Optical fiber and fiber laser device
An optical fiber includes a core and a cladding. An effective area A eff of light of a fundamental mode, having a wavelength of 1070 nm and propagating through the core, is 500 μm 2 or more. A numerical aperture NA of the core satisfies the following formula: NA ≧ ( 1.3 × 10 - 11 × a 4 / b 6 ) 1 / 6 where a (m) is a radius of the core and b (m) is a radius of the cladding. A V value, that is a waveguide parameter of the optical fiber, satisfies the following formula: V ≦ 1.3583 × b - 0.2555 .
1 . An optical fiber comprising:
a core of radius a (m); and
a cladding of radius of b (m), wherein
a numerical aperture NA of the core satisfies the following formula:
N
A
≧
(
1.3
×
1
0
-
1
1
×
a
4
/
b
6
)
1
/
6
,
the optical fiber includes a bent portion that is bent with a bending radius that is 100 times or more of the radius b (m) such that:
a V value, that is a waveguide parameter of the optical fiber, satisfies the following formula:
V
≦
1
.
3
5
8
3
×
b
-
0.2555
;
and
a fundamental LP01 mode of 1070 nm light propagates through the core with a loss of 0.001 dB/m and an effective area A eff of 500 μm 2 or more, while propagation of an axisymmetric LP03 mode is cutoff.
2 . The optical fiber according to claim 1 , wherein the effective area A eff is 600 μm 2 or more.
3 . The optical fiber according to claim 2 , wherein the effective area A eff is 800 μm 2 or more.
4 . The optical fiber according to claim 1 , wherein the V value satisfies the following formula:
V
≦
1.6509
×
b
-
0.1992
.
5 . The optical fiber according to claim 1 , wherein the numerical aperture NA is 0.05 or more.
6 . A fiber laser device comprising the optical fiber according to claim 1 .
7 . The optical fiber according to claim 1 , wherein a length of the optical fiber is greater than or equal to 20 meters and less than or equal to 40 meters.