Delay-disorder fiber Bragg grating recognition and calibration method for a Fourier domain mode-locked wavelength-swept laser-based interrogation system

Liang, Xiao; Li, Zhengying; Wang, Yiming; Hou, Yarong; Shen, Peng

doi:10.1364/ao.57.008148

Cited by 8 publications

(3 citation statements)

References 12 publications

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“…33,36 On the other hand, for distant FBGs, their reflection signals are folded back within the laser sweep period, hindering their identification. Methods for modulation of the laser sweep frequency 37 and pulse modulation of the laser swept light 38 have been reported for identification. However, no study is available on identification methods for buffered FDML laser, and highspeed measurements have not been achieved using this laser.…”

Section: Introductionmentioning

confidence: 99%

Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser

2022

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We propose a real-time measurement system that prevents overlapping reflection signals in fiber Bragg gratings (FBGs). The system combines a wavelength-swept laser using Fourier domain mode-locking (FDML) and a buffer stage with three optical paths to obtain a high-speed measurement rate of 304.2 kHz. Systems using high-speed wavelength-swept lasers are affected by the propagation time (delay) of the optical fiber. The delay causes problems such as inaccurate measurements, difficulty in distinguishing FBG reflection signals, and overlapping FBG reflection signals. To prevent these problems, we introduce a method for pulse modulation of a wavelength-swept laser by a fiber switch. This method allows for correction of delays by extracting and identifying only the reflection signal of the FBG at a specific wavelength. By identifying the reflection signals of all FBGs, the overlapping signals can be determined. Accordingly, we devise a measurement method that uses a fiber switch to shade light in the wavelength region of one FBG with overlapping signals from the wavelength-swept light of the laser. This method suppresses overlapping and allows only the reflection signal of the other FBGs to be extracted and demodulated. The proposed system uses bidirectional forward and backward scans with the wavelength-swept laser, such that the shaded FBG signals can be demodulated with either scanning direction. We demonstrate that the system using a threebuffered FDML laser can simultaneously measure the strain or vibration of FBGs installed at arbitrary distances.

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Section: Introductionmentioning

confidence: 99%

Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser

2022

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“…Our previous research proposed a method for correcting the delay with a bidirectional sweep of wavelength-swept lasers [28] [30]. To install FBGs at long distances or large intervals, correction methods by modulating the sweep rates of wavelength-swept lasers have been reported [33]. We introduced a delay correction method that used pulse modulation with wavelength-swept lasers to automatically recognize reflection signals from multiple FBGs installed at arbitrary long distances and removed delays [34].…”

Section: Introductionmentioning

confidence: 99%

High-Speed Interrogation System for Fiber Bragg Gratings With Buffered Fourier Domain Mode-Locked Laser

2021

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We develop a high-speed interrogation system with a wavelength-swept laser for sensing multiplexed fiber Bragg gratings (FBGs). High-speed and multipoint sensing is achieved by means of a buffered Fourier domain mode-locked (FDML) laser, a recently proposed high-speed wavelength-swept laser. This laser increases the measurement rate several times by tailoring the laser output with a buffer stage. The developed buffered FDML laser successfully achieves a measurement rate of 202.8 kHz using a general FDML laser driven at a sweep rate of 50.7 kHz. In order to detect reflection signals of FBGs at the high measurement rate, the measurement system introduces digital signal processing using a field programmable gate array (FPGA). However, FBG measurements with wavelength-swept lasers are affected by the propagation time (delay) in the optical fiber connecting from the laser to the FBG sensor, which reduces measurement accuracy. To overcome this limitation, the developed system uses a delay correction method with bidirectional sweep of the buffered FDML laser. The interrogation system with the buffered FDML laser achieves a time resolution of 4.9 µs without being affected by the delay.

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“…By solving this problem, the installation distance of the FBG sensor will not be limited; more flexible measurement will be possible, and application to a wider range of fields can be expected. To address this problem, a method has been proposed to drive a wavelength-swept laser at multiple sweep frequencies with the unidirectional sweeping [33].…”

Section: Introductionmentioning

confidence: 99%

Interrogation System With Automatic Recognition and Delay Correction Functions of Fiber Bragg Gratings by Pulse Modulation With Wavelength-Swept Laser

2019

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We propose an interrogation-system with automatic recognition and delay correction functions of fiber Bragg gratings (FBGs) by pulse modulation with a wavelength-swept laser. By pulse-modulating the light of a wavelength-swept laser, light with an arbitrary wavelength bandwidth can be extracted as the pulsed light. In the automatic recognition function of FBGs, the pulsed light is sequentially controlled to match the wavelength bandwidth of each FBG. This recognition method enables the selection and detection of a reflection signal from a single FBG. Therefore, reflection signals from multiple FBGs can be recognized individually. When multiple FBGs are installed at long distances, the reflection signal of each FBG is affected by the propagation time (delay). In the interrogation system with the wavelength-swept laser, the delay lowers the measurement accuracy. Therefore, a delay correction function using bidirectional sweeping of the wavelength-swept laser is used. The wavelength-swept laser using Fourier domain mode locking (FDML) is driven at a sweep frequency of 50.7 kHz with a sweep bandwidth of ∼60 nm. This study demonstrates that pulse-modulated FDML laser can automatically recognize reflection signals from multiple FBGs installed at arbitrary long distances. When the recognition process is complete, the interrogation system can perform real-time measurement with a time resolution of 9.9 µs, without being affected by delay that occurs when installing at a long distance.

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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

Cited by 8 publications

References 12 publications

Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser

Real-time measurement system for overlapping reflection signals of fiber Bragg gratings using high-speed wavelength-swept laser

High-Speed Interrogation System for Fiber Bragg Gratings With Buffered Fourier Domain Mode-Locked Laser

Interrogation System With Automatic Recognition and Delay Correction Functions of Fiber Bragg Gratings by Pulse Modulation With Wavelength-Swept Laser

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