This tool estimates total amplified spontaneous emission power over an optical bandwidth.
If you provide noise figure instead of nsp, the conversion used is:
For a wavelength bandwidth Δλ in nm, the calculator converts to frequency bandwidth using Δν ≈ (c/λ²)·Δλ.
- Enter amplifier gain in dB or linear form.
- Set the center wavelength and choose its unit.
- Enter optical bandwidth, as frequency or Δλ in nm.
- Select noise figure or nsp, then enter its value.
- Pick polarization count to match your measurement path.
- Press Estimate ASE Power to view results above.
- Use Download CSV or Download PDF for records.
| Gain | Wavelength | Bandwidth | Noise input | Polarizations | Typical outcome |
|---|---|---|---|---|---|
| 20 dB | 1550 nm | 0.1 nm | NF = 5 dB | 2 | ASE in µW–mW range |
| 15 dB | 1310 nm | 50 GHz | nsp = 2.0 | 1 | Lower total due to polarization |
| 25 dB | 1565 nm | 0.2 nm | NF = 6 dB | 2 | Higher ASE from wider bandwidth |
ASE in optical amplifiers
Amplified spontaneous emission is broadband noise generated when excited ions or carriers relax and the emitted photons are amplified by the same gain process as the signal. In many links, ASE sets the optical signal to noise ratio limit and determines how much filtering is required between stages.
Why gain and bandwidth matter
Total ASE power scales with the available gain (G − 1) and the measurement bandwidth B. A wider channel filter, an OSA resolution bandwidth, or a wider WDM passband collects more noise power. This is why the same amplifier can look quiet or noisy depending on the selected bandwidth.
Noise figure and nsp relationship
This calculator accepts either noise figure or the spontaneous emission factor nsp. Noise figure describes how much the amplifier degrades input signal to noise ratio. Converting NF to nsp needs the gain, because the contribution of spontaneous emission is reduced as gain increases toward the high gain limit.
Choosing a center wavelength
Optical frequency is computed from the chosen wavelength using ν = c/λ. For a fixed wavelength bandwidth Δλ, the equivalent frequency bandwidth grows as wavelength decreases because of the λ−2 dependence. Setting the correct wavelength is essential when you enter bandwidth in nm and want consistent results across bands.
Bandwidth units and conversions
You can enter bandwidth directly in Hz, kHz, MHz, GHz, or THz, or as Δλ in nm. When Δλ is used, the tool applies Δν ≈ (c/λ²)·Δλ around the center wavelength. This approximation is accurate for narrow spans and is widely used for quick engineering estimates and instrument conversions.
Polarization assumptions
ASE exists in two orthogonal polarizations for typical unpolarized operation, so Npol = 2 is a common choice. If your setup measures a single polarization path, or uses a polarization maintaining component that selects one state, choose Npol = 1 to avoid overestimating total collected noise.
Interpreting PSD outputs
Alongside total power, the calculator reports spectral density in W/Hz and dBm/Hz. PSD is useful when comparing different filters or instrument settings because it removes the bandwidth scaling. If you input Δλ in nm, the result also shows dBm/nm to match common OSA reporting and telecom specifications.
Practical design checks
Use the estimate to sanity check preamp noise, evaluate filter requirements, and compare stage stacking. A jump in ASE power can come from higher gain, higher NF, or simply a wider passband. For multi stage chains, compute per stage outputs using the same bandwidth reference to keep link budgeting consistent.
1) What does this calculator estimate?
It estimates total ASE noise power over your chosen optical bandwidth using gain, wavelength, and either noise figure or nsp. It also reports spectral density so you can compare different bandwidth settings consistently.
2) When should I use noise figure versus nsp?
Use noise figure when you have a datasheet value. Use nsp when you are modeling from physics parameters or fitting measurements. The conversion depends on gain, so matching your operating gain improves accuracy.
3) Why must gain be greater than 0 dB?
The model uses (G − 1). If G ≤ 1, there is no amplification and the simplified amplifier ASE expression is not applicable. For attenuation or passive links, use a different noise model.
4) What bandwidth should I enter for an OSA measurement?
Enter the instrument resolution bandwidth if you are estimating the noise captured per trace bin. For channel power behind a filter, enter the filter’s equivalent noise bandwidth in frequency or the passband width in nm.
5) Why does nm bandwidth depend on wavelength?
Because a fixed Δλ corresponds to different Δν at different center wavelengths. The conversion uses Δν ≈ (c/λ²)·Δλ, so the same 0.1 nm span represents a larger frequency span at shorter wavelengths.
6) What does dBm/Hz mean here?
dBm/Hz is the ASE power spectral density expressed per 1 Hz bandwidth. It lets you scale noise power to any bandwidth by adding 10·log10(B) in dB, which is helpful for filter comparisons and link budgeting.
7) How accurate is this estimate?
It is a first order engineering estimate. Real systems can deviate due to gain ripple, saturation, internal filtering, and wavelength dependent NF. Use it for quick checks, then validate with measured spectra and component models.