基于傅里叶域锁模波长扫描激光器的询问系统的延迟无序光纤布拉格光栅识别和校准方法。
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Delay-disorder fiber Bragg grating recognition
and calibration method for a Fourier domain
mode-locked wavelength-swept laser-based
interrogation system
XIAO LIANG,
1
ZHENGYING LI,
1,2,
*YIMING WANG,
1
YARONG HOU,
1
AND PENG SHEN
1
1
School of Information Engineering, Wuhan University of Technology, Wuhan 430070, China
2
National Engineering Laboratory for Fiber Optic Sensing Technology, Wuhan University of Technology, Wuhan 430070, China
*Corresponding author: zhyli@whut.edu.cn
Received 4 June 2018; revised 24 August 2018; accepted 1 September 2018; posted 4 September 2018 (Doc. ID 334303);
published 25 September 2018
Fourier domain mode-locking has been used in fiber Bragg grating interrogation for high-speed and long-distance
measurement. But the delays induced by long fiber between multisensors and interrogation systems result in
nonneglected wavelength error in this high-speed wavelength-swept system. More seriously, the cross-sweep cycle
and different distance delays may cause the delay-disorder problem which makes the system unable to determine
the order of the delayed peaks and unable to address the location of sensors with corresponding wavelength-
encoding characteristics. This paper proposes a novel delayed-peak recognition and calibration method in which
the laser works at four different scanning rates. We confirm the relationship between delayed peaks and sensors
with recognition parameters at two low rates and eliminate wavelength error at two high rates. Experimental
results show that this method recognizes the delayed peaks correctly and calibrates wavelength accurately with
error below 10 pm.
© 2018 Optical Society of America
OCIS codes: (060.3735) Fiber Bragg gratings; (140.4050) Mode-locked lasers; (280.0280) Remote sensing and sensors; (060.2370)
Fiber optics sensors.
https://doi.org/10.1364/AO.57.008148
1. INTRODUCTION
The fiber Bragg grating (FBG) has outstanding advantages such
as small size, resistance to electromagnetic interference, and
multiplexing capability in a single fiber [1], making FBG attract
considerable interest in measuring various physical quantities,
such as strain [2], temperature [3], and acceleration [4]. In par-
ticular, the application on vibration signal measuring of the
large-scale rotating machinery has received considerable interest
for fault diagnosis [5,6]. However, the high-frequency vibration
detection and the remote measurement capability for the large-
scale machinery raises a higher requirement for the FBG inter-
rogation system. Recently, the multiple FBG interrogation
system with ultrahigh speed and long-distance sensing has been
realized by using a Fourier domain mode-locked (FDML) laser.
Jung et al. [7] reported an ultrafast 31.3 kHz FBG sensor sys-
tem that operates in the 1.5 μm wavelength regions using
FDML as a high-speed wavelength-swept laser. Lee et al. [8]
developed the 1.3 μm FDML wavelength-swept laser operating
at a 40.6 kHz scanning rate. Kim et al. [9] realized a 30.8 kHz
high spe ed and 40 km long distance FBG sensor system.
Fernandez-Vallejo et al. [10]demonstrated2,100,and
200 km long-distance fiber laser systems for FBG demodulation.
In addition, wavelength division multiplexing (WDM) has been
used to compose an FBG array [7–10]. Due to the WDM ad-
vantage, in these FDML-based systems, FBG could be arranged
from short distance to long distance without spatial limit. This is
very convenient in practical engineering applications.
However, at high-speed wavelength sweeping, the difference
on round-trip delay of FBGs will cause unneglectable demodu-
lation error [11,12]. Currently, some novel methods have been
proposed to compensate the delayed FBGs. In our previous
work [11], we proposed an autocalibration method by switch-
ing two scanning speeds of a conventional wavelength-swept
laser to eliminate delay error. Additionally, a real-time delay
compensation in an FDML laser system is proposed by analyz-
ing the time differences between delayed FBG signals and non-
delayed Fabry–Perot etalon signals in the two scan regions with
opposite scan direction [12]. However, a new problem of
“delay-disorder” would make the previous compensation meth-
ods inapplicable. The delay-disorder problem occurs in two
kinds of practical engineering measurements: first, when
8148
Vol. 57, No. 28 / 1 October 2018 / Applied Optics
Research Article
1559-128X/18/288148-06 Journal © 2018 Optical Society of America
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