DFOS refers to Distributed Fiber Optic Sensing, which includes:
FBG: Fiber Bragg Grating
EFPI: Extrinsic Fabry-Perot Interferometer
OTDR: Optical Time Domain Reflectometry
OFDR: Optical Frequency-Domain Reflectometry
BOTDR: Brillouin Optical Time Domain Reflectometry
BOTDA: Brillouin Optical Time Domain Analysis
BOFDA: Brillouin Optical Frequency Domain Analysis
etc…
