Optical fiber distributed acoustic sensing based on NUFDM-NLFM

In the field of optical fiber distributed acoustic sensing, the combination of pulse compression and frequency division multiplexing will occupy a large bandwidth. In this paper, a novel distributed optical fiber acoustic sensor system is proposed, which can reduce the spectrum resources occupied by the combination of the above two technologies. The system continuously injects nonlinear frequency modulation detection pulses of different frequency ranges. The frequency response range of vibration is improved by frequency division multiplexing, and the spatial resolution is enhanced by nonlinear frequency modulation. Nonlinear frequency modulation also improves the sidelobe rejection ratio without loss of signal-to-noise ratio. In the experiment, eight frequencies were multiplexed using a 120MHz bandwidth. We achieved a spatial resolution of about 5m and a frequency response range of 1~20kHz on a 16.3km fiber.