1. SPLICER CLEANING AND MAINTENANCE (Specific to Fujikura machines)
Do not use any chemical other than pure alcohol (purity > 99%) to clean the objective lens, V-groove, mirror, liquid crystal display monitor, etc., of the splicer. Otherwise blurring, discoloration, damage or deterioration may result. The splicer requires no lubrication - oil or grease may degrade the splicing performance and damage the splicer. Be careful if you are using compressed air, for it is not always perfectly pure and will sometimes cause blurring. Keep in mind that fiber specifications are measured in terms of microns or millionths of a meter, and dirt particles invisible to the naked eye can wreak havoc on a splice.
Cleaning V-grooves If dirt particles are present in the V-grooves, proper clamping may not occur, resulting in higher splice loss. The V-grooves should be frequently inspected and periodically cleaned during normal operation. To clean the V-grooves, do the following: 1 Clean the bottom of the V-groove with an alcohol-impregnated thin cotton swab 2 Remove excess alcohol from the V-groove with a clean dry swab 3 If the dirt particles in the V-groove cannot be removed with an alcohol-impregnated thin cotton swab,
use a cleaved fiber end-face to dislodge particles from the bottom of the V-groove – then clean with an alcohol-impregnated thin cotton swab
4 Be careful to not touch the electrode tips 5 Never use excessive force when cleaning the V-groove – you may damage the V-groove arm
Cleaning Electrodes If the electrodes are not replaced after 1,000 arc discharges or cleaned periodically, this is likely to cause greater splice loss and reduced splice strength. To clean the electrodes, do the following: 1 Before cleaning the electrodes, always turn off the splicer 2 Loosen the screw located on the electrode cover and remove the electrode 3 Using a knife, scrape off the silica oxide buildup from the electrode 3 Wipe the electrode using an alcohol-impregnated lint-free tissue 4 Remove excess alcohol from the electrode using a dry lint-free tissue 5 When reinstalling the electrode, apply no more than 2kgf-cm torque when tightening the screw 6 Always replace the electrodes as a pair
Cleaning Objective Lenses If the objective lens’s surface becomes dirty, normal observation of the core position may be incorrect, resulting in higher splice loss or poor splicer operation. Therefore, clean both of them at regular intervals. Otherwise, dirt may accumulate and become impossible to remove. To clean the objective lenses, do the following: 1 Before cleaning the objective lenses, always turn off the splicer 2 Remove electrodes before cleaning objective lenses Gently clean the lenses (X-axis and Y-axis) surface with an alcohol-impregnated thin cotton swab 3 Using the cotton swab, start at the center of the lens and move the swab in a circular motion until you
spiral out to the edge of the lens surface 4 Remove excess alcohol from the mirror surface with a clean dry swab 5 Turn on the power and make sure that no smudges or streaks are visible on the monitor screen
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Cleaning Fiber Clamp Chips If dirt particles are present on the clamp chips, proper clamping may not occur, resulting in poor quality splices. The fiber clamp chips should be frequently inspected and periodically cleaned during normal operation. To clean the clamp chips, do the following: 1 Clean the surface of the chip clamp with an alcohol-impregnated thin cotton swab 2 Remove excess alcohol from the V-groove with a clean dry swab
Cleaning Wind Protector Mirrors If the wind protector mirrors become dirty, the fiber core position may be incorrect due to decreased optical path clarity, resulting in higher splice loss. To clean the mirrors, do the following: 1 Clean the mirror surface with an alcohol-impregnated thin cotton swab. Remove excess alcohol from
the mirror surface with a clean dry swab 2 Mirrors should look clean with no streaks or smudges
Cleaning Fiber Cleaver If the cleave blade or clamp pads of the fiber cleaver become contaminated, the cleaving quality could degrade. This may lead to fiber surface or end-face contamination, resulting in higher splice loss: 1 Clean the cleave blade and clamp pads with an alcohol-impregnated thin cotton swab. Remove excess
alcohol using a clean dry swab
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2. MINIMIZING FUSION SPLICE LOSS �
2.1 Safety Precautions �
Eye Protection ♦ Never look directly into the end of any optical fiber unless it is certain that no light is present in the fiber.
Laser light can damage your eyes. The light used for signal transmission in fiber optics is generally invisible to the human eye but may operate at power levels that can be harmful to the eye. Viewing it directly does not cause pain. The iris of the eye will not close involuntarily as when viewing a bright light. Consequently, serious damage to the retina of the eye is possible. Should accidental eye exposure to laser light be suspected, arrange for an eye examination immediately.
♦ After handling fiber, wash hands thoroughly before touching eyes or contact lenses. ♦ When using an optical tracer or continuity checker, look at the fiber from an angle at least 12 inches
away from the eye to determine if the visible light is present.
Protection from Fiber Scraps ♦ Small scraps of bare fiber produced as part of the termination and splicing process must be
disposed of properly in a safe container and marked according to local regulations, as it may be considered hazardous waste.
♦ There are two different types of cleavers, one in which the cut fiber fragment is disposed of automatically in the “garbage can” and one where the fiber fragment is loose in the vicinity of the cleave. In the latter case immediately locate the cut fiber fragment and place it in a suitable disposal container.
♦ Do not drop fiber scraps on the floor where they will stick in carpets or shoes and be carried elsewhere. Place them in a marked container or stick them to double-sided adhesive tape on the work surface.
♦ Thoroughly clean the work area when finished. Do not use compressed air to clean off the work area. Sweep all scraps into a disposal container.
♦ Do not eat, drink or smoke near the working area. Fiber particles can be harmful if ingested. Wash hands well after working with fibers.
♦ Carefully inspect clothing for fiber scraps.
1 Introduction: • It is important to handle bare fibers as little as possible from this point until the splice is
complete. Taking this precaution will minimize the chance of contaminating the fibers with dust or body oils, which may contribute to higher splice losses and lower tensile strengths.
• It also is important to complete the splicing process as quickly as possible, since delays will expose the fiber to additional airborne contaminants.
2 Clean optical fiber coating: • Clean optical fiber with an alcohol-impregnated lint-free tissue up to ± 300mm from the tip,
before placing the protection sleeve over the fiber.
• This will prevent dust particulates on the fiber coating surface from ending up inside the protection sleeve and potentially cause a weakness or increase in attenuation.
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3 Strip fiber coating: • Place the protection sleeve over the fiber, before stripping and cleaving.
• Strip outer coating to ± 40 mm.
• The stripping tool must be the proper size and designed for the fiber and coating combination being stripped.
4 Cleaning stripped fiber: • Clean the bare glass by pulling the fiber through an alcohol (purity> 99%) soaked lint-free wipe.
• Limit the time that the bare fiber is exposed to the atmosphere. 5 Fiber-end preparation:
• Since the primary attribute affecting single fusion splicing is the end angle, proper fiber-end preparation is a fundamental step in obtaining an acceptable fusion splice.
• Do not clean the fibers again after they have been cleaved. 6 Loading fibers into splicer:
• Touch only the coated portion of the fiber.
• Take utmost care not to bump the prepared fiber tips to maintain fiber end-face quality.
• If fiber coating has some memory curl, place the fiber so that the curve of memory is turned upwards.
• Hold fiber with fingers and close sheath clamp so that the fiber does not move.
• Make sure the fiber is placed in the bottom of the v-grooves.
• The fiber end-face must rest between the V-groove tip and electrode centerline
• If the fiber is not placed properly (i.e. moves in v-groove as the sheath clamps make contact with the fiber), reload fiber.
• Lower the splicer sheath clamps gently - all the way down. 7 Loading the spliced fiber into the tube heater:
• Place protection sleeve on the centering device located on the tube heater.
• Length gauge is set according to sleeve length in advance.
• The splicing point can be set in the center of the protection sleeve using the centering device.
• Transfer fiber with protection sleeve from centering device to tube heater
• While placing it in the tube heater, apply some tension on the fiber so the tube heater lids automatically close.
• Make sure the splice point is located at the center of the protection sleeve.
• Make sure the strength member in the protection sleeve is placed downwards. 8 Secure the splice into the splice organizer:
• Once the fiber is satisfactorily spliced and properly protected (typically with a heat shrink sleeve), the completed splice assembly will be secured into the splice organizer.
• Routing of the fibers must be checked within the splice organizer to assure that the proper fiber bending radius is maintained, and that the fibers are not inadvertently bent over any sharp edges.
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3. ERECTING SELF-SUPPORTING FIBER OPTIC CABLE
3.1 Safety precautions which should be observed when working on overhead routes
These practices listed below serve only as suggested guidelines. Your company’s safety precautions and practices take precedence over any recommendations given in this document. Before starting any aerial cable installation, all personnel must be thoroughly familiar with all applicable Occupational Safety and Health Act regulations, the Electrical Safety Code, and company safety practices and policies. Failure to do so can result in life-threatening injury to employees or the general public.
3.2.1 Ladders and poles: • Ensure that the ladder suits the application and is in a serviceable condition.
• Inspect and test poles/structures (for rot, termites or rust) before climbing the ladder.
• Never join two ladders to carry out work.
• Only one person may be on the ladder at any given time.
• Never climb higher than the third rung from the top.
• Make sure that the stepladder is fully open before climbing.
• Ensure that the ladder is positioned correctly (4:1 or 75° angle) and lashed to the pole.
• Utilize the correct PPE; safety belt, hard hat, boots, and gloves.
3.1.3 Shared pole routes and power crossings: • Only suitably trained and authorized personnel can work on shared pole routes or power crossings. • Abide by the Code of Practice for the joint use of structures for power and telecommunication lines. • When working under or near open wire power lines/crossings - Eskom must be contacted at their call
centre 086 020 4560 before engaging in any activities (even when the power lines are at a safe height/distance).
• When working in the vicinity of overhead power lines, test for stray currents using a high voltage power meter.
• When an unsafe condition is identified, stop working immediately.
3.1.4 Planting new poles:
• Plant new poles only when there is no existing utility and when a reasonable alternate route does not exist. Written permission must be obtained from the proper authorities before placing new poles, and all other utilities having underground plant in the area must be contacted so they can locate and mark their facilities prior to new pole placement.
3.2 Handling cable drums/reels: • Care must be taken to avoid cable damage during placement and handling. Fiber optic cable is
sensitive to excessive puling, bending and crushing forces. Any such damage may alter the cable's characteristics to the extent that the cable section may have to be replaced.
• If the cable ends are not secured, vehicle bouncing can cause the cable to loosen on the reel, resulting in kinks, irregular cable bundles, or cross-wraps.
• Always roll the drum in the direction of the arrow printed on the side of the drum.
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• Lightweight drums of fiber optic cable can be moved by hand, however, large drums must be moved using appropriate lifting equipment or an adequate number of personnel.
• Use cable jacks or a trailer to lift cable during the hauling process (never turn a drum on its side).
• Position the drum so that the cable will be rolled of the top of the drum towards the first pole. 3.3 Always attempt to pull with gravity: • For ease of installation, pull cables from a higher elevation to lower ones, whenever possible.
• Once the cable end is past the first pole, the pulling speed can be gradually and steadily increased.
• If sufficient support hardware is in place, pulling of ± 50m per minute are typical.
3.4 Pull on the strength members only: • The cable manufacturer gives you the perfect solution; they install special strength members, usually
duPont Kevlar aramid yarn.
• Most cables cannot be pulled by the jacket. Do not pull on the jacket unless it is specifically approved by the cable manufacturer and you use an approved cable grip/sock.
• Steel and fiberglass rods are also used as strength members in multifibre bundles.
• Cable socks must not be fastened with wire as the sharp edges may cause damage. Normal insulation tape around the open end of the sock must be used.
3.5 Pulling Grips • Pulling grips provide effective coupling of pulling loads to the jacket, aramid yarn, and central member
of fiber optic cables.
• Two well-known pulling grips are the Kellems wire mesh pulling grip and the Poulin pulling grip and swivel during cable pulls.
3.6 Pull-Line: • An 8mm polyester rope can be used for hauling. The 8mm polyester rope has low elasticity and can
minimize surge-induced fluctuation in pull-line tension.
• Some Telecommunication companies specify that galvanized steel wire, steel hauling rope, or ski-rope should not be used for hauling. Galvanized wire and steel rope may damage the cable pulleys, ducts
Figure 1. Pulling grips
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and/or existing cables during the hauling process. Conventional ski-ropes manufactured from nylon are not suitable, as their stretch factor is too high.
3.7 Center-Pulls: • On long cable pulls, you can use the center-pull technique.
• Place the cable drum approximately halfway and haul in one direction.
• The balance of the cable is then completely run off the drum into a figure 8 on a tarpaulin after which it is then hauled in the opposite direction.
• The figure 8 method should not be used for cables longer than 2500m as it becomes risky to manage a coil bigger than 1250.
3.8 Working bend radius for cable installation: • Place the cable drum ± 50m away from the first pole fitted with a pulley; this will prevent the cable
from bending too much when being erected.
• As a general rule, the minimum bend radius for a cable under tension is 15 times the nominal outside diameter of the cable. The minimum bend radius for cables not under tension is 10 times the nominal outside diameter of the cable.
Note: Using the bend radii listed in the table above may result in minor, cosmetic wrinkling of the outer sheath of armored cables. This wrinkling will not affect performance; however, to avoid this wrinkling, use a bend radius of 15 times the cable diameter.
3.9 Tension-Monitoring Equipment: • Fiber optic cable is subject to damage if the cable’s specified maximum tensile force is exceeded.
Except for short runs or hand pulls, tension must be monitored.
• A dynamometer can be attached to the coffin hoist to monitor tension in the pull-line, illustrated in figure 2.
Figure 2. Tensioning equipment
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Table 2. “Sag” examples (consult product information sheets for specific values). Cable Type Span (m)
Sag (m) Span (m) Sag (m)
Span (m) Sag (m)
Span (m) Sag (m)
Long Span Aerial Cable (Non-metallic, self-supporting cable with a span length � 500 m)
200 1.0
300 2.5
400 4.4
500 6.0
Medium Span Aerial Cable (Non-metallic, self-supporting cable with a span length � 250 m)
100 0.6
150 1.3
200 2.2
250 3.4
Short Span Aerial Cable (Non-metallic self-supporting cable with a span length � 100 m)
70 0.5
100 1.0
The performance figures quoted above are specific to cable designed for tropical climates, anticipating no ice, but winds up to 125 km/h.
3.10 Figure-eighting: • Figure-eighting can be used in order to pull in both directions from a central location or to make a
transition from the moving reel installation method to the stationary reel installation method.
Figure 3. Figure-eighting long lengths of cable
• If you are laying cable out for a long pull, use a figure-8 on the ground to prevent twisting (the figure-8 puts a half twist in on one side of the 8 and takes it out on the other, thus preventing twists).
• Fiber optic cable should not be coiled in a continuous direction except for lengths of 30 m or less. The preferred size for the figure-8 is about 4.5 m in length, with each loop 1.5 m to 2.4 m in diameter.
• Flip over the figure-8 so that the pulling-eye end of the cable is on top. This can be easily accomplished by three (3) people, one at each end of the eight, and one at the center.
• The use of a swivel between the pull-line and pulling grip is required to prevent the pull-line from imparting twists to the cable.
3.11 Temporary support hardware: • Cable pulleys must be placed on each pole so as to maintain the cable’s minimum bend radius
throughout the route, lowering pulling tension and to prevent the cable’s entanglement on obstructions in the right-of-way.
3.12 Terminating and supporting the cable: • When a route deviates with an angle greater than 10°, the cable must be terminated at deviating poles,
shown in figure 4.
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Figure 4. False Dead-end
Cables should be routed on the inside of poles at dead-ends and aerial crossovers. This practice, along with drip loops, will minimize the chance of damage should a pole in the cable route be damaged.
• Terminate the cable using the correct size galvanized thimble type dead-ends – if the dead-end fits too tight, it is likely to create a micro bend.
• Use galvanized thimble type dead-ends with a white marking is for: 48 fiber cables
• Use galvanized thimble type dead-ends with a black marking is for: � 24 fiber cables
• Use double Suspension hooks for terminations and single S-hooks for support clamps.
• The correct type of support clamp must be used at intermediary poles i.e. Bundex Clamp.
3.13 Splice Locations: • When selecting splice locations during the survey, consider the accessibility of these splicing locations
by splicing vehicles. These locations should not fall in sites where access is inconvenient or hazardous.
• Leave enough cable slack on each cable end to reach the ground and into a splice vehicle, plus 5m. This cable slack must be taken into account when ordering cable lengths.
• Store coiled splicing slack in an enclosed slack tray or on a slack wheel, secured to the pole directly below the suspended cable.
3.14 Tree and bush cutting: • Tree and bush cutting/trimming – a minimum radius of 1.5m around the cable is recommended.
• You are not permitted to cut or trim trees without prior consultation with the owner and the Department of Forestry.
• A list of the protected trees can be obtained from the Department of Water Affairs and Forestry. A license must be obtained to cut/trim a protected tree as stipulated in the National Forest Act 84/98.
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4. HAULING FIBER OPTIC CABLE
4.1 Safety precautions which should be observed when working in manholes or underground vaults:
These practices listed below serve only as a few suggested guidelines. Your company’s safety precautions and practices take precedence over any recommendations given in this document.
• To minimize hazards to yourself and others in or near the work area, set up barricades, manhole guards, and warning signs.
• Any material in the vicinity of a manhole should be arranged so that it can not fall into a manhole, or unnecessarily impede pedestrian or vehicle traffic.
• Explosive gases or vapors may be present in manholes due to leaking of nearby pipes or storage tanks of liquids or gases such as propane, gasoline, natural gas, or liquefied petroleum gas (LPG). In addition, explosive gases may be organically generated (i.e., methane).
• Before entering any manhole, test the manhole atmosphere with an approved meter or test kit for explosive gases. Failure to do so may result in serious injury from an explosion created by the mixture of explosive gases and oxygen.
• In addition to combustible gases, life threatening hazards may be present in the form of non-combustible gases (i.e., nitrogen, hydrogen sulfide, and carbon dioxide).
• Do not use any electrically energized devices in manholes unless they are certified for explosive environments.
• Never connect or disconnect electric lighting, tools, or heating equipment in a manhole. Mating or unmating an electric circuit may cause an electric arc.
• As long as the manhole is open, continuous forced-draft ventilation at a MINIMUM rate of 15 cubic metre per minute should take place.
• Always use a ladder when entering or leaving manholes. Keep hands free of tools or materials when descending or ascending a ladder.
• Ensure that the equipment outside the manhole does not endanger anyone in or outside the manhole.
• Use the correct equipment to lift the manhole or junction box lid or acquire additional assistance.
• Do not use fusion splicer’s or smoke in confined spaces as defined by OSHA.
• Utilize the correct PPE; safety boots, hard hat, and gloves. 4.2 Overhauling fiber optic cable: • Pulling a new fiber optic cable over an existing one is not recommended due to the possibility of
entanglement, excessive oscillation or surging that can be damaging.
• All avenues must be explored for alternatives than that of placing an optical fiber cable over an existing optical fiber cable that is not encapsulated with an inner duct.
• In certain instances, civil work may be necessary to lay a dedicated outer duct that is fully populated with inner ducts.
• One can also evaluate the possibility of moving “ small” copper cables in order to create spare duct capacity.
• Another option is to ascertain if an inner duct can indeed be overhauled over an existing copper cable on the particular route.
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4.3 Installing inner ducts: • An inner duct is semi-rigid plastic tubing commonly used in fiber optic installations to subdivide the
duct and to provide for future cable pulls.
• When placing one fiber optic cable in an inner duct, the “fill ratio” should generally not exceed 65%.
• Couplers “splice’’ inner duct sections together. Do not use couplers which reduce the inside diameter of the inner duct.
• During inner duct placement, care must be taken to avoid excessive tension and deformation of the inner duct. Excessive pull force may cause smooth-walled and longitudinally-ribbed inner duct to “neck down,” reducing its inside diameter.
• When constructing a new cable duct run, it is imperative to populate the dedicated outer duct with the maximum number of inner ducts during the initial installation.
• The inner ducts that are not populated with optic fiber cables must be sealed with pipe plugs after being installed.
4.4 Handling cable drums/reels:
Discussed in 3.2
4.5 Always attempt to pull with gravity: • For ease of installation, pull cables from higher elevation manholes to lower ones, whenever possible.
4.6 Tension-Monitoring Equipment: • Fiber optic cable is subject to damage if the cable’s specified maximum tensile force is exceeded,
except for short runs or hand pulls, tension must be monitored • The use of a winch with a calibrated maximum tension is an acceptable procedure. The control device
on such winches can be hydraulic or in the form of a slip clutch.
• The use of a breakaway link (swivel) can be used to ensure that the maximum tension of the cable is not exceeded. Breakaway links react to tension at the pulling eye and should be used as a fail-safe rather than a primary means of monitoring tension.
• A dynamometer may also be used to monitor tension. 4.7 Pull on the strength members only: Discussed in 3.4
4.8 Pull-Line:
Discussed in 3.6
4.9 Pulling Grips:
Discussed in 3.5
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4.10 Working bend radius for cable installation: • To arrive at a working bend radius for cable installation, multiply 15 times (15 x) the cable outside
diameter. Example: Cable Diameter = 11.8 mm (15 x 11.8 mm =177 mm).
• To find the minimum diameter requirement for pull wheels or rollers, simply double the minimum working bend radius.
• Situations that require use of a radius-maintaining device are encountered at feed and pull manholes, at bends, and where entrance and exit ducts in a manhole are offset.
4.11 Figure-eighting:
Discussed in 3.10
4.12 Center-Pulls:
Discussed in 3.7
4.13 Back feeding: • On cable pulls involving many bends, you can use the back feeding technique.
• Back feeding may be used to provide a series of shorter, lower-tension pulls in one direction.
• When back feeding, pull enough cable out of the manhole to reach the intended end point of the pull, plus racking and splicing slack.
• This cable should be “figure-eighted” as it emerges from the manhole.
4.14 Establish communication lines: • Establish communication lines between all crucial points (the pull, feed, and monitoring locations)
along the cable route via mobile radios, before starting any pull operation.
• Place personnel at all intermediate manholes to guide the cable and assist with the hauling process.
4.15 Cable lubricant: • Cable lubricant (Poly Water) is recommended for most fiber optic cable pulls as a means of lowering
pulling tension. Short hand-pulls may not require lubricant.
Figure 5. Unreeling cable and Completion of center pull operation
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4.16 Splice Locations: • At splice points, pull sufficient slack (typically 15m of slack from the lip of the manhole) to enable
splicing to take place outside the chamber (preferably inside a vehicle), plus enough slack to permit closure preparation and splicing.
• Store coiled splicing slack in the splicing manholes in an enclosed slack tray or on a slack wheel, secured to the chamber wall.
• When selecting splice locations during the survey, consider the accessibility of these splicing locations by splicing vehicles. These locations should not fall in sites where access is inconvenient or hazardous.
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5. SPLICE LOSS INCREASE: CAUSE AND REMEDY
A successful splice creates a smooth, uniform and homogeneous flow of glass at the cleaved ends to produce a continuous joint. Splice loss may be improved or worsened by additional arc discharges. Symptom Cause Remedy
Core axial offset
Dust on v-groove or fiber clamp chip
Clean v-groove and fiber clamp chip
Core angle
Dust on v-groove or fiber clamp chip Bad fiber end-face quality
Clean v-groove and fiber clamp chip Check if fiber cleaver is well conditioned
Core step
Dust on v-groove or fiber clamp chip
Clean v-groove and fiber clamp chip
Core curve
Bad fiber end-face quality Prefuse power too low, or prefuse time too short
Check if fiber cleaver is well conditioned Increase [Prefuse Power] and/or [Prefuse Time]
MFD mismatch
Arc power too low Increase [Arc Power] and/or [Arc Time]
Combustion
Bad fiber end-face quality Dust still present after cleaning fiber or cleaning arc
Check the cleaver – prepare & cleave fiber again Clean fiber thoroughly or Increase [Cleaning Arc Time]
Bubbles
Bad fiber end-face quality Prefuse power too low, or prefuse time too short
Check the cleaver – prepare & cleave fiber again Increase [Prefuse Power] and/or [Prefuse Time]
Separation
Fiber stuffing too small Prefuse power too high, or prefuse time too long
A vertical line sometimes appears at the splice point when MM fibers or dissimilar fibers (different diameters) are spliced. The good news is that it does not affect splice quality, such as splice loss or tensile strength.
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6. MINIMIZING MECHANICAL SPLICE LOSS Specific details and precautions in minimizing the splice loss will be covered in this section:
The 3M Fibrlok Optical Fiber Splice provides permanent mechanical splices for both single and multimode fiber • Remove Fibrlok splice from protective package. Load the splice into
the assembly tool by pressing firmly at the ends of the splice. • Strip ± 40mm coating from the fiber using a mechanical stripper. • Clean the bare glass by pulling the fiber through an alcohol soaked
lint-free wipe. • Cleave fiber to 12.5 mm. for both 250�m and 900�m coated fibers. • Do not clean the fibers again after they have been cleaved. • Hold the coated portion of the fiber only - do not allow the cleaved
end to contact any surface before insertion into the splice.
• Grasp the coated fiber ± 6 mm from the bare glass and move the fiber end onto the fiber alignment guide on the assembly tool such that the end is resting on the alignment guide outside of the splice.
• Note: When splicing 250�m to 900�m coated fiber, always insert the 250�m coated fiber first.
• Note: Fiber should be placed in the retention pad and inserted into the splice immediately following cleaning to reduce the risk of contamination. Note: Push fiber straight into fiber alignment guide - NEVER AT AN ANGLE.
• Gently continue pushing the fiber into the splice until resistance is felt. When fully inserted, the first fiber should be straight or have a slight bow of ± 3 mm.
• Prepare second fiber (strip, clean and cleave). • Gently push the second fiber in small increments straight through the
alignment guide into the fiber entry port. • As the coating of the second fiber enters the fiber entry port, watch for
the bow in the first fiber to increase. • This occurs when the end face of the second fiber contacts the first
fiber and pushes the first fiber slightly back out of the splice. • Continue gently pushing the second fiber until it meets resistance.
• At this point, the first fiber will have a larger bow than the second fiber and larger than it had initially.
• Push the first fiber back against the second fiber until there are equal bows in both fibers.
• Do not pull on either of the fibers following establishment of the bows in the first and second fibers. The fiber ends must be held together by the compressive forces induced by the bows to produce a low loss splice.
• If fiber bows are NOT observed to move as described, repeat the above mentioned steps - but DO NOT fully remove fibers from the splice.
• If bow movement is still not observed, remove fibers, strip, clean and re-cleave, checking for proper cleave length.
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• Finally, pivot the handle of the Fibrlok Assembly Tool down until it makes contact with the cap of the Fibrlok Splice.
• Squeeze the handle of the assembly tool as shown in order to close cap and actuate the splice.
• When possible, secure the tool to a work surface for added support. • A snap sound will be heard when the splice is actuated. • If you have to remake the splice, cut the fibers at each end of the
splice and re-splice – this will require a new Fibrlok and fresh fiber. DO NOT REMOVE FIBERS AND RE-USE FIBRLOKSPLICES.
7. THE MOST COMMON FIBER OPTIC CONNECTORS USED IN SA.
ST is the most popular connector for MM networks. It has a bayonet mount and a long cylindrical ferrule to hold the fiber. Most ferrules are ceramic, but some are metal or plastic. And because they are spring-loaded, you have to make sure they are seated properly. If you have high loss, reconnect them to see if it makes a difference.
� �
FC/PC has been one of the most popular SM connectors for many years. It screws on firmly, but make sure you have the key aligned in the slot properly before tightening. It's being replaced by SCs and LCs.
� �
SC is a snap-in connector that is widely used in SM systems for its excellent performance. It's a snap-in connector that latches with a simple push-pull motion. It is also available in a duplex configuration�
� �
LC is a new connector that uses a 1.25 mm ferrule, half the size of the ST. Otherwise; it's a standard ceramic ferrule connector, easily terminated with any adhesive. Good performance, highly favored for SM.
� �
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MT-RJ is a duplex connector with both fibers in a single polymer ferrule. It uses pins for alignment and has male and female versions. Used for MM only.
� �
Opti-Jack is a neat, rugged duplex connector cleverly designed around two ST-type ferrules in a package the size of a RJ-45. It has male and female (plug and jack) versions.
� �
7.1 CONNECTOR MAINTENANCE Connectors are designed to require minimum maintenance in order to provide reliable operation for many years. To ensure accurate readings and minimum insertion loss, it is important that fiber ends and optical ports be clean at all times. Proper cleaning also prevents the buildup of dirt, dust and other foreign substances - especially in connector pins.
Before you start the cleaning procedure you will need the following standard cleaning equipment: ♦ Isopropyl alcohol ♦ Lint-free wipe (Kimwipes) ♦ Cotton swabs (cleaning tips) ♦ Compressed air
Below are a few hints on how to keep your connectors in the best possible condition: ♦ When inserting a connector ferrule into a connector or adapter, ensure that the ferrule tip does not touch
the outside of the mating connector or adapter. Otherwise, the fiber end will rub against an unsuitable surface, producing scratches and dirt deposits on the fiber.
♦ Do not force the ferrule into the adapter. Note that the ceramic or metal sleeves inside the adapter are tightly fitted. Carefully rotate the ferrule in the adapter in order to align it with the connector key.
♦ Every time there is a disconnection or an undesirable contact, you must carry out the cleaning procedure. ♦ The use of protective caps is also necessary, but does not guarantee the cleanliness or the quality of a
patch cord. ♦ Cleaning connectors is difficult because the core diameter of a SM fiber is very tiny. This generally
means you will not be able to see scratches on the surface. In order to be certain of the connection’s surface condition and to be able to check it after cleaning, you need a fiber-optic microscope such as the EXFO FOMS-400X-UNIV.
♦ Warning: Never look into the end of an optical cable that is connected to an active source!
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Cleaning the Fiber Ends: ♦ Make sure the fiber is not active. ♦ Remove the protective caps. ♦ Gently wipe the fiber end with a lint-free wipe moistened with isopropyl alcohol. ♦ To dry, use a dry lint-free wipe first, and then use compressed air. ♦ When using isopropyl alcohol to clean an optical device, do not proceed immediately to dry the surface
with compressed air (except when you are cleaning very sensitive optical devices). This is because the dust and dirt are in solution and will leave behind a filmy deposit once the alcohol has evaporated. Therefore, you should first remove alcohol and dust with a soft tissue, and then use compressed air to blow away any remaining particles.
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8. FIBER OPTIC MEASUREMENT BASICS A few years ago, loss budget tolerance was not really an issue. Now, with higher data rates and optimized costs, the budget tolerance has shrunk considerably, and it is an accepted standard in the industry that budget loss tolerance should be no greater than 3 dB. In each of the test procedures described hereafter, you should inspect and clean the connectors before hooking them up to the test equipment or another device. Dirty connectors can induce errors during network testing or commissioning; so you should also clean the test patch cords and the patch panel. Both ends of every fiber junction need to be squeaky clean. Failing to do this can cause high loss and high reflection, as well as contaminate the equipment to which the connectors and patch cords will be connected.
Unless otherwise specified by the customer, test; MM Fiber at 850 and 1300 SM Fiber at 1310 and 1550. Table 4. Test Solutions Measurement Test Description 1 Optical budget loss (end to end or per
segment) (dB) Source and power meter
2 Optical return loss (dB) Single-ended test with a source and detector (measuring reflection)
3 Link characterization Single-ended measurement made with a ODTR
4 Connector verification Visual inspection using a microscope
5 Fiber identification/polarity Visible light source 8.1 Optical budget loss (end to end or per segment) (dB)
Table 6. Calculating the fiber loss Multiply the length of the fiber with the attenuation at each wavelength:
• Cable length in km X 3.5 dB/km @ 850 nm = fiber dB loss @ 850 nm
• Cable length in km X 1.5 dB/km @ 1300 nm = fiber dB loss @ 1300 nm
• Cable length in km X 0.35 dB/km @ 1310 nm = fiber dB loss @ 1310 nm
• Cable length in km X 0.27 dB/km @ 1490 nm = fiber dB loss @ 1490 nm
• Cable length in km X 0.22 dB/km @ 1550 nm = fiber dB loss @ 1550 nm
Table 7. Calculating the connector loss Multiply the number of connectors with the maximum allowable loss of 0.75 dB Count the connectors on each end as one each and each mated pair as one connector loss
• Number of connectors X 0.75 dB = Connector loss in dB
Table 8. Calculate the splice loss Multiply the number of splices with the maximum allowable loss of 0.3 dB
• Number of splices X 0.3 dB = Splice loss in dB
Table 5. Calculating the loss budget The loss of the fiber + The loss of all connections + The loss of all splices
= The total loss
Calculating the loss budget for a newly installed fiber optic link using a source and power meter, determines the maximum loss expected in a normal installation. The loss measured must be less than the loss calculated using the methods shown in tables 5 - 8.
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8.2 Optical return loss (dB)
• Purpose of Optical Return Loss Testing (ORL) Testing ORL testing measures the back reflection of connectors and components in high-speed digital and analog systems. This is single-ended test accomplished using a source and detector.
• Differences between ORL and OTDR Testing The port of an ORL tester is equipped with both a light source and a detector. The light source emits a continuous wave and the detector receives a reflected continuous wave to measure back reflection. With this in mind, the OTDR is designed with a different objective in mind. It emits pulses of light to find out the location of events; back reflection can be roughly evaluated with the returning pulse. This backscattered optical power is proportional to the fiber attenuation rate; however, the OTDR does not measure the actual attenuation of the fiber. As a result, OTDR’s are less accurate with respect to back reflection measurements.
• Consequences of Back reflection: • Less light is transmitted
• Causes interference with light source signals
• Creates higher bit error rate (BER) in digital systems
• Reduces signal-to-noise ratio (SNR) in analog systems
Another effect of back reflection is that light returns to the light source. Since a light source is designed to emit and not to receive, high back reflection can bring about several consequences:
• Causes fluctuations in the light source’s central wavelength
• Causes fluctuations in its output power
• Damages the light source permanently
8.3 Link characterization
• An optical time domain reflectometer (OTDR) is mainly used for troubleshooting - to pinpoint breaks in underground or aerial cables. Accidental digging by construction crews is a frequent problem. Fires often cause cable damage on aerial cables, resulting in loss of service. Cable cuts can also be the result of vandalism. In some countries (like South Africa), underground fiber cables even get stolen by mistake by people who want to melt the copper and sell it.
• OTDR analysis software is also designed to thoroughly locate all possible types of events, such as reflections, caused by connectors, fiber breaks or ends; losses, caused by splices or macro bends; or gains, caused by imperfect core alignments or diameter differences.
• A good-quality OTDR should be able to clearly point out all types of events on the trace to make them easily identifiable to the user.
• The OTDR traces can be archived (hard and/or soft copy) to be used as a reference against future degradation or cable cuts.
• However, the OTDR must never be used to establish cable loss – as explained in 8.2.
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8.4 Connector verification
• Cleaning connectors is difficult because the core diameter of a SM fiber measures only about 9 �m. This generally means you will not be able to see scratches on the surface. In order to be certain of the connection’ s surface condition and to be able to check it after cleaning, you need a fiber-optic microscope.
• To ensure accurate readings and minimum insertion loss, it is important that fiber ends and optical ports be clean at all times. Any connector that has a scratch across the core, or a scratch that appears to end in the core, must be rejected. Any connector with more than one scratch or an obvious scratch must also be eliminated. In addition, any patch cord showing obvious signs of wear on the ferrule, cladding or core must be rejected
• When using isopropyl alcohol to clean an optical device, do not proceed immediately to dry the surface with compressed air (except when you are cleaning very sensitive optical devices). This is because the dust and dirt are in solution and will leave behind a filmy deposit once the alcohol has evaporated. Therefore, you should first remove alcohol and dust with a soft tissue, and then use compressed air to blow away any remaining particles.
8.5 Fiber identification/polarity • A Visual Fault Locator can be used (along with an OLTS power meter and source) to trace the fibers
from end to end to ensure that the routing and polarization is correct.
• A Visual Fault Locator can also be used to pinpoint breaks, bends, faulty connectors/splices, as well as other causes of signal loss over distances of up to 5 km by sending a bright red laser at 635 nm.
Measurement units: dB or dBm? Power – an absolute value at a specific point in a link – measured in dBm
• Example: Power coming out of a transmitter Loss – a relative value – measured in dB
• Example: Loss in a fiber section Measurement units: dBm or watts? The dBm scale is logarithmic; it is the most common scale for telecommunications applications.
The formula to covert dBm into watts, or vice versa, is: dBm = log10 (mW)*10 mW =10^(dBm/10)
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