https://www.rp-photonics.com/bandwidth.html

より、以下の式で計算

Δv = c/λ^2 *Δ/λ

 Δv: frequency bandwidth (Hz), c: speed of light (m/s), λ: center wavelength (nm), Δ/λ: Wavelength bandwidth (nm)

ここで、1/Δv = Δt

 Δt: Pulse width (s)