Understanding Hole Pattern Formation During Microstructured Optical Fiber Draw

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This proposal was submitted and funded in response to solicitation NSF 03-537 High Speed Optical Communications and Networks.Microstructured fibers, also known as holey or photonic crystal fibers, have strong potential as a critical enabling technology for ultra-high capacity optical communications. For example, air-cored fibers have dispersion and loss figures that are orders of magnitude below that of standard single mode fiber. However, current microstructured fibers are limited by high optical attenuation (1 dB/km) caused by uneven hole size and hole patterns in the fiber. This proposal focuses on understanding the hole pattern distribution of microstructured optical fiber being drawn from a preform. This fundamental understanding is achieved by establishing a relationship between the preform's temperature distribution, viscoelastic and surface tension effects that dictate the fiber's hollow microstructure. Since glass viscosity is exponentially dependent on temperature, slight temperature variations can significantly change hole size, placement, and stability, resulting in high optical loss and performance degradation. This proposal will study the neck down and stability of a hollow fused silica rod. This simplifiedmodel will provide necessary fundamental insight to pursue this program's long-term goals, which are to explore new methods and conditions for hole pattern formation, placement and control, and to provide the fiber-optics community with robust mathematical modeling tools to enable accurate simulation of microstructured fiber devices and systems. In this study, we will: (1) Measure and expand currently limited infrared optical properties of high temperature fused silica glass at OFS Laboratories; (2) Develop a comprehensive radiation heat transfer model for hollow collapsing cylinders that participate in thermal radiation transport; (3) Develop a comprehensive neck downmodel capable of predicting the temperature distribution, hole formation and stability during draw; and (4) Extensively validate predictions with draw experiments performed at OFS Labs.The project is being jointly sponsored by the Thermal Transport and Thermal Processing Program of the Chemical and Transport Systems Division and the GOALI (Grant Opportunities for Academic Liaison with Industry) Program of the Design, Manufacturing and Industrial Innovation Division.