  A novel Brillouin optical time-domain analysis (BOTDA) system is proposed
using intensity-modulated optical orthogonal frequency division multiplexing
probe signal and direct detection (IM-DD-OOFDM) without frequency sweep
operation. The influence of peak to average power ratio (PAPR) of OFDM probe
signal on the recovery of Brillouin gain spectrum (BGS) is analyzed in theory
and experiment. The complex BGS is reconstructed by channel estimation
algorithm and Brillouin frequency shift (BFS) is located by curve fitting of
intensity spectrum. The IM-DD-OOFDM BOTDA is demonstrated experimentally with
25m spatial resolution over 2 km standard single mode fiber.
