US 7,679,753 B2 · Passively biased fiber-optic gyroscope and current sensor

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.

Claims10

Dependent claims

A passively biased fiber-optic sensor, comprising:

a source delivering a linear light;
a “zero to fast” fiber-optic quarter wave plate to convert the linear light to a circular light;
a 3×3 circular PM (Polarization Maintaining) fiber coupler which serves as a beam splitter and meanwhile a passive bias with a first end of a central arm receiving the circular light, and with a second end of the central arm cut short as a matched termination;
a sensing fiber loop whose two terminals are connected to two terminals of side fiber arms of the 3×3 circular PM fiber coupler;
and
a pair of detectors connected to another two terminals of the side fiber arms of the 3×3 circular PM fiber coupler.

3 more elements

A passively biased fiber-optic sensor, comprising:

a source providing a linear light;
a 2×2 single-mode fiber coupler with one arm receiving the linear light;
a 3×3 hybrid fiber coupler connected to an output arm of the 2×2 single-mode fiber coupler via a polarizer, wherein the 3×3 hybrid fiber coupler is made of one single-mode fiber and two linear hi-bi fibers with the two linear hi-bi fibers acting as a beam splitter that splits a received linear light beam into two linear light beams and meanwhile with three fibers together providing a 120° phase relation for passive bias of an interferometric sensor, wherein the 2×2 single-mode fiber coupler is cut short with an oblique angle at ends to form two matched terminations;
a sensing fiber loop whose two terminals are connected to output terminals of the two linear hi-bi fiber of the 3×3 hybrid fiber coupler to receive the two linear light beams traversing the sensing fiber loop in opposite directions;
and
a detector connected to a second fiber arm of the 2×2 single-mode fiber coupler to detect a signal carried by returned light beams through recombination and interference in a coupling region of a hybrid coupler.

3 more elements

Dependencies are inferred from the claim text.

Passively biased fiber-optic gyroscope and current sensor

Life of this patent

Passively biased fiber-optic gyroscope and current sensor

Life of this patent

Abstract

Claims10