Stimulated Brillouin Scattering, a nonlinear process in which intense, narrow-linewidth light generates an acoustic wave that reflects light backward, frequency-shifted by about 11 GHz at 1550 nm or 16 GHz at 1064 nm. Above threshold most of the power is sent back toward the source, often as violent pulses that destroy components. Threshold drops with longer fiber and narrower linewidth, so single-frequency amplifiers broaden the seed or use short, large-core fiber.
Backward power jumped and the isolator got hot, we hit SBS, turn up the phase modulation before trying that power again.
Broadening a single-frequency seed with a phase modulator to a few GHz raises the SBS threshold several-fold, at the cost of coherence length.
Also heard as
- stimulated Brillouin scattering
- Brillouin
Related terms
Linewidth
The spectral width of a single-frequency laser's output, usually given in Hz, kHz or MHz at half maximum.
LMA
Large Mode Area: fiber with an enlarged core that spreads light out to raise nonlinear and damage limits.
Optical isolator
A one-way valve for light that passes a beam forward and blocks reflections from returning to the laser.
Fiber laser
A laser whose gain medium is an optical fiber with a rare-earth-doped core, pumped by diodes.