2. Sheath. Optical cable sheath should not only adapt to many different and complex climatic environments, but also ensure long-term (at least 25 years) stability. Optical cable sheath should not only have certain strength, low thermal deformation, wear, water permeability, thermal shrinkage and friction coefficient, but also have strong environmental stress resistance and good material processability. Although the sheath material that is seldom used or badly used can pass the factory acceptance, it will crack and seep after being used for a period of time due to quality defects, and it will be more serious if the high-quality polyethylene sheath material is replaced by recycled plastic. The cable sheath made of high-quality sheath material is smooth, bright, uniform in thickness and free of bubbles, otherwise the skin of the cable will be rough, and because there are many impurities in the raw material, you can find that there are many tiny pits in the skin of the cable, and because of its thin thickness, the overall outer diameter of the cable will be much smaller than that of the high-quality cable. Indoor optical cables are generally made of high-quality flame-retardant PVC, with smooth and bright appearance, good flexibility and easy peeling; Otherwise, the skin will be poor in smoothness, and it is easy to adhere to tight-sleeved fiber and aramid fiber.
3. steel strip and aluminum strip. The steel belt and aluminum belt in optical cable are mainly used to protect optical fiber from mechanical side pressure and moisture-proof, and chrome-plated steel belt is generally used in better optical cable. For inferior optical cables, the chrome-plated steel strip is replaced by ordinary iron sheet or black leather (uncoated steel strip) with only one side rusted. After a long time, the corrosion will occur in the optical cable, and the hydrogen loss of the optical fiber will be aggravated. Moreover, because it is easy to separate from the sheath to form a comprehensive bonding sheath, the moisture-proof performance is also very poor. Others use tin-plated steel strip instead of chromium-plated steel strip, and the surface of tin-plated steel strip is inevitable, so it is easy to corrode in humid atmosphere and under the condition of surface condensation or immersion, especially in acidic conditions. The tin coating has poor heat resistance, and its melting point is only 232 degrees Celsius. In application, the peeling strength is uncertain due to the high temperature during sheath extrusion, which affects the moisture resistance of optical cables. Chromium, however, has a melting point of 19 degrees Celsius, and its chemical properties are very stable. It will not rust when placed in air or immersed in water at room temperature, and its corrosion resistance is very good. Because the surface is easy to oxidize to form a passivation layer, its environmental resistance is very good. In general, unqualified hot-bonded coated aluminum tape will replace qualified coated aluminum tape by tape casting, which will also affect the performance of optical cable.
4, steel wire. The steel wire in the optical cable is mainly used to protect the optical fiber from mechanical tension. Good optical cables generally use high-modulus phosphating steel wire with short-term tension of 15N or 3N N.. The inferior optical cable will be replaced by iron wire or ordinary steel wire with small diameter, which is easy to rust on the one hand; On the other hand, because the tensile strength is far less than 15N, the optical fiber may be strained during construction. High modulus phosphating steel wire is generally bluish gray, with good toughness and not easy to bend; The replacement iron wire can be bent at will when pinched in the hand for a long time, and the two ends of the optical fiber box will rust and break.
5. loosen the casing. Generally, the loose tube of optical fiber in optical cable is made of PBT (polybutylene terephthalate), which has high strength, no deformation and anti-aging. The loose tube of inferior optical cable is sometimes replaced by other materials, and its outer diameter is very thin, which makes it flat when pinched by hand, just like a drink straw, and it can't protect the optical fiber.
6. Water blocking hose. The water-blocking tape or yarn for optical cable has strong water-absorbing performance through the super-absorbent resin which is evenly distributed in the product. Under the combined action of soaking pressure, affinity and rubber elasticity, the super-absorbent resin can quickly absorb water several times its own weight. Moreover, the water-blocking powder will swell the gel immediately when it meets water, 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 water-blocking tape containing water-absorbing resin, in case the outer wall of the cable is damaged, the super-absorbent resin at the wound part will play a sealing role due to expansion, which can prevent water from entering to the minimum. Non-woven fabrics or paper tapes are usually used for inferior optical cables. Once the outer skin of the optical cable is damaged, the consequences will be very serious.
7. aramid fiber. Kevlar, also known as Kevlar, is a kind of high-strength chemical fiber, which is widely used in the military industry at present, and bulletproof vests are made of this material. It is a patented product of DuPont, which is the main cost component of indoor optical cable, and is mainly used to protect the tight sleeve fiber in indoor optical cable from mechanical tension. However, due to the high cost of aramid fiber, the outer diameter of inferior indoor optical cable is generally made very thin, so that the cost can be saved by reducing a few strands of aramid fiber, or a polyester yarn with an appearance similar to aramid fiber can be used instead (it is more common), and polyester yarn can hardly bear any tension. Thus, the optical fiber is easy to be pulled or broken when being laid.
8, optical fiber. Optical fiber is the core raw material of optical cable, and a good optical cable generally adopts the high-quality fiber core of a large factory. Inferior optical cables usually use low-grade optical fibers and smuggled optical fibers from unknown sources. These optical fibers are difficult to guarantee because of their complex sources, and sometimes multimode optical fibers are often mixed with single-mode optical fibers. However, ordinary small factories lack necessary testing equipment, so they cannot judge the quality of optical fibers, which makes it even more difficult to guarantee the quality. In addition, some people buy short lengths of optical fibers at low prices and then make them into optical cables after welding. Because the naked eye can't distinguish such optical fiber, the problems often encountered in construction are: low transmission rate, short distance, large fiber attenuation, inability to connect with pigtail fiber, lack of flexibility, easy to break when winding fiber, and even one fiber is multimode at one end and single mode at the other.
9. Coloring ink. In order to distinguish optical fibers in construction, national standards require that optical fibers and loose tubes should be colored with bright colors. High-quality optical cables are colored with high-quality ink according to standards, and the colors are very bright and not easy to fall off. Inferior optical cables will be colored with inferior ink or not colored at all. Inferior ink is not bright and sometimes easily dissolved in fiber paste, resulting in indistinguishable colors. Without coloring, it will bring great inconvenience to construction.
1. Product packaging. Generally, optical cables are packaged in shafts with wooden or iron wooden trays, and wooden sealing plates will be sealed on the outside of the trays to ensure that the stress and bending radius of heavy optical cables during the whole transportation are within the standard requirements. In order to save costs, inferior optical cables generally use very poor packaging trays, which almost fall apart when they arrive at their destinations. Some cables are shipped without trays, or they are sealed with trays 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 its structural design, materials and production technology. Because optical cables have not been widely used, although there are many hidden dangers in inferior products, many users and even integrators are still using them regardless of the situation. It is precisely for this reason that the negative impact of inferior optical cable on the industry will be even greater, because the value of optical cable itself is not great, but the cost of its laying process (direct burial, overhead, pipe threading, etc.) is amazing, and it is time-consuming and laborious. In addition, it is the basic medium in the whole communication link, so once there is a problem, no matter how expensive and high-end the hardware equipment at both ends of you is, the whole system will be completely paralyzed without exception, and the repair cycle will be very long.