tailieunhanh - SELECTED TOPICS ON OPTICAL FIBER TECHNOLOGY_2

Optical fibers, an important and promising material, have been the subject of intensive research and development due to their many scientific and practical applications. They are designed to guide light along its length by confining as much light as possible in its core. The interaction between the propagating light with the fiber material is the foundation of the development of various applications such as optical amplifiers, fiber lasers, sensors etc. The use and demand for optical fibers have grown in tandem with numerous new applications that have been continuously introduced by researchers and engineers | Part 3 New Optical Fibers 15 Crystalline Plastic Optical Fiber with Excellent Heat-Resistant Property Atsuhiro Fujimori Saitama University Japan 1. Introduction General polymer crystals essentially both crystalline and amorphous regions. It is well known that crystalline polymers construct hierarchical structures ranging from lamellae on the nanometer scale to spherulite on the mesoscopic The polymer crystals in these crystalline polymers are generally formed by the folding of the main chain. In many cases since these folded parts and interspherulite chains form the amorphous region crystalline polymers are essentially intermingled states of the crystalline and the amorphous regions. Therefore crystalline polymers are not a suitable candidate for use in plastic optical fibers POFs and film-type optical waveguides FOWs because of the occurrence of light refraction at the crystalline amorphous interface. Consequently amorphous POFs lack heat resistance and dimensional stability. However if the construction of extremely homogeneous crystalline POFs is realized crystalline POFs with excellent heat resistance and dimensional stability can be developed. The heat-resistant POFs will efficiently demonstrate their optical ability in a circuit exposed to a high temperature of more than 125 C so far there have been no products of heat-resistant POFs that can sustain temperatures higher than 125 C. If the heat-resistant POFs are realized light wiring in automobiles will also be achieved the heatresistant POFs will not only connect the AV equipment but also connect the control system around the engine. As a result the overall body of an automobile will become lighter. This future technology is based mainly on crystalline fluorinated polymers having a high crystallinity. Generally polytetrafluoroethylene PTFE - CF2-CF2 n- and its copolymers easily form rigid helices in order to yield extended-chain crystals. It seems difficult for PTFE to form a lamellae structure .

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