cables handbook

DETECON AL-SAUDIA CO. LTD LDTN Project

Handbook On Fibre Optic Cable Maintenance

Prepared Colour scheme Reviewed Checked Approved

Fayyaz Ahmad Sheikh Reinhold Mueller Mohamed Barray Juergen Fiebach Johann Graf

SE Engineering Cable Com Engineer Central Course Developer Manager Operation Project Manager

May 10, 2005 May 11, 2005 May 16, 2005 May 16, 2005 May 16, 2005

Thank you so very muchJohann Graf&

Juergen FiebachFor never ending support and guidance

You are a huge part of my ability to be productive and prolific

___________________________________________________________________________________ Fayyaz Ahmad Sheikh Page 1 / 35 SE Engineering Cable LDTN HQ RYD

Content:

1.

DEFINITION OF FIBRE OPTIC.......................................................................4

1.1 BASIC CONSTRUCTION OF OPTICAL FIBRE .........................................................4 1.2 CONSTRUCTIONAL DETAILS OF FIBRE OPTIC CABLE ........................................5 1.3 TYPES OF FIBRE OPTIC CABLES ..........................................................................6 2. 3. DEFINITIONS OF TERMS USED IN FIBRE OPTIC CABLE......................7 FIBRE OPTIC SPLICING ................................................................................10

3.1 PREPARATION OF FIBRE OPTIC CABLE FOR SPLICING .....................................10 3.2 OPTICAL FIBRE SPLICING PROCESS ..................................................................11 4. TESTING OF FIBRE OPTIC LINK ................................................................12

4.1 TOOLS AND TEST EQUIPMENT FOR THE JOB .....................................................12 4.2 MEASUREMENT OF OPTICAL POWER & LOSS ..................................................12 4.2.1 MEASURING POWER ..........................................................................................12 4.2.2 TESTING LOSS ...................................................................................................12 4.2.3 REFERENCING OPTICAL LOSS TEST UNIT..........................................................14 4.2.4 FIBRE LOSS VARIABLES ....................................................................................16 4.2.5 CALCULATING LINK LOSS.................................................................................17 5. OTDR TRACE ANALYSIS...............................................................................18

5.1 OTDR PARAMETERS .........................................................................................19 5.1.1 WAVELENGTH...................................................................................................19 5.1.2 INDEX OF REFRACTION .....................................................................................19 5.1.3 PULSE WIDTH OR DURATION ............................................................................19 5.1.4 RANGE OR DISTANCE ........................................................................................19 6. CLEANING OF CONNECTORS .....................................................................21

7. SPECIFICATIONS AND PROCEDURES FOR CABLE INSTALLATION & REPAIRS................................................................................................................22 7.1 CABLE DEPTH .....................................................................................................22 7.2 SPLICE POINTS....................................................................................................24 8. POINTS TO REMEMBER ................................................................................25

8.1 SAFETY FIRST!....................................................................................................25___________________________________________________________________________________ Fayyaz Ahmad Sheikh Page 2 / 35 SE Engineering Cable LDTN HQ RYD

8.2 ZERO TOLERANCE FOR DIRT .............................................................................26 8.3 TOOLS AND MATERIALS .....................................................................................26 8.4 DOCUMENTATION AND RECORD MAINTENANCE ..............................................26 9. CHECK LIST AND PROCEDURES FOR FINAL REPAIR/RELOCATION OF FIBRE OPTIC CABLE ......................................................................................27 9.1 9.2 9.3 9.4 9.5 9.6 9.7 9.8 CIVIL WORKS & PREPARATION IN THE FIELD ...................................................27 ORGANIZING MDT/TC ......................................................................................27 LIST OF TOOL & TEST EQUIPMENT....................................................................28 STAFF ARRANGEMENTS .....................................................................................29 EXECUTION OF TC/MDT .................................................................................29 TEST REQUIRED .................................................................................................30 PRIORITY OF SYSTEMS .......................................................................................30 EMERGENCY REPAIR PROCESS..........................................................................31

10. COLOUR SCHEME.........................................................................................32 10.1 10.2 10.3 10.4 24 FIBRE (6 TUBES - 4 TUBES)...........................................................................32 24-36 FIBRE.......................................................................................................33 24-48 FIBRE.......................................................................................................34 STANDARD COLOUR SCHEME ...........................................................................35

Figures:Figure 1: Basic construction of optical fibre..................................................................4 Figure 2: Constructional Details of Fibre Optic Cable ..................................................5 Figure 3: Some useful tools ...........................................................................................9 Figure 4: Loop back method ........................................................................................14 Figure 5: Side by side method .....................................................................................15 Figure 6: OTDR trace analysis ....................................................................................18 Figure 7:Cable trench...................................................................................................22

Tables:Table 1: Attenuation Criteria .......................................................................................17 Table 2: showing depth of Buried Fibre Optic Cables ................................................22


1. Definition of Fibre OpticFibre Optic is a thin strand of highly transparent glass or sometimes plastic that guide light. It is used as a medium for carrying information from one point to another in the form of light. A basic fibre optic system consists of a transmitting device, which generates the light signal; an optical fibre cable, which carries the light; and a receiver, which accepts the light signal transmitted. The fibre itself is passive and does not contain any active properties

1.1 Basic Construction of Optical FibreCoating Cladding

Coating 250m

Cladding Core 125m 8.3 ~ 9m

Core Cross Sectional View of a Single Mode Fibre Side View of a Single Mode Fibre

Figure 1: Basic construction of optical fibre

Core: The centre of the fibre through which the light is transmitted Cladding: The outside optical layer of the fibre that traps the light in the core and guides it along and even through curves Buffer coating or primary coating: A hard plastic coating on the outside of the fibre that protects the glass from moisture or physical damage.

Fibre optic cable functions as a "light guide," guiding the light introduced at one end of the cable through to the other end. The core and cladding are manufactured together as a single piece of silica glass. The core regions refractive index (or optical density) is greater than the cladding layer. The glass does not have a hole in the core, but is completely solid throughout. The light is "guided" down through the core. The cladding traps the light in the core using an optical technique called "total internal reflection. The third section of an optical fibre is the outer protective coating called the "primary buffer coating". This coating is typically an ultraviolet (UV) light-cured acrylate applied during the manufacturing process to provide physical and environmental protection for the fibre. During the installation process, this coating is stripped away from the cladding to allow proper termination to an optical transmission system.___________________________________________________________________________________ Fayyaz Ahmad Sheikh Page 4 / 35 SE Engineering Cable LDTN HQ RYD

1.2 Constructional Details of Fibre Optic Cable

Steel sheath for Grounding

Thread and Paper

Optical fibres

Outer Sheath (Jacket)

Dielectric Strength Element (Kevlar)

Gel Filled Buffer Tubes

Central Strength Member

Gel-Filled Buffer Tube Optical Fibres Central Strength Member Dielectric Strength Element (Kevlar) Thread & Paper Steel for Grounding Outer Sheath (Jacket) Double Layer for Direct Buried & Single Layer for Duct Cable Water Blocking Material (Jelly) Rip Cord

Figure 2: Constructional Details of Fibre Optic Cable


1.3 Types of Fibre Optic CablesThere are two types of fibre optic cable commonly used: 1. Multi Mode Cables: Over the years a variety of core sizes have been produced but these days there are only two main sizes for Multimode fibres. These cables are most widely used in data networks. The numbers 50/125 & 62.5/125 represent the diameters of the fibre core and cladding; these are measured in microns, which are millionths of a metre 2. Single Mode Cables: Single Mode cable has a core diameter of 8.3 to 10 microns. It is the most commonly used cable in Telecommunication for transmission systems. The numbers 8.3/125 represent the diameters of the fibre core and cladding Note: Both multimode and single mode fibres have an outside diameter of 125 microns - about 5 thousandths of an inch - just slightly larger than a human hair.


2. Definitions of Terms used in Fibre Optic CableTerminations Patch panels Connector Provides a centralized location for patching fibres, testing, monitoring and restoring cables. A non-permanent device for connecting two fibres or fibres to equipment where they are expected to be disconnected occasionally for testing or rerouting. It also provides protection to both fibres. A tube, which holds a fibre for alignment, usually part of a connector LC stands for Latched Connector and its interconnect is based upon the RJ-45 telephone interface. The LC Connector uses Zirconia ceramic ferrules in a free-floating and pull proof design SC Stands for Single Coupling. It is Square shaped snap-in connector that latches with a simple push-pull. The SC connector has the advantage (over ST) of being duplexed into a single connector clip with both transmit/receive fibres The MU stands for Miniature Unit fibre-optic connector, which features compact size, high packaging density, and high performance and a simple push-pull design. The MU connector ferrules are half the size of the standard FC, SC connectors and are excellent for high-density installations ST Stands for Straight Tip. The ST connector is spring-loaded bayonet mount and have a long cylindrical ferrule to hold the fibre The FC stands for "Face Contact" The anti-rotation key prevents fibre end face damage and rotational sensitivity and the floating ferrule prevents shock and vibration. Physical Contact Connector Flat Physical Contact Connector Angled Physical Contact Connector Super Physical Contact Connector Ultra Physical Contact Connector

Ferrule LC Connector

SC connector

MU Connector

ST Connector

FC Connector

PC Connector FPC Connector APC Connector SPC Connector UPC Connector

Splicing Splice enclosures

Splice panels Splice Mechanical Splice Fusion Splice Fusion Splicer

For long cable runs outside, the point where cables are spliced sealed up and buried in the ground, put in a vault of some kind or hung off a pole. Connect individual fibres from cables to pigtails A permanent joint between two fibres A splice where the fibres are aligned by mechanical means A splice created by fusing two fibres together An instrument that splices fibres by fusing them, typically by electrical arc


Measurements Attenuation Bandwidth Chromatic dispersion Decibels (dB) dBm Nanometer (nm) Optical Loss Optical Power

Optical Return Loss, back reflection Power budget Polarization Mode Dispersion Refractive index Scattering

Wavelength

The reduction in optical power as it passes along a fibre, usually expressed in decibels (dB). The range of signal frequencies or bit rate within which a fibre optic link or network will operate. A property of optical fibre due to which different wavelengths travel at different speeds and arrive at different times, resulting in spreading of a pulse in an optical wave guide. A unit of measurement for optical power, which indicates relative power. A -10 dB means a reduction in power by 10 times. Absolute Power, Optical power referenced to 1 milliwatt A unit of measure used to measure the wavelength of light (meaning one one-billionth of a meter) The amount of optical power lost during transmission of through fibre, splices, couplers, etc. expressed in dB. It is measured in "dBm", or decibels referenced to one milliwatt of power. While loss is a relative reading, optical power is an absolute measurement, referenced to standards. Absolute power is measured to test transmitters or receivers and relative power to test loss. Light reflected from the cleaved or polished end of a fibre caused by the difference of refractive indices of air and glass. The total amount of power lost in the link. Often used in terms of the maximum amount of loss that can be tolerated by a given link. The spreading of a pulse in an optical wave guide by virtue of different light paths lengths is called Modal dispersion. A measure of the speed of light in a material, a property of optical materials that relates to the velocity of light in the material The change of direction of light after striking small particles that causes loss in optical fibres and is used to make measurements by an OTDR A term for the colour of light, usually expressed in nanometres (nm) or microns (m). Fibre is mostly used in the infrared region where the light is invisible to the human eye.

Test Equipment Optical Power Meter Laser Source Optical Loss Test Set (OLTS) Reference Test Cables Mating Adapter Optical Microscope

An instrument that measures optical power from the end of a fibre An instrument that uses a laser or LED to send an optical signal into fibre for testing loss of the fibre A measurement instrument for optical loss that includes both a power meter and laser source Short, single fibre cables with connectors on both ends, used to test unknown cables. Also called couplers, allow two cables with connectors to mate. Used to inspect the end surface of a connector for dirt.


Fibre Stripper

Cleaning Tape

Round Jacket Stripper

Longitudinal Cable Jacket Slitter

No-Nik Stripper

Cutter

Buffer Tube Stripper

Cable cutter Air Jet Buffer Tube Stripper

Hand Air Blower

Scissor (Kevlar cutter)

Cleaver

Tweezers

Isopropyl Alcohol Swab Figure 3: Some useful tools


3. Fibre Optic SplicingThere are two methods of fibre optic splicing, fusion splicing & mechanical splicing. Mechanical splicing is usually carried out for emergency restorations whereas fusion splicing is done for permanent repairs of damaged cable or to connect the reels of cable during installation 1. Mechanical Splicing: Mechanical splices are simply alignment devices; designed to hold the two fibres ends in a precisely aligned position thus enabling light to pass from one fibre into the other. (Typical loss: 0.3 dB) 2. Fusion Splicing: Fusion splicing is the joining and fusing of two fibres by placing them between two electrodes, and discharging an electric arc over the fibres. This splice technique is non-reflective. Fusion splicing machine is used to precisely align the two fibre ends then the glass ends are "fused" together using electric arc. This produces a continuous connection between the fibres enabling lower loss and less back reflection than mechanical splicing because the resulting fusion splice points are almost seamless. (Typical loss: 0.1 dB)

3.1 Preparation of Fibre Optic Cable for Splicing1. Removal of outer jacket 2. Cutting of Kevlar 3. Cleaning of Buffer Tubes 4. Fixing of cable in the enclosure 5. Stripping of Buffer Tubes Remove the fibre optic cable's protective jackets and buffers to allow access to the optical fibre. Make sure the blades or cutting members are not damaging the buffer tubes. The Kevlar can be trimmed using scissors or Kevlar cutters. Clean the jelly on buffer tubes with isopropyl wipes. The cable should be fixed in the enclosure according to the recommendations of the manufacturer of the splice enclosure. The buffer tubes, like the outer jackets, can be removed by mechanical stripping tools. Use care not to kink or damage the internal coated fibres.


3.2 Optical Fibre Splicing Process1. Stripping of fibres 2. Cleaning 3. Cleaving 4. Splicing Once the coated fibre is exposed, Use fibre stripper to strip fibre to appropriate length. Take care not to damage the fibres in the process. After the coating is removed, clean the fibre with specially designed isopropyl alcohol wipes so that the fibre squeaks. A good cleave is the key to obtaining a good splice. Use cleaver to cut the fibre. After cleaving do not touch or clean the fibre. The fibre is now ready to be spliced mechanically or Fusion. Insert the fibre carefully in the mechanical splice or in the fusion splicer for splicing. While inserting in the mechanical splice make sure that fibre is inserted directly in the groove and do not touch any other surface. Fusion splicer will automatically align and fuse the fibre. In case of fusion splicing cover the splice with heat shrink sleeve and place it in the heater, for mechanical splice carefully close the mechanical splice. Organize the fibre in the enclosure properly Make sure that organising do not cause Micro-bending.

5. Protection

6. Organizing


4. Testing of Fibre Optic LinkCables need to be tested for Continuity, End-to-End Loss and any other potential problems. For long outside plant cables with intermediate splices, all individual splices need to be verified with an OTDR, since that's the only way to make sure that each one is good. Within the network testing for power is necessary as power is the measurement that tells whether the system is operating properly.

4.1 Tools and Test Equipment for the job1. 2. 3. 4. Source and power meter, optical loss test Reference test cables Cleaning materials - lint free cleaning wipes and pure alcohol OTDR and launch cable for outside plant jobs

4.2 Measurement of Optical Power & LossThere is a difference between the power coupled into a component like a cable or a connector and the power that is transmitted through it. This difference is what we call optical loss and defines the performance of a cable, connector, splice, etc. 4.2.1 Measuring power Power in a fibre optic system is like voltage in an electrical circuit. To measure power, attach the meter to the cable that has the output you want to measure. Turn on the transmitter/source and note the power the meter measures. 4.2.2 Testing Loss Following two methods are used to measure loss. Optical Loss Test Sets houses a light source and power meter in the same unit. For both methods two units of loss test sets (one at each end of the fibre under test) are required. 1. Single Ended Loss (Laser Source and Power Meter) This test is initiated from one end and result is displayed at far end unit.FasTesT Port Test Patch Cord Test Patch Cord Detector Port

Optical Loss Test Set Transmitter

Detector Port

Fiber Optic Link under Test

FasTesT Port Optical Loss Test Set Receiver

Figure 3: Single Ended Loss Measurement SETUP


2. Double Ended Loss (FasTest Method) In this test Laser source is initiated from one end and the results are displayed at both ends simultaneously. Both test method measure the loss of two ODF connectors (one on each end), the loss of cable and splices in between. Most commonly FASTTEST set-up method is used for loss testing.Test Patch Cord Detector Port

FasTesT Port

Test Patch Cord

_______________________________Detector Port Fiber Optic Link under Test

FasTesT Port Optical Loss Test Set Receiver

Optical Loss Test Set Transmitter

Figure 3: Double Ended Loss Measurement /

Prior to perform Loss test measurement: 1. A reference measurement must be stored in both units 2. The reference measurement includes the loss caused by the test set-up components including test Patch cords 3. The unit will store a reference reading of power level at the end of test Patch cord 4. This reference measurement is subtracted from the overall loss so the final loss result represents the loss of system under test alone


4.2.3 Referencing Optical Loss Test Unit There are two referencing methods in practice for Loss test sets and both results in accurate loss measurement: Loop-back Method with only one test jumper Side-by-Side Method with two test patch cords and a mating adapter 1. Loop back MethodSource or FasTesT Port Not to be disrupted once the reference is set. Detector Port, Disconnect this end and connect to ODF of FO link under Test once the reference is set

Optical Loss Test Set

Figure 4: Loop back method

The main advantage of the loop back referencing method is that there is no need to bring both units at same location. This is performed by connecting a single test patch cord from the units Source Port (FASTTEST Port) to Detector Port. 1. After performing the loop-back reference, simply disconnect the test patch cord from the Detector Port and connect it to the ODF of Fibre link Under Test. 2. It is very important not to disconnect it from the source port (FASTTEST Port) because the amount of light coupled or injected into the test patch cord varies from one connection to another. 3. If the test patch cord is disconnected from the source port, it is required to repeat the references. 4. The loop-back test is performed individually on each of the two units. 5. An important advantage of the loop-back method is that it automatically takes into account the loss of the test patch cord and Mating adapters, allowing a true measurement of the fibre itself.


2. Side-by-Side Method To perform the side-by-side reference procedure, two test patch cords are connected via a Mating adapter and then connect the test patch cord ends to the Source Port (FASTTEST Port) of both units.Mating Adapter Disconnect here to connect to ODF of FO link Under Test

FastTesT Port Not to be disrupted once the reference is set

Detector Port / Power Meter Port



Transmitter

Receiver

Figure 5: Side by side method

1. When using the side-by-side reference method, both units must be brought to a common site to take the appropriate references. 2. Once the side-by-side reference is performed, disconnect the test jumpers at the Mating Adopter and connect both test jumpers to the ODF of Fibre Link Under Test. 3. Much like the loop back reference, it is very important not to disconnect the test jumper from the source port as the amount of light coupled or injected into the test patch cord will vary from one connection to another. If the test patch cord is disconnected from the source port (FASTTEST Port), it is required to repeat the reference Note: Before measuring optical loss with an automated OLTS, referencing is a crucial procedure that should be performed before every test session. Performing a FasTesT: The purpose of a FasTesT is to test the fibre according to set parameters with minimum intervention from you. Although the FasTesT is performed with two units, one at each end of the fibre, it is initiated from only one unit and the result will be displayed at both units


4.2.4 Fibre Loss Variables Attenuation All fibre has losses from absorption and back reflection of the light caused by impurities in the glass. Attenuation is a function of wavelength and needs to be specified or measured at the wavelength in use. The higher the data rate, the shorter the distance the signal can travel before modal dispersion creates an inability to accurately detect the signal (i.e. a "1" from a "0"). Another dispersion effect, which causes pulse spreading, and limits distance is chromatic dispersion, where the broader spectrum of light can result in varying travel times for different parts of a light pulse. Although small and often insignificant, there is no perfect loss-less splice. Many errors in loss calculations are made due to a failure to include splices. Average splice loss is usually less than 0.1 dB. Like splices, there is no perfect loss-less connector. It is important to note that even the highest quality connectors can get dirty. Dirt and dust can completely obscure a fibre light wave and create huge losses. A 0.5 dB loss per connector is commonly the worst-case scenario assuming a cleaned and polished connector is used. There will always be a minimum of two connectors per fibre segment, so remember to multiply connector loss by two. It is common to add a loss as a design margin. Allowing 2 - 3 dB of loss can take fibre aging, poor splices, temperature and humidity, etc., into account and ensures a solid system.

Modal Dispersion

Dispersive Losses

Splices

Connectors

Safety Buffer

NOTE: To determine minimum/maximum losses and maximum distances you need to identify all of the above variables. Failure to identify even one of these variables can create potential problems

Terminology


4.2.5 Calculating Link Loss Losses occur at many points in a fibre optic system. We have to ensure that the light source launches enough power into the fibre to provide enough power at the receiver. The receiver has limited sensitivity. Transmitter output - Receiver input = Losses + Margin (All calculations are done in dB) For single mode fibre cable with two most commonly used wavelengths 1310 nm and 1550 nmThe attenuation measurement will vary depending upon which wavelength is in use. Attenuation is measured in dB and is quoted as attenuation in dB/km. Under mentioned is the most commonly used method to determine the maximum signal loss across a piece of pre-existing fibre (Link Loss) Loss/Km in dB 1310nm 0.35 1550nm 0.23Table 1: Attenuation Criteria

Loss Connector In dB 0.50 0.09 Splice

Optical Fibre Type Single Mode

The measured value of attenuation of a FO link should not exceed the sum of allowable attenuation of each component. These components are: The Fibre Optic cable The FO connectors The SplicesLink Loss (dB) = Cable Loss + Connector Loss + Splice Loss + (Safety Margin)

Cable Loss Connector Loss Splice Loss (Safety Margin)

= Cable length (Km) x Attenuation Coefficient (db/Km) = Number of Connector Pairs x Connector Loss (dB) = Number of Splices x Splice Loss (dB)= 2 ~ 3 dB depending upon the length of link


5. OTDR Trace AnalysisDead Zone

Dynamic RangeIn-Put EndFace Reflection Reflective Event (Connector, Mechanical Splice) Out Put End-Face Reflection

dB

End-to-End Loss

Non-Reflective Event (Fusion Splice, Bend)

Non-Reflective Event (Micro Bending)

Noise0M Distance (M)

Launch Level

Reflective Event Loss Dead Zone Reflective Event Dead Zone

NonReflective Event Loss

Non-Reflective Event Loss caused by Micro-Bending or Bad Splice

Figure 6: OTDR trace analysis


5.1 OTDR ParametersThere are four main settings that the technician must set on the OTDR before testing. Those are Wavelength, Index Of Refraction, Pulse Width and Distance 5.1.1 Wavelength The behaviour of an Optical system is directly related to the wavelength of transmission. Not only Optical fibre will exhibit different loss characteristics at different Wavelengths, but splice loss value also differ at different wavelengths. In general fibre should be tested with both wavelengths i.e. 1310 and 1550nm for single mode fibres. If testing is only to be performed at one wavelength it should be done with 1550nm considering the following points 1550nm will see longer distances down the fibre due to the lower attenuation as compared t0 1310nm 1550nm is more sensitive to losses incurred by bending during installation and organising of fibres in the splice enclosures after splicing 5.1.2 Index Of Refraction The index of refraction sets the OTDR to the proper speed of light for a particular fibre link being tested. Changing the IOR value will change the distances to events on the OTDR trace, and also the overall length of the fibre. The IOR of a particular fibre is usually provided by the manufacturer 5.1.3 Pulse Width or Duration This is another setting that must be selected to receive the clearest information from the OTDR trace. The length of time that the OTDR's laser is turned on is called the "pulse width". As the OTDR turns the laser on and off, the duration of the laser being on results in a pulse of a certain length. Shorter pulse widths provide better traces of events that are close together, as the shorter pulse widths will have shorter dead zones after reflective events. However, short pulse widths will result in a noisy, hard to interpret trace for long distance fibre link, as the OTDR process weaker returned signals Long pulse widths means more light energy is injected in the fibre. The more light injected means the more light is reflected back from the fibre to OTDR. It causes longer dead zones, and reduces resolution of events that are close to each other. Long Pulse width is therefore used to see long-distance down a cable The General Rule to set Pulse width is: o Short Fibre Link = Short Pulse Width o Long Fibre Link = Long Pulse Width Shorter pulse widths can be used on longer fibre links to give greater detail to events close to the OTDR and for fault analysis. 5.1.4 Range or Distance


The range on an OTDR is the maximum distance that OTDR will acquire data samples. This parameter is generally set at twice the distance of the end of the fibre Note: Neglecting to set any of these parameters properly can result in erroneous reporting by the OTDR Dead Zone: The OTDR is designed to detect the back scattering level all along the fibre link. It measures the back-scattered signals, which are much smaller than the signal sent to the fibre. When there is a strong reflection then the power received at the OTDR is much higher than the backscattered power, which saturates the OTDR. OTDR requires time to recover from the saturated condition. During this time OTDR cannot detect the backscattered signal accurately. The length of fibre, which is not fully characterized during the recovery period, is termed as dead zone. This affect is similar to the one when we are driving a car at night and that another cars headlight dazzles our vision momentarily. The dead zone depends on the pulse width, the reflectance, the loss and the location


6. Cleaning of ConnectorsProper cleaning of connectors is very important. The core diameter of a single-mode fibre is only about 9um. This generally means you cannot see streaks or scratches on the surface. Follow the under mentioned procedure to clean the connector: 1. Clean the connector by rubbing it on cleaning tape or a new, dry cotton swab using a small circular movement. 2. Blow away any remaining lint with compressed air. If the connector has greasy dirt on its tip follow the following procedure: 1. Take a new Moisten cotton swab with isopropyl alcohol. 2. Clean the connector by rubbing the cotton swab over the surface using a small circular movement. 3. Take cleaning tape and rub it in small circular motion to remove the alcohol dissolved sediment and dust. 4. 4. Blow away any remaining lint with compressed air Note: Do Not Forget to clean the connector with cleaning tape after cleaning it with isopropyl alcohol swab. L


7. Specifications and procedures for Cable Installation & Repairs7.1 Cable DepthThe depth at which buried cable can be placed will vary with local conditions i.e. Type of soil and Terrain. However fibre optic cable must be buried at a minimum depth of 80 cm. Location Soft Soil Hard Soil / Rock Soil Road Way crossing Depth 80 ~ 130 cm Minimum 80 cm Minimum 110 cm

Table 2: showing depth of Buried Fibre Optic Cables

Under mentioned diagram shows the typical layout of Direct Buried cable.

Back filling

Back filling

40 ~90 cm

80 ~130 Cm Warning Tape

Soft SandFibre Optic Cable

Soft Sand

20 cm

Soft Sand

Soft Sand

20 cm

Min 1Meter

Side View of TrenchLegend

Front View

Back filling Soft Sand Undisturbed Earth

Figure 7:Cable trench

In certain installation areas, for example, rights-of-way with limited access (public highways, private property boundaries, water ways, Culverts and under the bridges,___________________________________________________________________________________ Fayyaz Ahmad Sheikh Page 22 / 35 SE Engineering Cable LDTN HQ RYD

cable must be buried in a duct and if such constructions are done after the installation of cable, Fibre Optic cable must be protected in the affected area with PVC pipe, iron barring and concrete. Cable must be protected at all locations such as unimproved roads, streets and alleys that may later be paved or hard surfaced. CAUTION: Depths less than those specified may expose the cable to erosion or excavation damage In conditions where these depths are not feasible or permitted lesser depth is permissible provided additional protection in the form of concrete casements or sub duct is provided


7.2 Splice PointsSplice point locations must be chosen carefully to have easy access for future maintenance. Splicing must always be done in the car and in order to reach splicing vehicle, ensure a minimum of 10 ~ 15meters of extra cable on both cable ends at each splice point At Hand Holes and Man Holes place the cable slack vertically (in line with the cable route) In the case of a buried splice point, coil and bury the slack Horizontally as shown in the Figure belowSplicing Van 10~15M slack

80~120 cm

Warning Tape 20 Cm

Splice Pit 2 x 2 Meter Buried Splice Point Hand Hole Man Hole

Back fillingWarning Tape Tiles Direct Buried Splice

20 ~70 cm

80 ~130 Cm

Soft Sand Soft Sand

20cm 20cm 20 cm

Buried Joint Top View

Min 2Meter

Front ViewFigure 7: Arrangement of Buried Splice ___________________________________________________________________________________ Fayyaz Ahmad Sheikh Page 24 / 35 SE Engineering Cable LDTN HQ RYD

8. Points To Remember8.1 Safety First!Small scraps of glass i.e. cleaved-off ends of the fibres being terminated or spliced is very dangerous! They are extremely sharp and are basically glass needles that will easily penetrate flesh then break off and become nearly impossible to remove. Once in the body it will likely become infected. If they get into the eyes, they are very hard to flush out. Don't even think about what happens if you eat one. Always follow these rules when working with fibre. Find and dispose-off all cut fibre fragments immediately after cutting. Dispose-off all scraps properly Handle cut fibre fragments with tweezers only Do not drop them on the floor where they will stick in carpets or shoes and be carried elsewhere. It is your responsibility to ensure that no fibre fragments escape and injure someone. If you lose a fibre fragment you must look until you find it. Fibre fragments can stick to the cover of the cleaver. Move slowly when opening the cover. Always look on the inside of the cover if you dont see your fragment on the shelf of the cleaver. If you cant find your fragment, get more light on the subject and work area. Do not move the cleaver until the fragment has been found. Use a magnifying glass if you need to but FIND THAT FRAGMENT. Do not eat or drink anywhere near the work area. The light in Transmission system is infrared and you can't see it therefore always be careful with your eyes. When using a fibre optic microscope. NEVER look into a fibre unless you personally confirm no light is present. Use a power meter to check it.


8.2 Zero Tolerance for DirtWith fibre optics, our tolerance to dirt is near zero. Airborne particles are about the size of the core of SM fibre- they absorb lots of light and may scratch connectors if not removed! Dirt on connectors is the biggest cause of scratches on polished connectors and high loss measurements! Try to work in a clean area. Always keep dust caps on connectors & patch panels when not in use. Keep them covered to keep them clean. Use lint free pads and isopropyl alcohol to clean the connectors. After cleaning with isopropyl alcohol swab do not forget to clean it with the Cleaning Tape

8.3 Tools and MaterialsMake sure to have the proper tools for the job. Confirm that all tools are in good shape before you head out for the job. This includes all the cable tools and test equipment. Make sure that your test cables are good? Without that, good terminations are tested as bad every time. Make sure that your test equipment is fully charged and you have spare battery backup.

8.4

Documentation and Record Maintenance

It is very hard to troubleshoot cables when you don't know how long they are, where is the route or how they were tested originally! So keep good records. It is recommended that the following records be maintained and kept current always: Schematic drawings to include "as-built" information for street maps records Splice loss data End-to-end optical loss measurements End-to-end OTDR traces


9. Check List and Procedures for Final Repair/Relocation of Fibre Optic Cable9.1 Civil works & Preparation in the field1. 2. 3. 4. Opening of TC with TNOC for the excavation on the existing cable. Execution of Civil works. (Under supervision of MC cable technicians) Laying/Pulling of By Pass/New Cable Installation of enclosures and testing of New/Bypass cable. (Secure new splice enclosures with plastic foil (bag) to avoid water or sand intake) 5. Marking of cutting point for existing cable, keeping in mind the maintenance loop of 15 meter each side. 6. Assure site accessibility and secure work site with safety signs. (i.e. traffic signs, road cones, warning tape) 7. OTDR testing of Dark Fibre Measurement prior to MDT

9.2 Organizing MDT/TC1. Fibre utilization Form must be filled correctly for both sites of the section involved 2. All working and spare fibres at both sites (ODFs) must be clearly identified and labelled. 3. 4. Splicing Machines and Test Equipment must be checked prior to MDT. MC Supervisor is responsible to arrange a meeting with all scheduled staff, to determine tasks and procedures to be followed during MDT 5. MDT request


9.3 List of tool & Test equipmentItem in red are mandatory for emergency and final splicing (Item 1 to 18 in the list) 1. Fibre Phone sets (2X2) 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. Satellite Phone (in case of non GSM coverage) OTDR Cable locator (fault locating only) Testing Patch Cords Fibre Cleaning Cassette Power Meter (Max Tester) Laptop (for SDH Technician) Cleaning canned air (Air Jet) Mobile Generators Emergency Lights for night work. Floppy Disk for recording of OTDR test results. Alcohol wipes Lint free tissues Cable Ties different sizes Power extension cords Mechanical Splices (to connect fibre phones) Fibre Optic Preparation Tools a. Cleaver b. Cladding Stripper c. Cable outer sheath cutter d. Loose tube cutter (Jacket stripper) e. Kevlar cutting scissor f. Buffer stripper for ODF pigtails g. No Nik Stripper h. Tweezers 19. 20. 21. 22. 23. Splicing Machines Enclosures (already preinstalled during site / cable preparation) Splice protection (Heat shrink) sleeves Hot air gun Splicing Cars


9.4

Staff Arrangements

1. Each cable splicing team will comprise of Two-cable technicians and two labourers. 2. Two teams will work simultaneously at both splicing points. 3. For coordination and disconnection/reconnection of Fibres at ODF, SDH technician must be available at both terminal sites of the section involved. 4. At one terminal site SDH technician must have Laptop for testing in case of any problem /outage or loss of association at TNOC.

9.5 Execution OF TC/MDT1. MDT / TC approval from TNOC. 2. Contact and information to TNOC regarding TC/MDT 15 minutes prior to Start of MDT/TC. 3. Contact to TNOC at start time of MDT and get OK/ Go ahead from TNOC. 4. Keep TNOC on line; disconnect working fibres from ODF one by one at one site only. 5. Reconfirmation from TNOC regarding stability of systems. 6. In case of any unexpected outage reconnect fibre in co-cdinnexpecwith TNOC and


15. After completion of splicing for all fibres, reconfirmation from TNOC regarding stability of all working systems. 16. Fibres must be organized carefully in splice enclosure to avoid Micro-Bending. 17. Closing of splice enclosures and securing the cable with splice enclosure with heat shrink sleeve. 18. Inform TNOC when splice enclosures are closed permanent. 19. Preparation of cable maintenance loop and Storage of splice enclosure. 20. In case of direct buried cable, Backfilling 30Cm with sweat sand and placing of tiles above the Splice. 21. In case of Manholes, securing the splice on the brackets in the Manhole. 22. Installation of Marker posts. 23. Updating the drawing and submission of updated drawing and test results to LDN HQ.

9.6 Test Required1. OTDR testing from both terminal sites of the section involved immediately after splicing. 2. Section loss test with MaxTester immediately after splicing.

9.7 Priority of SystemsPriority of system changes according to the situation. Unprotected systems are always on Top priority. Following sequence of System Priority must be followed. 1. OLS 400 2. OLS 80 G 3. ADM 16 / SLM 16 4. ISM 5. ADM 4


9.8 Emergency Repair Process1. During the process of mechanical splicing, SDH technicians must be available at both sites of the section involved. 2. Care must be taken in opening and closing of ODF trays to avoid damage or micro-bending of pigtails and patch cords. 3. SDH technician must have power meter at one site and OTDR on the other site in order to perform continuity test. 4. After mechanical splicing of each Fibre, OTDR test must be performed to check the quality of the mechanical splice. 5. Prior to connect fibres with the system, Test with laser source and power meter must be conducted in order to ensure the correct sequence and continuity of fibres at both sites. 6. After above-mentioned tests, fibres must be connected to the system. 7. If the system is not restored, troubleshooting must be done according to the following steps. 8. First of all direction of failure must be identified. 9. Faulty Fibre No must be identified. 10. OTDR test must be performed to check the quality of mechanical splice. 11. If the quality of mechanical splice is good and trace shows through Fibre from mechanical splice point then continuity test with laser source and power meter must be performed in order to confirm the continuity of fibre and correct sequence at ODFs of both sites. 12. Both ODFs must be checked carefully for micro-bending of ODF pigtails or patch cords. 13. At all times SAT phone must be dispatched with cable team in order to avoid communication problem during restoration activities in the areas without GSM coverage


10. Colour scheme10.1 24 fibre (6 tubes - 4 tubes)24F(6-Tube) 24F(4-Tubes) Colour BLUE Colour BLUE Fibre No. 1 2 3 4 5 6

Tube No.

Fibre No. 1 2 3 4 5 6

1 Blue 2

Tube No. 1

ORANGE ORANGE GREEN GREEN BROWN BROWN BLUE ORANGE SLATE WHITE


10.2 24-36 fibre

24 FOC Tube No. 1 BLUE 2 ORANGE 3 WHITE 4 WHITE 5 WHITE 6 WHITEFibre No. Colour 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN Colour BLUE ORANGE GREEN BROWN SLATE WHITE BLUE ORANGE GREEN BROWN SLATE WHITE BLUE ORANGE GREEN BROWN SLATE WHITE BLUE ORANGE GREEN BROWN SLATE WHITE BLUE ORANGE GREEN BROWN SLATE WHITE BLUE ORANGE GREEN BROWN SLATE WHITE

36 FOCFibre No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Tube No. 1 BLUE

2 ORANGE

3 WHITE

4 WHITE

5 WHITE

6 WHITE


10.3 24-48 fibre24 FOC Tube No. 1 BLUE 2 ORANGE 3 WHITE 4 WHITE 5 WHITE 6 WHITE Fiber No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Color BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN BLUE ORANGE GREEN BROWN Color BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK 48 FOC Fiber No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 6 WHITE 5 WHITE 4 WHITE (Tray 3) 3 ORANGE (Tray 2) 2 BLUE (Tray 1) Tube No. 1

WHITE


10.4 Standard colour scheme

Colour BLUE ORANGE GREEN BROWN SLATE WHITE RED BLACK YELLOW PURPLE ROSE AQUA

Fibre No. 1 2 3 4 5 6 7 8 9 10 11 12


cables handbook

Documents

fibre optic splicing

definition of fibre

testing of fibre optic

fibre loss variables

types of fibre optic

cable depth

optical fibre splicing

cable installation repairs