Basics of Fiber Optic Cables

Ⅰ. Manufacture of fiber optic cables

The manufacturing process of fiber optic cables is generally divided into the following processes:

1. Screening of optical fibers: Select optical fibers with excellent transmission characteristics and qualified tension.

2. Dyeing of optical fiber: Standard full color spectrum should be used for identification. It is required that high temperature does not fade or migrate.

3. Secondary extrusion: Extrude the plastic with high elastic modulus and low linear expansion coefficient into a tube of a certain size, incorporate the optical fiber and fill it with moisture-proof and waterproof gel, and finally store it for a few days (not less than two days). 

4. Fiber optic cables twisting: twist several extruded optical fibers and strengthening units together.

5. Squeeze the outer sheath of the fiber optic cables: add a layer of sheath to the twisted fiber optic cables.

Ⅱ. Basic structure of fiber optic cables

There are four basic structures of fiber optic cables: slotted core optical cable, ribbon optical cable, central tube optical cable and loose tube optical cable.

1. Slotted Core Optical Cable

Since it is called this name, there is no doubt that there must be a part called the skeleton in the fiber optic cables. This kind of fiber optic cables is to use the groove of the plastic skeleton to accommodate the optical fiber. The cross section of the skeleton groove may be V-shaped, U-shaped, etc., and the longitudinal direction is spiral or sinusoidal. A skeleton slot can hold 5-10 coated optical fibers.

Slotted core optical cable has good protection performance for optical fiber, good lateral pressure strength, compact structure, small cable diameter, and it is suitable for pipeline laying. In addition, the fiber density is high, up to thousands of cores. But the manufacturing of the skeleton type optical fiber cable is complicated.

2. Ribbon Optical Cable

The ribbon optical cable is named after the optical fiber contained in the fiber optic cables is a ribbon optical fiber unit. The optical fiber ribbon unit is a rectangular optical fiber combination composed of several layers of optical fiber ribbons. We put the ribbon optical fiber unit into the large sleeve to be the bundle tube ribbon fiber optic cables; put it into the skeleton groove to be the skeleton ribbon fiber optic cables. Placed in the fiber optic sleeve and twisted around the central strength member, it is a layer twisted ribbon cable.

The ribbon optical cable is small in size, which can increase the density of optical fibers in the fiber optic cables and accommodate more optical fiber cores, such as 320-3456 cores. Ribbon fiber optic cables is suitable for the current rapid development of optical fiber access network.

3. Central Tube Optical Cable 

It is similar to the slotted core optical cable. It has a large tube in the center of the bundle-tube fiber optic cable to hold the optical fiber. This tube is called the big casing. The coated optical fiber is loaded into the large sleeve. These fibers are placed untwisted within a large ferrule with layers of strength members wound around the large ferrule.

This type of fiber optic cables has a simple structure and a simple manufacturing process. Its protection of optical fibers is better than that of other fiber optic cabless, and it is resistant to lateral pressure, which can improve the stability of network transmission. The fiber optic cable has a small cross-sectional area and light weight, and is especially suitable for overhead laying. The number of optical fibers in the bundle tube is flexible, but the number of optical fibers in the cable should not be too much.

4. Loose Tube Optical Cable

A loose tube optical cable is twisted around a central strengthening member to form an fiber optic cables. Tight-buffered or loose-buffered fibers refer to optical fibers that are covered with a protective jacket. Protective outerwear materials mainly include polypropylene, nylon-12, polyester elastomer, fluorine-46, fiber-reinforced plastics, directional stretch polymers, etc. The loose tube structure fiber optic cables is similar to the traditional cable structure, so it is also called classical fiber optic cables. The number of optical fibers that can be accommodated in this type of fiber optic cables is generally 6-12 cores, and there are also 24 cores. As the demand for the number of optical fibers increases, unitary stranding appears, that is, the optical fiber in the sleeve is not only one optical fiber core, but multiple optical fiber cores. This also expands the number of fibers that a stranded cable can accommodate.

The loose tube optical cable is easy to manufacture and the excess length of the optical fiber in the fiber optic cable is easy to control. The fiber optic cable has good mechanical and environmental performance, and can be used for direct burial, pipeline and overhead laying.

Ⅲ. Fiber optic cables VS optical fiber

1. Fiber optic cables

It is mainly composed of optical fiber, plastic protective sleeve and plastic sheath. There is no metal such as gold, silver, copper and aluminum in the optical fiber cable, and generally has no recycling value. An fiber optic cable is a communication line in which a certain number of optical fibers form a cable core in a certain way, and is covered with a sheath, and some are also covered with an outer sheath to realize optical signal transmission. That is to say, the fiber optic cable is a cable formed by optical fiber (optical transmission carrier) through a certain process.

2. Optical fiber

It is a thin and soft medium that transmits light beams. Most optical fibers must be covered with several layers of protective structures before use. The coated cable is called an fiber optic cable. So the optical fiber is the core part of the fiber optic cables. The optical fiber constitutes an fiber optic cable through the protection of some components and its subsidiary protective layer.

The protective structure of the outer layer of the optical fiber can prevent the surrounding environment from harming the optical fiber. Fiber optic cables include optical fiber, buffer layer and cladding. Fiber optics are similar to coaxial cables, except without the mesh shield. The center is the glass core for light propagation. Optical fibers are usually bundled and protected by a jacket. The core is usually a double-layer concentric cylinder of small cross-sectional area made of quartz glass. It is brittle and prone to breakage, so it needs an extra layer of protection.

Ⅳ. Fiber optic cables VS copper cable

Fiber optic cables offer several advantages over long distance copper cables.

1. Fiber optic cables are more environmentally friendly

Fiber optic cables bring many benefits to the environment. One of the most important benefits is that it reduces copper usage. While copper itself is not harmful to the environment, the mining and purification process used to make highly conductive copper cables can damage the environment. In contrast, silica, which is used to make fiber optic cables, is one of the easiest materials to mine or collect.

2. Fiber optic cables are immune to electromagnetic interference (EMI)

Electromagnetic Interference (EMI) is a problem in complex networks as well as some home networks. Electromagnetic interference can slow down data transfers and even corrupt packets. Electromagnetic interference on copper cables occurs when a sufficiently strong magnetic field penetrates the cable insulation and causes noise or interference. Electromagnetic interference can arise naturally from lightning, solar radiation, blizzards, and auroras. However, EMI can also originate from man-made devices and appliances such as toasters, ovens, televisions and mobile devices. Copper cables are susceptible to electromagnetic interference, while fiber optic cables are completely immune to such interference. Glass is impervious to magnetism, making fiber optic cables immune to electromagnetic interference.

3. Fiber optic cables reduce energy consumption

Fiber optic cables provide a more efficient means of transmitting data than copper cables. Even though 10GBase-T technology reduces power consumption of copper cables to 3.5 watts per 100 meters, fiber still uses less energy. It is estimated that OM4 fiber optic cables (one of the most common types of fiber optic cables) can transmit data over 400 meters using only 1 watt of power.

4. Fiber optic cables data transmission are faster

One of the biggest reasons why fiber optic cables are the first choice for data transmission is that their greater bandwidth provides faster speeds. Single-mode fiber optic cables are capable of delivering 100-940 Mbps (11.9-112 MB/s). In theory, single-mode fiber can even reach speeds of 1,000GB/s.

These ultrafast speeds are possible thanks to the materials used in fiber optic cables. Unlike copper cables, which transmit data via pulses of electricity, fiber optic cables are made of glass fibers that transmit data via pulses of light. Copper cables can only transmit data as fast as electricity, while fiber optic cables can transmit data at 70 percent of the speed of light. Transferring data at 70% the speed of light also means lower "ping" or latency, further improving certain applications such as video calling, online classes, streaming and online gaming.

5. Fiber optic cables cover longer distance

While copper cables are still used in many homes for local area networks, their use in larger facilities may not be ideal. In some cases, you must route data over longer distances due to server-to-host congestion and sheer physical space.

Copper cables (known as Ethernet cables in your home or office) are limited to 100m by LAN standards to ensure quality and signal strength throughout the network. In contrast, multimode fiber optic cables can be up to 1.2 miles in length without signal attenuation or weakening. Fiber-optic data can travel even farther, depending on changes in the cable and the electronic hardware used to pulse light through the cable.

6. Fiber optic cables are more durable

Glass fibers used in fiber optic cables are known to withstand large amounts of moisture and extreme temperatures before failing. As a result, networks using fiber optic cables are expected to reduce data cable failures by 50%. The durability of fiber optic cables also means fewer repairs and replacements. By using fiber optic cables, organizations will reduce downtime, saving them the hassle of troubleshooting and repair costs. It also means less waste and further contributes to a more sustainable environment.

Ⅴ. How to choose fiber optic cables?

In addition to the number of optical fiber cores and types of optical fibers, the selection of fiber optic cables also depends on the structure and outer sheath of the fiber optic cables according to the environment in which the fiber optic cables are used.

1. When laying cables vertically or horizontally in the building, we can choose tight sleeve fiber optic cables, distribution fiber optic cables or branch fiber optic cables that are commonly used in buildings.

2. We select single-mode and multi-mode fiber optic cables according to network application and fiber optic cables application parameters. Typically, indoor and short-distance applications are dominated by multimode fiber optic cables, and outdoor and long-distance applications are dominated by single-mode fiber optic cables.

3. When the fiber optic cables is directly buried outdoors, we should choose a loose sleeve armored fiber optic cables. When overhead, we can choose a loose-tube fiber optic cables with two or more reinforcing ribs and a black PE outer sheath.

4. When choosing cables for the interior of the building, we should consider its characteristics of fire resistance, toxicity and smog, and choose tight cables. Usually, in ducts or forced ventilation, we can choose flame retardant but non-toxic or flammable types. And in the exposed environment, we can choose flame-retardant, non-toxic and smoke-free types.

Ⅵ. How to distinguish the quality of fiber optic cables?

We can help you distinguish whether the fiber optic cables is of high quality from the following five aspects.

1. Reinforcing steel wire

The steel wire of the outdoor fiber optic cables of the regular manufacturer is phosphating. It has a gray surface. This kind of steel wire does not increase hydrogen loss after being cabled, does not rust, and has high strength. Inferior fiber optic cables are mostly replaced by thin iron wires or aluminum wires.

Identification method: the appearance is white. It can be bent freely in the hand. fiber optic cables produced with such steel wires will have additional hydrogen losses in the future. At the same time, once a long time, the two ends of the link fiber optic box will rust and break.

2. Outer sheath

Indoor fiber optic cables generally use polyvinyl chloride or flame-retardant polyvinyl chloride, and the appearance should be smooth, bright, flexible, and easy to peel off. The outer sheath of the fiber optic cables with poor quality has poor finish, and it is easy to adhere to the tight sleeve and aramid fiber inside. The main function of the outer sheath of the fiber optic cables is to cope with different and complex climate environments and ensure the stable use of the fiber optic cables for at least 25 years. The fiber optic cables sheath should not only have a certain strength, low thermal deformation, abrasion, water permeability, thermal shrinkage and friction coefficient, but also have the characteristics of strong environmental stress resistance and good material processing performance.

3. Loose tube

The loose tube containing the optical fiber in the fiber optic cables should be made of PBT material. Such casing has high strength, no deformation and anti-aging. Inferior fiber optic cables generally use PVC as the casing. The outer diameter of such a sleeve is very thin, and it will be flattened when pinched by hand.

4. Filler ointment

It is a substance present in the loose tube, mainly containing fiber grease and cable grease, to prevent water and moisture from penetrating into the cable. Because the optical fiber is extremely sensitive to HO- produced by water and moisture, water and moisture will expand the cracks on the surface of the optical fiber, resulting in a significant decrease in the strength of the optical fiber. The hydrogen gas produced by the chemical reaction between moisture and metal materials will cause the hydrogen loss of the optical fiber, resulting in an increase in the transmission loss of the optical fiber, which seriously affects the quality and service life of the fiber optic cables. The national standard requires water resistance performance: three meters of fiber optic cables, one meter of water column pressure, no water seepage for 24 hours. Under normal circumstances, the fiber grease should fill the entire loose tube, and the cable grease should fill every gap in the cable core under pressure.

5. Protective material steel strip, aluminum strip.

The steel tape and aluminum tape in the fiber optic cables are mainly used to protect the optical fiber from mechanical side pressure and moisture. Chrome-plated steel strips are generally used in better fiber optic cables. Unqualified fiber optic cables will have internal corrosion after a long time, resulting in poor moisture resistance. The tin-plated layer has poor heat resistance, and its melting point is only 232 degrees Celsius. In the application, due to the high temperature when the sheath is squeezed, there is uncertainty in the peel strength, which affects the moisture resistance of the fiber optic cables. The melting point of chromium reaches 1900 degrees Celsius. Its chemical properties are very stable, and it will not rust when placed in the air or immersed in water at room temperature. Because its surface is easily oxidized to form a passivation layer, it has good environmental resistance. For aluminum strips, unqualified thermal lamination coated aluminum strips will generally be used instead of qualified casting coated aluminum strips, which will also affect the performance of fiber optic cables.

Ⅶ. What are the connection methods of fiber optic cables?

1. Active connection

Active connection is a method of connecting sites to sites or sites to fiber optic cables using various fiber optic connectors (plugs and sockets). This method is flexible, simple, convenient and reliable, and is mostly used in computer network wiring in buildings. Its typical attenuation is 1dB/connector.

2. Permanent fiber optic connection (also known as thermal fusion)

This kind of connection is to melt the connection point of two optical fibers and connect them together by means of electric discharge. Generally used in long-distance connection, permanent or semi-permanent fixed connection. Its main feature is that the connection attenuation is the lowest among all connection methods, with a typical value of 0.01-0.03dB/point. But when connecting, it requires special equipment (fusion splicer) and professionals to operate, and the connection point also needs special container to protect.

3. Emergency connection (also known as cold fusion)

The emergency connection mainly uses mechanical and chemical methods to fix and bond two optical fibers together. The main feature of this method is that the connection is fast and reliable, and the typical attenuation of the connection is 0.1-0.3dB/point. However, the connection point will be unstable if used for a long time, and the attenuation will also increase greatly, so it can only be used for emergency in a short period of time.

Ⅷ. Uses of fiber optic cables

1. Lighting: These applications require high light transmission, but not necessarily high bandwidth or speed. These cables direct the light exactly where it is needed and with perfect focus. They are quiet, durable and easy to install.

2. National Defense: Advanced data security sector for military applications uses optical fiber for data transmission. The material is used in hydrophones for sonar and seismic applications, as well as in aviation wiring.

3. Broadcast: This type of cable transmits high-speed, high-bandwidth HDTV signals. Fiber optic cables are cheaper compared to the same amount of copper cables. Broadcasters use fiber to connect HDTV, CATV, VOD and other services.

4. Submarine environment: Since the optical fiber can be submerged in water and does not need to be replaced frequently, it is often used in high-risk environments, such as submarine cables.

5. Internet and cable TV: Internet and cable TV are two of the most common uses for fiber optics. The high bandwidth and faster speeds of fiber optic cables make them perfect for cable television. They are rapidly replacing coaxial cable systems. The dramatically increased bandwidth and higher speeds of fiber optics mean they have replaced copper and coaxial cables and become the cable of choice for internet systems. We can install fiber optics to support long-distance connections between computer networks in different locations.

6. Medical industry: Due to its thin and flexible characteristics, in some instruments, fiber optic cables are used to observe the internal components of the body. Surgical lasers, endoscopic lasers, microscope lasers, and biomedical lasers all use fiber lasers.

7. Communication: Fiber optic cables play an important role in the principle of optical fiber communication systems. They are used for both transmission and reception, and can improve speed and accuracy.

8. Aerospace applications: Almost all the properties of fiber optic cables that we mentioned earlier also make them perfect cables for aerospace applications. Not only that, but the ability of optical fibers to withstand low temperatures further enhances their applicability. They are used as sensors, communication cables, lighting, etc. They're even trying to create fiber optic cables in space to improve specs in zero-gravity environments.