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Proceedings Paper

Φ-OTDR signal amplification
Author(s): Petr Munster; Josef Vojtech; Petr Sysel; Radim Sifta; Vit Novotny; Tomas Horvath; Stanislav Sima; Miloslav Filka
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Paper 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 1st 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.

Paper Details

Date Published: 5 May 2015
PDF: 9 pages
Proc. SPIE 9506, Optical Sensors 2015, 950606 (5 May 2015); doi: 10.1117/12.2179026
Show Author Affiliations
Petr Munster, Brno Univ. of Technology (Czech Republic)
Josef Vojtech, CESNET z.s.p.o. (Czech Republic)
Petr Sysel, Brno Univ. of Technology (Czech Republic)
Radim Sifta, Brno Univ. of Technology (Czech Republic)
Vit Novotny, Brno Univ. of Technology (Czech Republic)
Tomas Horvath, Brno Univ. of Technology (Czech Republic)
Stanislav Sima, CESNET z.s.p.o. (Czech Republic)
Miloslav Filka, Brno Univ. of Technology (Czech Republic)

Published in SPIE Proceedings Vol. 9506:
Optical Sensors 2015
Francesco Baldini; Jiri Homola; Robert A. Lieberman, Editor(s)

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