Anti-PMD system

1. An anti-PMD system comprising:

an anti-PMD pulley ( 1 ) over which an optical fiber ( 4 ) is to roll and which is mounted to rotate about an axis of rotation (ar); and

at least two optical fiber guide devices ( 2 , 3 ) situated on either side of the anti-PMD pulley ( 1 );

the system being characterized in that the axis of rotation (ar) of the anti-PMD pulley ( 1 ) is stationary;

in that the only degree of freedom of the anti-PMD pulley ( 1 ) is rotation about the axis of rotation (ar) of the anti-PMD pulley ( 1 ); and

in that at least one of the guide devices ( 2 , 3 ) is movable in translation in a translation direction (dt) that is not orthogonal to the axis of rotation (ar) of the anti-PMD pulley ( 1 ).

2. An anti-PMD system according to claim 1 , characterized in that, while the optical fiber ( 4 ) is being drawn:

the guide device ( 2 , 3 ) that is movable in translation angularly offsets the optical fiber ( 4 ) relative to a plane (PP) perpendicular to the axis of rotation (ar) of the anti-PMD pulley ( 1 ); and

the anti-PMD pulley ( 1 ) applies twisting torque to the optical fiber ( 4 ) alternately in the clockwise direction and in the counterclockwise direction so as to reduce the PMD of the optical fiber ( 4 ).

3. An anti-PMD system according to claim 2 , characterized in that said translation direction (dt) of the guide device ( 2 , 3 ) that is movable in translation lies in a plane parallel both to the axis of rotation (ar) of the anti-PMD pulley ( 1 ) and the travel direction (dd 1 , dd 2 ) of the optical fiber ( 4 ) where it passes through the guide device ( 2 , 3 ) while the optical fiber ( 4 ) is being drawn.

4. An anti-PMD system according to claim 3 , characterized in that said translation direction (dt) is parallel to the axis of rotation (ar) of the anti-PMD pulley ( 1 ).

5. An anti-PMD system according to claim 1 , characterized in that the distance between at least one point of contact between the optical fiber ( 4 ) and the guide device ( 2 , 3 ) that is movable in translation, and at least one point of contact between the optical fiber ( 4 ) and the anti-PMD pulley ( 1 ) is less than or equal to the radius (R) of the anti-PMD pulley ( 1 ).

6. An anti-PMD system according to claim 5 , characterized in that the distance between at least one point of contact between the optical fiber ( 4 ) and the guide device ( 2 , 3 ) that is movable in translation, and at least one point of contact between the optical fiber ( 4 ) and the anti-PMD pulley ( 1 ) is less than or equal to half the radius (R) of the anti-PMD pulley ( 1 ).

7. An anti-PMD system according to claim 1 , characterized in that the guide device ( 2 , 3 ) that is movable in translation includes at least two guide fingers ( 21 & 22 ; 31 & 32 ) between which the optical fiber ( 4 ) passes while the optical fiber ( 4 ) is being drawn.

8. An anti-PMD system according to claim 7 , characterized in that the guide fingers ( 21 & 22 ; 31 & 32 ) are movable in rotation about mutually distinct axes ( 23 & 24 ; 33 & 34 ).

9. An anti-PMD system according to claim 7 , characterized in that the spacing between the guide fingers ( 21 & 22 ; 31 & 32 ) is such as to avoid damaging the covering on the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn, and to control the angular displacement between the plane of the optical fiber ( 4 ) and the plane (PP) of the anti-PMD pulley ( 1 ).

10. An anti-PMD system according to claim 1 , characterized in that the guide device ( 2 , 3 ) that is movable in translation is a V-groove pulley whose axis of rotation is parallel to the axis of rotation (ar) of the anti-PMD pulley ( 1 ).

11. An anti-PMD system according to claim 1 , characterized in that the movement in translation of the guide device ( 2 , 3 ) that is movable in translation is slower at the ends of the stroke of said movement than in the middle of the stroke of said movement so as to impart a twist profile to the optical fiber ( 4 ) that is being drawn that is triangular rather than being sinusoidal.

12. An anti-PMD system according to claim 1 , characterized in that at least the guide device ( 3 ) situated downstream from the anti-PMD pulley ( 1 ) relative to the travel direction (dd 2 ) of the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn is movable in translation in said translation direction (dt).

13. An anti-PMD system according to claim 12 , characterized in that the anti-PMD system further comprises additional optical fiber guide means situated downstream from the downstream guide device ( 3 ) relative to the travel direction (dd 2 ) of the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn.

14. An anti-PMD system according to claim 1 , characterized in that at least the guide device ( 2 ) situated upstream from the anti-PMD pulley ( 1 ) relative to the travel direction (dd 1 ) of the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn is movable in translation in said translation direction (dt), and in that the anti-PMD system further comprises additional optical fiber guide means situated upstream from the upstream guide device ( 2 ) relative to the travel direction (dd 1 ) of the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn.

15. An anti-PMD system according to claim 1 , characterized in that both guide devices ( 2 , 3 ) are movable in translation in said translation direction (dt).

16. An anti-PMD system according to claim 15 , characterized in that both the two guide devices ( 2 , 3 ) move in mutually opposite directions along said translation direction (dt).

17. An anti-PMD system according to claim 1 , characterized in that the anti-PMD pulley ( 1 ) is a deflector pulley.

18. An anti-PMD system according to claim 1 , characterized in that the anti-PMD system includes a deflector pulley, and in that the anti-PMD pulley ( 1 ) is situated downstream from the deflector pulley relative to the travel direction (dd 2 ) of the optical fiber ( 4 ) while the optical fiber ( 4 ) is being drawn.