SBS Threshold Power
Calculate Stimulated Brillouin Scattering threshold for optical fibers.
Fiber Parameters
Brillouin Parameters
The Brillouin gain bandwidth Δν_B is your value at this wavelength (it scales ≈ 1/λ²); the wavelength itself only sets the Brillouin shift.
Results
P_th = 21·K·A_eff·(1 + Δνs/ΔνB) / (gB·L_eff). The linewidth factor assumes a Lorentzian source; phase modulation or dithering of the source that spreads the spectrum over GHz raises the threshold much further, whereas on–off keying keeps about half the power in the carrier and so only roughly doubles it.
Threshold vs Source Linewidth
Threshold vs Fiber Length
Model and references
Textbook approximation. A standard approximation from the literature (for example paraxial, plane-wave or Gaussian-beam), valid within the range the page states. About the tiers
Smith critical power 21·K·A_eff·(1 + Δν_s/Δν_B)/(g_B·L_eff) for a CW pump: K = 1 co-polarized, 1.5 standard fibre, 2 scrambled; Lorentzian source linewidth. Undepleted pump. ν_B = 2n·v_A/λ.
- Smith R. G. (1972). Optical power handling capacity of low loss optical fibers as determined by stimulated Raman and Brillouin scattering. Appl. Opt. 11, 2489. Critical powers 16 (SRS) and 21 (SBS). doi:10.1364/AO.11.002489
- van Deventer M. O., Boot A. J. (1994). Polarization properties of stimulated Brillouin scattering in single-mode fibers. J. Lightwave Technol. 12, 585. Polarization factor K = 1.5. doi:10.1109/50.285349
- Kobyakov A., Sauer M., Chowdhury D. (2010). Stimulated Brillouin scattering in optical fibers. Adv. Opt. Photon. 2, 1. Review; depolarized pump K = 2. doi:10.1364/AOP.2.000001
- Agrawal G. P. (2019). Nonlinear Fiber Optics, 6th ed., §9.1 (Brillouin shift, gain g_B, linewidth). Academic Press. doi:10.1016/C2018-0-01168-8