Specifications

Token Ring Desing Considerations
RADring
Installation & Operation Manual
6-12 Fiber Optic Design Considerations 3/11/98 12:26
In dB, this means that 6dB more power (10 log4 = 6) is coupled into the
100/140 micron fiber. In practice, the ratio is even higher (close to 7dB,
considering the N.A. factor of the fiber). For the same reasons, the power
coupled into a 100/140 micron fiber is 4dB higher than the energy coupled
into a 62.5/125 micron fiber.
Note
The RADring modules can operate with all the common core diameters:
50/125, 62.5/125 and 100/140 microns.
Losses in Optical Fibers
Losses are expressed in dB.
Losses (dB) = 10log
P
P
in
out
Where P
in
is the power coupled into the fiber, and Pout is the power
reaching the other end of the fiber.
Typical losses of graded-index fibers at a wavelength of 820mm (the
common LED wavelength) are as follows:
50/125 micron: 3.0 - 3.5dB/km
62.5/125 micron: 3.5 - 4.0dB/km Multimode
100/140 micron: 4.5 - 5.0dB/km
9/125 micron: 0.6 - 1dB/km (at 1300nm wavelength) Singlemode
Calculation of Optical Link Budgets
The maximum link attenuation (optical "link budget") equals the power
coupled into the fiber at transmitter side minus receiver sensitivity.
Table 6-5 Typical Values of Link Budgets
Fiber type Output Power Sensitivity Link Budget
50/125 micron -22 dBm -32 dBm 10 dB
62.5/125 micron -18 dBm -32 dBm 14 dB
100/140 micron -14 dB -32 dBm 18 dB
9/125 micron -18 dBm -33 dBm 15 dB