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Models 5843, 5844, 5843S and 5844S
RS-232 or TTL
3.
APPLICATIONS
When planning a system using Model 5843HRT and Model 5844HRT Link/Repeaters, the following
considerations should be reviewed:
•
Data Rate
•
Optical Budget and the distance between connected units
•
Number of units in a loop configuration
•
Powering the Link/Repeaters
•
Type of communication including format
•
Selection of Fiber Optic Cable (FOC)
3.1
DATA RATE
Model 5843HRT and Model 5844HRT Link/Repeaters automatically support all data rates from 1200
bits per second (AC Coupled Factory Default) to 250 Kilobits per second. No internal selection nor
setting is required. However, it is necessary that all connected IED's be set at the same data rate.
3.2
OPTICAL BUDGET
The optical budget is a ratio of the receiver sensitivity to launched optical power, i.e. amount of light
loss available from the transmitter to the receiver. It is calculated on a log scale so that a 3 dB loss
is equal to half of the original power, 10 dB is one tenth of the original power, 20 dB is one
hundredth, etc. Many different elements in the optical circuit can induce losses to the power of the
signal. This attenuation must be taken into account when determining the distance that the signal
can be transmitted. The major factor is the attenuation of the fiber optic cable. Cable attenuation is
expressed as "X" dB per kilometer. Other factors of attenuation include FOC fittings (terminations,
splitters, etc.) FOC diameter, and FOC aging.
Optical budget is the result of the expression:
Optical Budget [dB] = 10 x log10
Each Model 5843HRT or 5844HRT Link/Repeater has a typical optical budget of 19.5 dB.
Each Model 5843SHRT or 5844SHRT Link/Repeater has a typical optical budget of 19 dB.
3.2.1
Cable Attenuation Factors
The following cable factors must be applied as corrections to the optical budget.
3.2.1.1
Diameter
Multi-mode:
FOC of different diameters will vary the available optical budget of a system
due to different FOC core diameters. The 19.5 dB typical optical budget is
applicable to 62.5µm diameter FOC. Table 1 shows the correction factors to
use on the available optical budget for different diameter cable.
Table 1
FOC Diameter
50µm
100µm
200µm
Receiver sensitivity [µw]
Launch Power [µw]
Factor
-3 dB
+4 dB
+7 dB
3-1
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