In this paper, the compensating scheme for the large noise induced by rainfall in the distributed optical-fiber vibration sensor engineering system (DFVSES) is proposed and demonstrated. DFVSES with rainfall compensation is made up of two subsystems using a common optical source and same optical circuit. Analyzing spectrum of the output signals under rainfall condition, and comparing the amplitude of the output signal for the sensing subsystem and the amplitude calculated from the amplitude of the output signal for the reference subsystem, the vibration can be got in the harsh climatic environments. We set up the experimental system, and the results show DFVSES with the scheme can effectively work under rainfall condition.
In this paper we propose and demonstrate the scheme of vibration pattern recognition and classification in the OTDR based distributed optical-fiber vibration sensing system. We set up the engineering system with signal processing PC for perimeter security in some high-tech park in Nanjing. Three types of disturbing actions, including climbing up and kicking at the wall by a person, and watering on the sensing optical fiber cable same as the rain falling on, are implemented. By using level crossing rate (LCR), we can obtain their individual pattern features, so that the eigenvalue database for three disturbing actions can be built in the system. By comparing three types of vibrations, the differences among these can be given out. The results show three vibration patterns can be recognized and classified effectively.
In this paper, the scheme for both reproducing vibration waveform and locating disturbed places in the OTDR based
distributed optical fiber vibration sensing systems is proposed and demonstrated. Based on the sampling law, the
vibration waveform is reproduced from the detecting pulses including original sensing signals by denoising selectively,
adjusting bias voltage and band-pass filtering. The vibrations at the frequencies of 500Hz and 1000Hz have been
experimentally located and reproduced, respectively, and the highest frequency of 1 kHz for reproducing
vibration waveform is realized at the repeat frequency of 2 kHz for the laser.