Research of High-Speed FBG Demodulation System for Distributed Dynamic Monitoring of Mechanical Equipment

Abstract

This paper designs and implements the high-speed FBG demodulation system which can demodulate multiple FBG sensors (up to 64 sensors in series per channel) of 4 channels synchronously. The system is based on the method of tunable F-P filter. Both the nonlinear effect and the temperature drift effect of the F-P filter are eliminated by applying the triangular-like drive signal and reference channels. In addition, a high-speed adaptive algorithm for peak-find is designed for the system. The experiment results show that, for the whole system, the stability is 2 pm, the resolution is 1 pm, the linearity is 0.999, the measurement precision is 20 pm, and the demodulation frequency is 4 kHz. Consequently, the system is very suitable for distributed dynamic monitoring of complicated mechanical equipment.

Effects of fiber Bragg grating design on dual-grating demodulation performance

“…According to [14], strong, medium and weak modulation depth were defined as 1.2 × 10 −3 , 1.2 × 10 −4 , 1.2 × 10 −5 , respectively. The maximum reflectivity was 100%, so with coupled mode theory equation ( 10) can be acquired…”

“…For those various FBG sensors, there are several signal demodulation methods [13,14]. The simplest method uses a spectrometer.…”

High-Speed Mach-Zehnder-OTDR Distributed Optical Fiber Vibration Sensor Using Medium-Coherence Laser

“…Distributed optical fiber vibration sensors have received great attention over the past decades for their significant advantages in safety, fully distributed sensing, and large-scale monitoring [1][2][3][4]. It is used for a variety of applications including intruder security [5], structure health monitoring [6], mechanical fault diagnostics [7], and oil pipelines leakage monitoring [8], where the signal can be modeled as a spatially resolved temporal disturbance.…”

Performance Optimization Design for a High-Speed Weak FBG Interrogation System Based on DFB Laser

“…With the practical advantages of small size, light weight, multiplexing capability, and resistance to electromagnetic interference (EMI) [ 1 ], fiber Bragg grating (FBG) has received considerable interest in the application of mechanical monitoring [ 2 , 3 , 4 ]. However, high-frequency vibration, a key parameter of mechanical monitoring, can hardly be measured with FBG, as the FBG demodulation speed which is commonly below a few kHz in conventional demodulation technologies such as grating matching [ 5 , 6 ], charge-coupled device (CCD) array [ 7 ], and tunable Fabry-Pérot (F-P) filter [ 8 ].…”