100
3 Optical Signal Attenuation and Dispersion
α uv =
154.2(0.06)
46.6(0.06) + 60
× 10
−2 exp
4.63
0.7
= 1.10 dB/km
(b) For the fiber with x = 0.06 and λ = 1.3 μm
α uv =
154.2(0.06)
46.6(0.06) + 60
× 10
−2 exp
4.63
1.3
= 0.07 dB/km
(c) For the fiber with x = 0.18 and λ = 0.7 μm
α uv =
154.2(0.18)
46.6(0.18) + 60
× 10
−2 exp
4.63
0.7
= 3.03 dB/km
(d) For the fiber with x = 0.18 and λ = 1.3 μm
α uv =
154.2(0.18)
46.6(0.18) + 60
× 10
−2 exp
4.63
1.3
= 0.19 dB/km.
Drill Problem 3.3 A silica fiber is doped with a 15% mole fraction of GeO 2 .
Compare the ultraviolet absorption at 860 nm and 1550 nm.
[Answer: 0.75 dB/km at 860 nm; 0.068 dB/km at 1550 nm.]
As Fig. 3.3 shows, absorption loss is small compared with scattering loss in the
ultraviolet, visible, and near-infrared regions ranging from 0.5 to 1.2 μm. In the
near-infrared region above 1.2 μm, the optical waveguide loss is predominantly
determined by the presence of OH ions and the intrinsic infrared absorption of the
constituent material. The intrinsic infrared absorption is associated with the characteristic vibration frequency of the particular chemical bond between the atoms
of which the fiber is composed. An interaction between the vibrating bond and the
electromagnetic field of the optical signal results in a transfer of energy from the
field to the bond, thereby giving rise to absorption. This absorption is quite strong
because of the many bonds present in the fiber. An empirical expression for the
infrared absorption in dB/km for GeO 2 –SiO 2 glass with λ given in μm is [5]
α I R = 7.81 × 10
11
× exp
−48.48
λ
(3.6)
3 Optical Signal Attenuation and Dispersion
α uv =
154.2(0.06)
46.6(0.06) + 60
× 10
−2 exp
4.63
0.7
= 1.10 dB/km
(b) For the fiber with x = 0.06 and λ = 1.3 μm
α uv =
154.2(0.06)
46.6(0.06) + 60
× 10
−2 exp
4.63
1.3
= 0.07 dB/km
(c) For the fiber with x = 0.18 and λ = 0.7 μm
α uv =
154.2(0.18)
46.6(0.18) + 60
× 10
−2 exp
4.63
0.7
= 3.03 dB/km
(d) For the fiber with x = 0.18 and λ = 1.3 μm
α uv =
154.2(0.18)
46.6(0.18) + 60
× 10
−2 exp
4.63
1.3
= 0.19 dB/km.
Drill Problem 3.3 A silica fiber is doped with a 15% mole fraction of GeO 2 .
Compare the ultraviolet absorption at 860 nm and 1550 nm.
[Answer: 0.75 dB/km at 860 nm; 0.068 dB/km at 1550 nm.]
As Fig. 3.3 shows, absorption loss is small compared with scattering loss in the
ultraviolet, visible, and near-infrared regions ranging from 0.5 to 1.2 μm. In the
near-infrared region above 1.2 μm, the optical waveguide loss is predominantly
determined by the presence of OH ions and the intrinsic infrared absorption of the
constituent material. The intrinsic infrared absorption is associated with the characteristic vibration frequency of the particular chemical bond between the atoms
of which the fiber is composed. An interaction between the vibrating bond and the
electromagnetic field of the optical signal results in a transfer of energy from the
field to the bond, thereby giving rise to absorption. This absorption is quite strong
because of the many bonds present in the fiber. An empirical expression for the
infrared absorption in dB/km for GeO 2 –SiO 2 glass with λ given in μm is [5]
α I R = 7.81 × 10
11
× exp
−48.48
λ
(3.6)