Polarization drift elimination fiber wrap design and method
View Patent ↗A fiber wrap and a method of rotating the fiber wrap without twisting a data cable are disclosed. The fiber wrap includes a sun gear, a sun cylinder coupled to the sun gear, a planetary gear in contact with the sun gear, a planetary cylinder coupled to the planetary gear, an outer housing in contact with the planetary gear, and a data cable coupled to the sun cylinder, the planetary cylinder, and the outer housing. The maximum bend radius of the data cable is determined by the equation: 2 πΔ DGD c λ wherein λ is optical wavelength and Δ DGD = 0.5 C s ( r R 2 ) 2 Δ L c - 0.5 C s ( r R 1 ) 2 Δ L c wherein C s is the stress-optics coefficient, c is the speed of light, R 1 is the bend radius at the end of the wrap motion, R 2 is the bend radius at the start of the wrap motion, r is the radii of the sun cylinder and the planetary cylinder, and Δ L = 10 360 2 π R 2 .
1. A method of rotating a fiber wrap without twisting a data cable comprising the steps of:
determining the maximum bend radius of the data cable using the equation:
2
πΔ
DGD
c
λ
wherein λ is optical wavelength and
Δ
DGD
=
0.5
C
s
(
r
R
2
)
2
Δ
L
c
-
0.5
C
s
(
r
R
1
)
2
Δ
L
c
wherein C s is the stress-optics coefficient and c is the speed of light, R 1 is the bend radius at the end of the wrap motion, R 2 is the bend radius at the start of the wrap motion, r is the radii of the sun cylinder and the planetary cylinder, and
Δ
L
=
10
360
2
π
R
2
;
passing the data cable through a central axel;
passing the data cable out of the central axel into a slot in a lower portion of a sun cylinder;
wrapping the data cable at least part way around the lower portion of the sun cylinder;
routing the data cable into a grove on a face of the lower portion of the sun cylinder;
passing the data cable into a channel in the outer surface of an upper portion of the sun cylinder;
wrapping the data cable around the upper portion of sun cylinder at least one time;
passing the data cable into a channel in the surface of a planetary cylinder;
wrapping the data cable at least partly around the planetary cylinder;
passing the data cable into a channel in an inner surface of an outer housing; and
passing the data cable through a slot in the outer housing.
2. The method of claim 1 , wherein only a portion of the data cable is in motion while the fiber wrap is in operation.
3. The method of claim 2 , wherein the data cable is one of a 0.9 mm cable, a 1.8 mm cable, a 2.0 mm cable, 2.4 mm cable, a 2.8 mm cable, and a 3.0 mm cable.
4. The method of claim 2 , wherein a slip ring holds the data cable in the channel in the inner surface of the outer housing.
5. The method of claim 4 , wherein the slip ring is comprised of a low friction material.
6. The method of claim 5 , wherein the coefficient of friction between the slip ring and the outer housing is less than one of 0.3, 0.2, and 0.1.
7. The method of claim 2 , wherein a cover is coupled to the housing.
8. The method of claim 7 , wherein the axel extends through the cover.
9. The method of claim 7 , wherein the cover is transparent.
10. The method of claim 2 , where the maximum bend radius is one of 1 inch, 1.25 inches, 1.5 inches, 1.75 inches, 2 inches, 2.25 inches, and 2.5 inches.