OPTIC FIBER WITH LOW LOSSES AT WAVELENGTH 1385 NM, METHOD OF MANUFACTURE THEREOF, AND MULTICHANNEL SYSTEM EMPLOYING SUCH FIBER Russian patent published in 2001 - IPC

FIELD: fiber optics. SUBSTANCE: rod of unimodal fiber is manufactured by method of axial precipitation from vapor phase. Ratio of outside sheath diameter to core of this rod does not exceed 7.5. Rod with core is dehydrated in chlorine- and fluorine-containing atmosphere at temperature near 1200 C in order to lower OH ion concentration to a value below 0.8 wt parts per 1 billion, after which rode is hardened in helium atmosphere at temperature near 1500 C to vitrify porous mass constituted by microparticles. Hardened rod is elongated with assistance oxygen-hydrogen burner to form OH ion layer on the surface of rod. Major part of this layer is removed from the rod surface during plasma etching process. After the latter operation, rode with core is inserted into glass tube with low OH ion content. Tube is squeezed to give blanc. The blanc is stretched out into optic fiber, which is covered by one or more protective sheathes. Fiber is characterized by losses at wavelength 1385 nm lowered to a level below that at wavelength 1310 nm, which enables use of all wavelength range from 1200 to 1600 nm for optical transmission and thereby provides conditions for creating multichannel spectral-compression systems capable of transmitting signals over a distance exceeding 10 km. EFFECT: improved performance characteristics. 12 cl, 9 dwg