Inputs
Formula used
How to use this calculator
- Enter your signal wavelength and input power.
- Set pump power, fiber length, and the peak gain slope.
- Add fiber loss and any extra insertion loss in your build.
- Provide saturation output power to model gain compression.
- Enter noise figure and noise bandwidth to estimate ASE and OSNR.
- Click Estimate Gain to view results above the form.
- Use the CSV/PDF buttons in the results card to export.
Example data table
| λ (nm) | Pin (dBm) | Ppump (mW) | L (m) | Gss (dB) | Pout (dBm) | OSNR (dB) |
|---|---|---|---|---|---|---|
| 1550 | -15.0 | 80 | 10.0 | 5.97 | -9.04 | 39.22 |
| 1550 | -10.0 | 120 | 12.0 | 8.48 | -1.55 | 43.62 |
| 1560 | -5.0 | 200 | 15.0 | 12.60 | 7.41 | 47.74 |
1) What an EDFA gain estimate represents
An erbium‑doped fiber amplifier (EDFA) boosts a signal by converting pump energy into stimulated emission around the 1550 nm window. A gain estimate expresses expected amplification in dB from input to output after internal fiber loss and connector losses. This tool is tuned for fast design choices, not full propagation physics.
2) Inputs that drive the result
Wavelength sets photon frequency used in the ASE estimate. Pump power, fiber length, peak gain slope, fiber loss, and insertion loss set the small‑signal gain. Typical starting ranges: pump 50–300 mW, length 5–25 m, peak slope 0.6–1.3 dB/m, loss 0.01–0.05 dB/m, insertion loss 0–2 dB.
3) Pump-limited gain slope behavior
The model uses a smooth pump‑limited factor so gains do not increase unrealistically at low pump. When pump power equals the pump saturation power, the effective gain slope reaches about half of the peak slope. Choosing a pump saturation power near 30–80 mW often gives reasonable curvature for quick sensitivity studies.
4) Small-signal gain for weak channels
Small‑signal gain is computed from the net gain slope (effective slope minus fiber loss) times length, minus extra insertion loss. This is useful when input channels are far below saturation. If the net slope is low or negative, the calculator will show little gain or even net loss, which can happen with under‑pumped or over‑length designs.
5) Saturation power and gain compression
Real EDFAs compress as output approaches a saturation level. The logarithmic saturation formula provides a stable estimate that transitions smoothly from the small‑signal regime to the compressed regime. Lower saturation power forces earlier compression, reducing both output power and effective gain for higher input signals.
6) ASE noise and noise figure
ASE grows with gain, optical frequency, and noise bandwidth. Noise figure (often 4–6 dB) sets the spontaneous emission factor in the high‑gain approximation. Doubling bandwidth doubles ASE power (≈+3 dB). Use a per‑channel bandwidth for WDM planning.
7) OSNR in practical bandwidths
OSNR is computed by comparing signal output power to ASE power in the same bandwidth. A common reference is 0.1 nm at 1550 nm (≈12.5 GHz). For receiver planning, use your receiver or filter bandwidth. Keep margin for filtering and system penalties.
8) Using the calculator for link budgets
Start from required gain and output target. Tune pump and length until small‑signal gain meets the goal, then verify saturated output and OSNR at worst‑case input. Export CSV/PDF to record the point and repeat for higher losses and different wavelengths.
FAQs
1) What wavelength range does the calculator accept?
The signal wavelength input is limited to 1450–1625 nm, covering S/C/L bands. Wavelength affects photon frequency used in the ASE estimate, so OSNR and ASE shift slightly with wavelength.
2) How do I choose peak gain slope?
Use a vendor datasheet or lab fit. As a starting point, 0.8–1.2 dB/m often matches medium‑doped EDF in C‑band. Adjust until the small‑signal gain at your pump and length matches measurements.
3) What does pump saturation power mean here?
It is a shaping parameter that controls how quickly gain slope rises with pump power. When pump equals pump saturation power, the effective gain slope reaches half of the peak slope in this model.
4) Why is the saturated output formula logarithmic?
A logarithmic form is a convenient engineering approximation for gain compression. It keeps output growth smooth as the amplifier approaches the chosen saturation power, and it avoids unrealistic outputs when the small‑signal gain is very high.
5) What bandwidth should I use for OSNR?
Use the bandwidth that matches your measurement or receiver reference. Common choices are 12.5 GHz (≈0.1 nm at 1550 nm) for OSA-style OSNR, or the electrical noise-equivalent bandwidth of your coherent receiver filter.
6) Can this replace a full EDFA simulation?
No. It is meant for quick feasibility checks and sensitivity studies. Detailed simulations should include wavelength-dependent cross sections, pump/signal propagation, excited-state absorption, and multi-channel gain dynamics.
7) How do I interpret the efficiency value?
Efficiency here is (Pout − Pin) / Pump, using optical powers. It indicates how effectively pump power is converted into additional signal power. It will drop when the amplifier is under-pumped, over-length, or strongly saturated.