Abstract: A hollow core fiber exhibiting selective birefringence is provided. The selective birefringence is induced by harnessing properties of surface modes that cause transmission loss and are otherwise considered as detrimental. Birefringence and signal loss in a preferred polarization state are engineered by fabricating an asymmetrical web structure surrounding the core. In one implementation the asymmetry in the web structure is induced by a thicker core web preferably at the core inner cladding interface, by selectively introducing defect cells at the hollow core inner cladding interface. The hollow core fiber further includes shunt cores to facilitate near single-mode transmission by additionally using intermittent bend-induced index matching to resonantly couple unwanted core modes including one or more, higher order modes to shunt modes.

Abstract: A process produces a glass overcladding tube from a silica gel body. The process includes passing the gel body through a hot zone under conditions that cause partial sintering of the gel body and repassing the gel body through the hot zone under conditions that further sinter the gel body into a glass overcladding tube.

Abstract: The invention involves fabricating a ceramic tube, e.g., a silica overcladding tube, with very little bow, e.g., about 0.3 mm per meter or less. In particular, the invention involves securing the tube by a handle that both allows the tube to hang plumb during treatment, and also is capable of deforming during such heat treatment to maintain the plumb arrangement.

Abstract: A process deals with gaseous by-products and tarry materials during formation of sol-gel bodies. Gaseous products from a dehydroxylation reactor pass into a gas-fluid contactor. During the early stages of heat treatment, an aqueous acid solution is recirculated through the contactor to trap basic and/or water soluble organic gaseous materials. The resultant solution and non-condensing gases pass into a reservoir. Volatile, undissolved organics exit from the reservoir with non-condensing reactor gases and are treated. Once the organics have burned out of the sol-gel body, recirculation of the aqueous acid solution is ceased, and the gas-fluid contactor is flushed. The water flow is then ceased and dry nitrogen is provided to the contactor. During the next stage of the sol-gel heat treatment, gaseous products from the dehydroxylation reactor pass through the contactor into the caustic scrubber. Once the heat treatment is complete, the contactor is flushed.