Abstract
Distributed fiber optic sensor for multi-parameter measurements plays a crucial role in various applications. In this work, distributed temperature/vibration fiber optic sensor with high precision and wide bandwidth is proposed and experimentally demonstrated. To improve the signal-to-noise ratio (SNR) and sensitivity of the system, the backscattering enhanced optical fiber (BEOF) is employed to provide strong and stable sensing signal. With the assistance of the coherent phase detection, a high precision measurement of phase can be achieved. In addition, the wavelet packet decomposition algorithm is put forward to effectively discriminate the quasi-static temperature and dynamic vibration signals. In the experiment, wide bandwidth vibration signal from 0.01 Hz to 20 kHz can be successfully detected. Owing to the high sensitivity of the system, the local temperature change within the range of only 10 cm can be captured with high precision of 0.095 °C. Besides, the system has a good capability of fast response to the external temperature variation where the response time is around 0.3 seconds, which is meaningful for the early warning of centimeters-level sized fire source in the special oil and gas pipelines monitoring applications.
Highlights
Integration of distributed temperature and vibration fiber optic sensing systems are becoming a pressing requirement in the industrial infrastructure monitoring [1], [2]
The system has a good capability of fast response to the external temperature variation where the response time is around 0.3 seconds, which is meaningful for the early warning of centimeters-level sized fire source in the special oil and gas pipelines monitoring applications
The backscattering enhanced optical fiber (BEOF) contains a series of consecutive backscattering enhanced points (BEPs) as shown red dots in Fig. 1(a), which is fabricated by laser exposure processing along the longitudinal direction of fiber
Summary
Integration of distributed temperature and vibration fiber optic sensing systems are becoming a pressing requirement in the industrial infrastructure monitoring [1], [2]. Yonas Muanenda et al integrated φ-OTDR with R-OTDR to achieve the up to 500 Hz vibration detection and the temperature resolution of 0.5 °C at 5 km SMF with 5 m spatial resolution [10] These sensors could not meet requirement for accurate measurement of temperature in some special security monitoring applications. By mean of the measurements of local birefringence and local φ-OTDR frequency shift, a distributed temperature and strain sensor with high precision of 0.04 °C/0.5 με along a 100 m-long polarization maintaining fiber has been experimentally demonstrated [12] These methods have an advantage in high precision measurement of temperature, it is difficult to realize the kHz-level vibration measurement due to a frequency-sweep processing in the demodulation. Temperature variation applied on short fiber length of only 10 cm can be successfully captured with high precision of 0.095 °C and fast response time approximately 0.3 seconds
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