3D non-destructive observation of thermal diffusion coefficient in optical fibers

The thermal diffusion coefficient (TDC) is key to acknowledging the opto-thermo behavior of the fibers. Traditional TDC measurement methods are mainly characterized by fiber-destructive, performing strict ion tests on the fiber’s cross-section. The measurement process needs complex fiber alignment and makes it difficult to describe the internal opto-thermo evolution. In this paper, we propose a three-dimensional (3D) non-destructive TDC observation method and demonstrate a new simplified mathematical model that describes the temporal relationship between the TDC and the dopant ion profile (DIP) with a Gaussian approximation. The TDC is determined, and the 3D DIP variation is observed. Two fiber types are applied to validate the proposed model. The experimental result fits well with the theory. This not only aids in a deeper understanding of the thermal diffusion process of dopants within fibers but also significantly enhances the stability of fiber device manufacturing.