CN213659033U - Optical cable suitable for leading-in cable application - Google Patents

Abstract

The utility model discloses an optical cable suitable for drop cable uses has two sheaths, two reinforcing layer, circular cross-section and tight buffer structure. The cable includes: a tight buffered optical fiber subunit comprising one to three buffered optical fibers (21) and a tight buffer layer (22); an inner reinforcing layer (23) comprising a polymer cladding surrounding the tight buffered optical fiber subunit; an inner jacket (24) comprising a polymer layer surrounding an inner reinforcing layer (23); an outer reinforcement layer (25); an outer jacket (26) comprising a polymer layer surrounding the outer reinforcing layer (25). Fiber optic cables are compact, unit-coupled fiber optic assemblies that are small and lightweight while still being robust enough for many indoor/outdoor drop cable installations. The small profile and circular configuration make the cable easy to connect.

Description

Optical cable suitable for leading-in cable application

Technical Field

The utility model relates to an optical cable suitable for drop cable uses relates to drop cable technical field.

Background

Fiber to the building (FTTP) for local telephone and cable service providers is rapidly evolving. This service requires a broadband fiber distribution network consisting of local fiber distribution cables installed in community and city streets. Local distribution cables employ high fiber count (multi-core) cables. A single "drop" line from the street to the house uses optical fiber or a small number of fiber optic cables. In many cases aerial descent lines are used, which have special requirements. In other cases, the cable is buried underground or installed in a conduit. These installations have different requirements.

To complete the optical circuit, the vertical cable must be terminated at the customer site. Fusion splicing of optical fibers is often the preferred termination method in which the optical fibers in the cable are fused to factory-connectorized fiber leads on the home terminal by heat applied by a fusion splicer. However, this termination method requires expensive capital equipment and highly skilled processes to produce robust joints at the customer site. More and more network installers are using connection components that allow plug-and-play installation at customer sites through relatively low skill processes. Most fiber optic cables are currently common, that is, have a single structure designed for a wide range of drop applications. However, due to the many current applications, the universal design is too large to connect. And these cables are stiff and difficult to bend or handle. Because of the shape of the raceways, they have a preferred axis of bending, making bending in the direction of the non-preferred axis difficult. The non-circular cross-section of the cable, and preferably the bending axis, makes the cable difficult to manufacture and handle. The non-circular cross-section portion is used for externally mounted hardware compatibility, which is not relevant to many current applications. The non-circular cross-section also makes the cable difficult to connect, necessitating the use of special transitions and jackets, and the rigidity imparted by the two strength members makes it difficult to polish the surfaces of the optical fibers mounted in the ferrules during the connection process.

SUMMERY OF THE UTILITY MODEL

To above problem, the utility model provides an optical cable suitable for drop cable uses has two sheaths, two reinforcing layer, circular cross-section and tight buffer structure. The fiber optic cable is a compact, unit-coupled fiber optic assembly that is small in size and light in weight, yet is sufficiently robust for many indoor/outdoor drop cable installations, and the compact size and round configuration allows for easy cable connectorization.

An optical cable suitable for drop cable applications, comprising: a tight buffered optical fiber subunit comprising one to three buffered optical fibers and a tight buffer layer; an inner reinforcing layer comprising a polymer cladding surrounding the tight buffered optical fiber subunit; an inner jacket comprising a polymer layer surrounding an inner reinforcing layer; an outer enhancement layer; an outer jacket comprising a polymer layer surrounding the outer reinforcing layer.

Preferably, wherein the diameter of the tight buffered optical fiber subunit is 1.2mm or less.

Preferably, wherein the cross-sectional area of the cable is less than 25 mm.

Preferably, the inner jacket comprises a flame retardant polymer.

Preferably, the material of the inner jacket is polyvinyl chloride, polyolefin (e.g., polyethylene or polypropylene), flame retardant polyolefin, polyurethane, or other suitable material.

Preferably, the sub-cable is made of aramid yarn or glass fiber, glass rod and aramid rod, and combinations thereof.

Preferably, the outer sheath is made of PVC.

Preferably, the outer sheath (26) comprises a tear-resistant cord.

Preferably, the combined thickness of the outer reinforcing layer and the outer sheath is typically between 1.5 and 3.0 mm.

Drawings

Fig. 1 is a schematic cross-sectional view of the optical cable of the present invention.

Reference numerals: a buffered optical fiber (21); a tight buffer layer (22); an inner reinforcement layer (23); an inner jacket (24); an outer reinforcement layer (25); an outer jacket (26).

Detailed Description

The utility model discloses a two sheaths, full medium, self-supporting cable are as shown in figure 1. The design includes a tight buffered optical fiber subunit with a buffered optical fiber 21 surrounded by a tight buffer layer 22. The tight buffered optical fiber subunit is a 250 micron fiber with a buffer diameter of 0.9 mm (buffer layer thickness 650 microns), or other tight buffered optical fiber subunits with diameters of 0.4 mm to 1.2mm are used. This allows termination using the features of standard fiber optic connectors. The tight buffer layer 22 completely surrounds the optical fiber, i.e., the buffer layer is in contact with the optical fiber coating of the optical fiber. Tight buffer layer 22 is a polymer, such as PVC, nylon, polyolefin, polyester thermoplastic elastomer, fluoropolymer, uv-curable acrylate, or a combination of these materials. While the preferred tight buffered optical fiber subunit contains one optical fiber, an equivalent cable design is a tight buffered optical fiber subunit having 1-3 optical fibers.

One feature of the cable design of the present invention is that cable strength is provided by two separate strength members concentric with the tight buffered optical fiber subunits, as compared to conventional cables. The two concentric strength layers are altered by the two concentric jacket layers.

The inner reinforcing layer 23 in fig. 1 is an inclusion of aramid imide. This provides reinforcement and allows the fiber optic connector to be crimped over the internal jumper using industry standard techniques. For outdoor applications, aramid yarns are coated with a water-soluble finish or the core is dusted with a wettable powder to provide water resistance. Other high strength polymer tapes or yarns may be used. By polymeric wrap is meant any polymeric tape, yarn, ribbon, etc. made from a high strength polymeric material.

The inner jacket 24 is made of a polymer layer having an outer diameter of less than 3.2mm, which is the diameter of an industry standard single cord. The combination of buffered optical fiber 21, tight buffer layer 22, inner reinforcing layer 23, and inner jacket 24 provides a fiber optic sub-cable that may be separated from the remaining cable in some applications to achieve a medium cable span. For example, the primary cable is routed to a connection area, such as a cable cabinet or enclosure, and the outer layer of the cable is stripped away leaving only the secondary cable routed to the fiber optic connection points. The outer diameter of the sub-cable has a relatively small standard jumper diameter, such as 2.5mm, 2.4mm, 2.0mm, 1.8mm, 1.7mm, or 1.6mm, to reduce the overall size of the drop cable and to produce a small diameter sub-cable. Thus, a suitable range of sub-cable diameters is 1.2mm to 3.2 mm. The inner jacket 24 may advantageously be made for flame retardant applications when needed indoors or indoors/outdoors.

The sub-cables are enclosed in an outer reinforcing layer 25 and an outer jacket 26. The outer reinforcing layer 25 may be made of any suitable linear strength member. An opening rope can be added to facilitate access to the inner sheath. For outdoor applications, water blocking materials may be provided, including water soluble coatings on the rebar, or water soluble powders, yarns, or tapes applied over the outer reinforcement layer. The outer jacket 26 is made of any suitable material. For outdoor applications, polyethylene with carbon black may be used. If low temperature functionality is desired, UV resistant polyurethanes can be used. If flame retardancy is desired, PVC, halogen-free flame retardants or fluoropolymers may be used. Ultraviolet degradation resistance or flame retardancy may be added as required.

As mentioned above, a significant feature of the optical cable of the present invention is the small diameter and cross-sectional area of the cable. The cable is made of a relatively complex design, namely two reinforcing layers and two sheath layers, and the total sectional area of the cable can be smaller than 25 mm. The preferred cable diameter is 4.5mm or less.

An important advantage of the optical cable design is that it is easy to terminate the connector with a standard. To create a factory terminated pigtail (connector at one end) or factory terminated jumper (connector at both ends) cable, the outer jacket and outer strength members are stripped back, exposing the inner jacket cords of the sub-cable. A length of heat shrink tubing can then be slid over the end of the cable to provide a seal for the transition between the outer cable jacket and the stripped end of the sub-cable. The sub-cable may then be terminated using standard cable procedures familiar to those skilled in the art. The connectors that can be used depend on the particular application. If the connecting cable is used for indoor installation, the termination may be made using standard indoor connectors. This list is given by way of example and not limitation. If the cable is to be installed outdoors, but the end of the cable is to be installed in an outdoor distribution frame or sealed weather terminal, a standard connector may be used. A combination of indoor, shrouded indoor connectors and hardened outdoor connectors may be used as desired.

As previously mentioned, the cross-section of the cable is substantially circular. However, a degree of ovality is acceptable. The term "substantially circular" is meant to include elliptical shapes.

Claims (5)

1. An optical cable suitable for drop cable applications, comprising: a tight buffered optical fiber subunit comprising one to three buffered optical fibers (21) and a tight buffer layer (22); an inner reinforcing layer (23) comprising a polymer cladding surrounding the tight buffered optical fiber subunit; an inner jacket (24) comprising a polymer layer surrounding an inner reinforcing layer (23); an outer reinforcement layer (25); an outer jacket (26) comprising a polymer layer surrounding the outer reinforcing layer (25).

2. An optical cable suitable for drop cable applications as claimed in claim 1, wherein said tight buffered optical fiber subunit has a diameter of 1.2mm or less.

3. A cable suitable for drop cable applications according to claim 1, wherein the cross-sectional area of the cable is less than 25 mm.

4. An optical cable suitable for drop cable applications as claimed in claim 1, wherein said inner jacket (24) comprises a flame retardant polymer.

5. A cable suitable for drop cable applications according to claim 1, wherein said outer jacket (26) comprises a tear-resistant cord.

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