1. Ointment
The ointment mainly includes fiber paste and cable paste. Under normal circumstances, the fiber paste should fill the entire loose tube, and the cable paste should fill every gap of the cable core under pressure. At present, the fiber paste is half full or less, and some cable pastes are only applied on the outside of the cable core, and some are not filled in the middle of the two ends of the optical cable.
In this way, the optical fiber will not be well protected, which will affect the transmission performance such as optical fiber attenuation, and the poor waterproof performance will not meet the national standard. Under normal circumstances, even if there is accidental water seepage, it is only necessary to repair the seepage section, and there is no need to start over.
(The national standard requires water blocking performance: three meters of optical cable, one meter of water column pressure, no water seepage for 24 hours.) If poor ointment is used, the above problems will also occur, and it may be due to the poor thixotropy of the ointment. , it will cause micro-bending loss of the optical fiber, and the transmission characteristics of the entire link will be unqualified; if the ointment is acidic, it will react with the metal material in the optical cable to react with H to precipitate hydrogen molecules, and the attenuation of the optical fiber will increase rapidly when it encounters H, resulting in the entire Link interrupt transmission.
2. Sheath
The optical cable jacket should not only adapt to many different and complex climatic environments, but also ensure long-term (at least 25 years) stability. The optical cable jacket should not only have a certain strength, low thermal deformation, wear, water permeability, thermal shrinkage and friction coefficient, but also have the characteristics of strong environmental stress resistance and good material processing performance.
Although the sheathing material that is used less or is not well used can pass the factory inspection, it will crack and seep after a period of use due to quality defects. If the recycled plastic is used to replace the high-quality polyethylene sheathing material, it will be even more serious.
The optical cable made of high-quality sheath material has a flat, bright, uniform thickness and no air bubbles after the cable is formed. Otherwise, the surface of the optical cable will be rough, and there are many impurities in the raw material. If you look closely, you can find that the outer sheath of the optical cable has many extremely small Wow, and because of its thin thickness, the entire outer diameter of the fiber optic cable will be much smaller than that of a high-quality fiber optic cable.
Indoor optical cables are generally made of high-quality flame-retardant polyvinyl chloride. The appearance should be smooth and bright, with good flexibility and easy peeling; otherwise, the outer skin will have poor finish, and it will be easy to stick to tight-sleeve fibers and aramid fibers.
3. Steel strip, aluminum strip
The steel tape and aluminum tape in the optical cable are mainly used to protect the optical fiber from mechanical side pressure and moisture resistance. Chrome-plated steel tape is generally used in the better optical cable. Inferior optical cables use ordinary iron sheets or black sheets (uncoated steel strips) with only one side that has been rust-proofed to replace chrome-plated steel strips. Over time, rust will occur in the optical cable, and the hydrogen loss of the optical fiber will also increase. It is easy to separate from the sheath to form a comprehensive bonding protective layer, and the moisture blocking performance is also very poor; some use tin-plated steel strips instead of chrome-plated steel strips, and the surface of tin-plated steel strips, air bubbles, etc. are unavoidable.
Therefore, corrosion is prone to occur in humid atmosphere and surface condensation or water immersion conditions, especially in acidic conditions. The tin-plated layer has poor heat resistance, and the melting point is only 232 degrees Celsius. Due to the high temperature when extruding the sheath, there is uncertainty in the peel strength, which affects the moisture resistance of the optical cable.
The melting point of chromium is 1900 degrees Celsius, and its chemical properties are very stable. It will not rust when placed in the air or immersed in water at room temperature. For aluminum tapes, unqualified thermal-lamination-coated aluminum tapes are generally used instead of cast-casting-coated aluminum tapes, which will also affect the performance of the optical cable.
4. Steel wire
The steel wire in the optical cable is mainly used to protect the optical fiber from mechanical tension.
A good optical cable generally uses high-modulus phosphating steel wire, and the short-term tensile force is 1500N or 3000N. The inferior optical cable will be replaced by iron wire or ordinary steel wire with a small diameter, which is easy to rust.
On the other hand, since the tensile strength is far less than 1500N, the fiber may be damaged during construction. High-modulus phosphating steel wire is generally blue-gray, has good toughness, and is not easy to bend; while the alternative iron wire can be bent at will when it is held in the hand for a long time, and the two ends of the hanging fiber box will rust and break.
5. Loose tube
The loose tube of the optical fiber in the optical cable is generally made of polymer PBT material (polybutylene terephthalate). Such a loose tube has high strength, no deformation, and anti-aging. The loose tube of the inferior optical cable is sometimes replaced by other materials. The outer diameter is very thin, and it will be flattened when pinched by hand. It is no different from the drinking straw and cannot protect the optical fiber.
6. Water blocking belt
The water-blocking tape or water-blocking yarn for optical cable has strong water absorption properties through the evenly distributed superabsorbent resin inside the product. Under the combined action of penetration pressure, affinity and rubber elasticity, the superabsorbent resin can quickly Inhale water several times its own weight.
Moreover, once the water-blocking powder encounters water, it will immediately swell the gel, and no matter how much pressure is applied to it, the water will not be squeezed out. Therefore, if the cable core is covered with a water-blocking tape containing a water-absorbent resin, in case the outer wall of the optical cable is damaged, the super-absorbent resin in the wound portion will expand to exert a sealing effect, thereby preventing the entry of water to a minimum.
Inferior optical cables usually use non-woven fabrics or paper tapes. Once the outer skin of the optical cable is damaged, the consequences will be very serious.
7. Aramid
Also known as Kevlar, it is a high-strength chemical fiber, which is currently most used in the military industry, and bulletproof vests are produced from this material.
It is DuPont's patented product and is the main cost component of indoor optical cables. It is mainly used to protect the tight-buffered fibers in indoor optical cables from mechanical tension. However, due to the high cost of aramid fiber, inferior indoor optical cables generally make the outer diameter very thin, which can save costs by reducing a few strands of aramid fiber, or use a polyester yarn similar in appearance to aramid fiber instead (already common) , while polyester yarn can hardly bear any tension. In this way, the optical fiber is easily pulled or broken during laying.
8. Optical fiber
Optical fiber is the core raw material in optical cable, and good optical cable generally adopts high-quality fiber core from large manufacturers. Inferior optical cables usually use low-grade optical fibers and smuggled optical fibers of unknown origin. These optical fibers are difficult to guarantee due to their complex sources. Sometimes multi-mode optical fibers are often mixed with single-mode optical fibers. Generally, small factories lack the necessary testing equipment and cannot detect optical fibers. The quality of the judgment is made, which makes it difficult to guarantee the quality.
In addition, some buy short sections of optical fibers at low prices and then make them into optical cables. Since such optical fibers cannot be distinguished by the naked eye, the problems often encountered in construction are: low transmission rate, short distance, large optical fiber attenuation, inability to connect with pigtails, lack of flexibility, easy to break when coiled, and even one fiber is damaged. Multimode, the other end is singlemode.
9. Coloring ink
In order to facilitate the identification of optical fibers during construction, the national standard requires that the optical fibers and loose tubes should be colored with bright colors. The high-quality optical cables are colored with high-quality ink according to the standard, and the colors are very bright and not easy to fall off. The inferior optical cables will be colored with inferior ink or No coloring at all. Inferior inks are not bright in color and are sometimes easy to dissolve in the fiber paste, resulting in indistinguishable colors. No coloring brings great inconvenience to construction.
10. Product packaging
Optical cables are generally packaged in wooden or iron-wood reels into shafts, and the outside of the reels will be sealed with wooden sealing plates to ensure that the stress and bending radius of the bulky optical cables during the entire transportation are within the standard requirements.
In order to save costs, low-quality optical cables generally use very poor packaging reels, which are almost disintegrated when transported to the destination. Some simply do not use reels, just wrap the optical cables and ship them, or use reels to seal them without wooden strips.
To sum up, the real difference between the advantages and disadvantages of optical fiber and cable comes from the comprehensive difference between the advantages and disadvantages of its structural design, materials and production processes. Because optical cables are still not widely popularized, and although inferior products have many hidden dangers, many users and even integrators still use them regardless of the occasion.
It is for this reason that inferior optical cables will have a greater negative impact on the industry, because as far as the optical cable itself is concerned, its value is not great, but the cost of its laying process (direct burial, overhead, pipe penetration, etc.) is very staggering. It is time-consuming and labor-intensive, and it is the basic medium in the entire communication link, so once a problem occurs, no matter how expensive and high-end the hardware devices at your two ends are, the entire system will be completely paralyzed without exception, and the repair cycle will be very long. , the loss will be ten million times the difference between the good and the bad.
