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Microstructured optical fibers (MOFs) as a novel type of light guiding media typically combine structural elements with very different chemical and optical behavior, e.g. silica - air, silica - high refractive index glasses. The applicative potential is very manifold: devices for telecommunication, nonlinear optics, sensing devices, fiber based gas lasers, etc. We report about preparation and characterization of selected total internal reflection (TIR) guiding MOFs: Air Clad Fiber, Suspended Core Fiber and heavy metal oxide (HMO) glass core MOFs. We fabricated Air Clad Fibers with extreme air fraction. The bridge width of about 0.13 m corresponds to a numerical aperture (NA) of about 0.6. Suspended core fibers for evanescent sensing were prepared by pressurized drawing of arrangements of three and four capillaries. By inflating the cavities the NA was increased up to 0.68. Material combined MOFs were prepared for nonlinear application (e.g. supercontinuum generation) with lanthanum aluminum silicate glass core. Thermochemical and optical behaviors of high nonlinear core glass candidates were investigated for alumina concentration up to 20 mol% and lanthanum oxide concentration up to 24 mol% in silica matrix. The manufactured HMO glass core MOF with a La2O3concentration of 10 mol% shows a similar background loss level like the unstructured HMO glass fiber about 1 dB/m.

Silica based microstructured holey fibers offer the possibility for filling with unconventional fiber materials. Of special interest are chalcogenide glasses due to their high refractive index and their nonlinear optical properties. We demonstrate two types of fibers: an index guiding fiber type with high-index glass core and silica cladding and a fiber with silica core surrounded by a periodic, hexagonal high-index glass structure giving antiresonant guiding properties. We prepared such fibers filled with arsenic sulphide glass and arsenic selenide glass by a pressurized infiltration technique. The manufacturing process is modelled on the basis of viscous glass flow parameters and is compared with experimental results obtained from the filled fibers. The propagation and spectral transmission properties of such fibers are measured and discussed.

The major challenge in the development of monolithic kW class CW fiber lasers is the efficient conversion of pump photons into a high brightness laser beam under the constraints of heat management, long term stability and nonlinearities. This article reviews the interaction of some fiber related aspects as e.g. fiber core composition, photodarkening and modality, as well as their influence on system complexity and power scalability. Recent work on active fibers, pump couplers, mode field adaptors and other fiber-optic components will be presented.