There are multiple definitions:
Brillouin frequency shift(English)
- the frequency difference at which the maximum amplification of the Stokes wave occurs
- BOTDA
- Laser technique
- https://doi.org…mge.2015.01.008
best fit sphere(English)
- calculated at a fixed optical zone of 8.0 mm
- BAD_D
- Ophthalmology
- https://doi.org…ijo.IJO_2111_20