High-Power Broadband Random Fiber Laser and High-Order Random Lasing Amplification for Long-Distance Large-Capacity High-Insertion Loss FBG Sensor Networks

Broadband light sources have important applications in optical sensing. Here, a 1.5 µm high-power broadband random fiber laser (RFL) based on supercontinuum (SC) generation is realized, for the first time. It is found theoretically that when both the dispersion parameter and slope of the laser fiber are small, while its Kerr nonlinear coefficient is large, the optical spectrum of the RFL can be broadened effectively. Thus, in the experiment, a 5.0 km G. 655 fiber is selected as the lasing medium, achieving a high-power output of 2.47 W, a 3-dB bandwidth of 20.40 nm with a flat spectrum and excellent stability. Such an output power is around 10 times higher than that of commercial amplified spontaneous emission (ASE) broadband light sources. Then, such a high-power broadband RFL is used in long-distance, large-capacity and high-insertion loss fiber Bragg grating (FBG) sensor networks for practical applications. In addition, to further enhance the sensing signal, a 1080 nm ASE pump is used to provide high-order random lasing amplification. As the results, one sensor network including 510 FBGs with a high-insertion loss of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>30 dB and a length of 87 km for electric powerline monitoring, and another sensor network containing 340 FBGs with a high-insertion loss of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula>20 dB and a length of 107 km for offshore wind turbine monitoring, are demonstrated, respectively. For both the FBG sensor networks, temperature and displacement sensing experiments are conducted, and excellent performances are achieved. In conclusion, such a combination of broadband RFL and high-order random lasing amplification provides a powerful way to realize FBG sensor networks where long-distance, large-capacity and high-insertion loss are essential.