High-Efficiency Random Fiber Laser Based on Strong Random Fiber Grating for MHz Ultrasonic Sensing
Liang Zhang, Ping Lü, Zichao Zhou, Yuan Wang, Stephen J. Mihailov, Liang Chen, Xiaoyi Bao
Abstract
An Erbium-gain random fiber laser based on a strong random fiber grating (RFG) is experimentally demonstrated and applied to MHz ultrasound wave detection. The strong RFG with up to −10 dB reflectivity as well as a highly-doped Erbium doped fiber (HD-EDF) enabled a highly efficient random laser radiation with 1-kHz narrow linewidth. With the RFG as the feedback and the sensing head, both burst and continuous ultrasonic signals of up to 8 MHz can be demodulated by dynamics analysis from the random lasing emission. Results show that the detected signal-to-noise ratio (SNR) of 5.1 MHz ultrasound signal remains larger than 43 dB. The proposed random fiber laser sensor provides a broad ultrasonic bandwidth, high sensitivity, simple structure, low cost and robustness to the harsh environment, suggesting prospective applications for ultrasonic wave-associated acoustic emission (AE) detection in structure health monitoring and biomedical diagnosis.