34Chapter 2 Calculating transmission distance
Table 7 shows typical loss values that can be used to calculate the transmission distance for the hub and spoke network in Figure 13.
Table 7 Hub and spoke signal loss values
Signal loss element | value |
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Loss budget | 30 dB |
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CWDM OADM insertion add loss | 1.9 dB |
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CWDM OADM passthrough loss | 2.0 dB |
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CWDM OMUX8 demux loss | 4.5 dB |
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System margin | 3 dB |
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Fiber attenuation | .25 dB per km |
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Table 8 shows the calculations used to determine maximum transmission distance for the hub and spoke network in Figure 13.
Table 8 Hub and spoke maximum transmission distance calculations
Result | Calculation |
Passthrough nodes | the number of OADMs between add OADM and OMUX |
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Passive loss | OADM add + OMUX8 demux + (passthrough nodes × OADM passthrough loss) |
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Implied fiber loss | loss budget – passive loss – system margin |
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Maximum transmission | implied fiber loss ÷ attenuation per kilometer |
distance |
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Transmission distance calculation for the hub and spoke network example in Figure 13:
•7 Passthrough nodes
•1.9 dB + 4.5 dB + (7 × 2.0)= 20.4 dB Passive Loss
•30 dB – 20.4 dB
•6.6 dB ÷ .25 dB= 26.4 km Maximum Transmission Distance
