various transmission wavelengths (Multimode at 850nm or 1300nm, or
Singlemode at 1310nm or 1550nm). Generally, higher wavelengths can
support longer distances. However, to calculate the amount of cable loss
more accurately by using the TIA/EIA Cable Loss Estimates, see Table3.3.
Table 3.3:The TIA/EIA Cable Loss Estimates
Fiber Type Loss Amount per 1 km
Singlemode 9/125μm fiber @ 1310nm 0.4dB / km
Singlemode 9/125μm fiber @ 1550nm 0.3dB / kmTable 3.3 assumes a continuous cable run without any devices, splices,
connector mating or other factors involved in signal loss. And it assumes
that the core/cladding diameter of the cable is the same throughout the
transmission line.
3.6.2 Calculating Maximum Cable Distance
To calculate the maximum cable distance possible for linking the
substations in the SCADA network,equations ( 3 - 1, 3 - 2) bellow are be used,
when the number of connectors, number of splices and the optical loss
budget (calculated belowin equation (2)) of the transmitting and receiving
devices/ports are known,connector loss (at 0.75dB per connector), splice
loss (at 0.1dB per splice) and a margin of error of 3dB as demonstrated
below.
Maximum Cable Distance = [Optical loss budget - 0.75dB number of connections -0.1dBnumber of
splices -3dB (as a margin of error)]/ cable loss (in dBs per km) ........................................ ( 3 - 1)
Optical loss budget = transmitter's power output (in dBs) - receiving port's minimum
sensitivity (in dBs) ......................................................................................... ( 3 - 2)
The main parameters (transmitter's power and receiving port's
minimum sensitivity) of transmission devices (switches) are taken from
table 3 .4 [ 43 ].