monotonously to zero in a total length of about 10.sup.2 times the unspun-state beat length of the anisotropic fiber. Moreover, a linearly polarized light of definite, not unpredictable orientation, can be transformed simply with the aid of a half-wave plate, for example, to other desired SOPs (states of polarization) at the output.

Abstract: A theoretical prediction controls, by a purely passive fiber-optic element, a seemingly uncontrollable linear polarization whose orientation is all but unpredictable. A transformation of an unpredictable polarization orientation into a definite pre-assigned polarization orientation is useful in coherent optical communication and other fiber-optic polarization-dependent systems. A method of making the device utilizes, in a nonconventional way, the presently available fiber-fabrication techniques. A preform of an on-drawing optical fiber of appropriate birefringence is twisted with a monotonously slow-decaying rotational speed. The device is attractive to all obvious advantages inherent to the all-passive nature of the fiber structure.