Abstract

The use of linearly chirped probe pulses in phase-sensitive optical time-domain reflectometry (ΦOTDR) technology has been recently demonstrated to allow for high-resolution, quantitative, and dynamic temperature or strain variation measurements in a simple and very robust manner. This new sensing technology, known as chirped-pulse ΦOTDR, had a maximum reported sensing range of 11 km. In this paper, a 75-km sensing range with 10-m spatial resolution is demonstrated by using bidirectional first-order Raman amplification. The system is capable of performing truly linear, single-shot measurements of strain perturbations with an update rate of 1-kHz and 1-nε resolution. The time-domain trace of the sensor exhibits a signal-to-noise ratio (SNR) in the worst point of >3 dB, allowing to monitor vibrations up to 500 Hz with remarkable accuracy. To demonstrate the capabilities of the proposed system, we apply <100 nε vibrations in the noisiest point of the fiber, with a frequency modulated from 70 to 150 Hz over a period of 10 s. The results obtained in these conditions demonstrate a vibration detection SNR of >20 dB (with only 300-ms analysis window and no postprocessing) and no evidence of nonlinearity in the acoustic response. The optical nonlinear effects that the probe pulse could suffer along the sensing fiber are thoroughly studied, paying special attention to potential distortions of the pulse shape, particularly in its instantaneous frequency profile. Our analysis reveals that, for proper values of peak power, the pulse does not suffer any major.

Single-shot distributed temperature and strain tracking using direct detection phase-sensitive OTDR with chirped pulses

J. Pastor-Graells, H. F. Martins, A. Garcia-Ruiz, S. Martin-Lopez, and M. Gonzalez-Herraez
Opt. Express 24(12) 13121-13133 (2016)

SNR enhancement in high-resolution phase-sensitive OTDR systems using chirped pulse amplification concepts

Juan Pastor-Graells, Luis Romero Cortés, María R. Fernández-Ruiz, Hugo F. Martins, José Azaña, Sonia Martin-Lopez, and Miguel Gonzalez-Herraez
Opt. Lett. 42(9) 1728-1731 (2017)

Quantitative measurement of dynamic nanostrain based on a phase-sensitive optical time domain reflectometer

Yongkang Dong, Xi Chen, Erhu Liu, Cheng Fu, Hongying Zhang, and Zhiwei Lu
Appl. Opt. 55(28) 7810-7815 (2016)

Optimization of long-range BOTDA sensors with high resolution using first-order bi-directional Raman amplification

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Opt. Express 19(5) 4444-4457 (2011)

Fiber-optic distributed acoustic sensor based on a chirped pulse and a non-matched filter

Dian Chen, Qingwen Liu, Yifan Wang, He Li, and Zuyuan He
Opt. Express 27(20) 29415-29424 (2019)