Abstract

A record net gain of 22-dB and improved twice gain-per-unit length (GPUL) of 110 dB/m in a 13-μm core, 20-cm length, and 300-nm broadband single-mode Cr-doped crystalline core fibers (CCFs) are demonstrated by AI-assisted image recognition growth. The gain is significantly higher compared to the previous core of 25-μm. Both high gain and GPUL are achieved thanks to a novel AI-assisted, image recognition applied to the precise control of the molten zone with luminance of 2.39 cd/m² for fabricating smaller core diameter of 13-μm. The AI-assisted growth is performed by capturing images of the molten zone, RGB image recognition, luminance calculation, and real-time luminance adjustment within required value. The gain of several core diameters and fiber lengths has been thereafter simulated, which agrees with measured result. The smaller core of 13-μm exhibits higher coupling efficiency that is 65% the previous core of 25-μm. A lower noise figure of 4.2-dB is also obtained. In this study, the proposed CDFs looks promising for broadband fiber amplifiers.