Abstract
In this manuscript, an optically passive fiber Bragg grating (FBG) interrogation system able to perform high-frequency measurement is proposed. The idea is mainly based on the use of an arrayed waveguide grating (AWG) device which is used to discriminate the fiber optic sensor (FOS) wavelength encoded response under test in function of its output channels. As made clear by the theoretical model studied in the proposed manuscript, the Bragg wavelength shift can be detected as in linear dependence with the proposed interrogation function which changes with the voltage produced by two (or more) adjacent AWG output channels. To prove the feasibility of the system, some experimental analyses are conducted with a custom electrical module characterized by high-speed and low-noise operational amplifiers. As static measurements, three FBGs with different full width at half maximum (FWHM) have been monitored under wide-range wavelength variation; while, as dynamic measurement, one FBG, glued onto a metal plate, in order to sense the vibration at low and high frequency, was detected. The output signals have been processed by a digital acquisition (DAQ) board and a graphical user interface (GUI). The presented work highlights the characteristics of the proposed idea as competitor among the entire class of interrogation systems currently used. This is because here, the main device, that is the AWG, is passive and reliable, without the need to use modulation signals, or moving parts, that affect the speed of the system. In addition, the innovative multi-channel detection algorithm allows the use of any type of FOS without the need to have a perfectly match of spectra. Moreover, it is also characterized by a high dynamic range without loss of sensitivity.
Highlights
The progress of technology utilized every day is based on many different physical phenomena that are possible to monitor due to specific sensors
- In order to achieve equivalent static state experimental characterizations, temperature solicitation was sensed by using three fiber Bragg grating (FBG) having three different full width at half maximum (FWHM) values. The aim of this experimental analysis is to prove that the interrogation capability with the proposed system is not depending on the FBG bandwidth. This peculiarity represents an advantage since, in the most employed interrogation systems based on the reconstruction of the FBG spectrum, a high FBG bandwidth may increase the uncertainty on the Bragg wavelength position
The capability to interrogate one or many fiber optic sensors with a system having a modular dynamic range has been investigated through a multichannel approach based on an arrayed waveguide grating (AWG) device
Summary
The progress of technology utilized every day is based on many different physical phenomena that are possible to monitor due to specific sensors. The FBG sensor is a diffraction grating created by modifying, in a controlled manner, the fiber core in a way to have a periodic perturbation of the refractive index These sensors work as an optical filter with a reflectance (usually Gaussian) characterized by a central wavelength called Bragg wavelength [1,2,3] which changes with temperature or strain variation. The light source is modulated in time changing in wavelength and the detection algorithm is based on the span time when the wavelength reflection occurs [17] This kind of interrogation has high accuracy and a higher cost, with a limit on the speed (best performances on static measurement). Other interrogation systems studied in literature are based on filtering [18], interference [19] or spectral imaging [20]
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.
