Design, features and characteristics of the optical cable

Progress will not stop. Every day, our life includes all new materials. A revolutionary discovery in terms of laying high-speed communications was the invention of an optical cable.

What is an optical cable

An optical cable is a special kind of cable for communication networks. The main difference from a standard cable is the method of energy transfer. Transmission is carried out with the help of a light flux, and not an electric current. By and large, an optical cable is a thread inside which the light moves. The main component is optical fiber. It is the most modern and most reliable environment for data transmission. Light through the fibers is transmitted over huge distances with virtually no loss and with great speed.

The main characteristics of an optical cable. Its advantages and disadvantages

The advantage of an optical cable in front of a cable is obvious. Among the most obvious points I would like to highlight:

• Incredibly high throughput. The optical cable is capable of transmitting a significant amount of information over a short period of time.
• Optical fiber does not emit electromagnetic waves. Accordingly, it is not capable of being exposed to electromagnetic radiation. As a result, the signal is protected from distortion.
• The cable is securely protected from unauthorized connection. An attempted unauthorized connection causes a violation of the integrity of the cable and termination of the data transfer. It is impossible to hide it.
• Very low signal attenuation. Modern fiber optical cable at a wavelength of 1500 nm has an attenuation index of about 0.3 dB / km. This makes it possible to locate adjacent repeaters and amplifiers at distances up to 100 km.
• Optical cable has less weight and volume than usual. For example, the diameter of a 900-pair telephone cable is 7.5 cm. It will be successfully replaced by an optical cable with a diameter of about 1.5 cm. Most of the cable will be made up of various protective covers. The diameter of the direct optical fiber is 0.1 cm.

• When using an optical cable, it is not necessary to ground the enclosure. This is due to the insulating properties of the optical fiber.
• Ability to use in enterprises with increased risk. It is connected with such a feature of optical fiber as the absence of sparking. Thanks to her, the optical cable is a fireproof material.
• Optical cable is a very economical material. Quartz is used for the manufacture of optical fibers, the element is very inexpensive and widespread. As a result, the cost of the optical cable itself does not differ from the cost of an ordinary cable.
• Durability. Nothing is eternal. Over time, all materials lose their properties, including optical cable. The attenuation increases. However, these processes are very slow. The rate of loss of optical cable properties is significantly lower compared to other kinds of cables. The term of trouble-free operation of the optical cable is at least 25 years.

Despite the large number of positive moments, the use of an optical cable has a number of drawbacks:

• High cost of communications with an optical cable. True, this is due to the use of additional expensive equipment. The cost of the optical cable itself is not too different from the cost of a conventional cable.
• The complexity of mounting networks with an optical cable. Connectors must be installed literally with micron accuracy. The connection itself must be done very accurately, smoothly. The presence of gaps is unacceptable. The interface must be smoothly polished. If the above requirements are not met, loss in speed and quality of the transmitted signal can not be avoided.
• Connections are performed by welding or gluing. When gluing, a special gel is used, which has the same refractive index as fiberglass.
• In the process of working with an optical cable, special tools are used. Installation of optical networks is carried out exclusively by highly qualified specialists.
• The optical cable may be damaged due to a sudden temperature drop. Fiberglass is cracking. To solve this problem, optical cables are launched into production, in the manufacturing process of which radiation-resistant glass is used. Unfortunately, this leads to a significant increase in cost.

As you can see, the shortcomings are not so significant. The popularity of optical networks is growing every day. At the same time, the cost of material is reduced and the number of specialists working with an optical cable is growing. With such a trend in the near future, these shortcomings themselves will become obsolete.

Types of optical cables

There are two types of optical cables:

1. Single-mode optical cable. All light rays in cables of this type move along one path and simultaneously approach the receiver. As a result, there is no distortion of the waveform. Single-mode cable is equipped with an optical fiber with a diameter of 1300 nm. Only light waves of the same length are transmitted. The use of single-mode cables facilitates the transmission of signal to longer distances than the use of multimode cables. This feature is associated with very small values ​​of dispersion and signal loss. When using a single-mode cable, laser light emitting diodes are used. The attenuation of the signal in a single-mode cable is very low, of the order of 5 dB / km.
2. Multimode optical cable. In this type of cable, the rays do not follow one path. Their trajectories are distinguished by a wide spread. The result is signal distortion at the receiver. When transmitting a signal over a multimode cable, conventional LEDs are used. This leads to a significant reduction in the cost of communication networks and an increase in the service life of transceivers. For a multimode cable, the wavelength of the light wave is about 850 nm with deviations of 30-50 nm. The signal attenuation in the cable can reach 20 dB / km. A cable of this type is allowed up to 5 km.

The main type of optical cable is currently multimode. This is due to its availability and cheapness. In the future, leading positions should go to a single-mode cable. Its excellent performance and low attenuation allow us to hope that over time the high cost of transceiving equipment will cease to be an obstacle to the dissemination of this high-quality material.

Optical cable design

The main components of the optical cable are:

1. Optical fiber. A thin glass thread, called a core or a living core. Covered with a shell of glass. The refractive index of the shell slightly differs from this index of the vein in the direction of decrease. That is why the light beam directed to the core extends exclusively over it. Often, to reduce the cost of material, the vein is made of plastic, not glass. Such optical fibers are worse. There are singlemode and multimode optical fibers. The core of single-mode fiber is very thin, its diameter is of the order of 10 microns. It is because of the insignificant diameter on the core that only one single mode of electromagnetic radiation is transmitted, which excludes the presence of dispersion distortions. But the core of multimode fiber is several times thicker, about 50 microns. This facilitates the propagation of several modes of radiation along it. Each of the modes propagates at a certain angle. The light pulse is subject to dispersion, which leads to the transformation of its shape from rectangular to bell-like.
2. Core.

To improve the strength of an optical cable, its optical modules, which are a polymer tube in which the optical fiber is freely disposed, are twisted around the core of the cable.

The core role is performed by the central power element, which protects the structure from the loads.

In the production of optical cables, twisting is used. The twisting elements are concentrically arranged along the central force element. The purpose of twisting is to achieve the presence of a space within which the transfer capacity of the cable is not affected by the load on compression, stretching and bending. Of course, the maximum value of these loads is limited to certain frames.

Around the central force element, fillers also wound. As fillers are:

1. Modules without fiber.
2. Copper cores
3. Plastic rods.

All of the above elements are fastened together by a tape or a sheath. Their totality is called the core.

1. Covers for protection and reinforcement. In connection with the absence of the need to shield the optical cable from an external electromagnetic obstacle, braid of metal is not used. However, there is a need for mechanical protection of the cable. For this purpose, the following materials are used:

• Kevlar thread;
• tape made of steel;
• wire made of steel.

2. Outer sheath. Protects the cable from external influences, both mechanical, and the effects of harmful substances, moisture.

Types of cable designs

There are the following types of designs:

• Cable for outdoor installation. The purpose is laying in the ground or in a pipe.

The sphere of application of single-lighted cables is the presence of 10 light-emitting diodes. But with more fiber, it is more appropriate to use a multitrack module or a bundle module.

Modules are wrapped in layers along the central force element.

Power elements are covered with a polyethylene sheath or a laminated shell made of polyethylene laminated with aluminum.

The module is filled with a hydrophobic compound.

It is possible to superimpose an additional layer of protective armor on the shell. Corrugated steel bands are ideally suited to protect against pests.

• Cable for internal installation. Used inside buildings. For cables of this type, there is no need for grounding, since they do not contain metal. Easy to use with ease and flexibility.

Distinguish cables:

1. Distributive. For individual wiring. Three types of construction based on the diameter of the module:

• under severe conditions of use - 0.27 cm;
• under standard conditions of use - 0.24 cm;
• under lightweight conditions of application - 0,20 cm.

They are laid in vertical shafts inside buildings or in channels located below the freezing level, between neighboring buildings.

2. Connecting. Used as cable jumpers or in the process of termination with plug connectors.

3. Special cable. These are universal cables used both on the outside and inside. Features of an optical cable of a similar type:

• full waterproof;
• no need for additional splice at the entrance to the building;
• availability of special fire requirements.

Species of special cables are a submarine cable and optical self-supporting cable, also called air.

Air cables are laid on poles. It can be lighting and communication poles, power lines, electric transport networks. There are a lot of options for the installation of air cables. It all depends on the model. A characteristic feature of the air cable is the high tensile strength. After all, the load on it is not limited only to its own weight. There is an increase in the load due to icing, wind.

Underwater cables are laid deep underwater. The central tube of a cable of this kind is made of copper and filled with a hydrophobic gel. But the armor is 2-3 layers of galvanized steel wire. Between layers and outside is a layer of polyethylene. As a result, the cable feels great at great depths and withstands significant pressure