Information Technology Reference
In-Depth Information
62.5 µm
Core
125 µm
Cladding
62.5/125 µm Multimode fiber—graded index
62.5 µm
Core
125 µm
Cladding
62.5/125 µm Multimode fiber—step index
8 µm
Core
125 µm
Cladding
125 µm Single mode fiber
FIGURE 5.7
Single- and multimode fiber optics operation.
Single-mode fiber can be used at many times that distance and is frequently used in
long distance distribution of T-carrier and Sonet signals. Typical attenuation for
62.5/125 multimode fiber is 3.5 dB/km at 850 nm and 1.0 dB/km at 1300 nm.
Typical numbers for single-mode 8 µm fiber are 0.5 dB/km at 1310 nm and 0.4
dB/km at 1550 nm. Table 5.6 lists representative values.
Transmission bandwidths of fiber-optic links are primarily limited by the band-
widths of the transmit and receiving devices, rather than the fiber core's transmis-
sivity. However, as you can see from the attenuation characteristics above, the
attenuation does vary somewhat with wavelength of the transmitted light.
TABLE 5.6
Typical Fiber Losses
Multimode Fiber (62.5/125 µm)
Single-mode Fiber
Wavelength, nm
850
1300
1310
1550
Loss, dB/km
3.5
1.0
0.5
0.4
