GE Reason H49
Technical Manual
H49/EN M/C22
53
6.6
Fiber 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 fiber optic budget is the difference between the power emitted into the fiber and
the sensitivity (minimum amount of power required) of the receiver connected
through the fiber 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.
Transmitted Power
Received Power
S0525ENb
Optical
Transmitter
Optical loss:
Connectors, fibers
Optical Receiver
Figure 33: Fiber Budget
For this product, the optical budget is given in the table below.
Fiber type
Multimode
62.5/125 micron
Single mode
9/125 micron
Power coupled into fiber
-19 dBm
-15 dBm
Sensitivity
-31 dBm
-34 dBm
In calculating the maximum distance, the following figures can be used as a guide, but
you should check with your supplier for precise figures.
Fiber type
Multimode
Single mode
Link budget
12 dB
19 dB
Typical connector loss
(1 per receiver, 1 per transmitter)
0.8 dB
0.8 dB
Safety Margin
4 dB
4 dB
Allowed link attenuation
6.4 dB
13.4 dB
Typical cable attenuation
1 dB/km
0.4 dB/km
Maximum range
2 km
15 km
Insertion of a patch panel (per panel)
2 dB
1 db
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