A Fiber Bragg Grating Interrogation System with Self-Adaption Threshold Peak Detection Algorithm

Abstract

A Fiber Bragg Grating (FBG) interrogation system with a self-adaption threshold peak detection algorithm is proposed and experimentally demonstrated in this study. This system is composed of a field programmable gate array (FPGA) and advanced RISC machine (ARM) platform, tunable Fabry–Perot (F–P) filter and optical switch. To improve system resolution, the F–P filter was employed. As this filter is non-linear, this causes the shifting of central wavelengths with the deviation compensated by the parts of the circuit. Time-division multiplexing (TDM) of FBG sensors is achieved by an optical switch, with the system able to realize the combination of 256 FBG sensors. The wavelength scanning speed of 800 Hz can be achieved by a FPGA+ARM platform. In addition, a peak detection algorithm based on a self-adaption threshold is designed and the peak recognition rate is 100%. Experiments with different temperatures were conducted to demonstrate the effectiveness of the system. Four FBG sensors were examined in the thermal chamber without stress. When the temperature changed from 0 °C to 100 °C, the degree of linearity between central wavelengths and temperature was about 0.999 with the temperature sensitivity being 10 pm/°C. The static interrogation precision was able to reach 0.5 pm. Through the comparison of different peak detection algorithms and interrogation approaches, the system was verified to have an optimum comprehensive performance in terms of precision, capacity and speed.

The Temperature Compensation of FBG Sensor for Monitoring the Stress on Hole-Edge

“…FBG sensors with two gratings were selected for the test, whose Poisson ratio is 0.25, the radius is 63.5 nm, and the temperature sensitivity coefficient is 23.5 pm/°C (sensitized fiber). For the interrogation of FBG sensor, the FBG interrogation system developed by our laboratory was utilized [30], the system was established with a FPGA+ARM integrated development platform (zynq7000). The frequency of FPGA is 100 MHz, the ARM is a dual-core processor and the frequency of each core is 866 MHz, the interrogation precision is 0.5 pm.…”

“…Thus, it is the best choice to realize and verify the effect of the decoupling algorithm described in this paper. The introduction and details can be found in the reference [30].…”

“…Through the comparison of fitting results, the variation of wavelength caused by temperature could be obtained. To monitor the stress of hole structure in aircraft, the compensation algorithm is implemented in the FBG interrogation system developed by our laboratory [30]. Results proved that the algorithm proposed can be integrated into FBG interrogator in practical application and has a high compensation precision.…”

Strain Transfer Characteristic of a Fiber Bragg Grating Sensor Bonded to the Surface of Carbon Fiber Reinforced Polymer Laminates

“…The interrogator SM-130 is the standard FBG interrogator, which is used to detect the signal of FBG sensors. The interrogation scheme of the SM-130 is based on the tunable Fabry-Perot filter [39]. The Fabry-Perot filter converts a broadband light into a single wavelength light to illuminate FBG sensors.…”

High precision uwCFBG wavelength calculation method based on correlation coefficient

“…Currently, two primary methods exist for detecting the center wavelength for FBGs. The first is the spectral maximum method, including the adaptive threshold method [13] and the Steger image correction method [14]. However, for the relatively plateaued peak of the chirped spectrum, there is a significant discrepancy between the maximum value and the center wavelength.…”