Basic Cable

You may already be familiar with cables used for electrical wiring. These cables typically consist of two or more insulated wires bundled together and surrounded by a protective outer covering called the jacket or sheath. In addition to holding the wires in place, the jacket or sheath protects the wires from the environment and damage that may occur during handling or installation.

Some of the largest cables, used for telephone transmissions, can be several inches in diameter and contain hundreds of wires, as shown in Figure 7.1. These cables are very heavy, difficult to bend, and expensive.

Fiber-optic cables like the one shown in Figure 7.2 do not need to be as large as the cable shown in Figure 7.1 because the bandwidth of an optical fiber over a long distance is many times greater than the bandwidth of a wire. Greater bandwidth means fewer optical fibers are required to carry the same information the larger cable is carrying. This results in a small, low-cost fiber-optic cable that is much easier to handle and terminate than the cable shown in Figure 7.1. Chapter 13, “Fiber-Optic System Advantages,” compares the performance of fiber-optic and copper cables.

Optical fibers are used in many different configurations and environments; manufacturers have created a wide variety of cable types to meet the needs of almost any application. The type of signal being carried and the number of optical fibers required are just two of the many considerations when selecting the right cable for an application. Other factors include the following:

• Tensile strength
• Temperature range
• Bend radius
• Flammability
• Buffer type
• Structure type
• Jacket type
• Weight
• Armor
• Crush resistance

The exact combination of these factors varies, depending on the application and operational environment. A cable installed inside an office building, for example, will be subject to less extreme temperatures than one installed outdoors or in an aircraft. Cabling installed in a manufacturing facility may be exposed to abrasive dusts, corrosive chemicals, or hotwork, such as welding, requiring special protection. Some cables may be buried underground, where they are exposed to burrowing or chewing animals, whereas others may be suspended between poles, subject to their own weight plus the weight of animals and birds who think the cables were put there for them.

Cable Components

Whether a cable contains a single optical fiber, several optical fibers, or hundreds of optical fibers, it has a basic structure in common with other cables. As shown in Figure 7.3, a typical fiber-optic cable consists of the optical fiber (made up of the core, cladding, and coating), a buffer, a strength member, and an outer protective jacket or sheath. Let's look at these components individually.

Loose Buffer

Loose buffer is also referred to as loose tube buffer or loose buffer tube. A loose buffer consists of a buffer layer or tube that has an inner diameter much larger than the diameter of the coated optical fiber, as shown in Figure 7.4.

The loose buffer provides room for additional optical fiber when the cable is manufactured. This extra room also allows the optical fiber to move independently of the buffer and the rest of the cable components. This is an important factor when the cable is subjected to temperature extremes. A variety of materials are used to make up a fiber-optic cable. These materials may not expand or contract the same way as the optical fiber during temperature changes. The additional fiber in the loose buffer will allow the cable to expand (increase in length) or contract (decrease in length) without placing tensile forces on the optical fiber.

Loose-buffered cable may be single-fiber or multifiber (not to be confused with single-mode and multimode fiber), meaning that it may have one or many optical fibers running through each buffer tube. In addition, a cable may contain a number of loose buffers grouped together, as shown in Figure 7.5. In such cables, loose-buffered tubes are grouped around a central core that provides added tensile strength and a resistance to bending.

Loose-buffered cables are designed for indoor and outdoor applications. For outdoor applications, the buffer tubes may be filled with a gel. The gel displaces or blocks water and prevents it from penetrating or getting into the cable. A gel-filled loose-buffered cable is typically referred to as a loose tube, gel-filled (LTGF) cable.

Fully waterblocked gel-free loose-tube cables are an alternative to gel-filled cables. A gel-free cable replaces the gel with a water-swellable tape. When the water-swellable tape makes contact with water, it quickly turns into a gel and swells. The swelling tape fills up the free space within the cable and blocks the water protecting the cable against damage from water ingress.

Loose-buffered cables are ideal for direct burial and aerial installations. They are also very popular for indoor/outdoor applications.

Tight Buffer

Tight-buffered cable is typically used in more controlled environments where the cable is not subjected to extreme temperatures or water. In short, tight-buffered cable is generally used for indoor applications rather than outdoor applications.

As shown in Figure 7.6, tight-buffered cable begins with a 250μm coated optical fiber. The buffer is typically 900μm in diameter and is applied directly to the outer coating layer of the optical fiber. In this way, it resembles a conventional insulated copper wire. The buffer may have additional strength members running around it for greater resistance to stretching.

One of the benefits of tight-buffered cable is that the buffered optical fiber can be run outside of the larger cable assembly for short distances, as shown in Figure 7.7. This makes it easier to attach connectors. The standard diameter of the buffer allows many different types of connectors to be applied.

Tight-buffered cables have some advantages over loose-buffered cables. Tight-buffered cables are generally smaller in diameter than comparable loose-buffered cables. The minimum bend radius of a tight-buffered cable is typically smaller than a comparable loose-buffered cable. These two advantages make tight-buffered cable the choice for indoor installations where the cable is routed through walls and other areas requiring tight bends.

Strength Members

You've already learned a bit about how strength members help increase a cable's tensile strength. The primary importance of these members is to ensure that no tensile stress is ever placed on the optical fiber. The installation of a fiber-optic cable may require a great deal of pulling, which places considerable tensile stress on the strength members. The strength members need to be able to support the installation tensile stresses and the operational tensile stresses.

Strength members may run through the center of a fiber-optic cable, or they may surround the buffers just underneath the jacket. Combinations of strength members may also be used depending on the application and the stress the cable is designed to endure. Some of the most common types of strength members are made of

• Aramid yarns, usually Kevlar™
• Fiberglass rods
• Steel

Aramid yarns, as shown in Figure 7.8, are useful when the entire cable must be flexible. These fine, yellowish or gold yarns are made of the same material used in high-performance sails, bulletproof vests, and fire protection gear. They have the advantages of being light, flexible, and quite strong. Aramid yarns may be used in cable subgroups if they will be bundled into larger cables.

Larger cables and most loose-buffered cables typically have a central member of either fiberglass or steel added, as shown in Figure 7.9. This central member provides tensile strength and a resistance to bending. This resistance to bending prevents the cable from being over-bent and kinking the loose-buffered tubes.

Although the tensile strength of steel is greater than the tensile strength of fiberglass, many applications require a dielectric, or nonconductive cable. Fiberglass is nonconductive whereas steel is not. Steel running through a cable outdoors makes an excellent lightning rod.

Jacket

The jacket is the cable's outer protective layer. It protects the internal components from the outside world. The jacket may be subject to many factors such as sunlight, ice, animals, equipment accidents, and ham-handed installers. The jacket must also provide protection from abrasion, oil, corrosives, solvents, and other chemicals that could destroy the components in the cable.

Jacket materials vary depending on the application. Typical jacket materials include

1. Polyvinyl chloride (PVC) PVC is used primarily for indoor cable runs. It is fire retardant and flexible, and it's available in different grades to meet different conditions. PVC is water resistant; however, PVC does not stand up well to solvents. In addition, it loses much of its flexibility at low temperatures.
2. Polyethylene This material is typically used outdoors. It offers excellent weather and sun resistance in addition to excellent water resistance and flexibility in low temperatures. Specially formulated polyethylene offers low-smoke, zero-halogen performance.
3. Polyvinyl difluoride (PVDF) This material is chosen for its low-smoke and fire-retardant properties for use in cables that run through airways or plenums in a building. PVDF cables are not as flexible as other types, so their fire safety properties are their primary draw.
4. Polytetrafluoroethylene (PTFE) This material is primarily used in aerospace fiber-optic cables. It has an extremely low coefficient of friction and can be used in environments where temperatures reach as high as 260° C.

Some cables contain multiple jackets and strength members, as shown in Figure 7.10. In such cables, the outermost jacket may be referred to as the sheath; the inner protective layers are still called jackets.

The ripcord is a piece of strong thread running through the cable just under the jacket or sheath as shown in Figure 7.11. When the ripcord is pulled, it splits the jacket easily to allow the fibers to be separated for connectorization or splicing. The ripcord reduces the risk incurred when cutters or knives are used to split the jacket. The ripcord will not penetrate the jackets of the individual simplex cables as a cutter or knife may when the blade depth is not accurately controlled.

Cordage

The simplest types of cables are called cordage and are used in connections to equipment and patch panels. They are typically made into patch cords or jumpers. The major difference between cordage and cables is that cordage has only one optical fiber/buffer combination in a jacket, whereas cables may have multiple optical fibers inside a jacket or sheath.

The two common types of cordage are simplex and duplex.

Simplex Cordage

Simplex cordage, shown in Figure 7.12, consists of a single optical fiber with a tight buffer, an aramid yarn strength member, and a jacket.

Simplex cordage gets its name from the fact that, because it is a single fiber, it is typically used for one-way, or simplex, transmission, although bidirectional communications are possible using a single fiber.

Duplex Cordage

Duplex cordage, also known as zipcord, is similar in appearance to household electrical cords, as you can see in Figure 7.13. Duplex cordage is a convenient way to combine two simplex cords to achieve duplex, or two-way, transmissions without individual cords getting tangled or switched around accidentally.

Distribution Cable

When it is necessary to run a large number of optical fibers through a building, distribution cable is often used. Distribution cable consists of multiple tight-buffered fibers bundled in a jacket with a strength member. These cables, like the one shown in Figure 7.14, may also feature a dielectric central member to increase tensile strength, resist bending, and prevent the cable from being kinked during installation.

Distribution cables are ideal for inter-building routing. Depending on the jacket type they may be routed through plenum areas or riser shafts to telecommunications rooms, wiring closets, and workstations. The tight-buffered optical fibers are not meant to be handled much beyond the initial installation, because they do not have a strength member and jacket.

Distribution cables may carry up to 144 individual tight-buffered optical fibers, many of which may not be used immediately but allow for future expansion.

Breakout Cable

Breakout cables are used to carry optical fibers that will have direct termination to the equipment, rather than being connected to a patch panel.

Breakout cables consist of two or more simplex cables bundled with a strength member and/or central member covered with an outer sheath, as shown in Figure 7.15. These cables are ideal for routing in exposed trays or any application requiring an extra rugged cable that can be directly connected to the equipment.

Armored Cable

Armored cable can be used for indoor applications and outdoor applications. An armored cable typically has two jackets. The inner jacket is surrounded by the armor and the outer jacket or sheath surrounds the armor.

An armored cable used for outdoor applications, shown in Figure 7.16, is typically a loose tube construction designed for direct burial applications. The armor is generally a corrugated aluminum tape surrounded by an outer polyethylene jacket. This combination of outer jacket and armor protects the optical fibers from gnawing animals and the damage that can occur during direct burial installations.

Armored cable used for indoor applications may feature tight-buffered or loose-buffered optical fibers, strength member(s), and an inner jacket. The inner jacket is commonly surrounded by a spirally wrapped interlocking metal tape armor. This type of armor, shown in Figure 7.17, is rugged and provides crush resistance. These cables are used in heavy traffic areas and installations that require extra protection, including protection from rodents.

Messenger Cable

When a fiber-optic cable must be suspended between two poles or other structures, the strength members alone are typically not enough to support the weight of the cable and any additional forces that may be placed on the cable. For aerial installations a messenger wire is required. The messenger wire can be external to the fiber-optic cable or integrated into the cable.

When the messenger wire is integrated into the fiber-optic cable, the cable is typically referred to as a messenger cable. These cables typically feature a 0.25″ stranded steel messenger wire. The messenger wire, sometimes referred to simply as the messenger, is integrated into the outer jack of the cable, as shown in Figure 7.18.

Also called figure 8 cable for the appearance of its cross section, messenger cable greatly speeds up an aerial installation because it eliminates the need to lash the fiber-optic cable to a pre-run messenger wire.

If a messenger wire is not incorporated into the cable assembly used, the cable will have to be lashed to messenger wire. A messenger wire is a steel or aluminum wire that supports the fiber-optic cable in an aerial installation. Either way, cables in aerial installations must be able to withstand loading from high winds, ice, birds and climbing animals, and even windblown debris such as branches.

Ribbon Cable

Ribbon cable is a convenient solution for space and weight problems. The cable contains fiber ribbons, which are actually coated optical fibers placed side by side, encapsulated in Mylar tape (see Figure 7.19), similar to a miniature version of wire ribbons used in computer wiring. A single ribbon may contain 4, 8, or 12 optical fibers. These ribbons can be stacked up to 22 high.

Because the ribbon contains only coated optical fibers, this type of cable takes up much less space than individually buffered optical fibers. As a result, ribbon cables are denser than any other cable design. They are ideal for applications where limited space is available, such as in an existing conduit that has very little room left for an additional cable.

As shown in Figure 7.20, ribbon cables come in two basic arrangements. In the loose tube ribbon cable, fiber ribbons are stacked on top of one another inside a loose-buffered tube. This type of arrangement can hold several hundred fibers in close quarters. The buffer, strength members, and cable jacket carry any strain while the fiber ribbons move freely inside the buffer tube.

The jacketed ribbon cable looks like a regular tight-buffered cable, but it is elongated to contain a fiber ribbon. This type of cable typically features a small amount of strength member and a ripcord to tear through the jacket.

While ribbon fiber provides definite size and weight savings, it does require special equipment and training to take advantage of those benefits. Connectors, strippers, cleavers, and fusion splicers must all be tailored to the ribbon fiber. For these reasons, ribbon fiber may not be the best solution in all situations.

Submarine Cable

Submarine cable is specially designed for carrying optical fiber underwater. Not all submarine cable is the same, however. Depending on the distance it will span and the type of service it will provide, submarine cable can take many different forms.

Submarine cable may be laid in trenches under the bottom of waterways where shipping or fishing activities threaten to snag or damage the cable, or it may be laid directly on the bottom of less-traveled waterways, or on the deep ocean floor where such activities do not penetrate. Figure 7.21 shows a multi-optical-fiber submarine cable with armor and metal strength members.

Aerospace Cable

Aerospace cables are designed to be installed in aircraft and spacecraft. These cables are designed to operate in extreme temperature environments. In addition, they must protect the optical fiber from the shock and vibration associated with aircraft and spacecraft. While the optical fiber used in many aerospace cables may be the same optical fiber used in other cable types, the coating, buffer, and jacket are typically different.

Applications

In Chapter 1, “History of Fiber Optics and Broadband Access,” you learned that since the turn of the century, fiber optics has helped to increase broadband download speeds by a factor of 5000. Just as the telecommunications industry is incorporating more and more optical fiber, so are the aerospace and avionics industries. The Boeing 787 Dreamliner has 110 fiber-optic links and over 1.7km of fiber-optic cable. The aerospace cable assembly shown in Figure 7.22 is similar to one that could be found on the Dreamliner.

Aerospace tight or loose structure cables can have a very wide temperature range based on the location where they are installed. Cables designed to be used inside avionics boxes or cabinets typically have a temperature range of –40° C to +85° C. Cables designed to be used between cabinets typically have a temperature range of –65° C to +125° C, whereas those cables used by the engines have a temperature range of –65° C to +260° C.

Cable Components

Figure 7.23 shows the components of a typical aerospace fiber-optic cable. This cable features a primary and secondary buffer. The primary buffer is the coating applied directly over the cladding of the optical fiber. Aerospace cables may use a variety of coatings depending on the temperature range required. A typical acrylate coating has a maximum operating temperature of 100° C whereas some high-temperature acrylates may perform at temperatures up to 125° C. Silicone, carbon, and polyimide coatings have greater temperature ranges than acrylate. Detailed information on optical fiber coatings can be found in Chapter 4.

The secondary buffer shown in Figure 7.24 is polytetrafluoroethylene (PTFE). The bondable layer surrounding the secondary layer is a polyimide tape, and the barrier layer is unsealed PTFE. The strength member is braided Kevlar, and the jacket shown in Figure 7.25 is extruded FEP (fluorinated ethylene propylene). This jacket material has a service temperature range of –100° C to +200° C as well as excellent chemical and UV resistance properties; it is also flame retardant.

Hybrid Cable

Hybrid cable, as applied to fiber optics, combines multimode and single-mode optical fibers in one cable. Hybrid cable should not be confused with composite cable, although the terms have been used interchangeably in the past.

Composite Cable

Composite cable, as defined by the National Electrical Code (NEC), is designed to carry both optical fiber and current-carrying electrical conductors. These cables may also contain non-current-carrying conductive members such as metallic strength members, metallic vapor barriers, metallic armor, or a metallic sheath.

The composite cable shown in Figure 7.26 consists of optical fibers along with twisted-pair wiring typical of telephone wiring. This arrangement is convenient for networks that carry fiber-optic data and conventional telephone wiring to the same user. Composite cable also provides installers with a way to communicate during fiber installation and provides electrical power to remote equipment, such as repeaters, along the fiber's route.

Fanout Kit

The fanout kit, shown in Figure 7.27, converts loose-buffered fibers into tight-buffered fibers ready for connectors. A typical fanout kit contains an enclosure sometimes called a furcation unit. The furcation unit attaches to the loose-buffer tube. Hollow tight-buffer tubes 900μm in diameter are applied over the optical fibers and passed into the furcation unit, which is then closed, locking the tight buffers in place on the fibers. After the fibers have the buffers applied, connectors can be attached for use in a patch panel or other protected enclosure.

Breakout Kit

The breakout kit, shown in Figure 7.28, is similar to the fanout kit in that it spreads the fibers from the loose-buffer tube through a furcation kit and provides 900μm tight buffers to be applied over the optical fiber. The breakout kit, however, is designed to allow the optical fiber to be connected directly to equipment with standard connectors.

In addition to buffer material, the breakout kit provides a 3mm diameter jacket with an aramid strength member that slips over the optical fiber. Heat-shrink tubing and epoxy is used to join the individual jackets to the cable.

Breakout kits and fanout kits are available to match the number of fibers in the cable being used, and some companies offer kits that can be used with ribbon cable. Different length buffer tubes are available for fanout kits.

Note that different vendors may use a variety of terms or trade names to refer to breakout kits and fanout kits.

NEC Fiber-Optic Cable Types

The NEC recognizes three types of fiber-optic cables in Article 770:

1. Nonconductive Cables containing no electrically conductive materials.
2. Conductive Cables containing non-current-carrying conductive members, including strength members, armor, or sheath.
3. Composite Cables containing optical fiber and current-carrying electrical conductors. These cables may also contain non-current-carrying conductive members such as metallic strength members, metallic vapor barriers, metallic armor, or a metallic sheath.

General-Purpose Cable

General-purpose cables, whether conductive or nonconductive, are resistant to the spread of fire. However, these cables are not suitable for plenum or riser applications.

Table 7.1 shows the cable types along with the markings each cable will contain. Markings should be clearly visible on the cable, as shown in Figure 7.29, and no cable should be used indoors unless it listed and contains the NEC cable type marking on it.

Marking	Type	Location	Permitted substitutions
OFNP	Nonconductive optical fiber plenum cable	Ducts, plenums, other air spaces	None
OFCP	Conductive optical fiber plenum cable	Ducts, plenums, other air spaces	OFNP
OFNR	Nonconductive optical fiber riser cable	Risers, vertical runs	OFNP
OFCR	Conductive optical fiber riser cable	Risers, vertical runs	OFNP, OFCP, OFNR
OFNG	Nonconductive optical fiber general-purpose cable	General-purpose use except for risers and plenums	OFNP, OFNR
OFCG	Conductive optical fiber general-purpose cable	General-purpose use except for risers and plenums	OFNP, OFCP, OFNR, OFCR, OFNG, OFN
OFN	Nonconductive optical fiber general-purpose cable	General-purpose use except for risers, plenums	OFNP, OFNR
OFC	Conductive optical fiber general-purpose cable	General-purpose use except for risers, plenums	OFNP, OFCP, OFNR, OFCR, OFNG, OFN

All indoor cables must be resistant to the spread of fire, and those listed as suitable for environmental air spaces such as plenums must also have low smoke-producing characteristics. Note in the substitutions list that nonconductive cables may always be substituted for conductive cables of an equal or lower rating, but conductive cables may never be substituted for nonconductive cables. Figure 7.30 shows the order in which cables may be substituted for one another.

The NEC also describes the raceways and cable trays that can be used with fiber-optic cables and the conditions under which each type of cable may be used. This information is covered in Chapter 12.

External Markings

A cable's external markings typically consist of the manufacturer's information, including the manufacturer's name and phone number, cable part number or catalog number, the date the cable was manufactured, and occasionally the industry standards the optical fiber complies to. Information about the cable itself includes the NEC cable marking, the fiber type (multimode/single-mode or core/cladding size), and sequential cable length markings in meters or feet.

Date, Industry Standards, and Fiber Type

The date the cable was manufactured can be very helpful in determining the performance standards of the optical fiber within the cable. As you learned in Chapter 5, “Optical Fiber Characteristics,” there have been significant changes in the performance of multimode optical fiber since the turn of the century. The cable shown in Figure 7.31 was manufactured at the turn of the century. In addition, the cable markings identify three standards that define the optical and geometrical performance of the optical fiber. These standards are

• Bellcore GR-409-CORE
• ISO/IEC 11801
• TIA/EIA-568-A

The cable shown in Figure 7.31 was manufactured in June 2000. Optical Fiber Cabling Component Standard TIA/EIA-568-B.3 superseded the Commercial Building Telecommunications LAN/WAN Cabling Standard TIA/EIA-568-A in April 2000. This is an example of cable being manufactured with optical fiber that did not comply with the latest published standards. As it has been mentioned before in this book, when a standard changes, old cable is not ripped out and replaced with new. A cable manufacturer with reels of TIA/EIA-568-A optical fiber on the shelf is not going to waste that inventory just because a standard changed.

The cable shown in Figure 7.32 was manufactured in May 2008. There are no standards markings on this cable, so determining the industry standard(s) that define the optical and geometrical performance of the optical fibers in this cable is not as straightforward as with the cable in Figure 7.31. However, there is a clue: the word “laser” is printed on the jacket. This implies that the optical fiber was optimized for a laser light source. The 50μm optical fiber core size is also printed on the jacket. Combining both pieces of data indicates that the optical fiber in the cable is OM3.

OM3 optical fiber cannot be found in TIA/EIA-568-B.3. However, it can be found in ANSI/TIA-568-C.3, which was published June 2008, one month after the cable shown in Figure 7.31 was manufactured. This is an example of a cable that contains an optical fiber that exceeds the transmission performance parameters of a current published standard. As mentioned previously in this book, standards define a minimum level of performance and many manufacturers offer products that exceed the minimum performance levels. Oftentimes the working groups within standards organizations are playing catch-up, creating standards for products that currently exist and may have been in widespread use for several years or more.

Remember, you can always contact the cable manufacturer using the phone number printed on the cable to determine the optical and geometrical performance of the optical fiber.

Color Codes

As with copper wiring, optical fibers running in cables must have some way of being distinguished from one another so that they can be connected properly at each end. TIA-598-C provides color-coding schemes for premises jackets and optical fibers within a fiber-optic cable. Table 7.2 shows the color-coding scheme for individual fibers bundled in a cable.

Table 7.3 shows the color coding used on premises cable jackets to indicate the type of fiber they contain, if that is the only type of fiber they contain.

Cable Numbers

The color-coding schemes for premises jackets and optical fibers within a fiber-optic cable described in TIA-598-C are not always used. For example, the jacket colors of every simplex cable shown in Figure 7.33 are the same. You can identify a specific simplex cable by locating the number that is printed on the jacket. The simplex cable number is printed every 6″ along the entire length of the cable.

With all numbering or coloring schemes, there are advantages and disadvantages. In an area that is not lit well, it can be difficult to correctly identify colors. In addition, how well color differences are perceived can vary from person to person. Numbering eliminates color perception problems.

Sequential Markings

A cable's external markings may include sequential markings, as shown in Figure 7.34. Sequential markings are numbers that appear every 2' or 1m. These markings are useful in determining how much cable is left on a reel, measuring off large runs of cable, or simply determining the length of a piece of cable without pulling out a tape measure.

The numbers themselves indicate cable length, not optical-fiber length. To measure the length of the cable using the sequential markings, first determine the measurement standard that is being used. Next, subtract the number at the low end from the number at the high end. The difference between the two is the length.

Because some measurements dealing with fiber optics use meters rather than feet, you may need to convert any measurements in feet to the metric system. The formula for converting length is

1. 1 foot = 0.3048 meter

Let's practice measuring out a length of cable using sequential markings. To find the length in meters of a cable that has sequential markings of 846 at one end and 2218 at the other end, and the markings are measuring the cable in feet, you first determine the distance between the markings using this formula:

1. 2218 – 846 = 1372 feet

Now, convert feet to meters:

1. 1372 × 0.3048 = 418.2 meters

Remember that the length of the cable is not necessarily the length of the optical fiber inside of it. In loose tube cable, the fiber is actually slightly longer than the cable. This fact becomes important if fault location procedures tell you that there is a fault at a specific distance from the end of the fiber. That distance could be short of the measured distance on the outside of the cable since the fiber wanders inside of the buffer tube.

Determine the Cable Type from the NEC Markings

Article 770 of the NEC states that optical fiber cables installed within buildings shall be listed as being resistant to the spread of fire. These cables are also required to be marked.

You have been asked to install the two cables shown later in a riser space. From the markings on the cables, determine the cable types and determine if each cable can be installed in a riser space.

The cable marked OFNR is a nonconductive riser cable and the cable marked OFNP is a nonconductive plenum cable. Per the NEC cable substitution guide in Figure 7.30, both cables can be installed in a riser space. However, only the cable marked OFNP can be installed in the plenum space.

Identify the Fiber Number from the Color Code

TIA-598-C defines a color code for optical fibers within a cable assembly.

You have been asked to identify the fourth and seventh tight-buffered optical fibers in the 12-fiber cable shown here. There are no numbers on the tight buffers; however, each buffer is colored as defined in TIA-598-C. What are the colors of the fourth and seventh tight-buffered optical fibers?

Table 7.2 lists the optical fiber color codes as defined in TIA-598-C. The color for fiber number 4 is brown and the color for fiber number 7 is red.

Determine the Fiber Number from the Cable Markings

The color-coding schemes for premises jackets and optical fibers within a fiber-optic cable described in TIA-598-C are not always used.

You have been asked to identify simplex cable number nine in the 12-fiber cable shown here. Describe the location of that cable.

Simplex cable number 9 is located in the upper-left corner.

Identify the Optical Fiber Type from the Color Code

Premises cable jacket colors are defined in TIA-598-C.

It is your first day on the job and your supervisor has asked you to get some laser-optimized multimode optical fiber from the back of the van. The van contains several different cables, each with a different jacket color. What is the jacket color of the laser-optimized cable?

Table 7.3 list the premises jacket colors as defined in TIA-598-C. The color for the laser-optimized cable is aqua.

Determine the Optical Fiber Type from the Cable Markings

Premises cable jacket colors are defined in TIA-598-C. However installed cables may not comply with revision C of this standard.

You have been asked to identify the optical fiber type in the cable shown here. The jacket color is slate and this cable was not intended for military applications. What type of optical fiber is used in this cable?

This cable was manufactured in 1999, 6 years before TIA-598-C was published. It does not comply with this standard. However, the optical fiber type is printed on the jacket. The optical fiber in this simplex cable is 62.5/125μm multimode.

Determine the Cable Length Using Sequential Markings

Many markings are found on a cable. Sequential markings typically appear every 2 feet or every 1m.

You have been asked to determine the length of fiber-optic cable coiled up on the floor. The sequential markings for this cable are meters. The marking on one end of the cable is 0235 and the marking on the other end is 0485. How long is this cable?

To find the length of the cable, determine the distance between the markings as shown here:

1. 485m – 235m = 250m