US 8,542,366 B2 · Sensing coil and sensing unit for sagnac optical fibre current sensor

Abstract

A sensing coil for a Sagnac interferometer current sensor is disclosed, the sensing coil (14) being composed of an optical fiber (for example a spun polarizing Hi-Bi fiber) that is arranged in use to transmit a single elliptical polarization state and the sensing coil comprising at least two interconnected loops (15 and 16 or 26 and 27 or 28 and 29). At least one of the loops is arranged in use to enclose a current conductor (11, 12 or 25) and the loops are interconnected such that light propagating in a first direction (23 or 30) in the first loop will propagate in a second, opposite, direction (24 or 31) in the other or, if more than one, in each other loop, whereby the sensing coil provides minimal sensitivity to rotational movement. Also disclosed are a sensing unit (FIG. 5) that incorporates the sensing coil and a current sensor (FIG. 1) that incorporates the sensing unit.

Claims18

Dependent claims

A sensing coil for a Sagnac interferometer current sensor, the sensing coil being composed of an optical fibre that is arranged in use to transmit a single elliptical polarisation state and the sensing coil comprising at least two interconnected loops, a first of the loops being arranged in use to enclose a current conductor and the loops being interconnected such that light propagating in a first direction in the first loop will propagate in a second, opposite, direction in the other or, if more than one, in at least one other loop,

wherein the sensing coil is formed with two only loops and wherein the respective loops are wound with turns and enclosed areas that satisfy the relationship
N1×A1=N2×A2, where
N1=number of turns in the first loop,
A1=area enclosed by the first loop,
N2=number of turns in the second loop and
A2=area enclosed by the second loop;
and
wherein both the first and the second interconnected loops are wound in opposite directions about a common axis and are arranged in use to enclose portions of a current conductor.

5 more elements

A sensing unit for a Sagnac interferometer current sensor, the sensing unit being connectable in circuit with a current busbar and the sensing unit comprising:

a) a carrier having first and second conductor portions that are arranged in use to be connected in series with the current busbar, and
b) a sensing coil composed of optical fibre that is arranged in use to transmit a single elliptical polarisation state and which comprises interconnected first and second loops respectively enclosing the first and second conductor portions, the loops being interconnected such that light propagating in a first direction in the first loop will propagate in a second, opposite, direction in the second loop,
wherein the carrier comprises first and second spaced-apart conductor members which are connectable in series with the busbar and which respectively are secured to the first and second conductor portions, and
wherein the first and second conductor portions are formed as projections of a common plate portion of the carrier, and the sensing coil is carried between the conductor members and the common plate portion.

1 more element

Dependencies are inferred from the claim text.

Sensing coil and sensing unit for sagnac optical fibre current sensor

Life of this patent

Sensing coil and sensing unit for sagnac optical fibre current sensor

Life of this patent

Abstract

Claims18