The process of planning the power budget is a process of configuring optical amplifiers (OAs). The optical power at the transmit end must meet the requirements of incident optical power. The optical power at the receive end must be within the receiver sensitivity range.
In a DWDM system, an OA (Erbium-doped fiber amplifier or Raman amplifier) the power loss introduced by line fiber, optical modules, and optical components needs to be compensated for by an OA (Erbium-doped fiber amplifier or Raman amplifier).
Amplifiers must be configured after calculating the fiber attenuation of the entire link and considering the system margin (3 dB when there is no special requirement) in the network design phase. Then, proper adjustment must be made based on the configuration of dispersion compensation modules.
As shown in Figure 1, the transmit reference point at station A is S, and the receive reference point at station B is R. L indicates the transmission distance between point S and point R. The loss of the regenerating section is calculated as follows:
Loss of the regenerating section (dB) = L (km) x a (dB/km) + b (dB)
NOTE:
a is the attenuation coefficient (dB/km). b is the insertion loss of the fiber connectors at the jump stations (dB).
According to ITU-T Recommendations, the attenuation coefficient is 0.275 dB/km in the engineering design (end-of-life value). To realize long-haul transmission of optical signals, the optical power of signals must be large enough to offset the attenuation of the fibers. The attenuation coefficient of ordinary G.652 and G.655 fibers at 1550 nm window is 0.22 dB/km. The default comprehensive fiber attenuation coefficient is 0.275 dB/km. This takes factors such as optical connectors and fiber redundancy into consideration.
By default, the insertion loss of the fiber connectors at the jump stations is 1 dB unless otherwise specified.
If the user provides the actual loss of each line during network planning, you can add the system engineering margin directly to the actual measured value. Generally, the system engineering margin is 3 dB in the budget. If the optical supervisory channel (OSC) is used, consider the extra power of fiber line units, which is considered 1 dB (the insertion loss of the FIUs at the two ends) in the budget. If the electrical supervisory channel (ESC) is used, ignore the extra power during budget planning.
