1. Optical fiber is a thin and soft medium that transmits light beams. Most optical fibers must be covered by several layers of protective structures before use. The coated cable is called an optical cable. Therefore, the optical fiber is the core part of the optical cable, and the optical fiber is formed by the protection of some components and the auxiliary protective layer.
The protective structure of the outer layer of the optical fiber can prevent the surrounding environment from damaging the optical fiber. The optical cable includes an optical fiber, buffer layer, and cladding. Optical fiber is similar to coaxial cable except that it does not have a mesh shield. At the center is the glass core for light propagation.
Fibers are usually bundled into bundles and protected by an outer shell. The fiber core is usually a double-layer concentric cylinder made of quartz glass with a small cross-sectional area. It is brittle and easy to break, so it needs an additional protective layer. So this is the difference.
2. Optical fiber cable (optical fiber cable): It is mainly composed of optical fiber (glass fiber as thin as hair) and plastic protective sleeve and plastic sheath. There is no metal such as gold, silver, copper, and aluminum in the optical cable, and it generally has no recycling value. An optical cable is a communication line in which a certain number of optical fibers form a cable core in a certain way, which is covered with a jacket and some are also covered with an outer sheath for optical signal transmission. Namely: Optical cable is a cable formed by the optical fiber (optical transmission carrier) through a certain process.
The advantages of optical fiber optic fiber cable are a new generation of transmission media. Compared with copper media, optical fiber has greatly improved in terms of safety, reliability and network performance. The bandwidth of optical fiber transmission greatly exceeds that of copper cables, and the maximum supported distance is more than two kilometers. Optical fiber cable has the advantages of good anti-electromagnetic interference, strong confidentiality, fast speed, and large transmission capacity.
At present, there are two different types of optical fibers, which are single-mode optical fibers and multi-mode optical fibers. Multimode fiber is generally used for network connections in the same office building or in relatively close areas. The single-mode optical fiber transmits data with higher quality and longer transmission distance and is usually used to connect networks between office buildings or geographically dispersed. If you use fiber optic cable as the network transmission medium, you need to add equipment such as optical transceivers.
How to distinguish the quality of optical cable
The ointment mainly includes fiber paste and cable paste. Normally, the fiber paste should fill the entire loose tube, and the cable paste should fill every gap of the optical fiber cable core under pressure. At present, there is a way to fill the fiber paste with half full or less, some of the cable paste only apply a layer on the outside of the cable core, and some are not filled between the two ends of the optical cable.
In this way, the optical fiber will not get good protection, affect the transmission performance such as optical fiber attenuation, and the waterproof performance will not reach the national standard. Once the optical cable accidentally seeps, it will cause the entire link to seep and be scrapped. Under normal circumstances, even accidental water seepage only needs to be repaired, and there is no need to revisit it.
(The water-blocking performance required by the national standard is: three meters of optical cable, one meter of water column pressure, and no water seepage for 24 hours.) The same problem will also occur if the poor ointment is used, and it may be due to poor thixotropy of the ointment It will cause micro bending loss of the optical fiber, and the transmission characteristics of the entire link are unqualified; if the paste is acidic, it will also react with the metal material in the optical cable to precipitate hydrogen molecules, and the attenuation of the optical fiber will rapidly increase when it encounters H, causing the entire The link is interrupted.
The fiber optic cable jacket must not only adapt to many different complex climate environments but also ensure long-term (at least 25 years) stability. The cable sheath must not only have a certain strength, low thermal deformation, wear, water permeability, thermal shrinkage and friction coefficient, but also have strong environmental stress resistance and good material processing properties.
Although less or poorly used sheath materials can pass the factory acceptance, they will crack and seep after a period of use due to quality defects. It is even more serious if high-quality polyethylene sheath materials are replaced with recycled plastics.
The optical cable made of high-quality sheath material is smooth, bright, uniform in thickness and free of bubbles after the cable is formed, otherwise there will be a rough phenomenon of the optical cable skin, and because there are many impurities in the raw material, you can find that there are many very small outer skins, Wow, and because of the thin thickness, the entire outer diameter of the optical cable will be much smaller than that of a high-quality optical cable.
Indoor optical cables are generally made of high-quality flame-retardant polyvinyl chloride. The surface should be smooth, bright, flexible, and easy to peel; otherwise, the outer skin will be poor in smoothness and easy to stick to tight fibers and aramid.
3. Steel belt and aluminum belt.
The steel belt and aluminum belt in the optical cable are mainly used to protect the optical fiber from mechanical side pressure and moisture resistance, and the chrome-plated steel belt is generally used in better optical cables. Inferior optical cables are replaced with chrome-plated steel strips by ordinary iron skin or black skin (uncoated steel strip) with only one side anti-rust treated. Over time, corrosion 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 and does not form a comprehensive bonding sheath, and the moisture barrier performance is also very poor; some use tinned steel strips instead of chrome-plated steel strips. The surface of tinned steel strips, air bubbles, etc. are inevitable.
Therefore, under a humid atmosphere and surface condensation or water immersion, corrosion is easy to occur, especially under acidic conditions. The tin plating layer has poor heat resistance, and the melting point is only 232 degrees Celsius. Due to the high temperature when the jacket is extruded, the peel strength is uncertain, 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 at room temperature or immersed in water. Its corrosion resistance is very good. Because the surface is easily oxidized to form a passivation layer, it has good environmental resistance. The aluminum tape generally appears to replace the qualified film-coated aluminum tape of the casting method with an unqualified hot-bonded film-coated aluminum tape, which also affects 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 with a short-term tensile force of 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 one hand;
On the other hand, because the tensile strength is far less than 1500N, the optical fiber may be damaged during construction. The high-modulus phosphating steel wire is generally blue-gray, with good toughness, and is not easy to bend; while the replacement iron wire is generally pinched in the hand and can be bent at will for a long time, the two ends of the fiber optic box will rust and break.
5. Loose casing.
The loose tube of the optical fiber in the optical cable generally uses polymer PBT material (polybutylene terephthalate). Such a loose tube has high strength, no deformation and anti-aging. The loose tube of inferior fiber optic cable is sometimes replaced with other materials, the outer diameter is very thin, flattened by hand, it is no different from a drinking straw, and it cannot bear the protection of optical fiber.
6. Water blocking zone.
The water-blocking tape or water-blocking yarn for optical cable has the strong water-absorbing performance of the super-absorbent resin that is evenly distributed inside the product. Under the combined effect of penetration pressure, affinity, and rubber elasticity, the super-absorbent resin can quickly Inhale water several times its own weight.
Moreover, the water blocking powder will swell the gel immediately when it encounters water, and no matter how much pressure is applied to it, the water will not be squeezed out. Therefore, covering the cable core with a water-blocking tape containing a water-absorbent resin, in case the outer wall of the optical cable is damaged, the superabsorbent resin of the wound part expands and exerts a sealing effect, which can prevent the entry of water to a minimum.
Inferior fiber optic cable usually uses non-woven fabric or paper tape. Once the cable sheath is damaged, the consequences will be very serious. 7. Aramid. Also known as Kevlar wire, it is a high-strength chemical fiber that is currently used mostly in the military industry. Bulletproof vests are produced from this material.
It is DuPont’s patented product and the main cost component of indoor optical cables. It is mainly used to protect the tight-fitting fibers in indoor optical cables from mechanical tension. However, due to the high cost of aramid, inferior indoor optical cables generally have a very small outer diameter, which can save costs by reducing a few strands of aramid, or use a polyester yarn that looks like aramid to replace (it is more common), And 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 most important raw material in optical cables. Good optical cables generally use high-quality fiber cores from major manufacturers. Inferior optical cables usually use low-grade optical fibers and smuggled optical fibers of unknown origin. These optical fibers are difficult to guarantee because of their complicated sources. Sometimes multimode optical fibers are often mixed with single-mode optical fibers. Generally, small factories lack the necessary testing equipment and cannot deal with optical fibers. To make judgments on the quality of the products, making it difficult to ensure quality.
In addition, some are used to buy short-length optical fibers at low prices and then make them into optical cables. Due to the inability to distinguish such optical fibers with the naked eye, the problems often encountered during construction are: low transmission rate, short distance, large fiber attenuation, cannot be docked with pigtails, lack of flexibility, easy to break when coiled fiber, or even a fiber Multimode, the other end is single mode.
In order to facilitate the differentiation of optical fibers during construction, national standards require that optical fibers and loose tubes should be colored brightly. High-quality optical cables are colored with high-quality inks according to the standard, and the colors are very bright and not easy to fall off. Inferior optical cables are colored with poor-quality ink or No coloration at all. Inferior inks are not bright in color and sometimes easily dissolve in cellulite, which makes the colors indistinguishable. Uncolored does not cause great inconvenience to the construction.
10. Product packaging.
The optical cable is generally packed in a wooden tray or an iron-wood tray. The outer surface of the tray is sealed with a wooden sealing plate to ensure that the stress and bending radius of the bulky optical cable throughout the transportation are within the standard requirements.
In order to save costs, inferior optical cables generally use very poor packaging trays. When they are shipped to their destinations, they are almost close to the shelf. Some of them simply do not use the trays. They are shipped around the optical cable, or the trays are not sealed with wooden strips.
In summary, the real advantages and disadvantages of fiber optic cables come from the difference between the structural design, materials, and production technology. Because the optical cable has not yet been widely popularized, although there are many hidden dangers of inferior products, many users and even integrators still use them regardless of the occasion.
It is for this reason that the negative impact of inferior optical cables on the industry will be greater because, for the optical cable itself, its value is not great, but the cost of its laying process (direct burial, overhead, pipe penetration, etc.) is very amazing. And it takes time and effort, plus it is the basic medium in the entire communication link, so once there is a problem, no matter how expensive and high-end your hardware equipment at both ends, the entire system will be completely paralyzed without exception, and the repair cycle will be very long, The loss caused will be ten million times the difference between the advantages and disadvantages.
Post time: 2020-06-17