How to choose the components for internal plant installations

The choice of components for the installation of optical fiber in the internal plant is influenced by several factors, including the choice of communications equipment, the physical routing of the cable network and the codes and regulations of the construction. If a corporate LAN type network is designed, it is likely that a fiber optic backbone network will be included to connect the rooms where the computers are to the connecting rooms.

The connection rooms house the switches that convert the backbone network ( backbone ) from fiber to copper UTP cables for cable-connected desktops, and to copper or fiber for wireless network access points. At some desks, especially in engineering or design departments, fiber may be required to the desk because it offers greater bandwidth. Insecurity systems (alarms, access control systems, CCTV cameras), additional cables or fibers and construction management systems may be required).

To design fiber optic cable networks it is necessary to coordinate with all the people involved in one way or another in the network, including IT staff, company management, architects and engineers, etc., to ensure that all wiring requirements are analyzed simultaneously so that resources can be shared.
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As in the OSP design, let's first analyze the fiber choice. Most networks in the internal plant use multimode fiber; however, many users now install hybrid cables with single-mode fibers for future extensions. The OM1 62.5 / 125-micron fiber that was used for almost two decades has been replaced by the new OM3 50/125 laser-optimized fiber, as it offers significant advantages over bandwidth and distance.

Almost all the equipment works as well with the OM3 50/125 fiber as it worked with the OM1 62.5 / 125 fiber, but it is always a good idea to check with the equipment manufacturers to make sure. In the network design documentation, remember to include the instruction to mark all cables and connection panels with water color labels, to indicate that it is the OM3 fiber.

Use of wiring standards

Use of wiring standards

Many documents related to cable network design focus on industry standards that apply to communications systems and cable networks. It is important to understand why and who create these standards. These standards are created by manufacturers of products intended for other manufacturers, not users or installers.

As one member of one of the standards committees once stated, the standards are "mutually agreed specifications for product development." They guarantee that products belonging to different manufacturers work together properly. The main purpose of the standards is not to train installers or end-users since that is the responsibility of the manufacturers of the products that meet the standards.

Where you can get information about the relevant standards. Buying expensive documentation of the standards is not usually the appropriate way to learn about them. The manufacturers that created the standards and develop products that meet these standards provide informational material for you and your customers.
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Almost all wiring manufacturers include a section at the end of their catalogs, or on their websites, which analyzes the relevant standards. It explains how the systems are, what components they use to develop them and how they should be tested. There is nothing better than a vendor's catalog or a file downloaded from your website to access the information you need about the standards.

OTDRs are the most complex fiber optic instruments

Test with OTDR
OTDRs are the most complex fiber optic instruments that can take a snapshot of fiber and show the location of splices, connectors, faults, etc. OTDRs are powerful test instruments for fiber optic cable networks, as long as you understand how to properly configure the instrument for testing and interpret the results. When used by a skilled operator, OTDRs can locate faults, measure cable length and verify splice loss. To some extent, they can also measure the loss of a cable network. The only fiber optic parameters that do not measure is the optical power in the transmitter or receiver. There is a lot of information in the OTDR plot, as shown in the actual plot of the image below.

C8-10 OTDR trace

OTDRs are almost always used in external plant cables to verify the loss of each splice and find tension points caused by the installation. They are also widely used as tools for solving external plant problems since they can locate problem areas such as the loss caused by the tension placed on a cable during installation. Most OTDRs lack the distance resolution to be used in the shorter cables that are typical of internal plant networks.
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OTDRs are available in versions for standardized, single-mode or multi-mode fiber optic systems, in the appropriate wavelengths. To use an OTDR correctly, it is necessary to understand how it works, how to properly configure the instrument and how to analyze the paths. OTDRs offer a "self-test" option, but if you use that option without understanding the OTDR and without manually checking your work, it usually leads to problems.

Fiber Optic Check

After all fiber optic cables are installed, spliced ​​and terminated, they must be tested. With each fiber optic cable network, you must check continuity and polarity, point-to-point insertion loss and then solve any problem that could occur in each fiber of each cable. If it is a long external plant cable with splices along with it, you may also want to verify the individual splices by testing with OTDR (optical reflectometer in the time domain), since it is the only way to ensure that each splice is made correctly. If you are the network user, you may also be interested in testing the power of the transmitter and receiver, since the power is the measurement that indicates whether the system is operating properly.

Testing is the main subject of most industry standards since there is a need to verify the specifications of the components and systems in a consistent manner. A list of TIA and ISO standards on the optical fiber is available on the FOA website. Most of these tests are related to manufacturing tests to verify the operation of the components and are not relevant to the installation tests.

The testing of fiber optic components and cable networks requires several evaluations and measurements with the most common tests listed below. Some involve the inspection and judgment of the installer, such as visual inspection or tracking, and other sophisticated instruments that provide direct measurements are used. The optical power, required to measure the power of the source, the power of the receiver and, when used with a test source, to measure the loss or attenuation, is the most important parameter and is required for almost all tests of optical fiber. The backscatter measurements performed by an OTDR are the measurements that remain in importance, especially for testing external plant facilities and troubleshooting. 

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Measurements of the geometric parameters of the fiber and the bandwidth or dispersion are essential for fiber manufacturers but are not relevant to the field test. Every installation requires the solution of installed cable and network problems. but they are not relevant to the field test. In every installation, the solution of installed cables and networks problems is required. but they are not relevant to the field test. Every installation requires the solution of installed cable and network problems.

Anaerobic and polished adhesive

Anaerobic and polished adhesive

These connectors use a quick-drying "anaerobic" adhesive that heals faster than other types of adhesives. Several techniques are used to apply this adhesive, even by injecting it into the connector before inserting the fiber or simply bypassing the adhesive over the fiber with a cloth before inserting it into the connector. These adhesives dry in 5 minutes if left alone or in 30 seconds if a chemical accelerator is used. 

Anaerobic connectors work well if their technique is good, but some do not have the wide temperature range that epoxy adhesives have. Many installers use Loctite 648, with or without the accelerator solution, as it is neater and easy to use.

The termination process
The termination process is similar for all types of adhesive/polished connectors. You should start by preparing the cable, stripping the outer jacket and cutting the reinforcement elements. Then, you must peel the fiber with a special tool that removes the plastic coating without damaging the fiber. Then you should clean the fiber and set it aside. You must apply the adhesive on the connector or on the fiber, and then the fiber is inserted and crimped to the body of the connector.

When the adhesive is dry, the fiber is then cut near the end of the splint.  Polishing includes three steps: first, perform a "polishing in the air" to wear the cut fiber near the splint surface. Then, polish with two sandpaper of different weights on a rubber pad using a polishing disc to keep the fiber perpendicular to the surface. 
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Look at the end of the splint with a microscope to inspect the fiber optic. Read the chapter on testing (checking) for more information on inspecting the connectors.

The distance between the ends of the fiber causes two problems

Insertion loss and reflectance. The cone of light that is formed from the connector will overflow over the fiber core that receives the light and will be lost. In addition, the air space at the junction between the fibers causes a reflection when the light experiences the change in the refractive index when transmitted from the fiberglass to the air in that space. This reflection (called Fresnel reflection) amounts to about 5% in the usual, smooth and polished connectors, and means that no connector that has an air gap will have an optical loss level of less than approximately 0.3 dB. This reflex is called reflectance or loss of optical return, and it can become a problem in laser-based systems. A number of connector polishing techniques are used to create a convex end in the fiber and thus ensure physical contact of the fiber ends and reduce reflectance as much as possible. In mechanical splices, the return reflection can be reduced by using non-perpendicular cuts that cause these reflections to be absorbed by the fiber coating.


The fiber end must be properly polished and clean to minimize optical loss. A rough or dirty surface can scatter or absorb light. Since the optical fiber is so small, the usual dirt that is present in the air can be a major cause of optical loss. If the connectors are not terminated, they must be covered with dust caps provided by the manufacturer to protect the end of the splint from dirt. You should never touch the end of the splint because the oiliness of our skin causes dirt to adhere to the fiber. Before connecting and testing it is recommended to clean the connectors with lint-free cloths moistened with isopropyl alcohol, or with dry fiber cleaners.
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There are two directional causes of optical loss due to improper alignment of the fibers: the differences in the numerical aperture (AN) and in the diameter of the core that are inherent in the fibers to be joined. These differences will create connections that have different optical loss levels depending on the direction in which the light propagates. The light that comes from a fiber with a higher AN will be coupled and saturated to the core of the fiber that receives that light and will be more sensitive to the angularity and space between connectors so that the transmission of a fiber of greater AN to an of lesser AN will record a greater optical loss than would be recorded in the opposite direction. Likewise, the light that comes from a fiber with a larger core will register a high optical loss when coupled to a smaller diameter fiber and, conversely, when a fiber of small diameter is coupled into a large diameter fiber, a loss is obtained minimal optics since the light is much less sensitive to the distance between the ends of the fibers or to the lateral deviation.

Components and types of Fiber optic

Fiber optic in detail.
Core: in silica, molten quartz or plastic. In it, the optical waves propagate. Diameter: 50 or 62.5  µm for multimode fiber and 9 µm for single-mode fiber.
Optical case: Generally of the same materials as the core but with additives that confine the optical waves in the core.
The protective coating: it is usually made of plastic and ensures the mechanical protection of the fiber.
Types of optical fibers
Singlemode fiber: Potentially, this is the fiber that offers the greatest information transport capacity. It has a passband of the order of 100  GHz / km. The largest flows are achieved with this fiber, but it is also the most complex to the implant.

The drawing shows that only the rays that have a trajectory that follows the fiber axis can be transmitted, so it has earned the name of "single-mode" (propagation mode, or path of the light beam, unique). They are fibers that have the diameter of the core in the same order of magnitude as the wavelength of the optical signals they transmit, that is, about 5 to 8  mm.

If the core is made of a material whose refractive index is very different from that of the roof, then it is referred to as single-mode stepped fibers. The high flows that can be achieved constitute the main advantage of single-mode fibers since their small dimensions imply delicate handling and entail connection difficulties that are still poorly dominated.
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Multimode gradual gradient index fiber: Multimode gradual gradient index fibers have a passband that reaches up to 500  MHz / km. Its principle is based on the fact that the index of refraction inside the core is not unique and decreases when it moves from the core to the roof.
The light rays are focused on the fiber axis, as can be seen in the drawing. These fibers allow reducing the dispersion between the different propagation modes through the fiber core. The multimode fiber of gradual gradient index of size 62.5 / 125  m (core diameter / shell diameter) is standardized, but other types of fibers can be found:

What kind of fiber optic?

When reading an article or when talking with someone about fiber optics it is important to know what fiber optic they are referring to. Not all fiber optic cables are the same. In this book we will focus on the optical fiber used in communications; however, it can also be used in lighting, in medical controls, in non-destructive tests and in the manufacture of sensors for physical measurements.

In the field of communications, there is the optical fiber for "external plant", which is used for telephone networks, cable television (CATV), metropolitan networks, services, etc., and the fiber used for the internal plant, that is, the one found in buildings and in various facilities. In the same way that "cable" can have many meanings - the optical fiber that is used for electric power, security, ventilation, heating and air conditioning (HVAC), closed-circuit television (CCTV), Local area networks (LAN) or telephony is not the same, which can generate great confusion for the beginner. Let's define some terms.

External plant

Telephone, cable television, and internet companies use fiber optic, which is almost entirely outside buildings and referred to as an external plant (OSP),   as it hangs from poles, it is underground, it goes through underground ducts or it can even be submerged underwater. Most cross long distances, ranging from a few meters to a few hundred kilometers.

Generally, the cables of the external plant have a very high amount of fibers, up to 288 or more. Cable designs have been optimized according to your application: duct cables are optimized to be tensile and resistant to moisture; underground cables are optimized to resist moisture and rodent damage; the aerial cables are in front of the continuous traction and extreme weather conditions, and submarine cables are optimized to resist moisture penetration. The installation requires special equipment, such as cable handles, and even trailers to transport huge cable reels.

The long distances involve spliced ​​cables since the cables are not made of lengths greater than 4-5 km. (2.5 - 3 miles), and most splices are made by fusion splices. Connectors (usually SC or LC) are spliced ​​at the end of the cable, turning them into connectorized fiber cables ( pigtails). After installation, all fibers and splices are tested with an OTDR (optical reflectometer in the time domain).

If this seems costly, you're right! Generally, the installer has a temperature-controlled vehicle, be it a truck, a trailer and/or a truck with a crane. Investing in fiber optic fusers, OTDR and other equipment can be quite expensive. Most of the telephony facilities in the external plant are carried out by the same telephone companies, while a small number of a large number of specialized installers perform cable television installation, public and municipal services.

Wiring in the internal plant

On the contrary, the wiring in the internal plant (wiring in buildings and other facilities) implies shorter distances, rarely greater than a few hundred meters, generally with less fiber per cable. Mostly multimode fiber is used, except in the case of the informed user who installs hybrid cable with multimode fiber and single-mode for future high bandwidth applications.

Practically no fusion splices are used in these types of facilities. The cables for the connection between buildings can be double-coated, one of polyethylene for the external plant over another of PVC, for installations in buildings that require cable coverings with fire-retardant properties. Today, connectors generally have less loss than splices, and connection panels provide greater flexibility for movements, additions, and modifications.

The most used connectors are those of type SC or ST, and those of type LC are beginning to be more popular. The terminations are made by installing connectors directly at the ends of the fiber, mainly through the use of splicing techniques with pre-polished adhesives or connectors. The tests are performed with a source and a meter, but each installer should have an indicator for light flashes to verify the continuity of the fiber and the connection.

Unlike the technician working in the external plant, the cable installer working in the internal plant (which generally also installs the power cable and the cat. 5/6 cable for LAN networks) probably makes a relatively minor investment in tools and equipment. There are thousands of wiring installers that perform fiber optic work; They discovered that it is not "a science", and that their small initial investment in training, tools and testing equipment is recovering rapidly.

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Installers

Not many installers perform both types of wiring: in external plant and in the internal plant. The companies that do it are generally large and have separate departments that perform each type of wiring with different personnel. Most contractors only perform wiring in the internal plant.

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Emission of a soliton wave from a nonlinear waveguide with a PTS cladding.
The results of numerical simulation of the emission of a soliton wave from an optical waveguide in which the sheath is made of a nonlinear material (polyacetylene para toluene sulfonate ( PTS )) are presented. This material with cubic non-linearity and self-focusing demonstrates a defocusing nonlinearity, which imposes restrictions on max. nonlinear gain changes. The influence of these restrictions on the emission of a soliton wave in the 1st transverse dimension is investigated. The results of numerical simulation for emission in 2 dimensions are proposed.

Emission of pulsed nonlinear surface waves and solitons by nonlinear waveguides with a gradient refractive index.
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The results of a study of pulsed beam propagation in nonlinear ion-exchange waveguides are presented. The limiting values ?? of the input power and film thickness were calculated to obtain emission using the variational method provided that there was no dispersion. Analytical expressions that can be obtained are obtained. used to calculate propagation characteristics.

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A short catalog of fiber-optic cables manufactured by Samara Optical Cable Company CJSC is presented. The equipment used in the production process is considered.

Temporary demultiplexing, which uses selective Raman amplification.

A fiber-optic transmission system is proposed in which a non-linear optical fiber demultiplexer is used. The time-multiplexed optical signal is transmitted along the first optical path, and the pump signal is transmitted differently. The pump pulses are synchronized with the pulses in the multiplexed optical signal, which highlighted. The amplification of the selected optical signal was carried out using a Raman amplifier.

 

40 Gb / s GaAs P - HEMT driver module for optical communications systems.

A 40 Gbit / s driver module was developed and implemented, which includes a set of 2 distributed amplifiers. The IC is made using 0.15 µm GaAs technology of transistors with high electron mobility. The characteristics of the module are given.

Converter/interface between RF and fiber optic cables.

The electronic-optical interfaces (in particular, converters) intended for connecting cables transmitting information on RF carriers to fiber-optic cables are considered. A duplex converter/interface is proposed, connecting several broadband RF cables with 2 optical ones.

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Compensation of optical dispersion.

A new method for compensating the dispersion of optical fibers is proposed. Compensation of optical dispersion is achieved using a polarizing beam splitter, which has 3 ports, which compensates for the dispersion of the fiber and devices that change the polarization mode. The principle of operation of a device that implements the proposed compensation method is considered.

Advances in Science and Technology in the Field of Fiber Optic Communications

A two-wave optical communication network with a ring architecture for a computer group.
A fiber-optic communication network is described for which the value of the message wavelength is part of the address. The network architecture has the form of a double ring, and the connection between the rings is carried out by tracing the signals along the wavelength. 2 wavelengths are used, one of which is used to transfer data inside the ring, and others to go to another ring.
Optical interconnects for multiple access with code division multiplexing and a communication network based on spectral multiplexing with temporary access.
A new architecture of optical interconnects based on the method of spectral multiplexing with time access is proposed. The possibility of using a similar architecture in communication systems with multiple access is considered. The use of spectral multiplexing with time access allows developing the concept of optical multi-station access with code division multiplexing, which will significantly reduce the cost of optical communication networks with a transmission rate of ~ Tbit / s.
Integrated information network on a combined (coaxial fiber) cable.
The structure of a duplex integrated information network in which hybrid cables (coaxial fiber) are used is considered. Functions, methods of formation, monitoring and control of 3 subsystems: KTV, data transmission between computers and cable telephone systems are developed in detail. Given that. system data
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The use of optical fibers of variable diameter and multichannel connectors for connecting fiber-optic communication networks using multimode and single-mode optical fibers.
The problem of making connections between optical fibers used in the composition of local fiber-optic communication systems and long-distance communication systems using single and multimode fibers is considered. The possibility of solving the problem using optical fibers or waveguides with a change in fiber diameter or waveguide width along the path and the use of multichannel devices for connecting optical fibers is shown. It is shown that the use of optical fibers with a variable diameter reduces the insertion loss when connecting systems.

Fiber Optical cable safety

Remember the last time you looked into your company's safety plan with a view to finding items related to
working with fiber in it?

Do not remember? This is not surprising, because in many organizations safety precautions when working with optical cables do not pay due attention.

Consider several aspects of safety when working with optical fiber: the classification of radiation sources according to their degree of danger to eyesight, methods of working with optical fibers and the use of chemicals.

As a result of the development of the industry for many years, we have several types of radiation sources of different power, operating at well-defined wavelengths (see table). Three types of fiber optic systems are used: LEDs, conventional lasers, and vertical-cavity laser (Vertical-Cavity Surface-Emitting Laser - VCSEL). There are several options for these three types of devices: lasers with a Fabry-Perot resonator and distributed feedback, as well as surface and end radiation LEDs. In addition, amplifiers are widely used to amplify optical signals, including Semiconductor Optical Amplifier (SOA) and more common amplifiers based on the Erbium-Doped Fiber Amplifier (EDFA).

Table: Sources of radiation used in telecommunications.
Note. Some lasers, including the VCSEL type, are listed with two classes at once since they exist in versions with different powers and for different applications. If in doubt, choose a more powerful Class 3 laser.

In North America, the main standard issued by the American Institute of Laser (Laser Institute of America) in 1988, which defines safety measures when working with optical cable systems, is ANSI Z136.2. (see “Classification of laser radiation sources according to their degree of danger to eyesight”).

Radiation detection.

Among the instruments used to detect radiation, the most common are optical power meters. They contain photodetectors, with the help of which the radiation power of various wavelengths is measured. In addition, other devices are also used - photosensor cards that respond to infrared radiation incident upon them with appropriate electronic activation, and infrared vision devices that convert infrared radiation with wavelengths of 800 and 1300 nm into visible light. Using the latter, the power characteristics of radiation sources are usually determined.

Specialists dealing with optical data transmission technology must be guided by the rule that any fiber can be active. Therefore, you should never look into the outlet of the transmitter or into the end of the connector.

For inspection of elements of optical cable systems, the most common instrument is a microscope. It is clear that it allows you to explore the surface of the fiber end, but is not able to detect the infrared radiation emanating from it. To control the quality of fiber surface treatment, microscopes with a magnification of 200-400 times are suitable. Usually, a laser filter is built into them to protect the eyes, attenuating the radiation level by 2–35 dB depending on the wavelength. Microscopes with filters are somewhat more expensive than conventional microscopes but safer. Always use precisely such microscopes in your work and, before ordering them, study the specification of each of them.
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Cheaper microscopes, with a magnification of 30-100 times, which are equipped with many kits for installing optical cable systems, often do not have filters at all. When working with them, the probability of accidental eye damage is high. Therefore, such devices are not recommended to be used either to control the quality of fiber processing or to verify compliance with safety requirements. In any case, when working with such a microscope, the user should always wear glasses that protect the eyes from laser radiation.

FOCL (fiber optic communication lines) details

The highest throughput among all existing means of communication has an optical fiber (dielectric waveguides). Fiber-optic cables are used to create fiber-optic communication lines - fiber-optic communication lines that can provide the highest speed of information transfer (depending on the type of active equipment used, the transmission speed can be tens of gigabytes or even terabytes per second).

In addition to the unique transmission characteristics, quartz glass, which is the FOCL carrier medium, has one more valuable property - low losses and insensitivity to electromagnetic fields. This sets it apart from conventional copper cable systems.

This information transfer system, as a rule, is used in the construction of working facilities as external highways, combining disparate structures or buildings, as well as multi-story buildings. It can also be used as an internal carrier of a structured cabling system (SCS), however, complete SCS made entirely of fiber are less common - due to the high cost of building optical communication lines.
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The use of FOCL allows locally combining jobs, ensuring high-speed Internet downloads simultaneously on all machines, high-quality telephone communications, and television reception.

Sections of the certified fiber optic technician course

It has a very important practical part that supposes approximately 70% of the time of the course. In the practical part, we work on fiber optic cables, connectors, splices, use test equipment and design a fiber-optic network as learned in the course. To begin each practical workshop, the teacher shows in great detail how the different techniques and methods are performed working with fiber optics and constantly monitors progress and teaches how to improve the technique.
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To obtain the official CFOT certification, participants must pass a final written exam. The exam is the test type with the book closed and consists of 100 questions. The minimum score is 70% correct answers. In addition, the skills and techniques of working with fiber optics in practical workshops must be demonstrated.

If you wish to attend the certified fiber optic technician course or receive more information, fill out and send the following contact form and we will send it to the course organizer immediately.

You can also find information on other technical courses and seminars in our Calendar of Technological Events or watch the recording of our Webinars.