Polarization drift eliminating fiber wrap design and method
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 D G D c λ wherein λ is optical wavelength and Δ D G D = 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 fiber wrap comprising:
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, wherein 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 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
.
2. The fiber wrap of claim 1 , wherein data cable is not twisted.
3. The fiber wrap of claim 1 , further comprising a hollow axel that is coupled to the sun gear, through which the data cable passes.
4. The fiber wrap of claim 1 , wherein the sun cylinder is comprised of an upper portion and a lower portion, wherein the upper portion and the lower portion are coupled together.
5. The fiber wrap of claim 4 , wherein the upper portion of sun cylinder has a smaller diameter than the lower portion of sun cylinder.
6. The fiber wrap of claim 5 , wherein the upper portion and lower portion of sun cylinder are two distinct units.
7. The fiber wrap of claim 4 , wherein the lower portion of the sun cylinder has a slot extending from the center of the sun cylinder to the outer edge of the lower portion of the sun cylinder though which the data cable passes.
8. The fiber wrap of claim 7 , wherein the upper surface of the lower portion of the sun cylinder has a groove in which the data cable sits.
9. The fiber wrap of claim 4 , wherein the upper portion of sun cylinder has a channel in the outer surface in which the data cable sits.
10. The fiber wrap of claim 1 , wherein the data cable is a fiber optics cable.
11. The fiber wrap of claim 10 , 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.
12. The fiber wrap of claim 4 , wherein the inner surface of the outer housing has a channel in which the data cable sits.
13. The fiber wrap of claim 12 , further comprising a slip ring to hold the data cable in the channel in the inner surface of the outer housing.
14. The fiber wrap of claim 13 , wherein the slip ring is comprised of a low friction material.
15. The fiber wrap of claim 14 , 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.
16. The fiber wrap of claim 1 , further comprising a cover coupled to the outer housing.
17. The fiber wrap of claim 15 , wherein the axel extends through the cover.
18. The fiber wrap of claim 15 , wherein the cover is transparent.
19. The fiber wrap of claim 1 , 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.