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Wiedamark is your one stop solution for LED and Fiber Optic Lighting Systems. The principles of fiber- optic cable installation. By Eric R. Pearson, Pearson Technologies Inc. When examining what makes a fiber- optic network successful from the standpoints of installation and performance, the characteristics can be organized into groups of four. A successful fiber- optic network installation will have four characteristics: 1) low optical power loss, 2) low installation cost, 3) low time of installation, and 4) high reliability. Likewise, there are four goals of fiber- optic cable installation: 1) avoid breakage, 2) avoid reduced power at the receiver, 3) avoid reductions in reliability, and 4) proceed in a safe manner. To meet these four goals, the installer must recognize and respect certain principles. In this article, I organize these principles into four groups: 1) environmental limits, 2) installation limits, 3) National Electrical Code compliance, and 4) end preparation. With this definition of responsibility, the installer might not need to be concerned with environment limitations. However, network designers may not recognize all relevant environmental conditions. In order that the installer recognize and avoid common field problems, we provide this first principle: Respect environmental limits. The installer installs the cable in environmental conditions that are within the limits. Should the cable be exposed to conditions in excess of its limits, the cable can fail to protect the fibers. Such failure can lead to fiber breakage and excessive attenuation rate. While not exhaustive, this list of five environmental conditions represents most of the conditions that have resulted in installation problems: moisture, operating temperature range, bend radii, crush load and use load along with vertical rise distance. Moisture. An installer can install a cable that is not moisture- resistant in an environment that contains moisture. In such a case, the cable can channel moisture into electronics, develop increased attenuation rate and fiber breakage due to frozen water, and/or experience reduced fiber strength and breakage due to attack from the chemicals in groundwater. Operating temperature range. If an installer installs cable in an environment with temperatures outside of the cable’s operating range, the cable can exhibit increased attenuation and/or degradation of cable materials. In the former case, there may be insufficient power at the receiver for proper link operation. In the latter case, the fibers may break. Bend radii. During installation, the installer can bend a cable to less than either the short- term bend radius (2. In these cases, the cable can develop an increased attenuation rate, fiber breakage or reduction in fiber strength. Such a situation can occur in an underground conduit path, in which the conduit sweep, or elbow, has a radius less than either bend radius (2. In this situation the cable path—its environment—is forcing a violation of the bend radius. Crush loads. If an installer installs a cable in an environment that imposes either a long- or short- term crush load in excess of the cable’s limit, the cable can experience increased attenuation rate and fiber breakage. Such a situation can occur when an indoor, tight- tube cable is directly buried. Use load. An installer can install a cable with long- term, or use, load on the cable in excess of the cable’s rating. Such a condition can occur when the cable is installed between widely spaced buildings, widely spaced telephone poles, widely spaced power transmission towers, and up a long vertical rise. Two problems can occur—increased attenuation rate and fiber breakage. An installer should limit the long- term load to a value less than or equal to the cable’s rating. To do so, the installer obtains the use load from the manufacturer, typically from a data sheet or from the manufacturer’s website. The installer also should limit vertical rise distance. The use load and the vertical rise distance are different statements of the same characteristic. The vertical rise distance is the distance to which the cable can be installed vertically without support. The installer limits the cable to a vertical distance less than the vertical rise limit. To do so, the installer obtains the vertical rise limit from a data sheet. The installer can achieve a total vertical rise distance in excess of this limit by supporting the cable at a separation no greater than this limit. Indoor loose- tube cables can allow the fibers to slide out of the cable. Thus the installer installs service loops in vertical loose- tube cable. Installation limits. There are two types of cable installation: 1) pulling the cable into its path, and 2) placing the cable in its location. The installer installs the cable with conditions that are within the limits of the cable. The overall principle is to respect installation limits. During the cable pull, the installer respects five installation limits: 1) no twisting, 2) installation load, 3) installation bend radius, 4) installation temperature range, 5) storage temperature range. No twisting. Avoidance of fiber breakage requires that fiber cables be installed without twisting. In order to avoid twisting, the installer uses a pulling swivel between the pulling rope and the cable. The installer attaches the pull rope and the cable to the pulling eye. In order to comply with the installation load limit, the installer must know the load limit and have a method for limiting the load applied to the cable. The installer will learn the limit from the data sheet for the cable, creating two principles: 1) Know the installation load limit; 2) Limit the installation load. There are three methods by which an installer can limit the short- term, or installation, load applied to a cable. In addition, there are two methods for reducing the applied installation load. The three methods have the advantage of providing concrete evidence that the installation load has not been exceeded. These methods are the use of 1) a pulling eye with a swivel with a shear pin, 2) a pulling device with a slip clutch, and 3) a pulling device with a load gage. The eye has a shear pin, which is rated at a load less than the maximum installation load of the cable. For example, a cable with a rating of 6. If the installer exceeds the rating, the shear pin (not the cable) breaks. The installer can use a pulling eye with a swivel without a shear pin if the installer has some other method of limiting the load applied to the cable. Pullers have two methods to provide such limitation. These methods are a slip clutch and a load gage. An installer can set the slip clutch of a puller to a level less than the installation load of the cable. Should the applied load exceed the level set, the clutch clips, eliminating fiber damage. An installer can set the load gage of a puller to a level less than the installation load of the cable. Should the applied load exceed the level set, the load gage stops the pulling motor without fiber breakage or damage. The load gage has an additional advantage; it allows attachment of a chart recorder, which provides proof that the installer did not load the cable in excess of its rating. Reducing the load. These three methods limit the load but do nothing to reduce the load. There are two methods for reducing the load applied to the cable: lubricant and a “Figure- 8” installation. The installer uses a cable lubricant to reduce friction and load on the cable. While copper- cable lubricants exist, the installer uses a fiber- cable lubricant, as such a lubricant is matched to the jacket of the cable. The second method for reducing the load is pulling the cable by hand in multiple, reduced- length pulls. Breaking a long pull into multiple pulls of reduced length reduces the load on the cable. If the installer installs the cable in multiple pulls, he or she will store the cable at intermediate locations in a “Figure 8” pattern. The advantage of this method is reduced load. The disadvantage is increased labor cost. During a “Figure 8” pull, the installer pulls the cable into the first manhole and out of a subsequent manhole. The subsequent manhole may be the next manhole along the cable path, or the Nth manhole along the cable path. The installer determines this manhole by the load the installer is willing to impose on the cable. As the installer pulls the cable from the manhole, he or she places the cable on the ground in a “Figure 8” pattern. This pattern can be 1. For practical reasons, the pattern is rarely stacked more than 2. When the installer has pulled the cable out of the manhole, the installer and several helpers pick up the “Figure 8” and flip it over so the cable end is on top. The installer puts the cable back into the same manhole along the cable path. At this manhole, the installer repeats the Figure 8 pattern on the ground. The installer can repeat this process as many times as desired, until the cable is installed along the entire path. The installer can use the Figure 8 method for both unidirectional pulls, and mid pulls. In a mid pull, the installer pulls the cable in one direction. The installer places the remaining cable in a Figure 8 pattern on the ground. Finally, the installer pulls the cable from the Figure 8 pattern in the opposite direction. Some professional installers use a fourth method for limiting the load they apply during installation. This method requires pulling a 6. The assumption is that it is essentially impossible to create a 6. This method does not have the advantage of providing concrete evidence that the installers have not exceeded the installation load. All four methods require attachment of a pull rope to the cable. The installer attaches a pull rope to a cable so that the cable strength members support the load and no load is imposed on the fibers. The installer has at least the following five attachment possibilities. Attachment of the pull rope around the outside of the cable jacket. Attachment of the pull rope to a Kellems grip that grips the cable through the jacket. Fiber Optic Cable for network wiring using single mode fiber, multimode fiber & OM3 cable: Cabling Installation & Maintenance. July 3. 1, 2. 01. Mayflex, a distributor of converged IP solutions based in Birmingham, UK, announced tha..
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