Sept. 11, 2015, 4 p.m.

Fiber Optic Transmission Lines

fiber, волс, OTDR, рефлектометр

Pulse reflectometers OTDR (Optical Time Domain Reflectometer) operate on a similar principle, which is used in reflectometers for testing electrical cables. Reflectometer submits a powerful light pulse into the optical fiber, as well as an electrical reflectometer submits powerful probe pulse in the electrical cable. At the same time it carried out the measurement of power and pulse delay time that is returned back to the OTDR. The difference between the electric OTDR is that the metallic conductor returns only pulses that are reflected by strong inhomogeneities in the cable, that is, from the location of cable deformation, while the optical fiber return pulses are not only places of large irregularities, but also due to the Rayleigh effect scattering. Rayleigh scattering occurs due to changes in the refractive index of the optical fiber when it is stretched during manufacture. Such inhomogeneities arising in the manufacture of the optical fiber is extremely small, but have some effect on the scattering of the light beam that is scattered by these irregularities in all directions, including back to the OTDR.

Passage of the light beam from the optical fiber OTDR
Sept. 6, 2015, 3:54 p.m.

Fiber Optic Transmission Lines

fiber, волс, измерения, оптический тестер

There are two methods of measuring the loss in the optical fibers which, in accordance with G. 651 and G. 652, is considered the reference - fiber breakup method and the method of insertion loss. The loss measurements are made by means of optical testers. In the method of fiber breakup P1 measured power (in dBm), passed through the fiber. The fiber breaks off at a distance of about two meters away from the injection point and measured radiation power P2 (dBm), passed through a short section of the remaining fiber. The value of loss in the fiber is determined as the difference between A (dB) = P1 (dBm) - P2 (dBm)

Measurement of losses by the breakup of fiber
Aug. 3, 2015, 3:28 p.m.

Fiber Optic Transmission Lines

fiber, волс, компоненты

Passive Components Fiber-optic communication lines are divided into the following types:

  • optic connectors and splitters;
  • optical converters;
  • optical isolators;
  • optical switches.

Splitters

The most important passive components are FOL optic connectors and splitters, which are used for consolidation or separation of optical signals.

Functional diagram of the splitter
Aug. 2, 2015, 3:18 p.m.

Fiber Optic Transmission Lines

fiber, волс, монтаж

Installation of couplings

Mounting of couplings shall be in accordance with installation instructions for the particular type of coupling of the manufacturer (supplier) couplings. Connection of optical fiber mounting couplings should be carried out under the control of the welding method of attenuation OTDR. The value of a welded joint fiber attenuation, calculated in the direction A - B, B - A, should not exceed 0.1 dB. Each coupling after installation should be the marked sheet of lead or plastic ring tag. Each mounted clutch must be drawn up in duplicate passport. One copy is placed in the sleeve, the second is attached to the as-built documentation. If it provided by the project, and then the optical coupling OK stock placed in a specially made case, which must be secured to the support.

On the local communication networks, mainly to be used optical coupling of domestic manufacturers, designed to meet current technical requirements and compliance with the declaration of the Ministry of Information Technologies and Communications of the Russian Federation. Is allowed to use on the local networks of optical coupling of the foreign producers if the certificate of conformity and standard solutions for installation, mounting and protection of optical couplers in their places of assembly.

Optical Coupler for armored OK, laid in the ground, should ensure that:

  • the ability to electrically connect the screens or metal power elements matched OC structural elements of at least 2.5 mm2;
  • the ability to lead wires of the metallic elements construction OC, separately for each OC to connect to an external ground.
Aug. 1, 2015, 3 p.m.

Fiber Optic Transmission Lines

fiber, волс, конструкция

Introduction

Currently, the Russian market is widely featured products, both domestic and foreign manufacturers of optical couplings for installation of cables. Widely known and used clutch of such manufacturers as: Raychem (Belgium), Reichle & DeMassari (Switzerland), RXS / Simens (Germany), ZM (USA), Fujikura (Japan), Ericsson (Sweden), the Nokia (Finland), AT & T (USA), Pirelli (Italy), Alcatel (Germany).

These companies provide a wide choice of all types of couplings each customer to solve any problem. Along with the delivery of the coupling component manufacturers of the necessary additional accessories such as brackets, housings, additional accessories and consumables items. Deliver them also the necessary equipment and tools, including even the tables of the installation work.

July 29, 2015, 2:47 p.m.

Fiber Optic Transmission Lines

fiber, волс, монтаж

Basic concepts and definitions

The most responsible operation in the process of construction of fiber-optic, predetermining the quality and range is the installation of optical fibers. Such a combination of fibers and installation cables are produced in the manufacturing process as well as during the construction and operation of cable lines.

Installation is divided into permanent (fiber welding) and temporary (plug connectors). Fiber optic connectors typically are valves designed for adjusting and fixing the fibers to be connected, as well as mechanical protection for the splice.

The main requirements for connectors are:

  • simple structure;
  • small transient loss;
  • resistance to external mechanical and climatic influences;
  • reliability;
  • In addition to the detachable connectors are required constancy of parameters during re-docking.

Insertion loss connection of optical fibers in a cable transmission path, are divided into external and internal.

External referred to the losses associated with the features of the connection method, including the preparation of the ends of optical fibers, and comprising lateral displacement of the core, diversity ends, the slope of the axes, the angle of the fiber end face, the Fresnel reflection.

I nternal losses are associated with the properties of the resulting optical fiber and, for example, variations in core diameter, numerical aperture, the refractive index profile, netsirkulyarnostyu core Concentricity core and cladding.

July 28, 2015, 1:56 p.m.

Fiber Optic Transmission Lines

fiber, волс, ВОК

Classification of fiber optic cables

Fiber-optic cables (FOC) - a cable products, containing a number of optical fibers and the reinforcing member enclosed in a common envelope, on top of which, depending on the operating conditions of the protective cover can be imposed.

Fiber-optic cables are classified by purpose and conditions of use, as shown in the figure below.

Since FOC less durable than electric cables, they must be protected from the harmful effects of the environment and human activities, which include mechanical stress (tension, bending, compression, torsion, shock, vibration); temperature changes; water penetration.

June 29, 2015, 1:47 p.m.

Fiber Optic Transmission Lines

fiber, волс, модовая дисперсия

Distinguish mode dispersion, which is caused by a large number of modes in the optical fiber and the chromatic dispersion associated with the incoherence of light sources actually operating in a certain range of wavelengths.

Consider the propagation of the light beam along the multimode fiber. In this case there are two modes, the two beams. The first extends along the longitudinal axis of the fiber, while the other is reflected from the interfaces of media. Thus the path of the second light beam is greater than the first. As a result, when the two beams carrying the electromagnetic energy are added together, compared oblique beam with an axial beam is the time delay, which is calculated by the following formula:

c – speed of light
l – fiber length
n 1 , n 2 – refractive indices of the core and shell

June 29, 2015, 1:36 p.m.

Fiber Optic Transmission Lines

fiber, волс, потери

The most important parameters are the optical fiber loss and attenuation of the transmitted energy. These parameters define the range of the FOC and on its effectiveness. Attenuation in optical fibers due to manifestation of the following losses:

α c – own loss of fiber waveguides
α k – additional cable losses
α ik – absorption loss in the infrared region
α pr – the loss caused by the presence of impurities in the optical fibers

Proper loss fibers consist, in turn, an absorption loss of α p and scattering loss α r :

Attenuation due to the absorption due to the losses on the dielectric polarization depends strongly on the properties of the fiber material and is calculated by the following formula:

tgδ – dielectric loss tangent

The attenuation in the infrared region, situated in the wavelength range of more than 1.6 microns, calculated by the formula:

C and k – constant coefficients. For quartz glass C = 0,9; k = (0,7—0,9) мкм.

June 28, 2015, 7:22 p.m.

Fiber Optic Transmission Lines

fiber, волс, типы волс

Depending on the number of the operating frequency propagating waves (modes) of the fibers and is separated into one multimode. The number of modes is dependent on the ratio of the diameter of the fiber core and the wavelength for optical fibers having step-index is calculated as follows.

α – fiber core radius,
λ – wavelength,
Δ – relative refractive index difference.

Since n 1 and n 2 have very similar meanings, the nominal value ∆ for most optical fibers is within

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Last comments
b
Nov. 9, 2019, 7:28 p.m.
bastonc

спасибо ещё раз. огромное, за уделённое время
b
Nov. 9, 2019, 7:24 p.m.
bastonc

Спасибо Вам большое. Буду изучать.
Nov. 9, 2019, 4:58 p.m.
Evgenij Legotskoj

Добрый день. По первым двум вопросам вы найдёте ответ в этой статье - PyQt5 - Урок 008. Работа с QTableWidget (Обновление урока 006) Что касается последнего вопроса, то я вам…
Nov. 9, 2019, 1:50 p.m.
Evgenij Legotskoj

Как и обещал, вы можете посмотреть новую статью QML - Урок 037. Кастомизация кнопок в QML (Обновление урока 002) . Там же найдёте ссылку на Git репозиторий. Не забудьте поставить звёз…
b
Nov. 8, 2019, 6:40 p.m.
bastonc

Приветствую. Подскажите пожалуйста пару моментов. 1. Как сделать столбец не редактируемый, а остальные ячейки остаются редактируемыми 2. Как оталвливать события двойного клика для реда…
Now discuss on the forum
s
Nov. 15, 2019, 10:06 p.m.
sladkoewka

За пример буду очень благодарен, т.к. я новичок и с подобным пока не работал.
Nov. 15, 2019, 6:37 p.m.
Intruder

Евгений, почитав про эту проблему пришел к выводу, что либо нужно говорить очередь, либо все вернуть из библиотеки (dll в моем случае) в приложение, потому что в приложении все работает просто з…
Nov. 15, 2019, 5:06 p.m.
Evgenij Legotskoj

Ну тогда не знаю )) Я большую часть времени на C++ с Qt работаю, а PyQt5 у меня боком. Так что, чем можем помочь ))
H
Nov. 15, 2019, 4:18 p.m.
Hyperfish

Да, пробовал, с преобразованием int array[]={1,2,3,4,5,6,7} в jintArray(array). Если так, то программа компилируется без ошибок и предупреждений, но вываливается с ошибкой времени выполнени…
Nov. 15, 2019, 2:48 p.m.
Evgenij Legotskoj

Ну собственно поэтому я и сказал, что бесполезное это занятие.
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