Fabrication and characterization of negative curvature hollow core polymer optical fibers for near-infrared light guidance

Durgun, Engin
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Bilkent University
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Polymer optical fibers (POFs) have attracted significant attention for their short-distance data transmission, industrial automation, and chemical and biological sensing applications. The low cost, lightweight, flexibility, accessibility, and ease of material processing features of the polymers make them superior to their silica counterparts. Moreover, compared to conventional POFs, hollow core polymer optical fibers (HCPOFs) exhibit light guidance through the air, significantly reducing material absorption loss in the near-infrared (NIR) region. Structuring the cladding part with the appropriate fiber material can further modify the light-guiding properties of HCPOF with low transmission loss in NIR. Several methods have already been employed for the successful fabrication of POFs, but the possibility of fabricating intricate geometry-based HCPOFs with these approaches and optimization of fabrication methods are yet to be resolved. This study explored the stack and draw technique and fused deposition modeling (3D printing) approaches to find the fabrication feasibility of long-length and intricate geometry-based negative curvature-based HCMPOFs with two different polymeric materials. A detailed investigation was carried out on the modified thermal drawing process to achieve well-structured HCMPOFs directly drawn at high tension from the fabricated preforms. Moreover, during the thermal drawing, expansion and contraction of the core and cladding part of the fibers were frequently observed. Inflation of the cladding tubes during the fiber drawing was required to preserve the designed structure in the fibers. This was achieved by applying gas pressurization inside the fibers in both preforms made by the stack and draw technique and 3D printing. Optical characterization is performed using Supercontinuum (SC) Laser in the 600 − 1700 nm wavelength range. Differences in the transmission spectra between core and cladding structures significantly prove the light-guiding prop-erties of the proposed HCMPOFs. The transmission losses of the HCMPOFs were measured using Optical Spectrum Analyzer (OSA), and were found to average 49.26 dB/m for stack and draw-based fabricated six-tube HCMPOF and 16 dB/m for 3D printed six-pointed star cladding-based HCMPOF. Further investigation is carried out on bend-induced loss against the mechanical effects of the 3D printed intricate geometry-based HCMPOF at different bending angles. The lower transmission loss with a low bend-induced loss against the mechanical effects of HCMPOFs explicitly shows the potential of using HCMPOFs as an alternative to conventional polymer optical fibers for visible and infrared light guidance.

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Hollow-core negative curvature polymer optical fibers (NC-HCPOFs), Near-infrared (NIR), Stack and draw technique, Fused deposition modeling, Poly-carbonate, Transmission loss, Bend loss
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