Frequency Response Enhancement by Periodical Nonuniform Sampling in Distributed Sensing

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Abstract
The sensing fiber length and the use of averaging methods limit the maximum detectable frequency response range of vibration in phase-sensitive optical time domain reflectometry (φ-OTDR), especially for long-haul monitoring. We propose a method to significantly extend the frequency response range of φ-OTDR systems by impressing vibration signals on a set of backscattering signals that are carried by different wavelengths within one measurement interval. The sampled traces are recombined into a trace group using a time multiplexing method, leading to higher effective sampling rate at each sensing point on the sensing fiber, which allows for a larger frequency response range. In experiments, two pulses carried by different wavelengths with a time delay of 0.75 μs are launched into a 3024-m long sensing fiber, and frequency response range of 30 kHz is realized. The system can overcome the tradeoff between the frequency response range and the sensing fiber length.
Funding Information
  • National Natural Science Foundation of China (61377066)
  • Fundamental Research Funds for the Central Universities (CDJZR12125502, 106112013CDJZR120002, 106112013CDJZR160006)

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