Fundamental DATS Sensor Numerical Model for High- and Low-Frequency Stimuli

Distributed Acoustic and Temperature Sensing (DATS) uses Rayleigh backscattering and coherent light pulses to monitor dynamic temperature and vibration over several kilometers. This paper introduces and validates a model for describing the input-output behavior of a DATS system based on heterodyne detection scheme. The model encompasses not only the description of optical paths and signals but also the data processing involved to obtain useful and measurable signals, thus being a more complete description of coherent Φ-OTDR based DATS. Simulation results are validated by physical experiments with DATS system, a commercial fiber stretcher and a thermal bath. For vibration analysis, the model was evaluated under three strain intensities, showing compatible theoretical, simulated, and experimental results. Tests with a frequency sweep from 100 Hz to 1 kHz, confirmed the consistency between simulation and experiment. A simulation of temperature variation of 2 Kelvin in a 60-meter fiber section was also performed, which yielded results consistent with the experiment. The complete input-output model is simple and provides reliable results, making it wellsuited for temperature and vibration simulations, which can precede equipment deployment in several applications.