Alstom DS Agile H38 Series, Инструкция по установке и эксплуатации

Страница: 56 / 59

H38x/EN GL/D11 Global Documentation
Page 52/53 DS Agile H38x
9. APPLICATIONS
9.1 Fibre Optic budget calculations
Optical power is expressed in Watts. However, the common unit of power measurement is
the dBm, defined by the following equation: Power (dBm) = 10 log Power (mW) / 1 mW.
The fibre optic budget is the difference between the power emitted into the fibre and the
sensitivity (minimum amount of power required) of the receiver connected through the fibre
optic cable.
Link Power Budget = Transmitter Power (dBm) - Receiver Sensitivity (dBm). The distance
over which the signals can be transmitted and successfully received is affected by the optical
loss as shown in the figure below.
FIGURE 17: FIBRE BUDGET
For this product the optical budget is given in the table below.
Fibre type Multimode Single mode
62.5/125 micron 9/125 micron
Power coupled into fibre -20 dBm -15 dBm
Sensitivity -31 dBm -31 dBm
Link budget 11 dB 16 dB
In calculating the maximum distance, the following figures can be used as a guide, but you
should check with your supplier for precise figures.
Fibre type Multimode Single mode
Connector loss
(1 per receiver, 1 per transmitter) 0.8 dB 0.8 dB
Safety Margin 4 dB 4 dB
Typical cable attenuation 1 dB/km 0.4 dB/km
Insertion of a patch panel (per panel) 2 dB 1 db