The working principle of fiber optic cable air blowing technology


The concept of air blowing technology for fiber optic cable and micro cable

The optical fiber and cable micro-cable air blowing (JETnet) technology is the world's first optical fiber cable air blowing and laying technology by NKF Optical Cable Company of the Netherlands. Process (ie mother tube + sub-tube + micro-cable laying technology). This technology uses the method of air blowing and laying the cable, first blowing the micro-pipe into the laid mother pipe, and then blowing the micro-cable into the micro-pipe in batches according to customer needs. The technology can be widely used in backbone networks, metropolitan area networks, and access networks.


1.1 Types of Microtubules

Micropipes are an important part of the air blowing system. Just like urban roads, the micropipes must be laid to the destination before the microcables are laid, and they are required to be laid in place at one time. Because the micropipes laid for the first time and the micropipes laid for the second time may be entangled, in a protective pipe (protective pipe: the protective pipe refers to the pipe that protects the micropipe bundle, and this pipe can be used for air blowing Silicon core pipes, PVC pipes for traction, sub-pipes for local telephone pipes, grid pipes and other pipes for laying optical cables) cannot be laid in batches. The following 2 types:


1.1.1 Cluster tube

The cluster tube is a bit like the honeycomb tube commonly used in our local telephone pipes. It is composed of a microtube bundle and an outer sheath composed of loose microtube units. There is no adhesion between the sheaths, and there can be relative displacement. The advantage of the cluster tube is that the density of the tube is high, which can accommodate the most microtubes in the effective space. The disadvantage is that the flexibility is poor, the opening and sectioning of the pipeline is inconvenient (referring to the thick-walled outer sheath), the inner microtubule is difficult to divide, and the impact resistance is also poor, because the microtubule unit is tightly protected by the protection tube. Wrapped together, the deformation of the protective tube can directly cause the deformation of the microtubule.

fiber optical cable

At present, according to the different uses of the project, the cluster pipe is divided into direct buried type, pipeline type, bundled type, flat type, overhead type, flame retardant type, anti-termite type and armored type. Distinguished from the shape, the cluster tube has round, polygon, square and flat type. The round bundles are mostly bundled with a thick-walled outer sheath, the polygonal bundles are generally bundled with a thin-walled outer sheath, and the square and flat bundles have thick-walled and thin-walled outer sheaths.


Directly buried cluster tube: The directly buried cluster tube is composed of a thick-walled outer sheath plus a standard wall thickness microtube unit or a thin-walled outer sheath and a thick-walled microtube unit. Due to the difficulty of cutting and improving the flexibility of the bundled tube, the bundled tube of the thick-walled outer sheath began to transform into the bundled tube of the thin-walled outer sheath. The directly buried bundled pipe can be directly purchased into the groove of the pipeline.


Pipe-type cluster pipe: The pipeline-type cluster pipe is composed of a thin-walled outer sheath and a micro-pipe unit of standard wall thickness, which is suitable for laying in buildings and air blowing or traction in pipelines with protective pipes.


Bundled microtube bundles: The bundled bundles use thinner nylon ropes to combine the microtubule units by bundling, which can be used for traction, air blowing and direct burial laying. The laying method depends on the microtubules. The wall thickness of the unit and the material of the protective tube. This shape of the cluster tube can maximize the use of the space of the protection tube and the channel, and the combination is very flexible. In a 40/33mm protective tube, 4 groups of 6 microtube units of 4/3mm can be blown in each group.


Flat cluster tube: The flat cluster tube is mostly used for standard channels excavated by machinery in urban areas. The width of this channel is very narrow, so the flat cluster tube is very suitable for this channel, and at the same time at the level of the line Turning points are no problem either. However, for a line with high and low fluctuations, it is more difficult to lay the bundled tube at the direction change point. To solve this problem, a flat cluster tube that can be rolled into a circle has been developed.


Overhead type cluster tube: The overhead type cluster tube is a cluster tube with a figure 8 structure. The manufacturer combines the cluster tube and the reinforcement unit of the overhead support, which is suitable for access and drop-off.


Flame-retardant cluster tube: The flame-retardant cluster tube is mainly composed of low-halogen smokeless micro-pipe units and outer sheaths, and is used for direct laying in buildings.


Anti-termite cluster pipe: The outer sheath of the anti-termite cluster is made of a material that enhances the mechanical strength of the pipe and provides chemical protection to prevent termite damage.


Armored cluster tube: The armored cluster tube uses a layer of corrugated steel tape in the outer sheath to protect the microtube bundle, which can effectively prevent animals from biting.


Thick-walled outer sheath and standard-walled micro-tube unit combined direct-buried cluster tube Thin-walled outer sheath and thick-walled micro-tube unit Combination of direct-buried cluster tube with very thin outer sheath and standard wall The tube-type cluster tube composed of thick microtubule units has no outer sheath, and all standard wall thickness microtubule units are bundled with thin ropes


The flat cluster tube composed of thin-walled outer sheath and thick-walled microtubule units is composed of thick-walled microtubule units of the same diameter or a combination of thick-walled microtubule units of different diameters. The "8"-shaped overhead cluster tube or the overhead micro tube unit for household use is composed of the outer sheath of the wall and the hanging wire.


1.1.2 Microtubule unit

The microtube unit is composed of HDPE material and silicon core layer on the inner wall. Generally speaking, the inner wall of the microtube with a diameter of more than 5mm has a diversion groove, while the inner wall of the microtube with a diameter of less than 5mm has no diversion groove. . At present, the outer diameter of microtubules in the world is generally from 3mm to 16mm. The number of fiber cores that can be accommodated in a microtube ranges from 1 core to 288 cores or even higher. When the optical fiber unit and the micro-cable are blown in the air, the silicon core layer mainly plays the role of reducing the friction coefficient between the cable tubes. After the air blowing, the silicon core layer remains on the inner wall of the microtube, which is conducive to future maintenance and cable replacement. Microtubule units have standard wall thickness and thickened microtubules. Microtubules with standard wall thickness can be used for traction and air blowing, and thickened microtubule units can be used for direct burial.


4 sets of 4 sets of 40/33mm silicon core tubes, each set of 6, a total of 24 bundled bundles of 4/3mm, 5 sets of 10/8mm bundled tubes in a 40/33mm silicon core tube Microtubule unit.


The advantages of microtubule units are:

1. Simple and flexible laying method:

If the protective tube is a silicon core tube, a micro-pipe blower (Superjet MD) can be used to blow a certain number of micro-tube bundles into the laid protective tube at one time according to the shape of the mold according to the inner diameter of the protective tube. If the protection pipe is other pipes, such as PE sub-pipes, grid pipes, PVC pipes, etc., the micro-pipe bundles can also be laid into the existing pipes by means of traction technology or water laying technology. If there is no empty protection tube, the expansion technology of the microtube can also consider whether air blowing, water laying or pulling of the microtube can be carried out according to the ratio between the inner diameter of the protection tube and the outer diameter of the existing optical cable in the protection tube, and whether air blowing or pulling is possible how many microtubules.


2. The pipeline can be upgraded and expanded as long as there is an empty protection pipe:

Air-blown microtube bundles can make full use of existing pipeline resources for pipeline expansion, especially in old urban areas and places where pipeline resources are lacking. As long as there is one empty protection tube, the pipeline can be expanded to 3-5 or even more, and the expansion capacity depends on the inner diameter of the protection tube and the outer diameter of the microtube. See 1.3 for the relationship between the protection tube and the air blowing microtube unit.


3. The combination of microtubule bundles can be selected according to the needs:

During air blowing and pulling, we can choose microtube units with different diameters according to the requirements of the number of microcable cores. From the table above, in one 40/33mm protective tube, we can lay 5 10/8mm microtubes; we can also lay 2 12/10mm and 1 14/12mm microtubes, but these 2 groups Different combinations of microtube bundles can have a great impact on the number of cores of air-blown microcables. The combination of 5 10/8mm microtubes can accommodate up to 480 cores, but the combination of 2 12/10mm and 1 14/12mm microtubes can accommodate a maximum of 720 cores.


4. The upgrade of the pipeline can be carried out in parallel with the development:

Because the microtubule system has strong parallel upgrade and vertical upgrade ability, the direct head of the microtubule and the branched joint of the protection tube can be installed and connected anytime and anywhere, so that the microtubule can be quickly connected to any position of the network. After the micro-pipes are laid, the micro-cables can be laid in the micro-pipes in batches and stages according to the market demand, without predicting the future market, and without covering the networks with and without demand.


5. Minimize the cost of expansion and maximize the utilization of pipelines:

With the increasing cost of new construction of pipelines, pipeline expansion has become impossible in many places. Then, using the expansion technology of microtubes can not only rapidly increase the utilization rate of the pipeline, but also greatly increase the number of optical fiber cores in each microtube. For example, the diameter of a 192-core fiber optic cable is 14.5mm, usually only one fiber optic cable is blown in a 40/33mm silicon core tube, while a 96-core micro-cable has a typical diameter of 6.5mm, which can be Five 96-core microcables are laid in one 40/33mm silicon core tube, and the number of optical fiber cores can reach 480 cores, and these 480-core microcables do not need to be laid at one time, and can be laid in stages according to market demand, saving The initial investment cost of the market.


6. Provide better protection for micro-cables:

For the air-blown micro-tube and micro-cable, the micro-tube and micro-cable are all slack in the protective tube, and no stress is generated. When the protection tube is subjected to external tensile force, the excess length of the microtube and the microcable in the protection tube can automatically compensate for the deformation of the protection tube when the protection tube is stretched. According to the principle of air blowing, the microtube bundle cannot fill the entire pipe, so there needs to be a certain space between the microtube and the protection tube. This space also enhances the mechanical strength of the microtube and ensures that the surface of the protection tube is slightly deformed when it occurs. , the microtubule unit can avoid deformation by displacement in the deformed protective tube, and will not directly cause damage to the microtubule. Because the air-blown microtube bundle is loose in the protective tube, when the protective tube is impacted and stretched by the outside world, the microtubes have a high buffer capacity.


7. The most convenient network maintenance and the fastest cable replacement:

When the micro-cable in the micro-duct system fails, the reserved micro-cable in the line can be quickly blown to the obstacle point by the method of air blowing. Only 1 splice box is needed to repair the obstacle point. The traditional line needs 2 splice boxes and 1 section of optical cable, if the optical cable has no excess wire. When the micro-cable in the network needs to be replaced, the air blowing technology can also quickly blow out the old micro-cable and blow the new micro-cable in.

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