Optical fiber cooling tube
An optical fiber cooling tube includes an internal cavity through which an optical fiber passes and a set of injection passages that are distributed along the tube, open into the cavity, and are oriented in a contraflow direction relative to the direction in which the optical fiber moves.
1. An optical fiber cooling tube comprising:
an internal cavity having a diameter larger than an outer diameter of an optical fiber passed through the cavity in a flow direction from a first end of the tube to a second end of the tube, which is opposed to the first end;
injection groups that are distributed along the tube, open into said cavity, and are oriented in a contraflow direction relative to the flow direction in which said optical fiber moves; and
aspiration groups that are distributed along the tube, open into said cavity and are oriented in the contraflow direction relative to the flow direction in which said optical fiber moves,
said injection groups, of which there are at least three each comprising one or more injection passages, alternating along said tube with said aspiration groups, of which there are at least three each comprising one or more aspiration passages, the only openings to the outside of the tube being said injection passages, said aspiration passages and the first and second ends of said tube.
2. The optical fiber cooling tube claimed in claim 1 wherein said cavity has a cross section that is sufficiently narrow at said injection passages for an exterior surface of a boundary layer of gas entrained by said optical fiber when said tube is in use to be closer to the cavity walls than to an exterior surface of said optical fiber, wherein said cross section area of the cavity at said injection passages from 3 mm 2 to 10 mm 2 .
3. The optical fiber cooling tube claimed in claim 1 , wherein each injection group comprises either one injection passage or a plurality of injection passages with the same axial position relative to said tube and regularly distributed radial positions relative to said tube and each aspiration group comprises either one aspiration passage or a plurality of aspiration passages with the same axial position relative to said tube and regularly distributed radial positions relative to said tube.
4. The optical fiber cooling tube claimed in claim 3 wherein all said injection passages are connected to a common feeder passage and all said aspiration passages are connected to a common evacuation passage.
5. The optical fiber cooling tube claimed in claim 1 , wherein said internal cavity widens to form a chamber between the injection and aspiration groups.
6. The optical fiber cooling tube claimed in claim 1 , wherein said internal cavity narrows to form a bottleneck between the injection and aspiration groups.
7. The optical fiber cooling tube claimed in claim 1 , wherein the distance along said tube between the injection and aspiration passages is less than 100 mm.
8. The optical fiber cooling tube claimed in claim 7 wherein the distance along said tube between the injection and aspiration passages is from 10 mm to 50 mm.
9. The optical fiber cooling tube claimed in claim 1 , wherein said tube comprises at least ten aspiration groups, for at least half of said aspiration groups farthest from the ends of said tube, the gas aspirated is either reinjected directly or recycled, and, for at least each aspiration group nearest one end of said tube, the gas aspirated is neither reinjected directly nor recycled.
10. The optical fiber cooling tube claimed in claim 1 , comprising a plurality of modules each comprising a single injection group and a single aspiration group.
11. The optical fiber cooling tube claimed in claim 2 wherein said injection passages open onto the cavity walls.
12. The optical fiber cooling tube claimed in claim 1 , wherein said injection passages open onto the cavity walls.
13. The optical fiber cooling tube claimed in claim 1 wherein said injection passages have elongate orifices, a largest dimension of said orifice is along the axis of said tube, and a smallest dimension of said orifice is the cross section plane of said tube.
14. The optical fiber cooling tube claimed in claim 13 wherein said largest dimension is from one and a half times to four times said smallest dimension.
15. The optical fiber cooling tube claimed in claim 14 wherein said largest dimension is from twice to three times said smallest dimension.
16. The optical fiber cooling tube claimed in claim 13 wherein said smallest dimension is less than 1 mm.
17. The optical fiber cooling tube claimed in claim 16 wherein said largest dimension is from 1 mm to 5 mm.
18. The optical fiber cooling tube claimed in claim 1 , wherein an injection angle of said injection groups, which are oriented in the contraflow direction, is from 30 degrees to 60 degrees.
19. The optical fiber cooling tube claimed in claim 18 wherein said injection angle is approximately 45 degrees.
20. The optical fiber cooling tube claimed in claim 1 , wherein the injection groups and the aspiration groups are disposed along said tube such that the optical fiber, which is inserted into the first end of the tube and passed through the tube in the flow direction to exit the tube from the second end, first passes an injection passage of the injection groups before passing any aspiration passage of the aspiration group.
21. The optical fiber cooling tube claimed in claim 1 , wherein the injection groups and the aspiration groups, which are oriented in the contraflow direction, are angled toward the first end of the tube.