Different PON specifications are used for calculating optimal distance without attenuation between optical transmitter and optical receiver at distances from 10 km to 20 km. There are three classes of worst-case attenuation ranges, that are used for power-budget calculations:
- Class A: 5 to 20 dB
- Class B: 10 to 25 dB
- Class C: 15 to 30 dB
- These attenuation ranges are calculated, resulting from many factors:
- optical fiber
- optical splitters
Also designer of the network should remember that the additional splices and fiber lengths after repairs, environmental factors and unexpected degradation in any passive components may affect attenuation as well.
The table below shows the maximum power budgets, with high-quality components and under ideal conditions within three optical network classes.
It is assumed that fiber is having attenuation of 0.25 dB/km at 1550 nm. Attenuation is higher for calculating at 1310nm – 0.5 dB/km. All the values are given for three different Optical Splitting Ratios of 1 : 16, 1 : 32 and 1 : 64.