Abstract
Under realistic scenarios, more fiber Bragg gratings (FBGs) are always expected to be multiplexed in one sensor array to share the expensive optical components and electrical devices. However, either the sensing number or the interrogation frequency is limited in previous works due to the huge amount of data generated from large-scale sensing arrays. This paper presents a field-programmable gate array (FPGA)-based dynamic wavelength interrogation system for thousands of identical FBGs. With the advantages of parallel controlling and pipeline processing, FPGA can accelerate the data-processing rate of the wavelength interrogation, realizing a continuous-running and real-time sensing system. The signal-processing system precisely synchronizes the generation of interrogation pulses, the acquisition of reflected signals, and the processing of the wavelength-related data, making the interrogation frequency fundamentally limited by the round-trip time of light pulses traveling in the fiber. Multiple sensing arrays can be independently carried out simultaneously, affecting hardly the interrogation frequency. Experimental results show that over 4000 FBGs with a 3-m spatial resolution in four channels are interrogated with a 150-Hz sensing frequency, 3-nm dynamic range, and ±5.9-pm sensing precision, greatly improving the interrogation frequency while ensuring the multiplexing number.
Highlights
Fiber Bragg grating (FBG) sensors have been widely used to measure the temperature, strain, and vibration distributions of civil and industrial infrastructures for structural health monitoring due to their simplicity, corrosion resistance, immunity to electromagnetic interference, and multiplexing capacity [1,2,3,4]
We demonstrate a real-time interrogation of four-channel sensing arrays, each containing over 1000 FBGs along a 3-km distance, and the sensing frequency is 150 Hz with a 3-nm dynamic range and ±5.9-pm precision
The design contains the functional modules with carefully optimized pipeline architecture: the signal-conditioning module, the FBG location module, the wavelengthinterrogation module, and the LabVIEW-based software (LBS) module
Summary
Fiber Bragg grating (FBG) sensors have been widely used to measure the temperature, strain, and vibration distributions of civil and industrial infrastructures for structural health monitoring due to their simplicity, corrosion resistance, immunity to electromagnetic interference, and multiplexing capacity [1,2,3,4]. For some specific applications, such as the modal frequency measurement of bridges [3], impact localization in the plate structure of ships [8], and micro-seismic monitoring [9], large multiplexing capacity and high-speed responses are desired To achieve this goal, the interrogators have to be able to measure and track the reflected peak wavelengths from a large-scale multiplexed array as fast as possible. Conventional peak-detection techniques proposed in the literature, such as the maximum detection, the centroid detection, and the polynomial fitting algorithms, are fast and easy to implement and have been widely used to determine the wavelength of FBGs [16,17,18] They are affected by wavelength resolution and the signal-to-noise (SNR) ratio of the system. The system can be updated to support more channels with few changes
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
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 call
