5
pulse that can pass a fiber × the fiber length. The modal bandwidth is a comprehensive index
reflecting the optical characteristics of a multimode fiber.
International Telecommunication Union (ITU) defines multimode fiber types in its G series
standards. The commonly-used multimode fiber is defined in the ITU G.651 standard. The
G.651-compliant fiber transmits light at the wavelength range 800 nm to 900 nm or 1200 nm to
1350 nm.
Table 2 Multimode fiber grades
Fiber mode Fiber grade Fiber diameter (m)
Modal bandwidth at
850 nm (MHz*km)
Multimode fiber
OM1 62.5/125 200
OM2 50/125 500
OM3 50/125 2000
Other factors that influence the transmission distance of multimode fibers include interface type,
central wavelength, and fiber grade. For more information, see Table 3.
Table 3 Multimode fiber
specifications
Interface type
Central
wavelen
th
(nm)
Fiber grade Transmission distance
1000BASE-SX 850
OM1 < 275 m (902.23 ft)
OM2 < 550 m (1804.46 ft)
10GBASE-SR 850
OM1 < 33 m (108.27 ft)
OM2 < 82 m (269.03 ft)
OM3 < 300 m (984.25 ft)
10GBASE-LRM 1310
OM1 < 220 m (721.78 ft)
OM2 < 220 m (721.78 ft)
OM3 < 220 m (721.78 ft)
• Single-mode fibers
Single-mode fibers (SMFs) have a small core size, typically 9 μm or 10 μm, and can transmit light
in only one mode. Single-mode fibers suffer little intermodal dispersion and are suitable for
long-haul communication. Single-mode fibers transmit light at the central wavelength of 1310 nm
or 1550 nm.
Telecommunication Industries Alliance (TIA)/Electronic Industries Alliance (EIA) defines that
single-mode fibers use yellow outer jackets with the mark "SM".
ITU defines single-mode fiber types in its G series standards. The mostly-commonly used
single-mode fibers are defined in ITU G.652 and G.655 standards. Table 4 desc
ribes features of
the G.652 and G.655-compliant fibers.
