Calculator
Formula used
Group delay dispersion is the second derivative of spectral phase with respect to angular frequency: GDD = d²φ/dω².
For propagation in a uniform medium or fiber, the accumulated dispersion is: GDD = β2 · L, where β2 = d²β/dω² and L is length.
When using the dispersion parameter D (often in ps/(nm·km)): β2 = - (λ² / (2πc)) · D, with wavelength λ and speed of light c.
How to use
- Select the calculation mode that matches your available data.
- Enter length for β2 or D modes; use consistent units.
- Provide β2 directly, or enter D and wavelength to convert.
- Optionally enter pulse FWHM to estimate dispersion broadening.
- Click Compute, then download CSV or PDF for reporting.
Example data table
| Case | Mode | Inputs | Expected sign | Typical magnitude |
|---|---|---|---|---|
| Telecom fiber | D | D = 17 ps/(nm·km), λ = 1550 nm, L = 10 km | Negative β2, negative GDD | ~ -2.2×103 ps² |
| Short fiber patch | β2 | β2 = -21.7 ps²/km, L = 2 m | Negative | ~ -4.34×10-2 ps² |
| Compressor setting | Phase | φ2 = -12000 fs² | Negative | ~ 104 fs² |
| Stretcher | Phase | φ2 = 1.2×106 fs² | Positive | ~ 106 fs² |
| Waveguide section | β2 | β2 = 0.08 fs²/mm, L = 50 mm | Positive | ~ 4 fs² |
Values are illustrative; use your device specifications for accurate results.