Abstract: A fiber optic buffer tube containing fiber optic ribbons centrally located within the buffer tube and a gel compound surrounding the fiber optic ribbons. Disposed within the gel compound, between the walls of the buffer tube and the fiber optic ribbons are water swellable yarns and/or particles. The water swellable yarns and/or particles volumetrically expand when in contact with water that has penetrated the buffer tube. The water swellable yarns/particles also provide greater surface area which helps to hold gel compound, at elevated temperature, within the tube and thus to prevent the fiber optic ribbons from coming into contact with the walls of the buffer tube, thereby preventing signal attenuation problems.

Abstract: An optical fiber cable including a buffer tube wherein the optical unit is maintained in an axial center location of the buffer tube and protected from contact with an inner wall of the buffer tube. At least first and second gel layers are interposed between the buffer tube and the optical unit, wherein the first gel layer surrounds the optical unit, the second gel layer surrounds the first gel layer, and the first and second gel layers have different rheological properties. The inner gel layer may have a yield stress and a viscosity which are lower than a yield stress and a viscosity of the outer gel layer. The lower yield stress and viscosity of the inner gel layer serves to maintain the optical unit in an axial center position within the buffer tube and facilitates easy re-positioning of the optical unit to the axial center position when the buffer tube is flexed or bent. As a result, the optical unit may be maintained in a low stress state and stress-induced attenuation may be prevented.

Abstract: Fiber optic cable containing optical fibers and a silicone waterblocking gel for low temperature applications. The silicone waterblocking gel has an extremely low crystalline melting point and may be used in low temperature environments since it does not experiencing low temperature attenuation caused by crystallization of the base oil at temperatures below about −45° C. Examples of the waterblocking silicone gel are poly(alkyl)(aryl)siloxane and mono or polyhalogenatedsiloxane.

Abstract: A fiber optic buffer tube containing fiber optic ribbons centrally located within the buffer tube and a gel compound surrounding the fiber optic ribbons. Disposed within the gel compound, between the walls of the buffer tube and the fiber optic ribbons are water swellable yarns and/or particles. The water swellable yarns and/or particles volumetrically expand when in contact with water that has penetrated the buffer tube. The water swellable yarns/particles also provide greater surface area which helps to hold gel compound, at elevated temperature, within the tube and thus to prevent the fiber optic ribbons from coming into contact with the walls of the buffer tube, thereby preventing signal attenuation problems.

Abstract: The present invention is directed to a novel construction of buffer tubes for fiber optic cables which offers a way to access the optical fibers inside a buffer tube while reducing the risk of damaging the fibers, as sometimes occurs when cutting the outer layer of the buffer tube. A buffer tube for use in a fiber optic cable of the present invention comprises a tube having a tube wall, the wall having an inside and outside surface, wherein an inner portion of tube wall, nearest the inside surface, is made of a material having a higher notch-sensitivity than an outer portion of the tube wall nearest the outside surface.

Abstract: A seal for sealing the space between a cable and the ends of the corrugated conduit. The seal includes a seal body including a base portion, an engagement portion attached to the base portion and being insertable in the space between the cable and the conduit, and a retainer disposed on the engagement portion for engaging at least one of the corrugations of the conduit. The base portion preferably has a groove for retaining an O-ring such that the O-ring tightly circumscribes the cable to create a seal. The retainer preferably includes helical threads disposed on the outside surface of the engagement portion. Alternatively, however, the retainer can include a rib which engages a corrugation or one or more protrusions which engages a corrugation. Further, the seal body is preferably split into two halves so that it can be installed onto the cable without requiring access to the end of the cable. In addition, the seal body may include two halves interconnected by a hinge so that it is one-piece.

Abstract: The present invention adds a gel-swellable layer in fiber optic cables to aid in protecting the fibers within the cable. The gel-swellable layer can be placed on the fibers, individual ribbons, stacks of ribbons and on the inner surface of tubes by various methods, such as co-extrusion, and can be cured by either heat curing or UV curing. The gel-swellable layers of this invention can be either smooth or textured. When the fibers are placed into the tubes and the tubes are filled with the water resistant gel, the gel-swellable layer absorbs some of the gel causing it to “swell”. As a result of the “swelling” a certain volume of gel is absorbed by the layer, thus reducing the capability of the gel to flow at elevated temperatures. Additionally, the swelled layers create a desirable stiffness transition from harder (less swelled) particles at the surface of the fiber to softer (more swelled) particles on the surface of the swelled layer.