The composition of the central tube optical cable

Commonly used outdoor optical cables are divided into two structures: central bundle tube type and layer stranded optical cable:

① Central tube optical cable: The center of the optical cable is a loose tube, and the strengthening member is located around the loose tube. Such as the common GYXTW type optical cable, the number of cores of the optical cable is small, usually less than 12 cores.

GYXTW optical cable:

Bundle tube: The material of the beam tube is PBT, which is hard but flexible and resistant to lateral pressure. Some small factories use PP instead of PBT, which can reduce the cost by half, but the optical fiber inside the cable is easy to break during transportation and construction. The color of PP is translucent.

Colored optical fiber: In order to distinguish each core optical fiber in the communication engineering of the optical cable, a layer of colored plastic is extruded on the bare fiber. The outdoor optical cable is to dye each core bare fiber with ink of different colors. The color of the ink is the same as that of the indoor cable, and there are also 12 types. The color spectrum of the industry standard of the Ministry of Information Industry is as follows: blue, orange, green, brown, gray, ( White), red, black, yellow, purple, pink, green. The use of natural colors instead of white is permitted provided that identification is not affected.

Color-locked optical fiber: In order to protect the optical fiber, a layer of 250 micron translucent resin is coated on the surface, and when the optical fiber is made into an optical cable, each core fiber needs to be colored with a different color, so some foreign optical fiber manufacturers cover the optical fiber during production. There are 12 different colors of resin on it, so that the optical cable factory does not need to color it when it is used. The advantage of this is that it saves a coloring process, but the disadvantage is that it cannot be used to flexibly distribute fibers.

Water-blocking tape: The water-blocking tape is made of water-blocking powder added between two layers of non-woven fabrics. Once the optical cable enters the water, the powder will expand dozens of times after absorbing water and produce a jelly-like gel to block the water and go deeper into the optical cable. spread everywhere.

Non-woven fabric: Some manufacturers will replace the water-blocking tape with a non-woven fabric that is much cheaper than the water-blocking tape to reduce costs. There is no difference in appearance. Once the outer sheath of the optical cable is broken, the non-woven fabric cannot block water.

Embossed steel strip: The outer surface of the water-blocking strip is covered with an embossed steel strip. The main function of the steel strip in the optical cable is to resist lateral pressure, pull, prevent mice from biting, and protect the bundle tube.

Steel wire: We can see two parallel steel wires on the outside of the steel belt. The function of the steel wire is to enhance the tension of the optical cable. The gray steel wire on the surface is phosphating, and the silver steel wire on the surface is galvanized to prevent the steel wire from rusting. Galvanized steel wire is more expensive than phosphating steel wire.

Optical cable sheath: Outdoor optical cables generally use medium-density polyethylene (MDPE), and some customers specify high-density polyethylene (HDPE). The cost of using high-density PE is slightly higher. There are also orders specifying that low-smoke and halogen-free materials (LSZH) should be used as sheaths. Many manufacturers also use recycled materials as optical cable sheaths to reduce costs. The optical cables made of this material have rough skins, contain a lot of impurities, and are prone to cracking and water seepage. The source of recycled materials is to crush some wire and cable skins, plastic bottles, slippers, etc. and return them to the furnace for re-granulation.

Because there are only 12 colors of optical fibers, the national standard (also international standard) central bundle tube optical cable can only have 12 cores at most. There are also some non-standard central beam tube cables with more than 12 cores, but generally no more than 24 cores. The method is to select one of the two optical fibers of the same color and spray a bar with an inkjet printer at a certain distance to distinguish them. Cables with more than 12 cores generally use layer twisting.

Small central bundle tube fiber optic cable JET

This structure is used a lot in foreign countries, and the fiberglass yarn (or aramid fiber, high-strength yarn) is added to the bundle tube with the optical fiber and then the sheath is extruded. The optical cable is relatively soft, has a certain tensile force, and can be used indoors and outdoors. Aerial, through the pipe are more aspects.

② Layer stranded optical cable: multiple bundle tubes equipped with optical fibers are stranded on the central core strength member in a twisted manner. Such optical cables such as GYTS, GYTA, etc., can obtain larger cores by combining loose tubes. number of optical cables. The color separation of stranded loose tubes usually uses red and green collars to distinguish colors, which is used to distinguish different loose tubes and different optical fibers. The number of cores of the layer-stranded optical cable can be relatively large, and it can be produced with optical fiber ribbons, which can achieve more than one thousand cores.

Optical cables with 60 cores and below often use a 5-tube structure, such as a 60-core optical cable, with 5 bundle tubes, and 12 optical fibers in each bundle tube. Generally, the stranded optical cable below 12 cores is twisted together with a bundle tube containing 12 core optical fibers and 4 solid filling ropes. It can also be twisted with 2 6-core bundle tubes and 3 filling ropes, or it can be matched in other ways.

GYTS type optical cable: In the layer twisted optical cable red, this type and GYTA are the most common. Twist several bundle tubes on a thicker phosphating steel wire, fill the gaps of the twisted cable with water-blocking cable paste, and wrap a circle of plastic-coated steel tape on the outside, and then extrude the sheath.

GYTA type optical cable: The structure of this optical cable is the same as that of GYTS, except that the steel tape is replaced by aluminum tape. The lateral pressure resistance index of the aluminum strip is not as high as that of the steel strip, but the anti-rust and moisture-proof performance of the aluminum strip is better than that of the steel strip. In some environments where the pipe is worn, the GYTA type is used, and the service life of the optical cable is longer.

GYFTY-type optical cable: This type of optical cable is to twist several bundle tubes on a non-metallic reinforced core, fill the twisted gap with cable paste or keep a circle of water-blocking tape, and directly squeeze the sheath without adding armor.

There are many evolutions of this model. It is used in some overhead environments. In order to increase the tensile force of the optical cable, some aramid fibers should be added to the stranded cable core and then extruded sheath. If the central reinforcement uses steel wire instead of non-metallic reinforcing core (FRP), the model is GYTY, without F (representing non-metallic).

FRP reinforced core: This material is generally made of glass fiber, and the strength of the same outer diameter is greater than the tensile force of the steel wire. It is characterized by non-conductivity, and it is safer to use overhead in a minefield environment. When training optical fibers, we know that optical fibers are drawn from high-purity glass and are not afraid of lightning. However, the metal parts in the middle of the optical cable are easily burned by direct lightning strikes when the optical cable is overhead. Seeing the model with F, we should know that it is mainly lightning protection. The cost of strengthening with FRP is slightly higher than that of steel wire.

Type 53 optical cable: We have seen some models such as GYTA53, GYTY53, this type is to add a layer of steel armor and sheath on the outside of GYTA, GYTY optical cable. Applied in those occasions where the environment is relatively harsh. When you see 53, you should know that it is an extra layer of armor and an extra layer of sheath.

8-shaped optical cable: This kind of optical cable is used more in some countries with large land and sparse population. A sling is added outside the bundle tube or layer stranded optical cable. The sling is generally twisted with 7 steel wires with a diameter of 1.0 mm. , or 1 piece of galvanized steel wire with a diameter of 2.5mm.

Bundle type 8 cable GYXTC8S:

Layer stranded steel armor GYTC8S, layer stranded aluminum armor GYTC8A

Fiber-to-the-home optical cable: This type of optical cable requires small outer diameter and low cost, and is suitable for passing through pipes or wiring troughs.

FTTH optical cable:

This kind of optical cable generally uses LSZH as the sheath, two FRP reinforcements, and two cores of G657 optical fibers in the middle. The outer diameter is very small, and the optical fiber can be exposed by tearing directly without professional cable opening tools.

Ordinary drop cable GYXTPY:

The structure of this kind of optical cable is: directly extrude the sheath after adding two parallel steel wires outside the bundle tube, no steel armor, small outer diameter and low cost. Used in fiber-to-the-home projects. Some economically underdeveloped countries also like to ask for this kind of structured optical cable because the price is cheap.

ADSS optical cable: This optical cable is made of GYFTY optical cable with aramid and then extruded with a layer of sheath.

This kind of self-supporting optical cable is used on outdoor high-voltage utility poles. In addition to the number of cores of the optical cable, the quotation also needs to know several indicators to calculate the cost.

Span: That is, the distance between each pole. In a communication project, if the distance between the designed poles is farther, the amount of poles will be reduced, but the optical cable must be strengthened by its own tension in the air. The amount of aramid in the optical cable The larger it will be, the cost of the cable will increase accordingly.

Wind speed: The greater the wind in the use environment, the greater the amount of aramid fiber used in the cable, and the higher the cost.

Ice slush: If it is in a severe cold area, icicles will form on the outer skin of the optical cable after being exposed to rain, which will increase the tension of the optical cable in the air, and also increase the amount of aramid fiber, and the cost will increase accordingly. There is no need to consider this factor for use in non-severe cold areas.

The above three indicators are based on the use environment to calculate the amount of aramid fiber used in the cable. As we have introduced earlier, aramid fiber is a kind of reinforcing fiber with high cost.

Arc resistance: ADSS optical cables are used on high-voltage utility poles, and arc discharge from high-voltage wires will burn the optical cable sheath, so ADSS optical cables are generally made of arc-resistant materials for sheathing. Usually the arc is 110KV (kilovolt) and 220KV. The effect of conventional arc-resistant materials in 220KV environment is not very good, and OPGW optical cables are generally used instead.

OPGW optical cable: This kind of optical cable is to install the optical fiber in the aluminum tube, and then twist multiple aluminum tubes and steel wires. It is an all-metal structure, and it is protected against lightning by grounding at both ends.