Abstract
Recently, phase-sensitive Optical Time-Domain Reflectometry (Φ-OTDR)-based vibration sensor systems have gained the interest of many researchers and some efforts have been undertaken to push the performance limitations of Φ-OTDR sensor systems. Thus, progress in different areas of their performance evaluation factors such as improvement of the signal-to-noise ratio (SNR), spatial resolution (SR) in the sub-meter range, enlargement of the sensing range, increased frequency response bandwidth over the conventional limits, phase signal demodulation and chirped-pulse Φ-OTDR for quantitative measurement have been realized. This paper presents an overview of the recent progress in Φ-OTDR-based vibration sensing systems in the different areas mentioned above.
Highlights
Owing to their insensitivity to electromagnetic interference, corrosion resistance, electrical insulation, intrinsic safety, good concealment, low cost, etc., optical fiber sensors have demonstrated their superiority over other existing types of sensors [1,2]
The Φ-OTDR sensor systems were limited by a low signal-to-noise ratio (SNR), reduced dynamic range (DR), spatial resolution (SR) in the range of tens of meters, a tradeoff between the frequency response bandwidth and sensing range, and the nonlinear relationship between the detected vibration and the optical intensity signal, which hindered the use of Φ-OTDR systems for quantitative vibration measurements [6,7,8]
As the important thermal noise in the high-bandwidth PD used in the chirped-pulse Φ-OTDR system can facilitate the relative intensity noise transfer from the Raman pump to the detected signal associated with the necessity to avoid the nonlinear effects of the modulation instability, there is need to pay careful attention to the optical pulse peak-power and the Raman pump powers
Summary
Owing to their insensitivity to electromagnetic interference, corrosion resistance, electrical insulation, intrinsic safety, good concealment, low cost, etc., optical fiber sensors have demonstrated their superiority over other existing types of sensors [1,2]. Among the various optical fiber sensors, the phase-sensitive Optical Time-Domain Reflectometry (Φ-OTDR)-based sensor system has attracted much more interest for use as a dynamic vibration sensor because of its high sensitivity, large dynamic range, full distribution, simple configuration and relatively easy processing scheme. These types of sensors find applications in the fields of security such as monitoring pipelines, national borders, military bases, state buildings, prisons, embassies, seismic wave detection, etc. In order to enhance the system performance, many research works have applied different techniques and signal processing methods to push the limitations imposed on Φ-OTDR systems by such factors
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