Reduction of Faraday effect in optical ground wire (OPGW) cables
AssigneeCiena Corporation
InventorDavid Raymond Doucet
Life of this patent
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Abstract
New optical ground wire (OPGW) cable structures are proposed. These OPGW cables are designed to reduce or minimize the net magnetic field B∥NET parallel to the direction {circumflex over (z)} of light propagation resulting from a lightning strike on the cable. A reduction in the net magnetic field B∥NET parallel to the direction {circumflex over (z)} of light propagation yields a reduction in the amount and speed of state of polarization (SOP) rotation resulting from a lightning strike on the cable due to the Faraday effect. OPGW cables constructed according to these new OPGW cable structures fulfill their dual function to shield the high-voltage conductors from lightning strikes and to support coherent optical communications.
Claims12
An optical ground wire (OPGW) cable comprising:
- a core element carrying one or more optical fibers;
- N layers of concentric stranded wires, where N is an integer and N≧2, the stranded wires comprising strands of higher electrical conductivity wire and strands of lower electrical conductivity wire,
- wherein the wires are stranded in a right-hand, clockwise lay direction in M of the layers and the wires are stranded in a left-hand, counter-clockwise lay direction in the remaining (N−M) layers, where M is an integer, M is less than N, and M≧1, and
- wherein a total number of strands of the higher electrical conductivity wire in the M layers whose wires are stranded in the right-hand, clockwise lay direction is equal to a total number of strands of the higher electrical conductivity wire in the remaining (N−M) layers whose wires are stranded in the left-hand, counter-clockwise lay direction.
An optical ground wire (OPGW) cable comprising:
- a core element carrying one or more optical fibers;
- an inner layer of concentric stranded wires stranded in an inner helix structure characterized by an inner diameter Dinner and by an inner pitch pinner;
- and
- an outer layer of concentric stranded wires stranded in an outer helix structure characterized by an outer diameter Douter and by an outer pitch pouter,
- wherein the wires are stranded in a right-hand, clockwise lay direction in one of the layers and the wires are stranded in a left-hand, counter-clockwise lay direction in the other layers, and
- wherein an actual ratio of an outer current Iouter in the wires of the outer layer to an inner current Iinner in the wires of the inner layer is within 10 percent of an ideal ratio of the outer current Iouter to the inner current Iinner, the actual ratio calculated as a ratio of combined resistivity of the strands of the inner layer to combined resistivity of the strands of the outer layer, and the ideal ratio calculated as:
- (
- I
- outer
- I
- inner
- )
- IDEAL
- =
- D
- outer
- D
- inner
- ×
- sin
-
- (
- arctan
-
- (
- π
-
-
- D
- inner
- p
- inner
- )
- )
- sin
-
- (
- arctan
-
- (
- π
-
-
- D
- outer
- p
- outer
- )
- )
- .
Dependencies are inferred from the claim text.