Abstract
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 $9.9~\mu \text{s}$ , without being affected by delay that occurs when installing at a long distance.
Highlights
O PTICAL fiber sensors have proven to be effective in infrastructure sensing because of their excellent performances such as high resistance to electromagnetic noise, high explosion resistance, and low loss [1]
The light of the Fourier domain mode locking (FDML) laser amplified by the optical amplifier (OAMP) was incident on an optical spectrum analyzer (OSA) via the fiber optical switch (FSW)
The above results show that the interrogation system automatically recognized reflection signals from multiple fiber Bragg gratings (FBGs) installed at arbitrary long distances by the pulse-modulated FDML laser
Summary
O PTICAL fiber sensors have proven to be effective in infrastructure sensing because of their excellent performances such as high resistance to electromagnetic noise, high explosion resistance, and low loss [1]. Interrogation systems must install a recognition method that can recognize the reflection signal from the FBG with a delay of multiple cycles 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. 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]. When the recognition process is complete, the interrogation system can simultaneously measure reflection wavelengths of multiple FBGs installed at arbitrary distances at a time resolution of 9.9 μs, without being affected delay
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
