1. Link Budget Concept
The optical link budget is the difference between transmit power and receiver sensitivity, representing the maximum tolerable loss.
2. Formula
Power Margin = Tx power − Rx sensitivity − fiber loss − connector/splice loss − device loss (e.g. Mux/Demux) + amplifier gain
3. Example Parameters
- Tx power: 0 dBm (100G LR4)
- Rx sensitivity: -9.5 dBm
- Fiber loss: 0.22 dB/km (SMF) × distance
- Connector: 0.3-0.5 dB each
- Mux/Demux IL: 3-4.5 dB
4. Margin Requirement
A power margin of ≥ 3 dB is typically required to ensure long-term reliability under aging and temperature drift. If insufficient, add EDFA or revise the design.
5. Recommendation
Always compute end-to-end link budget at design time. For high-risk scenarios, OTSLink engineering reviews OSNR, dispersion and amplifier configuration.
