Aircraft Detection Using Phase-Sensitive Optical-Fiber OTDR

Aircraft detection plays a vital role in aviation management and safe operation in the aviation system. Phase-Sensitive Optical Time Domain Reflectometry (Φ-OTDR) technology is a prevailing sensing method in geophysics research, structure inspection, transportation detection, etc. Compared with existing video- or radio-based detection methods, Φ-OTDR is cost-effective, suitable for long-distance detection, and resistant to severe weather conditions. We present a detection system using Φ-OTDR technology and analyze the character of the acoustic signal of aircraft. Instead of runway monitoring in the airport or noise detection in the air, this study focuses on the detection of seismic vibration signal excited by the sound of aircraft. The Chebyshev filter is adopted to eliminate the impact of background noise and random noise from the original vibration signal; the short-time Fourier transform is used for time-frequency analysis. The experimental results showed that the seismic vibration signal excited by the aircraft sound is mainly low-frequency, which is under 5 Hz. Time delay of aircraft vibration signal in different locations of the optic fiber is recorded by the sensing system. The Doppler effect is also revealed by the time-domain analysis: the frequency increases when the aircraft is approaching and decreases when the aircraft moves away.

GEOECOLOGICAL RISKS OF TECHNOGENIC NOISES AT LOW FREQUENCIES

The article considers the estimation and prevention problem of ecologically dangerous influence of technogenic noises generated by moving transport, such as heavy tracked and wheeled transport, railway transport. The influence on the man and the environment of a low-frequency controlled CV-40 seismic vibrator [1] used for seismological research separately is considered. The influence of vibrations located in the area of low and infra-low frequencies is estimated. The field records of technogenic noises are analyzed. Numerical analysis and estimation of levels of geoecological risks associated with seismic vibration in the ground and acoustic oscillations in the atmosphere are presented. Spectral and spectral-time analysis of technogenic noises records are performed. The main ecologically dangerous frequency areas, which are the most characteristic for these sources, are separated. The dynamics of changes of the vibration velocity level over distances for heavy wheeled and tracked types of transport has been determined.