Additive Manufacturing Fiber Preforms for Structured Silica Fibers with Bismuth and Erbium Dopants

Dear Editor Silica optical fibers have attracted a lot of attention because they are widely used in communications and sensing, and forming today’s internet backbone. Driving much of the Internet-of-Things (IoT) evolution, optical fibers are expanding from a single function transmission technology to perform multiple functions and a growing need for various custom-design application-specific optical fibers. Current optical fiber manufacturing based on chemical vapor deposition (CVD) technologies together with stack-and-draw approaches used for structured optical fibers faces numerous challenges in enabling more complex geometries multimaterial composite fibers and multicore fibers. The additive manufacturing, or 3D printing, offers a solution to address all those challenges, and may potentially disrupt the optical fibers fabrication and bring in an evolution to IoT. The additive manufacture of optical fiber preforms and optical fiber has recently been proposed and demonstrated. A key challenge of 3D printing-based silica optical fibers is the high processing temperatures of silica glass that conventional top down approaches demand. For this reason, we exploited and extended recent reports of small-scale glass “bulk or slice ” printing beyond a few millimeters to centimeters to demonstrate it was possible to additively manufacture optical fibers. Further, various active dopants were introduced. These include oxides and ions of bismuth and erbium to create additively manufactured bismuth and erbium co-doped optical fiber (BEDF). These fibers are known to have an ultra-broadband near infrared (NIR) luminescence covering the whole telecommunications O-L bands with 830 nm pump excitation, potentially appearing to be a promising active medium of fiber amplifiers for the next generation of fiber communication system. In this letter, we report BEDFs with one and seven cores drawn from 3D printed preforms. The capability of 3D printing technology to produce complex and arbitrary fiber structures was demonstrated without the necessary timeconsuming separation and integration processes involved in the traditional preform manufacture. In addition, a range of dopants, namely Bi, Er, Ge, Ti and Al are introduced, further proving its diverse materials manufacturing capability. Care is needed in adjusting drawing conditions and method as the number of cores increases, leading to effective lower melting points in the preform. As reported in ref. 16, the fabrication of 3D printed preforms involved five steps: (1) preparing UV sensitive resin embedded with amorphous silica nanoparticles; (2) printing designed preform utilizing a commercial DLP 3D printer; (3) filling the prepared resin into the holes of the