Brillouin-Random Laser and Fiber Bragg Gratings for All-Fiber High-Resolution Sensing

This letter presents the development of a high-resolution all-fiber strain sensing system using a narrow linewidth Brillouin-random laser (BRL) in conjunction with a fiber Bragg grating (FBG). The so-called BRL-FBG sensor system is based on a Brillouin fiber laser with a linewidth narrowed by a random laser obtained with a nanoparticle (NP) doped optical fiber, especially manufactured for a higher Rayleigh scattering. The BRL results indicated a 74.68% reduction of the laser linewidth when the NP-doped fiber is used. Furthermore, the laser presented a power stability of 92.36%. Then, the BRL signal is fed to an FBG, subjected to small axial strain variation and the convolution between both signals result in the reflected optical power variations as a function applied strain, where a $0.05 \mu \epsilon$ strain sensing resolution is obtained. Thus, the proposed system can be employed on the high-resolution sensing of different physical parameters with potentially high acquisition frequency.