Optically active nanoparticles-embedded optical fiber for random fiber laser distributed sensor

This paper presents the development of a multifunctional photonic device using nanoparticle (NP)-doped fiber as an optical amplification medium and distributed sensing element simultaneously. The proposed system comprises a linear cavity Random Fiber Laser (RFL) in which the NP-doped fiber is used as an amplification medium due to the erbium ions in the NP composition and a distributed cavity due to the enhanced Rayleigh scattering of the fiber. In this case, the RFL is employed as a distributed sensor by means of localized changes on the optical transmission and reflection signals when temperature and strain are applied along the NP-doped fiber. The proposed RFL is analyzed in terms of stability and configurations. In this case, the RFL demonstrated a maximum output power of around 17 mW with a power stability demonstrated by 0.07 nm variations in wavelength stability tests. The RFL distributed sensor validation, and the sensor system was submitted to simultaneous variation of temperature, strain, and location of the mechanical disturbance, where the Random Forest machine learning method was employed for the simultaneous assessment of all three parameters. The results show high accuracy of the sensor system, where relative errors of 0.02%, 2.0%, and 5.3% were found for temperature, strain, and location of strain application along the laser cavity, respectively. Therefore, the proposed RFL distributed sensor is a feasible solution for dynamic monitoring of different physical parameters, which can close the gap between the distributed optical fiber sensors and applications that require lower cost and high portability.