Abstract

Subject of study. An all-fiber grating sensor system has been applied to composite forming monitoring for real-time monitoring of the changes of temperature and strain in the forming process. The purpose of the work is the optimization of sensor parameters based on fiber-optic Bragg gratings by reducing the effect of photoelectric conversion errors during signal demodulation. Method. Two kinds of fiber gratings, including polarization maintaining fiber gratings, have been used as sensing elements and demodulation elements. The all-fiber sensing system for real-time monitoring of the composite forming process has been built. The system acquires the optical signals related to the parameters to be measured, records the optical power of the signal, and converts it to the wavelength shift in real time. The temperature and strain can be calculated in real time according to the wavelength. The fiber grating with a linear spectrum used as a linear demodulator is designed and developed by us. Main results. The demodulator has a linear demodulation in the range of 1544–1556 nm with a linearity of 2.21 dB/nm, and the sensor has a dynamic range of 1200°C and 11,000 µɛ. The experimental results show that the all-fiber grating sensor system we designed can clearly reflect the changes of temperature and strain of the composites during the forming process. In the steady state, the maximum temperature difference is less than 10°C, and the maximum strain difference is less than 100 µɛ, which is consistent with the actual situation. Practical significance. The demonstrated feasibility of the sensor system provides a new idea for demodulation and monitoring for the composite forming process. Through further optimization, it can realize more rapid and accurate real-time monitoring for the composite forming process.

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