Method for manufacturing single mode optical fiber having low polarization mode dispersion
View Patent ↗A method for manufacturing a single mode optical fiber with a reduced PMD (Polarization Mode Dispersion), by drawing an optical fiber preform composed of a core and a clad surrounding the core, includes (a) heating the optical fiber preform to a high temperature using a furnace, and drawing an optical fiber from an outlet of the furnace at a linear velocity (V f ) of 500 mpm or above by means of neck-down drawing; and (b) impressing a spin on the optical fiber by means of a spin impressing device provided on a drawing path of the optical fiber, wherein a maximum spatial frequency of spin (y) impressed on the optical fiber satisfies the following equations Exp ( 24 t - 12 ) ≤ y ≤ - 20 × log ( V f 500 ) + 25 and t=(0.21×CladOval)+(0.04×CoreOval)+(0.17×ECC), where y is a maximum spatial frequency of spin [turns/m], V f is a drawing velocity [mpm], CladOval is a clad ovality [%], CoreOval is a core ovality [%], and ECC is an eccentricity [μm].
1. A method for manufacturing a single mode optical fiber with a reduced PMD (Polarization Mode Dispersion), by drawing an optical fiber preform composed of a core and a clad surrounding the core, the method comprising:
(a) heating the optical fiber preform to a high temperature using a furnace, and drawing an optical fiber from an outlet of the furnace at a linear velocity (V f ) of 500 mpm or above by means of neck-down drawing; and
(b) impressing a spin on the optical fiber by means of a spin impressing device provided on a drawing path of the optical fiber,
wherein a maximum spatial frequency of spin (y) impressed on the optical fiber satisfies the following equation:
Exp
(
24
t
-
12
)
≤
y
≤
-
20
×
log
(
V
f
500
)
+
25
and
t
=
(
0.21
×
CladOval
)
+
(
0.04
×
CoreOval
)
+
(
0.17
×
ECC
)
where y is a maximum spatial frequency of spin expressed in turns per meter, V f is a drawing velocity expressed in meters per minute, CladOval is a clad ovality expressed in a percentage, CoreOval is a core ovality expressed in a percentage, and ECC is an eccentricity expressed in μm.
2. The method for manufacturing a single mode optical fiber with a reduced PMD according to claim 1 ,
wherein the spin impressing device makes spin movements in clockwise and counterclockwise directions alternately with canting at a predetermined angle with respect to a drawing axis.
3. The method for manufacturing a single mode optical fiber with a reduced PMD according to claim 1 ,
wherein the maximum spatial frequency of spin (y) allows the optical fiber to have a PMD of 0.5 ps/km 1/2 or less.
4. The method for manufacturing a single mode optical fiber with a reduced PMD according to claim 2 ,
wherein the maximum spatial frequency of spin (y) allows the optical fiber to have a PMD of 0.5 ps/km 1/2 or less.