Patent Description:
With the rapid development of communication technology, a conventional cable communication technology is gradually replaced by an optical fiber communication technology due to its own limitations. A physical channel for transmission is also correspondingly changed from an electric cable into an optical fiber cable. Optical fiber remote has emerged along with remote radio unit and an optical fiber repeater technology. The excellent transmission characteristic of an optical fiber is used to extend the coverage of a baseband signal and a radio frequency signal, to facilitate the site selection of a base station and the installation of an antenna feeder and utilize carrier frequency resources appropriately. The optical fiber remote technology develops relatively fast in recent years. A remote optical cable is used between a radio remote unit (RRU) and a baseband processing unit (BBU) to implement data transmission between the RRU and the BBU.

With the continuous development of mobile communication networks, conventional <NUM>-core and <NUM>-core remote optical cables can no longer satisfy -multi-scenario universal requirements. In the era of <NUM> networks that are about to be fully deployed, <NUM> communication base stations will be densely deployed. Therefore, a fronthaul network becomes a critical path for connecting base stations (active antenna units, AAUs). According to market research, currently, a fronthaul path of one <NUM> base station requires <NUM> to <NUM> core optical fibers, and it is considered that one BBU/distributed unit (DU) is connected to <NUM> to <NUM> AAUs. As the quantity of AAUs increases, the quantity of optical fiber cables to be used increases accordingly. In consideration of the problems such as the costs caused by constructions for many times and the construction is difficult in remote area or severe environments, a large-core-number, bundle-type, environmentally-resistant optical fiber cable is more suitable for use.

Especially, when an optical fiber cable is in a low temperature condition, a sheath material has relatively high shrinkage performance, but an optical fiber does not shrink. As a result, the optical fiber has an excessively large excess length in the optical fiber cable and tends to bend and fold in the optical fiber cable, causing an increase in additional attenuation in the optical fiber and impact to the transmission performance of the optical fiber.

<CIT> mentions an optical fiber cable, which comprises a core wrapped by a tubular member, an inner jacket and an intermediate jacket both made of a plastic material and surrounding the tubular member in sequence, and a plurality of strength member, which may be steel wires or glass rods, being partially embedded in each jacket. The strength members wrapped helically about bedding layers, while the bedding layers are added between the tubular member and the inner jacket, and between the inner jacket and the intermediate jacket.

<CIT> discloses a method of manufacturing an optical cable, which can prevent the degradation of characteristics of the optical cable due to generation of voids caused by gasification of a fiber reinforced plastic (FRP), wherein the optical fiber cable and a tension member made of a FRP are coated by extruding a thermoplastic resin around them.

<CIT> discloses an optical fiber cable comprising a cable core, an inner sheath layer covering the outer side of the cable core, and an outer sheath layer covering the outer side of the inner sheath layer, wherein six first non-metallic strengthening cores are embedded into the inner sheath layer, and distributed on a concentric circle with the center of the cable core.

The technical problem to be resolved by the present invention is to provide a high and low temperature resistant remote optical cable and a process of manufacturing the same, the optical cable is applicable to transmission scenarios of indoor and outdoor communication base stations, can be used in high and low temperature conditions and has adequate tensile resistance and crush resistance characteristics.

To solve the foregoing technical problem, the present invention provides a high and low temperature resistant remote optical cable as defined in claim <NUM>.

In a preferred embodiment of the present invention, the cable core is a bundle unit formed by performing bundle coating on <NUM> to <NUM> fiber units.

In a preferred embodiment of the present invention, the fiber unit is a colored fiber or a tight-buffered fiber.

According to the present invention, the fiber unit has an excess length of -<NUM>% to <NUM>.

In a preferred embodiment of the present invention, the inner reinforcing layer and the outer reinforcing layer are both formed by directly burying a plurality of aramid fibers.

In a preferred embodiment of the present invention, the outer sheath is tube-extruded to cover the outer side of the inner sheath, and a gap is provided between the inner sheath and the outer sheath, wherein the gap being configured to be filled by the outer reinforcing layer.

According to the present invention, the inner sheath and the outer sheath are both made of a low smoke zero halogen (LSZH) flame-retardant sheathing material.

To resolve the foregoing technical problem, the present invention further provides a process of manufacturing a high and low temperature resistant remote optical cable as defined in claim <NUM>.

In a preferred embodiment of the present invention, the fiber unit in step S1 is a colored fiber obtained by coloring a bare fiber or a tight-buffered fiber obtained by extruding a bare fiber.

As compared with the prior art, the invention has the following beneficial effects:.

Reference numerals in the drawings: <NUM>, cable core; <NUM>, fiber unit; <NUM>, bundle unit; <NUM>, inner reinforcing layer; <NUM>,inner sheath; <NUM>, inner-layer nonmetal reinforcing member; <NUM>, outer reinforcing layer; <NUM>, outer sheath; <NUM>, outer-layer nonmetal reinforcing member; and <NUM>, coating layer.

The present invention is further described below with reference to the accompanying drawings and specific embodiments, to enable a person skilled in the art to better understand and implement the present invention. However, the embodiments are not intended to limit the present invention.

Referring to <FIG>, an embodiment of a high and low temperature resistant remote optical cable of the present invention includes a cable core <NUM>, an inner reinforcing layer <NUM>, an inner sheath <NUM>, an outer reinforcing layer <NUM> and an outer sheath <NUM> that sequentially cover the cable core <NUM>. Three inner-layer nonmetal reinforcing members <NUM> are inserted in the inner sheath <NUM>. The inner-layer nonmetal reinforcing members <NUM> are uniformly distributed in the inner sheath <NUM> in the circumferential direction. In this embodiment, the three inner-layer nonmetal reinforcing members <NUM> can be connected to form a regular triangle structure. The same numbers of outer-layer nonmetal reinforcing members <NUM> as the inner-layer nonmetal reinforcing members <NUM> are inserted in the outer sheath <NUM>. The outer-layer nonmetal reinforcing members <NUM> are disposed on extension lines of the connection lines between the cable core <NUM> and the inner-layer nonmetal reinforcing members <NUM>. Coating layers <NUM> are provided on the outer surfaces of the inner-layer nonmetal reinforcing members <NUM> and the outer-layer nonmetal reinforcing members <NUM>. In a process of covering the outer sheath <NUM> or the inner sheath <NUM>, a high-temperature sheathing material melts the coating layers <NUM>. The coating layers <NUM> can improve the bonding strength between the nonmetal reinforcing members and the inner sheath <NUM> and the outer sheath <NUM>, so that the shrinkage of the inner sheath <NUM> and the outer sheath <NUM> in a low temperature condition can be suppressed, thereby improving the low temperature resistance performance of an optical fiber cable. According to the claimed invention, the inner sheath <NUM> and the outer sheath <NUM> are both made of an LSZH flame-retardant sheathing material. The LSZH flame-retardant sheathing material has advantages such as high flame retardancy, a low shrinkage rate, low temperature resistance, high temperature resistance, corrosion resistance, sunlight resistance, aging resistance, crack resistance, environmental friendliness, color uniformity, appropriate softness and hardness, easy for processing, bending resistance, thin wall processing, high strength, rodent resistance, and low costs and prices, and is suitable for use in high and low temperature and environmentally complicated conditions.

Referring to <FIG> and <FIG>, an embodiment of a process of manufacturing a high and low temperature resistant remote optical cable in this embodiment includes the following steps:.

In this embodiment, the three outer-layer nonmetal reinforcing members <NUM> can also be connected to form a regular triangle structure. The two regular triangle structures have the same facing angle, making it convenient for an optical fiber cable to bend during blocking or construction. In a process of blocking the optical fiber cable, the optical fiber cable needs to be wound around a wooden drum. If the positions of the inner-layer nonmetal reinforcing members <NUM> are different from those of the outer-layer nonmetal reinforcing members <NUM>, the optical fiber cable is subject to different internal stress, and the optical fiber cable cannot conveniently bend in one direction and as a result the optical fiber cable cannot be wound around the wooden drum. To ensure that the outer-layer nonmetal reinforcing members <NUM> are disposed on the extension lines of the connection lines between the bundle unit <NUM> and the inner-layer nonmetal reinforcing members <NUM>, in the outer sheath forming process of this embodiment, an adjustment-free eccentric die is used, so that the positions of the outer-layer nonmetal reinforcing members <NUM> can be fixed.

Specifically, the cable core <NUM> is the bundle unit <NUM> formed by performing bundle coating on <NUM> to <NUM> fiber units <NUM>. The bundle unit <NUM> bundles the fiber units <NUM>, so that a high-density use requirement can be satisfied, the quantity of the fiber units <NUM> can be increased, and the duty cycle of the fiber unit <NUM> in the optical fiber cable can be increased. In addition, a bundle layer in the bundle unit <NUM> can also protect the fiber units <NUM> to some extent.

Specifically, the fiber unit <NUM> is a colored fiber or a tight-buffered fiber. The colored fiber is obtained by applying a layer of colored ink on the outer side of a bare fiber. The plurality of fiber units <NUM> are colored according to the standard color codes (blue, orange, green, brown, gray, white, red, black, yellow, purple, pink, and cyan) of optical fibers. The tight-buffered fiber may provide one more layer of protection for the optical fiber. A tight-buffered material may be an LSZH or nylon material.

According to the claimed invention, the excess length of the fiber unit <NUM> is a negative excess length of -<NUM>% to <NUM>. Because the fiber unit <NUM> has a particular extensibility, in a process of covering the inner sheath <NUM> outside the fiber units <NUM>, the stringing tension of the fiber unit <NUM> is adjusted, to enable the fiber unit <NUM> to have a zero excess length or a slight negative excess length in the inner sheath <NUM>. In this way, when the optical fiber cable is in a low temperature environment and the inner sheath <NUM> and the outer sheath <NUM> shrink, the fiber unit <NUM> may then have a positive excess length relative to the inner sheath <NUM> and the outer sheath <NUM>, to prevent the fiber units <NUM> from accumulating in the cable core <NUM> to avoid additional attenuation loss.

Because the remote optical cable has a relatively long laying distance, the thickness of the sheath needs to be minimized to reduce the outer diameter and weight of the optical fiber cable. Specifically, the wall thicknesses of the inner sheath <NUM> at two sides of the inner-layer nonmetal reinforcing members and the wall thicknesses of the outer sheath <NUM> at two sides of the outer-layer nonmetal reinforcing members are all less than <NUM>. In addition, the surface of the sheath needs to be prevented from dents or the inner layer needs to be prevented from fracturing.

Specifically, the inner reinforcing layer <NUM> and the outer reinforcing layer <NUM> are both formed by directly burying a plurality of aramid fibers. The aramid fibers have the performance of low density, a high tensile modulus, high fracture strength, and a low fracture extension rate, and further have relatively high corrosion resistance performance, no electrical conductivity, relatively high resistance performance against chemicals other than strong acids and strong alkali. The inner reinforcing layer <NUM> and the outer reinforcing layer <NUM> formed by the aramid fibers further enhance the tensile resistance performance of the optical fiber cable.

Specifically, the sheath <NUM> is tube-extruded to cover the outer side of the inner sheath <NUM>. A gap is provided between the outer sheath <NUM> and the inner sheath <NUM>. The tube-extrusion die is used in place of an extrusion die, to prevent the outer sheath <NUM> to tightly cover the outer side of the inner sheath <NUM>. The gap is provided, so that in one aspect, during the extrusion of the outer sheath <NUM>, the aramid fibers can be prevented from being extruded to avoid the accumulation of the aramid fibers. In another aspect, the outer sheath <NUM> and the inner sheath <NUM> are not bonded together, and do not shrink synchronously at a low temperature.

Specifically, the inner sheath <NUM> is tube-extruded to cover the outer side of the cable core <NUM>. The tube-extrusion die is used in place of an extrusion die, to prevent the inner sheath <NUM> from pressing the cable core <NUM>.

Claim 1:
A high and low temperature resistant remote optical cable, comprising a cable core (<NUM>), an inner reinforcing layer (<NUM>), an inner sheath (<NUM>), an outer reinforcing layer (<NUM>) and an outer sheath (<NUM>) that sequentially cover the cable core (<NUM>), wherein at least three inner-layer nonmetal reinforcing members (<NUM>) are inserted in the inner sheath (<NUM>), the inner-layer nonmetal reinforcing members (<NUM>) are uniformly distributed in the inner sheath (<NUM>) in the circumferential direction, the same number of outer-layer nonmetal reinforcing members (<NUM>) as the inner-layer nonmetal reinforcing members (<NUM>) are inserted in the outer sheath (<NUM>),
wherein coating layers (<NUM>) are disposed on both the outer surfaces of the inner-layer nonmetal reinforcing members (<NUM>) and the outer-layer nonmetal reinforcing members (<NUM>), and
wherein the cable core (<NUM>) is a bundle unit (<NUM>) formed by performing bundle coating on a plurality of fiber units (<NUM>),
wherein the outer-layer nonmetal reinforcing members (<NUM>) are disposed on extending lines of connection lines between the cable core (<NUM>) and the inner-layer nonmetal reinforcing members (<NUM>),
the inner sheath (<NUM>) and the outer sheath (<NUM>) are both made of a low smoke zero halogen, LSZH, flame-retardant sheathing material, and
the fiber units (<NUM>) have an excess length of -<NUM>% to <NUM>.