Knowledge

How to identify the pros and cons of optical cables?

Feb 07, 2022

1. Outer skin: Indoor optical cables are generally made of polyvinyl chloride or flame retardant polyvinyl chloride. The appearance should be smooth, bright, flexible and easy to peel. The outer skin of the cable with poor quality is not smooth, and it is easy to stick to the tight sleeve and aramid fiber inside.

The PE sheath of the outdoor optical cable should be made of high-quality black polyethylene. After the cable is formed, the outer sheath is flat, bright, uniform in thickness and free of small air bubbles. The outer skin of inferior optical cable is generally produced with recycled materials, which can save a lot of cost. Such optical cable skin is not smooth. Because there are many impurities in the raw material, the outer skin of the optical cable made has many tiny pits, which will crack and enter after a long time. water.

2. Optical fibers: Regular optical cable manufacturers generally use A-grade fiber cores from large manufacturers. Some low-cost and inferior optical cables usually use C-grade and D-grade fibers and smuggled fibers of unknown origin. These fibers have complex sources and take a long time to leave the factory. It is often already wet and discolored, and multimode fibers are often mixed with single-mode fibers. Generally, small factories lack the necessary testing equipment and cannot make judgments on the quality of the fibers. Since such optical fibers cannot be distinguished by the naked eye, the common problems encountered in construction are: narrow bandwidth and short transmission distance; uneven thickness, which cannot be connected to the pigtail; the optical fiber lacks flexibility and breaks when the fiber is coiled.

3. Reinforced steel wire: The steel wire of the outdoor optical cable of the regular manufacturer is phosphating, and the surface is gray. Such steel wire does not increase the hydrogen loss after cabling, does not rust, and has high strength. Inferior optical cables are generally replaced by thin iron wires or aluminum wires, and the identification method is very easy - the appearance is white, and it can be bent at will when you hold it in your hand. The optical cable produced with such steel wire has a large hydrogen loss, and the two ends of the hanging optical fiber box will rust and break after a long time.

4. Steel armor: Regular production enterprises use longitudinally-wrapped steel strips with anti-rust paint on both sides, and ordinary iron sheets are used for inferior optical cables, usually only one side has been treated with anti-rust treatment.

5. Loose tube: The loose tube of the optical fiber in the optical cable should be made of PBT material. Such a tube has high strength, no deformation, and anti-aging. Inferior optical cables are generally made of PVC casing. The outer diameter of such a casing is very thin, and it is flattened when squeezed by hand, which is a bit like a straw for drinking beverages.

6. 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 optical cable core under pressure. The fiber paste is half full or less, while the cable paste is only a layer outside the cable core, and some is not filled in the middle of the two ends of the cable. In this way, the optical fiber will not be well protected, affecting the transmission performance such as optical fiber attenuation, and the poor waterproof performance cannot meet the national standard. Once the optical cable sees water accidentally, the entire link will be scrapped. 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 that the water blocking performance is: three meters of optical cable, one meter of water column pressure, and no water seepage for 24 hours.) If the 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.

7. Aramid: Also known as Kevlar, it is a high-strength chemical fiber, which is most used in the military industry. Military helmets and bulletproof vests are produced from this material. As of 2013, only DuPont and Aksu in the Netherlands can produce it, and the price is about 300,001 tons. Both indoor optical cables and power overhead optical cables (ADSS) use aramid yarns as reinforcements. Due to the high cost of aramid fibers, low-quality indoor optical cables generally make the outer diameter very thin, so that a few strands of aramid can be used to save costs. Such an optical cable can easily be pulled and broken when passing through the tube. Because ADSS optical cable determines the amount of aramid fiber in the optical cable according to the span and wind speed per second, it is generally not afraid to cut corners.

8. Water-blocking tape: The water-blocking tape or water-blocking yarn used for optical cable has strong water absorption performance through the evenly distributed super absorbent resin inside the product. Under the combined action of penetrating pressure, affinity and rubber elasticity, Super absorbent resin can quickly absorb water several times its own weight. Moreover, once the water blocking powder meets water, it will swell the gel immediately, 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 sheath of the optical cable is damaged, the consequences will be very serious.


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