2. Sheath, optical cable sheath should not only adapt to many different dirty climatic environments, but also ensure long-term (at least 25 years) stability. Wire coil 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 data processing function. Although the rarely used or poorly used sheath material can pass the factory inspection, it will crack and leak after a period of use due to its quality shortcomings. If recycled plastic is used instead of high-quality polyethylene sheath material, the situation will be more serious. The cable made of high-quality sheath material has a smooth, bright, uniform thickness and no bubbles, otherwise it will show a rough appearance, and because there are many impurities in the material, it can be found that there are many tiny pits on the cable sheath, and because of its thin thickness, the total outer diameter of the cable will be much smaller than that of the high-quality cable. Indoor optical cables are usually made of high-quality flame-retardant PVC, which has smooth and bright appearance, good flexibility and easy peeling. Otherwise, it will show the appearance of poor skin smoothness, simple and compact fibers and adhesion of aramid fibers.
3. Steel strip and aluminum strip. The steel strip and aluminum strip in optical cable are mainly used to protect optical fiber from mechanical lateral pressure and moisture. Chrome-plated steel belts are usually used for better optical cables. For inferior optical cables, the chrome-plated steel strip is replaced by ordinary iron sheet or black skin (uncoated steel strip) with one side rusted. After a long time, the optical cable will corrode and the hydrogen loss of the optical fiber will increase. Moreover, because it is easy to separate from the sheath, it is impossible to form an induction bonding sheath, and its moisture-proof function is also poor. Others use tinned steel strip instead of chrome-plated steel strip. The surface of tin-plated steel strip and bubbles are inevitable coils, which are easily corroded under humid atmosphere and condensation or immersion conditions, especially under acidic conditions. Tin coating has poor heat resistance, and its melting point is only 232 degrees Celsius. In use, the moisture-proof function of optical cable is affected by the high temperature and uncertain peeling strength when the sheath is extruded. The melting point of chromium is 1900 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 easily oxidized to form a passivation layer, its environmental resistance is excellent. Aluminum tape usually replaces qualified coated aluminum tape with unqualified thermal bonding, which will also affect the performance of optical cable.
4. Steel wire, steel wire in optical cable is mainly used to protect optical fiber from mechanical tension. Good optical cables are generally made of high-modulus phosphating steel wire, with short-term tension 1500N or 3000N n. Defective optical cables will be replaced by iron wires or ordinary steel wires with extremely small diameters, so on the one hand, they are simply corroded; On the other hand, because the tensile strength is far from 1500N, the optical fiber may be strained during construction. High-modulus phosphating steel wire is usually cyan, with good tolerance and not easy to bend; However, the replacement wire will be twisted at will when it is held in your hand for a long time, and both ends of optical fiber box will rust and crack.
5. Loose tube, the loose tube containing optical fiber in optical cable usually adopts polymer PBT data, and the loose tube such as coil has high strength, no deformation and aging resistance. The loose tube of defective optical cable is sometimes replaced by other materials, and the outer diameter is very thin, which will be flat when pinched by hand, just like a drink straw, which can not bear the maintenance of optical fiber.
6. Water-blocking tape, the water-blocking tape or water-blocking tape for optical cable has a strong water-absorbing function through the super absorbent resin evenly distributed inside the product. Under the combined action of osmotic pressure, affinity and rubber elasticity, super absorbent resin can quickly absorb several times its own weight of water. Moreover, the water-blocking powder will swell the gel when it meets water, and no matter how much pressure is applied to it, the water cannot be squeezed out. Therefore, when the cable core is coated with water-absorbent resin, the outer wall of Wan Yi optical cable is damaged, and some super-absorbent resin in the wound shows sealing effect due to swelling, which can prevent moisture from entering to the maximum extent. Nonwoven fabrics or paper tapes are usually used for defective optical cables. Once the sheath of the optical cable is damaged, the consequences will be very serious.
7. Aramid, also known as Kevlar, is a kind of high-strength chemical fiber, which is currently used most in military industry. Bulletproof vests are made of this material. It is a patented product of DuPont, which is the primary cost component of indoor optical cable. It is mainly used to maintain the tight-sleeved optical fiber in indoor optical cable from mechanical tension. However, due to the high cost of aramid fiber, the outer diameter of indoor optical cable with defective coil is usually made very thin, so it can be replaced by cutting the cost of several strands of aramid fiber or using a polyester yarn with similar appearance, which can hardly accept any tension. In this way, the optical fiber is easily pulled or broken when it is laid.
8. Optical fiber, which is the core raw material of optical cable. Good optical cables generally choose high-quality fiber cores from big manufacturers. Inferior optical cables usually use original optical fibers and smuggled optical fibers from unknown sources. These optical fibers are difficult to guarantee because of their messy sources, and sometimes multimode optical fibers are often mixed with single-mode optical fibers. Usually, small factories lack the necessary inspection equipment, so it is difficult to judge the quality of optical fiber, and it is even more difficult to ensure the quality. In addition, some of them are welded with short optical fibers bought at low prices and then made into optical cables. Because the naked eye can't distinguish this kind of optical fiber, the problems often encountered in construction are: low transmission rate, short interval, large optical fiber attenuation, inability to connect with pigtails, lack of flexibility, easy time-sharing when winding optical fibers, and even multimode at one end and single mode at the other.
9. Coloring ink. In order to distinguish optical fibers during construction, national specifications require optical fibers and loose tubes to be painted with obvious colors. High-quality optical cables are colored with high-quality ink according to specifications, and the color is very obvious and not easy to fall off. However, defective optical cables will be colored with defective ink or not. The color of defective ink is not obvious, and sometimes it is easy to dissolve in fiber pulp, making it difficult to distinguish the color. Not coloring will bring great inconvenience to the construction.
10. For commodity packaging, optical cables are usually packaged in the shafts of wooden or iron wooden pallets, and wooden sealing plates are sealed outside the pallets to ensure that the stress, bending radius and other conditions of heavy optical cables during all transportation are within the standard requirements. In order to save money, defective optical cables usually use poor packaging trays and simply fall apart when they are transported to their destinations. Bobbins are cool and don't need to be coiled, so optical cables are transported around. Maybe they don't need to be sealed with wooden strips.