Published On: Thu, Feb 27th, 2020

Optical cables – Some important practical knowledge

Author: Radoje Jankovic

Introduction
In this paper I will not talk about the theory of optical cables and optical fibers because there is a wealth of literature on this. I will focus mainly on practice and the basic necessary information that is important to practitioners.

Fig. 1.  Some types of optical cables

I used catalog information and some technical instructions for fiber optic cables and fibers to create this paper. I also showed more of my photos and photos I got from colleagues who are professional in fiber optics.

  1. Optical fiber labels

The standard optical fiber labels are shown here.

1.1 optical fiber: a fiber shaped waveguide made of dielectrics

1.2 core: area in the middle of the fiber, mainly with a higher refractive index, through which most of the energy is transferred

1.3 cladding: a dielectric material that surrounds the fiber optic core

1.4 primary coating: a thin layer applied directly to the wrap, usually at the same time as the fiber extraction, in one or more layers, to preserve the entirety of the wrap

1.5 secondary coating: a sheath applied directly to the primary protection to enhance optical fiber protection during handling and use

1.6 colored coating: a thin sheath on primary or secondary protection to distinguish fibers by color

1.7. Fiber buffer: a material or assembly of materials that protects fibers from physical damage

1.8. Fiber jacket: any subsequent protection applied to the secondary or colored protection to reinforce the fiber at exercise

2. Labels relating to the optical cable

The standard labels for an optical cable would be as follows.

2.1 Optical cable: an assembly containing one or more optical fibers or fiber bundles within a common cover intended to protect the optical fibers from environmental influences, as long as it maintains the transmission quality of the optical fibers NOTE: the cable may also contain metallic conductors.

2.2. Fiber unit: a basic element composed of fibers protected by buffers, used to make optical cables

2.3. Fiber Ribbon: a set of parallel individually shielded optical fibers arranged in a linear order under the same flat protection

2.4 Fiber Bunch: A set of unused fiber optics packed together with a small link

2.5 Fiber bundle: a fiber stack within a single element, such as a tube or groove of fiber optic cable

2.6 Cable core: the inner part of a cable containing optical fibers

2.7 Strength member: cable element, metal or non-metal, that mechanically reinforces the cable, especially against stretching and compression

2.8 Sheath: cable element surrounding the cable core to provide protection against environmental impact and mechanical action

2.9 Bumper (screen): conductive layer or layers for controlling the electric field inside the insulation. It can provide a flat surface at the borders of the insulation and help to eliminate the spaces between those borders

2.10 Cable shield: a grounded metal layer that retains an electric field inside the cable or protects the cable from external influences

2.11 Armoring: a cover consisting of metal bands or wires, principally intended to protect against external mechanical action 3

2.12 Loose cable: cable in which the optical fibers are to some extent movable within the cable structure

2.13 Tight cable: cable in which optical fibers are not mobile within the cable structure

2.14 Loose tube cable: a loose cable whose fiber units are tubes containing moving tubes or bands of fibers

2.15 Slotted core cable: cable in which the fiber units, or one or more fibers or strips of fibers or tubes containing them, are arranged in coiled grooves in the circular core of the cable or in the cable with more than one cable ezgara

2.16 Ribbon cable: cable in which optical fibers are arranged in fiber strips

2.17 Aerial cable: cable intended to be supported or supported

2.18 Self supporting cable: an overhead cable that does not require a special support device

2.19 Duct cable: cable intended for placement in cable ducts

2.20 Cable for direct burial: cable intended for direct grounding

2.21 Indoor cable: cable intended for laying in buildings,

2.22 Drop cable: cable intended to cover the outside of the network, especially from the junction box to the user’s property

2.23 Underwater cable: cable intended for laying in shallow water

2.24 Microduct fiber unit cable: an optical cable unit suitable for installation by blowing in a small diameter pipe

2.25 Microduct optical fiber cable: Optical cable suitable for inflowing in small diameter pipes

2. The meaning of the three digits of optical cables is as follows:

According to international standards, all fiber optic cables are marked with three digits, the meanings of which are as follows:

– # 211 – Optical installation cable for internal mounting on the holders, for one-way and two-way signal transmission, in accordance with standards SRPS EN 60794-2-11 and ISO / IEC 11801;

– # 221 – fiber optic distribution distribution cable, for indoor mounting, contains multiple fibers, in accordance with standards SRPS EN 60794-2-21 and ISO / IEC 11801;

– # 231 – Optical installation ribbon cable for internal mounting on holdings, in accordance with standards SRPS EN 60794-2-31 and ISO / IEC 11801;

– # 242 – Fiber optic installation cable for internal mounting, for one- and two-way signal transmission, containing IEC class A4 multilayered fibers, in accordance with standard SRPS EN 60794-2-42;

– # 311 – optical cable for external mounting by laying in a pipe, then directly in the ground, by tying it to special ropes or other telecommunication cables (as hanging), in accordance with standard SRPS EN 60794-3-11;

– # 312 – fiber optic cable for external installation by laying in a pipe or directly into the ground, intended for wiring on the holds, in accordance with standards SRPS EN 60794-3-12 and ISO / IEC 11801;

– # 321 – Optical self-supporting cable, intended for wiring on the holds, in accordance with standards SRPS EN 60794-3-21 and ISO / IEC 11801;

– # 322 – optical self-supporting cable, intended for short and medium distances, for laying on telecommunication supports, in accordance with IEC 60794-3-22;

– # 331 – fiber optic cable intended for bridging rivers and lakes, as well as for laying on the coast, in accordance with standard SRPS EN 60794-3-31;

– # 341 – Optical cable for laying in rain and sanitary sewers, in accordance with standard SRPS EN 60794-3-41;

– # 351 – optical cable for installation in high-pressure gas pipelines, in accordance with standard SRPS EN 60794-3-51;

– # 361 – Optical cable for installation in drinking water pipelines, in accordance with standard SRPS EN 60794-3-61;

– # 411 – fiber optic cable in single-layer earth rope with aluminum alloy wires, in accordance with standard SRPS EN 60794-4-10;

– # 412 – fiber optic cable in a two-layer earth rope with aluminum alloy wires, in accordance with standard SRPS EN 60794-4-10;

– # 413 – Optical self-supporting cable for laying alongside power lines, in accordance with standard SRPS EN 60794-4-13;

– # 414 – Fiber optic hanging cable for connection to power lines, in accordance with standard SRPS EN 60794-4-14;

– # 511 – small diameter optical cable for blowing by blowing in small diameter pipes and protected small diameter pipes, in accordance with standard SRPS EN 60794-5-11;

– # 521 – unit of optical cable for laying by blowing in small diameter pipes and protected small diameter pipes, in accordance with standard SRPS EN 60794-5-21. Only the letter J is used with this numeric part of the mark.

4. Optical cable protection information

Data on optical cables are divided into so-called There are usually four fields.

1. In this field, enter the part of the label on materials and the degree of protection achieved.

2. The marking of the type and degree of protection from the biological and mechanical action on the cable, which is achieved by applying a layer, reinforcement, bumpers and other materials, are as follows:
– ZG protected from rodents, and a milder degree of protection,- rodent protected;
– Rodent resistant OG, more stringent and protective, –  rodent resistant;
– ZT termite protected  –  termite protected;
– ZS ballistic protection, –  antiballistic.

3. The designation of the materials for protection against water and moisture penetration, in addition to the already mentioned sheaths, bumpers and fittings, are:
– G gel;
– B swelling straps or threads;
– M core filling mixture.

4. The following markings shall be used to indicate the required degree of protection of the optical cable against water and moisture penetration:
– ZV longitudinal protection against water and moisture penetration, milder degree of protection, –  water protected;
– NV impermeable longitudinal protection against penetration of water and moisture, more stringent degree of protection, – watertight

5. Core data

Optical cable core information is classified as follows:

1. The core data labels refer to its contents, then the fiber pattern, and for the fiber / metal hybrid cable cores, the labels also provide information on copper pairs.

2. The markings of the core elements are as follows:
– tube for housing and protecting fibers, –  tube;
– C tube in which fibers are mobile, –  loose tube;
– CC central tube, –  central tube; 

– Rm ribbed carrier with m grooves, –  slotted core;
– CRm m-grooved central rib carrier, –  central slotted core; 

– Tm tape with m pipes, – ribbon;
– JTm reinforced tape with m tubes, –  encapsulated ribbon;
– Sn bundle of n optical fibers;
– O fiber bumper, –  fiber buffer;
– ÷ mobile optical fiber is without special marking;
– P half-pressed secondary fiber protection;
– Compressed secondary fiber protection;
 ÷ symmetrical pair intended for transmission of analog and digital signals is without special marking;
– P pair for DC power supply

6. Some other important information…

a. The color of its protection is used to indicate the fiber number of a fiber element within a single cable element. For this purpose, in accordance with IEC 60304, the following colors, in alphabetical order, are used: white, yellow, green, purple, orange, blue, pink, gray, brown, turquoise, red and black.

b. In addition to the colors mentioned above, it is permissible to use fibers of natural color protection before using these colors. Only The natural color protection fiber may be marked first in the cable element.

c. If the cable element contains more than 12 optical fibers, then the consecutive numbers of the next 12 fibers are marked in the same order of colors as the first 12 fibers, with the addition being completed in one of the following ways: rings, solid or dashed lines along the fiber, coil and similarly. One of the 12 colors mentioned is also used for the supplementary mark, and the fiber that would be followed in that order is then indicated by the natural protection color and the corresponding supplementary mark.

d. Optical cable elements of particular importance may be: tubes, ribbed fiber supports, fiber bundles, fiber strips, and also a central tube or central ribbed carrier. For their marking, colors are used, the same as for marking optical fibers, applied to the surfaces of tubes and fiber supports, then strips in those colors that wrap fiber bundles, and also numbers on ribs of fiber supports or on wrapping strips can be used, as and more.

e. When applying cable elements by layer, the first and the second such element are determined in each layer, for the beginning and direction of decomposition in the layer. It is recommended that the first element be red and the second green, while the other elements may be natural, or the remaining colors mentioned above. The direction of decomposition must be the same in all layers.

f. In previous words of this guideline should be fully applied in marking the use of optical / metal hybrid cable cores in the part relating to optical fibers and the elements containing them.

g. The relevant provisions of IEC 60708 shall apply to the designation of symmetrical pairs intended for the transmission of analogue and digital signals, depending on the mode of their use.

h. Standard insulation colors for protective earth conductors, neutral and phase conductors are used to indicate pairs intended for the purposes of DC power supply. In agreement between the seller and the buyer, the application of these five colors uniquely ensures the serial numbers of pairs and the polarization of the DC power supply by direct current.

7. Optical Dataline color code

The following colors are used for identi cation of  bers in loose tubes of standard optical cables (with reference to VDE 0888-3, IEC 60304):

1 Red

2 Green

3 Yellow

4 Blue

5 White

6 Violet

7 Orange

8 Black orange

9 Grey

10 Brown

11 Pink

12 Turquoise

13 Red/Black

14 Green/Black

15 Yellow/Black

16 Blue/Black

17 White/Black

18 Violet/Black

19 Orange/Black

20 Natur/Black

21 Grey/Black

22 Brown/Black

23 Pink/Black

24 Turquoise/Black

25 Red/Black/Black

26 Green/Black/Black

27 Yellow/Black/Black

28 Blue/Black/Black

29 White/Black/Black

30 Violet/Black/Black

31 Orange/Black/Black

32 Natur/Black/Black

33 Grey/Black/Black

34 Brown/Black/Black

35 Pink/Black/Black

36 Turquoise/Black/Black

The first color is the basic color of the fiber, secon and third colors are applied as rings on the fiber. For optical cables with stranded units the following colors are used:

1 unit: red (counting unit)

2 unit: green ( direction unit)

3 all other units are natural color

4 blinds are black

Optical cable construction

The basic structural elements of the non-metallic fiber optic cable intended for retraction in the tube are shown in Figure 1.

The core of the optical cable consists of:

a discharge element,

optical fibers which are placed inside the secondary protection tube,

a filling mass and a belt insulation with elements for unloading. 

Fig. 2. Optical cable construction…

Optičko vlakno  (0,25 mm) = Optical fiber (0.25 mm)

Vodonepropusna masa za punjenje cevčica sekundarna zaštita = Watertight tubing filler secondary protection

 Cev sekundarne zaštite optičkog vlakna (polyester) = Secondary fiber optic tube (polyester)

Masa za punjenje jezgra kabla = Cable core filler mass

Pojasna izolacija sa nitima za ojačanje od Kevlara = Belt insulation with Kevlar reinforcement threads

Centralni rasteretni element kabla – Central unloading cable element

Spoljašnji zaštitni omotač kabla = External cable sheath

The central tensioning element of the cable may be made of high-tensile steel galvanized wire or, in the case of non-metallic, epoxy / polyester resin impregnated glass ropes. The diameter of the central element of the cable complies with the requirements regarding the mechanical characteristics of the cable.

Secondary protection tubes contain up to 6 optical fibers that differ in color from primary protection. The dimensions of the tubes are:

2.0 / 1.20mm (+/- 0.05mm, outer / inner pipe diameter) for structures with one or two opt. fibers in the same tube sec. protection,

2,8 / 1,70mm (+/- 0,06mm, outer / inner pipe diameter) for structures with four or six optical fibers in the same pipe sec. protection.

NON-METAL OPTICAL CABLES FOR LAYING IN THE PIPE INHALED
TO SM 03 (or 04) …

The TO SM 03 … and TO SM 04 … optical cables are made without metal elements and are intended to be inserted into the pipe by means of a blow-in process. Aramid fiber and a glass-plastic discharge element are used for the cable support elements. The cables are made with secondary protection in the form of a tube with filling of the space with a waterproof mass. Cables can be polyethylene (03) or PV Ca (04).

Fig. 3. 1. Centralni rasteretni element kabla = Central unloading cable element

2. Optičko vlakno  = Optical fiber

3. Sekundarna zaštita = Secondary protection

4. Pojasna izolacija = Belt insulation

5. PE sheath or PVC

ARMED OPTICAL CABLES FOR DIRECT LAYING THE GROUND TO SM 19 P …

The TO SM 19 P … optical cables are made with steel strip reinforcement and are intended for direct laying in the ground. Aramid fiber and unloading element made of galvanized steel wire (or glass-plastic) are used for the cable support elements. The cables are made with secondary protection in the form of a tube with filling of the space with a waterproof mass.

Fig. 4. 1. Centralni rasteretni element kabla = Central unloading cable element

2. Optičko vlakno  = Optical fiber

3. Sekundarna zaštita = Secondary protection

4. Pojasna izolacija  = Belt insulation

5. PE plašt 1. =  PE sheath 1.

6. Armatura  = Armature

7. PE plašt 2. = PE sheat 2.

OPTICAL CABLES FOR INSERTION INTO CABLE PIPING TO SM 09 P …

Fiber optic cables of the type TO SM 09 P … are made with a layered sheath of Al – copolymer tape 0.20mm thick, which is glued to the polyethylene sheath, and are intended for insertion into the pipes of the city cable sewer. Aramid fiber and unloading element made of galvanized steel wire (or glass-plastic) are used for the cable support elements. The cables are made with secondary protection in the form of a tube with filling of the space with a waterproof mass.

SELF-BEARING OPTICAL CABLES
TO SM 31 P …

The TO SM 31 P … fiber optic cables are made with laminated 0.20mm thick copolymer tape, which is glued to the polyethylene sheath, and is intended for installation on overhead posts for ranges. 50m. The central tensioning element of the cable is made of fiberglass (or galvanized steel wire). The cables are made with secondary protection in the form of a tube with filling of the space with a waterproof mass. 

Support cable (5) is made of steel TO SM 03 [(9×24) xIIx0.4×3.5 + (1×24) xIIIx0.35×5] CMAN (G652D + G655)

wire nom. diameter 3.0mm.

Fig. 5. 1. Centralni rasteretni element kabla = Central unloading cable element

2. Sekundarna zaštita = Secondary protection

3. Pojasna izolacija  = Belt insulation

4. Al-kopolimer traka debljine 0.20 mm = Al – copolymer tape 0.20mm thick,

5. Noseće Fe uže prečnika 3 mm = Fe rope diameter of 3 mm

6.  Spoljašnji PET plašt = Outer PET sheat

OPTICAL VERSES WITH 24 FIBERS

Fig. 6. Optical cable

Fig. 7. OPTICAL VERSES WITH 24 FIBERS

1.1 Fiber Optic 168 x SM G652D
1.2 Fiber Optic 24 x SM G655
2 Secondary Pipe Protection
3 Vessel Filler Thixotropic

Fig. 8. dkmax. » 17,5 mm, Gk » 226 kg/km

 4 Optical vein

5 Unloading elements

5.1 Central unloading element (insulated) – non-metallic (FRP)

5.2 Peripheral unloading element (aramid yarn – Twaron)

6 Cable core filled with waterproof mass

7 Belt insulation (2 × paper tape)

8 PET sheath (2.0 mm thickness)

TO SM 03 (12×24) xIIx0.4×3.5 CMAN G652D

Fig. 9. dkmax. » 19,6 mm, Gk » 286 kg/km

4 Optical vein

5 Unloading elements

5.1 Central unloading element (insulated) – non-metallic (FRP)

5.2 Peripheral unloading element (aramid yarn – Twaron)

6 Cable core filled with waterproof mass

7 Belt insulation (2 × paper tape)

8 PET sheath (2.0 mm thickness)

TO SM 03 [C (7×24) xIIx0.4×3.5 + (1×24) xIIIx0.35×5]
CMAN (G652D + G655)

Fig. 10.  dkmax. » 15,6 mm,  Gk » 175 kg/km

4 Optical vein

5 Unloading elements

5.1 Central unloading element (insulated) – non-metallic (FRP)

5.2 Peripheral unloading element (aramid yarn – Twaron)

6 Cable core filled with waterproof mass

7 Belt insulation (2 × paper tape)

8 PET sheath (2.0 mm thickness)

TO SM 03 [C (11×24) xIIx0.4×3.5 + (1×24) xIIIx0.35×5]
CMAN (G652D + G655
)

Fig. 11. dkmax. » 17,5 mm, Gk » 210 kg/km

Fig. 12. dkmax. » 19,6 mm, Gk » 286 kg/km

4 Optical vein

5 Unloading elements

5.1 Central unloading element (insulated) – non-metallic (FRP)

5.2 Peripheral unloading element (aramid yarn – Twaron)

6 Cable core filled with waterproof mass

7 Belt insulation (2 × paper tape)

8 PET sheath (2.0 mm thickness)

9. Methods of testing the characteristics of optical fibers and cables

According to the IEC, the characteristics of optical fibers and cables that are measured are divided into four main groups:

1. Transmission and optical characteristics
• attenuation
• bandwidth
• pulse dispersion
• boundary wavelength
• zero wavelength
• refractive index profile
• numerical aperture

2. Geometric characteristics
• Dimension of core and sheath
• Nonconcentricity of core and sheath
• Ellipticity
• Geometric characteristics of individual components of the cable (outer diameter of the optical vessel, central unloading element, cable core and cable, as well as the thickness of the secondary protection tube and sheath, etc.)

3. Mechanical characteristics
• Fiber optic attenuation due to elongation force
• Optical cable resistance to shock, bending, compression and twisting

4. Resistance to environmental influences
• change in attenuation due to climate
change • change in attenuation due to the action of energy field and nuclear radiation
• water permeability of optical cable and the like.

At a short distance from the point of penetration of light into the optical fiber, the change in its transmission characteristic (attenuation, dispersion) is a nonlinear function of distance due to the width of the input pulse, the decrease of light power according to the exponential law, and the exchange of energy between modes. This is the so-called transition mode. When the “steady state” is established, that is, the linear dependence of the transmission characteristics on the length, then one can talk about the definition of the parameters of long transmission lines, which are not affected by the conditions of penetration of light air into the fiber optic core.

Fig. 13.

Multimode fibers support a large number of stretching modes (air dispersion), but “leaky” modes occur at shorter distances, which interfere with measurement accuracy. “Fluid dispersion” is a consequence of the spread of the light beam in many directions. As the laser beam moves away from the source, photons propagating at too high an angle disappear due to reflection and leakage at the optical fiber boundaries, so that at larger scatterings these “modes” are completely eliminated. In order to in the shortest possible distance a steady state is achieved, a mode mixer is used, that is, the optical fiber is pressed against a rough surface, or it bends around a profile of a certain diameter. This bending should not be confused with the bending of the optical fiber at a critical angle, which is carried out to deliberately eject the photon from it and to roughly read the light beam parameters.

The transmission properties of an optical cable depend on the transmission properties of the embedded optical fibers and the cabling technology. When measuring the characteristics of an optical cable, bare fibers are always obtained, and measurement methods are used that are no different from those used to test the properties of the optical fiber itself.

Cabling is the process of applying protective sheaths to one or more optical fibers with primary protection to protect them from the action of external factors (mechanical, chemical and other influences). In this way, the last two sets of IEC characteristics are affected.

7.2 Transmission and optical characteristics

7.2.1 Optical fiber attenuation measurement

The attenuation of light power in an optical fiber is the result of absorption, scattering, and waveguide effects. Two basic methods are used to measure the total loss of signal transmission through a fiber:

• Cutback technique – the earliest used method, which is based on the comparison of the measured light power at short and long lengths, under the same conditions of light air entering the optical fiber.

• Backscattering method – backscattering is a feature of an optical fiber whose principle was used with a time domain optical reflectometer.

7.2.1.1 Measurement of attenuation by clipping technique

This is a destructive technique that requires access at both ends of the optical fiber, and the measurement process itself consists of two measurements of light output.
First, the power at the far end of the optical fiber is measured, and then without any change at the input end, the fiber intersects a few meters from the source, and the power is measured again.

The mean attenuation of the optical fiber is calculated by the expression:

a = (10 / L) log Pb / Pd (dB / km)


where
Pd and Pb are the measured optical power at the far and closer to the cut off end of the optical fiber, respectively,
and L is the geometric distance between the measuring points.

Adhering to the order of action in applying this method is very important in order to determine the correct amount of energy input into the optical fiber. It is also very important to preserve the same conditions of immission of light beam into the optical fiber, as this can affect the value of the attenuation measured.

The attenuation values ​​can only be extrapolated to optical fibers in equilibrium state, which is achieved either by the method of controlling the numerical aperture of the source, and the size of the air, or by applying a “mixer” mode. In case the primary protection refractive index is less than the envelope refractive index, the mode mixer is used both at the beginning and at the end of the optical fiber.

7.2.1.2 Loss method entered

In this method, the light power P1 is measured first, at the output of the short reference fiber, which connects the optical source and the measuring device. Thereafter, it binds the test fiber to the reference fiber via the connector and measures its output power P2.

Impairment is calculated by the expression:

a = 10 log P1 / P2 (dB)

The results must be corrected for the value of the losses on the connectors.

10. Illustrated practice of working with fiber optic cables

I took the photos in this section personally and got it from colleagues who are professional in fiberoptics.

Fig. 14. Optical fibers by Radoje Jankovic

Fig. 15. Optical fibers by Radoje Jankovic.

Fig. 16. Optical fibers by Radoje Jankovic.

Fig. 17. Optical fibers by Radoje Jankovic.

PRACTICAL WORKS AND PROCESSING OF FIBER OPTICAL CABLES

Fig. 18.

Fig. 19.

Fig. 20.

Fig. 21.

Fig. 22.

Fig. 23.

Fig. 24.

Fig. 25.

Fig. 26.

Fig. 27.

Fig. 28.

Fig. 29.

Reference

  1. UPUTSTVO O OZNAČAVANJU OPTIČKIH KABLOVA, RS
  2. Catalog of Holding ˝Kablovi˝ a.d.

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Optical cables – Some important practical knowledge