Abstract
As a fully distributed sensor, the phase-sensitive optical time domain reflectometer (φ-OTDR) has attracted remarkable attention in real-time vibration detection. We present a dual-channel φ-OTDR (DC-φ-OTDR), formed by two single-channel φ-OTDRs (SC-φ-OTDR), to monitor running vehicles on a highway. In the double-channel system, an improved algorithm (will be referred to as the CDM&V) is proposed to alleviate the strong dependence of vibration detection on the differential step as in the widely used conventional differential method (CDM). The DC-φ-OTDR is first tested over campus road before applying it to locate moving vehicles on the highway. For comparison purposes, both the DC-φ-OTDR and SC-φ-OTDR are used to monitor the vehicles with respective signal processing methods of the CDM and CDM&V. The experimental results at campus show that the dual-path scheme can undoubtedly reduce vibration misjudgment relative to the single one due to the very small possibility of false measurements occurred simultaneously at the same location in both channels. In signal demodulation, the CDM&V greatly relaxes the constraints on the differencing interval for identifying the vehicle-caused vibration. With a step size of 5 or lower, the CDM fails to locate the running vehicle at z=~8.5 km, but the CDM&V successfully demonstrates the feasible capability of locating the vibration. With an increase in the differential interval, both the CDM and CDM&V are able to detect the vibration signal, but with the latter showing a much better noise suppression performance and hence a larger SNR. Importantly, in comparison with the SC-φ-OTDR system, the DC-φ-OTDR exhibits a considerable enhanced SNR for the detection signal regardless of which processing algorithm (i.e., CDM, CDM&V) is used. The vehicle locations positioned by the DC-φ-OTDR are confirmed by the monitoring cameras.
Highlights
Highway is playing an increasingly important role in economic growth for any country
The noise level could be further suppressed for k = 30 by the conventional differential method (CDM)&V as seen in the third column of Figure 5. These results demonstrate the powerful capability of the DC-φ-OTDR in terms of positioning the moving vehicles on the highway with a considerably improved SNR, which are in accordance with those concluded over the campus road
The work successfully demonstrates a DC-φ-OTDR to locate the vehicles on the highway
Summary
Highway is playing an increasingly important role in economic growth for any country. Phase-sensitive optical time domain reflectometry (φ-OTDR) is the most commonly utilized Rayleigh-based DOFS owning to φ-OTDR offers a much higher sensitivity to external vibrations In this technique, an ultra-narrow linewidth laser pulse is launched into the sensing fiber, any mechanical vibrations would change the coherent interaction over a great number of Rayleigh scattering units within a pulse duration. The second is the noises from temporal intensity fluctuation of laser pulses, laser phase noise and photodetector thermal and shot noise Both reduce the signal-to-noise (SNR) of the time-domain traces in SC-φ-OTDR, leading to a decreased sensitivity to vibration events and an increased probability of unreliable vibration measurements. We firstly validate the DC-φ-OTDR on a campus road, and apply it to monitor the running vehicles on the highway along a 9 km-long armored cable
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
