User Documentation

Planning
2053260000/05/2015
23
2.7.3 Cable lengths for bre-optic cabling
Determining the cable length of bre-optic cables is more time-consuming and
dependent on various factors. Put simply, all attenuations that affect the bre-
optic cable run must be lower than the power budget of the active devices.
Power budget ≥ ∑Attenuation
connector
+∑ Attenuation
splices
+∑Attenuation
cable
* Cable length
• Power budget: difference between the capacity of the output signal of device
1 and the readable input capacity of device 2 (e.g.: 4 dB with Multimode)
• Attenuation
connector
: the attenuation of all connectors of the transmission path
(depending on the plug type, in each case approx. 0.3 dB)
• Attenuation
splices
: the attenuation of all splices along a transmission path (in
each case approx. 0.1 to 3.0 dB)
• Attentuation
cable
: the attenuation of the cable depending on the wavelength of
the light (e.g.: 1.5 dB/km at 1,300 nm wavelength of a Multimode bre)
• Cable length: length of the cable in km (e.g.: 1.2 km)
For example, the result could be as follows for the above equation:
4 dB ≥ 2 * 0.3 dB + 2 * 0.1 dB + 1.5 dB/km * 1.2 km = 2.6 dB
→ the cable length ts