Silica microstructured optical fiber with centralized inclusion of seven GeO2-doped capillaries and induced twisting. Part I: fabrication of pilot samples

Abstract

This work introduces first time fabricated spun silica microstructured optical fiber (MOF) with inclusion of seven GeO2doped capillaries, placed in the central part of MOF cross-section, and induced twisting up to 730 revolutions per meter. Part I discusses technological issues for manufacturing of described complicated twisted fiber optic structure, while Part II presents some results of test series, performed for successfully manufactured twisted MOF pilot samples with typical hexagonal geometry under hole radius 4.40 µm and pitch 9.80 µm, outer "telecommunication" diameter 125 µm, and center part, formed by seven hollow GeO2-doped ring cores with inner radius 2.50 µm, pitch 8.80 µm and refractive index difference n=0.030. Following measurements were performed: measurements of transmission spectra under various twisting order, far-field laser beam profiles, some attempts of fusion splicing of typical telecommunication optical fibers and fabricated MOF with insertion loss estimation, and spectral response measurements of both single and group WDM (Wavelength Division Multiplexing)-channels of commercially available telecom WDM-system under inclusion of 2 m length MOF into various spans of short-range lab fiber optic link.