Non-Step-Scanning Rayleigh–Brillouin Distributed Fiber-Optic Sensing System Utilizing Double Sideband Modulation

The utilization of distributed fiber-optic sensing systems has become prevalent in monitoring both static parameters such as temperature or strain, and dynamic parameters like vibration. In order to measure multi-parameters simultaneously, we combine Rayleigh scattering and Brillouin scattering in a single sensing system. The time-gated digital optical frequency domain reflectometry is employed for vibration sensing and the Rayleigh backscattering of linear frequency modulation pulse is used as the probe of BOTDA for temperature sensing. The multi-frequency probe enables a non-step-scanning single-end BOTDA system. To simplify the hybrid system, we employ an intensity modulator for frequency modulation and pulse generation, replacing acousto-optic modulators. Both the positive and negative sidebands are received and modulated for demarcating static and dynamic parameters. This simplified system achieves sub-meter spatial resolution for vibration within a 12-km sensing range and offers a temperature measuring range of approximately 500
$^\circ \text{C}$
, which is also non-step-scanning and immune to coherent fading.