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High NA Single Mode Fiber.

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Final rept. 15 Sep 78-15 Mar 79,

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Single mode fibers offer a useful medium for new sensor applicatios based on optical phase change detection. Examples are the optical gyroscope and temperature and acoustic sensors. Many of these applications require the single mode fiber to be used in a tightly coiled configuration. One limiting factor in sensor development is that single mode fibers with a numerical aperture NA of less than .15 exhibit a sharp increase in attenuation when subjected to bending and microbending. To overcome this limitation, the development of a high NA greater than .15 single mode fiber was started under contract N00173-78-C-0196 to achieve improved handling and performance characteristics with respect to reduced bending and microbending losses. Single mode fibers with numerical apertures 0.2 were developed using core compositions of SiO2GeO2, SiO2GeO2P2O5, and SiO2PeO5 and a B2O3SiO2 cladding, and fabrication techniques were investigated which minimize the central index dip in the core of these fibers. The high NA fibers were evaluated for optical attenuation strung and spooled, at wavelengths of 0.63, 083 and 103 micron. In contrast to 0.1 NA single mode fibers which do not transmit when spooled, high NA fibers showed no significant attenuation increase when wound onto 10 cm diameter spools. Fiber attenuation was found to increase as a function of numerical aperture from 2.57 dBkm for a 0.1 NA fiber, to 16.6 dBkm for a 0.23 NA fiber at 0.83 micron evaluation wavelength. Selected single mode fibers showed variations in mean tensile strength from 1414 Nsq mm to 5413 Nsq. mm with N values of 7.5 and 55 respectively.

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  • Fiber Optics and Integrated Optics

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