Φ-OTDR signal amplification

Petr Munster; Josef Vojtech; Petr Sysel; Radim Sifta; Vit Novotny; Tomas Horvath; Stanislav Sima; Miloslav Filka

doi:10.1117/12.2179026

5 May 2015 Φ-OTDR signal amplification

Petr Munster, Josef Vojtech, Petr Sysel, Radim Sifta, Vit Novotny, Tomas Horvath, Stanislav Sima, Miloslav Filka

Proceedings Volume 9506, Optical Sensors 2015; 950606 (2015) https://doi.org/10.1117/12.2179026
Event: SPIE Optics + Optoelectronics, 2015, Prague, Czech Republic

Abstract

Phase-sensitive optical time-domain reectometry (Φ-OTDR) seems to be the most appropriate solution for acoustic vibration along standard optical fiber detection. In general the sensing system measures phase changes of the received Rayleigh back-scattered signal in the fiber. Since the back-scattered signal intensity is decreased about tens of decibels in comparison to the forward propagating pulse power level, the received signal power level is very low. That is why the main limiting parameter of the system is the power level of the back-scattered signal, which limits maximum achievable distance. For long reach sensing it is necessary to create high power optical pulses with short time-duration. Direct pulse amplification by erbium doped fiber amplifier (EDFA) is an issue because of the pulses low repetition rate. We have designed and verified a simple method using a holding beam for amplifying of pulses with low repetition rate by standard telecommunication EDFA booster instead of deployment of an expensive optical shutter. A second CW laser with a different wavelength for EDFA stabilization is used in our setup. Because a pulse losses its energy during propagation in the fiber and with longer distances by 1^st order Raman amplifier (RA). In telecommunications this amplifier is used to compensate for fiber losses. The second setup uses remote amplification by remotely pumped erbium doped fiber (EDF) placed after a few tens of kilometers of sensing fiber. A pump laser is placed in the transmitter part of the system from where EDF is pumped. In this paper, we present an overview of few techniques for Φ-ODTR signals amplification and their verification by measurement.

Citation Download Citation

Petr Munster, Josef Vojtech, Petr Sysel, Radim Sifta, Vit Novotny, Tomas Horvath, Stanislav Sima, and Miloslav Filka "Φ-OTDR signal amplification", Proc. SPIE 9506, Optical Sensors 2015, 950606 (5 May 2015); https://doi.org/10.1117/12.2179026

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