Effects of pump pulse extinction ratio in Brillouin optical time-domain analysis sensors
Fecha
2017Autor
Versión
Acceso abierto / Sarbide irekia
Tipo
Artículo / Artikulua
Versión
Versión publicada / Argitaratu den bertsioa
Impacto
|
10.1364/OE.25.027896
Resumen
We report on two previously unknown non-local effects that have been found to impair
Brillouin optical time-domain analysis (BOTDA) sensors that deploy limited extinction ratio
(ER) pump pulses. The first one originates in the increased depletion of the pedestal of the pump
pulses by the amplified probe wave, which in turn entails a reduced amplification of the probe
and a measurement distort ...
[++]
We report on two previously unknown non-local effects that have been found to impair
Brillouin optical time-domain analysis (BOTDA) sensors that deploy limited extinction ratio
(ER) pump pulses. The first one originates in the increased depletion of the pedestal of the pump
pulses by the amplified probe wave, which in turn entails a reduced amplification of the probe
and a measurement distortion. The second effect is due to the interplay between the transient
response of the erbium-doped fiber amplifiers (EDFA) that are normally deployed to amplify the
pump and the pedestal of the pump pulses. The EDFA amplification modifies the pedestal that
follows the pulses in such a way that it also leads to a distortion of the measured gain spectra
after normalization. Both effects are shown to lead to non-local effects in the measurements
that have similar characteristics to those induced by pump pulse depletion. In fact, the total
depletion factor for calculations of the Brillouin frequency shift (BFS) error in BOTDA sensors
is shown to be the addition of the depletion factors linked to the pump pulse as well as the
pedestal. A theoretical model is developed to analyze both effects by numerical simulation.
Furthermore, the effects are investigated experimentally in long-range BOTDA sensors. The
pedestal depletion effect is shown to severely constrain the probe power as well as the minimum
ER of the pulses that can be deployed in BOTDA sensors. For instance, it is shown that, in
a long-range dual-probe BOTDA, an ER higher that 32-dB, which is above that provided by
standard electro-optic modulators (EOM), is necessary to be able to deploy a probe power of
-3 dBm, which is the theoretical limit for that type of sensors. Even more severe can be the
limitation due to the depletion effect induced by the EDFA transient response. It is found that the
impairments brought by this effect are independent of the probe power, hence setting an ultimate
limit for the BOTDA sensor performance. Experimentally, a long-range BOTDA deploying a
26-dB ER EOM and a conventional EDFA is shown to exhibit a BFS error higher than 1 MHz
even for very small probe power. [--]
Materias
BODTA sensors,
Pump pulses
Editor
Optical Society of America
Publicado en
Optics Express, Vol. 25, Issue 22, pp. 27896-27912 (2017)
Departamento
Universidad Pública de Navarra. Departamento de Ingeniería Eléctrica y Electrónica /
Nafarroako Unibertsitate Publikoa. Ingeniaritza Elektrikoa eta Elektronikoa Saila
Versión del editor
Entidades Financiadoras
Spanish Ministerio de Economía y Competitividad (TEC2013-47264-C2-2-R and TEC2016-
76021-C2-1-R); FEDER funds; Universidad Pública de Navarra; German Research Foundation
(DFG SCHN 716/13-1).