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 method and apparatus for high velocity dual coating optical fibers includes passing the fiber to be coated through an entrance die into a coating reservoir, to which liquid coating material is supplied under pressure. The diameter of the die passage and the pressure of the fluid is sufficient to prevent air from entering the reservoir. The coated fiber is passed through a centering and sizing die wherein the recirculation of excess coating material is controlled to produce centering forces on the fiber at the high fiber velocity, and wherein the initial coating is sized. The fiber is then passed through a second coating reservoir into an exit die which sizes the second coating. Upon leaving the exit die, the coatings are cured.

Abstract: This invention is a process of contactless monitoring the tension in a moving fiber, such as during the process of drawing optical fibers from preforms, and a non-contacting tension gauge which allows measurement of fiber tension at line speed. The device can be used to monitor the tension during the run without any adverse effects on fiber performance. The measurement may be steady, intermittent or sinusoidal as appropriate. The process includes the steps of sensing an initial position of a moving optical fiber, applying a gas jet onto a section of the optical fiber in a direction transverse to the direction of movement of the fiber so as to cause deflection of the moving fiber axially of the gas jet, sensing the magnitude of deflection of the fiber relative to the said initial position, and, depending on the magnitude of deflection, adjusting the tension in the fiber so as to cause the change in the magnitude of deflection to a preselected value.

Abstract: A hermetically coated optical fiber is produced by contacting a hot fiber with an organic material such as acetylene. The heat of the fiber causes decomposition and results in a hermetic, carbonaceous coating. This coating is essentially impermeable to both water and hydrogen.

Abstract: Optical fibers having ultraviolet-cured coatings and reduced optical transmission losses are produced. An ultraviolet-absorbing material is incorporated in at least one coating layer. This reduces damage in the glass fiber due to the ultraviolet-curing radiation, while still allowing rapid curing of the coating. Single layer coatings and dual layer coatings are described. A single layer coating having reduced microbending losses due to partial curing of the inner portion of the coating is also described.