Engineering nanoparticle features to tune Rayleigh scattering in nanoparticles-doped optical fibers

Abstract

Rayleigh scattering enhanced nanoparticles-doped optical fibers are highly promising for distributed sensing applications, however, the high optical losses induced by that scattering enhancement restrict considerably their sensing distance to few meters. Fabrication of long-range distributed optical fiber sensors based on this technology remains a major challenge in optical fiber community. In this work, it is reported the fabrication of low-loss Ca-based nanoparticles doped silica fibers with tunable Rayleigh scattering for long-range distributed sensing. This is enabled by tailoring nanoparticle features such as particle distribution size, morphology and density in the core of optical fibers through preform and fiber fabrication process. Consequently, fibers with tunable enhanced backscattering in the range 25.9–44.9 dB, with respect to a SMF-28 fiber, are attained along with the lowest two-way optical losses, 0.1–8.7 dB/m, reported so far for Rayleigh scattering enhanced nanoparticles-doped optical fibers. Therefore, the suitability of Ca-based nanoparticles-doped optical fibers for distributed sensing over longer distances, from 5 m to more than 200 m, becomes possible. This study opens a new path for future works in the field of distributed sensing, since these findings may be applied to other nanoparticles-doped optical fibers, allowing the tailoring of nanoparticle properties, which broadens future potential applications of this technology.

Toward Engineered Nanoparticle-Doped Optical Fibers for Sensor Applications

“…Another approach which can be used to control the size of the nanoparticles is to increase the drawing temperature. It has been reported that by heating up to 100 or 200 °C above the usual drawing temperature allows reducing the size of the nanoparticles (Fuertes et al, 2021). Here, the dissolution mechanism would occur.…”

“…Actually, nanoparticle morphology can change vastly during the fiber drawing process. In particular, nanoparticles can elongate (Vermillac et al, 2017b;Fuertes et al, 2021). This phenomenon provides us a way to regulate their size distribution by inducing breakups of the elongated particle threads.…”

Narrow-Linewidth Er-Doped Fiber Lasers With Random Distributed Feedback Provided By Artificial Rayleigh Scattering

“…To create a compact artificial Rayleigh scattering fiber, we applied the femtosecond laser direct writing technique allowing for the distributed modification of refractive index inside transparent materials [19]. This approach has been previously shown to be a good alternative to nanoparticle-doped fibers [20], due to the possibility to induce scattering structures with arbitrary geometry in almost any type of optical fiber without violating the integrity of the protective coating. In terms of structural changes inside the material, the significant enhancement of scattering in the femtosecond laser exposure region is the result of the formation of nanogratings with typical crack thickness of ~1~10 nm and periods of ~100 nm, which has been previously studied using scanning electron microscopy and demonstrated in a number of papers [21][22][23].…”

Physics and applications of Raman distributed optical fiber sensing

“…Based on the features of fiber scattering, the optical fiber sensing technology can be classified into Rayleigh fiber sensing, Brillouin fiber sensing and Raman fiber sensing. Among these, the Rayleigh optical fiber sensing is commonly used to detect attenuation characteristics 17 , 18 and vibrations (phase optical time domain reflection sensing 19 ) of the optical fiber. Brillouin optical fiber sensing can measure the temperature and strain distribution along the optical fiber 20 – 24 , and can obtain a high spatial resolution for long sensing distances.…”