Fiber optic cable construction and types.
Multimode vs. single-mode
Multimode cable has a large-diameter core and multiple pathways of light. It is most commonly available in two core sizes: 50-micron and 62.5-micron.
Multimode fiber optic cable can... more/see it nowbe used for most general data and voice fiber applications such as adding segments to an existing network, and in smaller applications such as alarm systems and bringing fiber to the desktop. Both multimode cable cores use either LED or laser light sources.
Multimode 50-micron cable is recommended for premise applications?(backbone, horizontal, and intrabuilding connections). It should be considered for any new construction and for installations because it provides longer link lengths and/or higher speeds, particularly in the 850-nm wavelength, than 62.5-micron cable does.
Multimode cable commonly has an orange or aqua jacket; single-mode has yellow. Other colors are available for various applications and for identification purposes.
Single-mode cable has a small (8–10-micron) glass core and only one pathway of light. With only a single wavelength of light passing through its core, single-mode cable realigns the light toward the center of the core instead of simply bouncing it off the edge of the core as multimode does.
Single-mode cable provides 50 times more distance than multimode cable does. Consequently, single-mode cable is typically used in high-bandwidth applications and in long-haul network connections spread out over extended areas, including cable television and campus backbone applications. Telcos use it for connections between switching offices. Single-mode cable also provides higher bandwidth, so you can use a pair of single-mode fiber strands full-duplex at more than twice the throughput of multimode fiber.
Fiber optic cable consists of a core, cladding, coating, buffer strengthening fibers, and cable jacket.
The core is the physical medium that transports optical data signals from an attached light source to a receiving device. It is a single continuous strand of glass or plastic that’s measured (in microns) by the size of its outer diameter.
All fiber optic cable is sized according to its core’s outer diameter. The two multimode sizes most commonly available are 50 and 62.5 microns. Single-mode cores are generally less than 9 microns.
The cladding is a thin layer that surrounds the fiber core and serves as a boundary that contains the light waves and causes the refraction, enabling data to travel throughout the length of the fiber segment.
The coating is a layer of plastic that surrounds the core and cladding to reinforce the fiber core, help absorb shocks, and provide extra protection against excessive cable bends. These coatings are measured in microns (µ); the coating is 250µ and the buffer is 900µ.
Strengthening fibers help protect the core against crushing forces and excessive tension during installation. This material is generally Kevlar® yarn strands within the cable jacket.
The cable jacket is the outer layer of any cable. Most fiber optic cables have an orange jacket, although some types can have black, yellow, aqua or other color jackets. Various colors can be used to designate different applications within a network.
Simplex vs. duplex patch cables
Multimode and single-mode patch cables can be simplex or duplex.
Simplex has one fiber, while duplex zipcord has two fibers joined with a thin web. Simplex (also known as single strand) and duplex zipcord cables are tight-buffered and jacketed, with Kevlar strength members.
Because simplex fiber optic cable consists of only one fiber link, you should use it for applications that only require one-way data transfer. For instance, an interstate trucking scale that sends the weight of the truck to a monitoring station or an oil line monitor that sends data about oil flow to a central location.
Use duplex multimode or single-mode fiber optic cable for applications that require simultaneous, bidirectional data transfer. Workstations, fiber switches and servers, Ethernet switches, backbone ports, and similar hardware require duplex cable.
PVC (riser) vs. plenum-rated
PVC cable (also called riser-rated cable even though not all PVC cable is riser-rated) features an outer polyvinyl chloride jacket that gives off toxic fumes when it burns. It can be used for horizontal and vertical runs, but only if the building features a contained ventilation system. Plenum can replace PVC, but PVC cannot be used in plenum spaces.
“Riser-rated” means that the jacket is fire-resistant. However, it can still give off noxious fumes when overheated. The cable carries an OFNR rating and is not for use in plenums.
Plenum-jacketed cables have FEP, such as Teflon®, which emits less toxic fumes when it burns. A plenum is a space within the building designed for the movement of environmental air. In most office buildings, the space above the ceiling is used for the HVAC air return. If cable goes through that space, it must be “plenum-rated.”
Distribution-style vs. breakout-style
Distribution-style cables have several tight-buffered fibers bundled under the same jacket with Kevlar or fiberglass rod reinforcement. These cables are small in size and are typically used within a building for short, dry conduit runs, in either riser or plenum applications. The fibers can be directly terminated, but because the fibers are not individually reinforced, these cables need to be terminated inside a patch panel, junction box, fiber enclosure, or cabinet.
Breakout-style cables are made of several simplex cables bundled together, making a strong design that is larger than distribution cables. Breakout cables are suitable for riser and plenum applications.
Loose-tube vs. tight-buffered
Both loose-tube and tight-buffered cables contain some type of strengthening member, such as aramid yarn, stainless steel wire strands, or even gel-filled sleeves. But each is designed for very different environments.
Loose-tube cable is specifically designed for harsh outdoor environments. It protects the fiber core, cladding, and coating by enclosing everything within semi-rigid protective sleeves or tubes. Many loose-tube cables also have a water-resistant gel that surrounds the fibers. This gel helps protect them from moisture, so the cables are great for harsh, high-humidity environments where water or condensation can be a problem. The gel-filled tubes can also expand and contract with temperature changes. Gel-filled loose-tube cable is not the best choice for indoor applications.
Tight-buffered cable, in contrast, is optimized for indoor applications. Because it’s sturdier than loose-tube cable, it’s best suited for moderate-length LAN/WAN connections, or long indoor runs. It’s easier to install as well, because there’s no messy gel to clean up and it doesn’t require a fan-out kit for splicing or termination.
Indoor/outdoor cable uses dry-block technology to seal ruptures against moisture seepage and gel-filled buffer tubes to halt moisture migration. Comprised of a ripcord, core binder, a flame-retardant layer, overcoat, aramid yarn, and an outer jacket, it is designed for aerial, duct, tray, and riser applications.
Interlocking armored cable
This fiber cable is jacketed in aluminum interlocking armor so it can be run just about anywhere in a building. Ideal for harsh environments, it is rugged and rodent resistant. No conduit is needed, so it’s a labor- and money-saving alternative to using innerducts for fiber cable runs.
Outside-plant cable is used in direct burials. It delivers optimum performance in extreme conditions and is terminated within 50 feet of a building entrance. It blocks water and is rodent-resistant.
Interlocking armored cable is lightweight and flexible but also extraordinarily strong. It is ideal for out-of-the-way premise links.
Laser-optimized 10-Gigabit cable
Laser-optimized multimode fiber cable assemblies differ from standard multimode cable assemblies because they have graded refractive index profile fiber optic cable in each assembly. This means that the refractive index of the core glass decreases toward the outer cladding, so the paths of light towards the outer edge of the fiber travel quicker than the other paths. This increase in speed equalizes the travel time for both short and long light paths, ensuring accurate information transmission and receipt over much greater distances, up to 300 meters at 10 Gbps.
Laser-optimized multimode fiber cable is ideal for premise networking applications that include long distances. It is usually aqua colored.
Black Box Explains... Fan-out kits.
Furcating is the process of adding protective tubing to each fiber within a loose-tube cable. It can be a headache-inducing task if you dont have the right tools. If you... more/see it nowbend the cable or buffer tubes past their recommended bend radius, or if you allow them to kink, youll end up with substandard cable connections and splices that can break down over time. And, if the cable is outdoors, it can become exposed to the elements. The end result: a damaged cable without optimal transmission performance.
Thats why a fan-out kit is an absolute must during furcation. These kits enable you to branch out the fragile fiber strands from a buffer tube into protective tubing so you can add a connector. And, you can do it without using splicing hardware, trays, and pigtails.
To separate the fibers, use the kits fan-out assembly, which is color-coded to match the fiber color scheme. The assembly protects the cables bend radius. It also eliminates excessive strain on the fibers by isolating them from tensile forces.
Several types of fan-out kits are available for both indoor and outdoor cross-connects. The outdoor kits include components that compensate for wider temperature fluctuations. Some kits are used to terminate loose-tube cables with 6 or 12 fibers per buffer tube. Others enable you to furcate and terminate more than 200 loose-tube cable fibers, sealing the cable sheath and providing a moisture barrier at the point of termination. These kits require no additional hardware.
Although its recommended that you terminate loose-tube cable at a patch panel, that might not always be possible. For this, there are spider type fan-out kits, which affix a stronger tubing to the bare fiber. The tubing is typically multilayered, consisting of a FEP inner tube that holds the individual fiber, an aramid yarn strength member, and an outer protective PVC jacket. Once you strip back the cable jacket, you thread the fibers into the fan-out inserts. collapse
Black Box Explains... Buffers
A buffer (also called a spooler or a cache) is a temporary storage device used to share printers and compensate for a difference in speed and data flow between two... more/see it nowdevices. Buffers use RAM (Random-Access Memory) to take in data and hold it until the receiving device handles it.
A buffer serving a computer can be installed either internally or externally. Internal computer buffers are common in the forms of keyboard inputs, data caches, and video memory. An external buffer is usually used for printing.
An external buffer downloads jobs to the printer, freeing the computer so you can get back to work sooner.
A print buffers ports can be serial, parallel, or serial and parallel. Because a buffers ports operate independently of each other, a buffer also can be made to perform serial-to-parallel or parallel-to-serial conversion or to change the word structure and/or serial data rate (baud rate) of the data.
While most buffers are FIFO (First In, First Out), some advanced units can function as random-access buffers. For most serial buffers, hardware flow control is required, but some also support software (X-ON/X-OFF) control. Most buffers support printing of multiple copies of a document, provided the buffer has enough memory to store the entire print job. collapse
Black Box Explains...Speaker sound quality.
A human with keen hearing can hear sounds within a range of about 20 Hz to 20 KHz. But most human speech is centered in the 1000 Hz range, so... more/see it nowmost old-fashioned analog telephone networks provided audio bandwidth only in this range. This range transmits most voice information but can fail to register voice subtleties and inflections.
Because these older analog phone systems had such a narrow bandwidth, headset manufacturers built their products to operate only in those particular frequencies.
When digital networks and fiber optic connections came into use, however, they provided a much wider bandwidth for voice transmission. This led to a corresponding increase in headset sound quality.
Today, quality headsets take advantage of increased network bandwidth and typically can reproduce sounds in the 300 Hz to 3500 Hz range. This makes voices far easier to understand and enables you to pick up all the nuances and inflections of your caller’s voice. collapse
Black Box Explains...Category 6.
Category 6 (CAT6)–Class E has a specified frequency of 250 MHz, significantly improved bandwidth capacity over CAT5e, and easily handles Gigabit Ethernet transmissions. In recent years, it has been the... more/see it nowcable of choice for new structured cabling systems. CAT6 supports 1000BASE-T and, depending on the installation, 10GBASE-T (10-GbE).
10-GbE over CAT6 introduces the problem of Alien Crosstalk (ANEXT), the unwanted coupling of signals between adjacent pairs and cables. Because ANEXT in CAT6 10-GbE networks is so dependent on installation practices, TSB-155 qualifies 10-GbE over CAT6 up to 55 meters and requires it to be 100% tested. To mitigate ANEXT in CAT6, it is recommended that you unbundle the cables and increase the separation between the cables.
You can always contact Black Box Tech Support to answer your cabling questions. Our techs can recommend cable testers and steer you in the right direction when you’re installing new cabling. And the advice is FREE! collapse
Black Box Explains...vDSL.
VDSL (Very High Bit-Rate Digital Subscriber Line or Very High-Speed Digital Subscriber Line) is a “last-mile” broadband solution for both businesses and homes, providing economical, high-speed connections to fiber optic... more/see it nowbackbones.
VDSL enables the simultaneous transmission of voice, data, and video on existing voice-grade copper wires. Depending on the intended applications, you can set VDSL to run symmetrically or asymmetrically. VDSL’s high bandwidth allows for applications such as high-definition television, video-on-demand (VOD), high-quality videoconferencing, medical imaging, fast Internet access, and regular voice telephone services—all over a single voice-grade twisted pair. The actual VDSL distances you achieve vary based on line rate, gauge and type of wire, and noise/crosstalk environment.
Black Box Explains...What to consider when choosing a rack.
There are several things you should consider when choosing a rack.
What kind of equipment will you be putting in it? If you need frequent access to all sides of... more/see it nowthe equipment, an open rack is more convenient than a cabinet. If your equipment needs ventilation, a rack poses no air circulation limitations. And don’t neglect aesthetics. Will customers or clients see your installation? A rack with cable management looks much neater.
Finally, consider security. Because a rack is open, you need to take steps to secure your equipment. Set up your rack in a locked room so prying fingers can’t access your network equipment.
Racks come in various sizes and installation styles. Some are freestanding; some are designed to be wallmounted. Some can be a combination of both styles, sitting on the floor but attaching to the wall for more stability.
Understanding rack measurements.
The main component of a rack is a set of vertical rails with mounting holes to which you attach your equipment or shelves.
The first measurement you need to know is the width between the two rails. It’s commonly given in inches, measured from one mounting hole to the corresponding hole on the opposing rail. The most common rail width is 19"; 23" rails and racks are also available. Most rackmount equipment is designed to fit 19" rails but can be adapted for wider racks.
The next important specification is the number of rack units, which is abbreviated as “U.” This is a measurement of the vertical space available on the rails. Cabinets and racks and rackmount equipment are all measured in rack units. One rack unit (1U) is equal to 1.75" of usable vertical space. So, for example, a device that’s 2U high takes up 3.5" of rack space. A rack that’s 20U high has 35" of usable space.
Because the widths are standard, the amount of vertical space is what determines how much equipment you can actually install. Remember this measurement of usable vertical space is smaller than the external height of the rack.
Getting power to your equipment.
Unless you want to have a tangle of extension cords, you’ll need to get one or more power strips for your rack. Consider which kind would be best for your installation. Rackmount power strips come in versions that mount either vertically or horizontally. Some have outlets that are spaced widely to accommodate transformer blocks—a useful feature if most of your equipment uses bulky power transformers.
Surge protection is another important issue. Some power strips have built-in surge protection; some don’t. With the money you have invested in rackmount equipment, you’ll certainly want to make sure it’s protected.
Any mission-critical equipment should also be connected to an uninterruptible power supply (UPS). A UPS prevents your equipment from crashing during a brief blackout or brownout and allows enough time to shut everything down properly in the event of an extended power outage. Choose a rackmount UPS for the most critical equipment or plug the whole rack into a standalone UPS.
Your equipment may look very tidy when it’s all mounted. But unless you’re very careful with your cables, you can create a tangle you’ll never be able to unravel.
Plotting your connections in advance helps you to decide the most efficient way to organize the cables. Knowing where the connections are tells you whether it’s better to run cables horizontally or vertically. Most network problems are in the cabling, so if you let your cables get away from you now, you’re sure to pay for it down the road.
There are many cable management accessories that can simplify your racks. collapse
Black Box Explains... Bridges
If you work with legacy networks, you have doubtlessly encountered bridges. Bridges perform the same function as today’s switches in that they connect multiple network segments to create one homogenous... more/see it nownetwork, while keeping each segment isolated from the others.
Bridges operate on MAC-layer addresses and are protocol independent, so they transfer data between workstations without understanding the protocol. Since they don’t have to understand the protocol, they require little or no configuration.
Once you connect the bridge to the network, it automatically learns the addresses of all connected nodes and then creates an internal address table of this information.
When the bridge sees a packet, it checks the packet’s destination address against its internal list. If the address indicates the packet needs to be forwarded, the bridge passes the packet to the appropriate segment. If a bridge doesn’t know where a packet belongs—for example, when a station is first powered on—it passes on the packet.
Bridges can also distinguish between local data and remote data, so data traveling from one workstation to another in the same network doesn’t have to cross the bridge.
Although they are no longer in general use, Black Box stocks bridges for use as replacement parts in legacy networks. Replacing bridges with bridges rather than switches is often preferable because bridges are generally available with the BNC and AUI interfaces often found in older networks. Also, some bridges are able to link to other protocols such as RS-530 and X.21, enabling you to use these media to establish Ethernet network connections.
Black Box Explains...MIMO wireless.
Multiple-Input/Multiple-Output (MIMO) is a part of the new IEEE 802.11n wireless standard. It’s a technique that uses multiple signals to increase the speed, reliability, and coverage of wireless networks. It... more/see it nowtransmits multiple datastreams simultaneously, increasing wireless capacity to up to 100 or even 250 Mbps.
This wireless transmission method takes advantage of a radio transmission characteristic called multipath, which means that radio waves bouncing off surfaces such as walls and ceilings will arrive at the antenna at fractionally different times. This characteristic has long been considered to be a nuisance that impairs wireless transmission, but MIMO technology actually exploits it to enhance wireless performance.
MIMO sends a high-speed data stream across multiple antennas by breaking it into several lower-speed streams and sending them simultaneously. Each signal travels multiple routes for redundancy.
To pick up these multipath signals, MIMO uses multiple antennas and compares signals many times a second to select the best one. A MIMO receiver makes sense of these signals by using a mathematical algorithm to reconstruct the signals. Because it has multiple signals to choose from, MIMO achieves higher speeds at greater ranges than conventional wireless hardware does.
Black Box Explains...Breakout-style cables.
With breakout- or fanout-style cables, the fibers are packaged individually. A breakout cable is basically several simplex cables bundled together in one jacket. Breakout cables are suitable for riser and... more/see it nowplenum applications, and conduit runs.
This differs from distribution-style cables where several tight-buffered fibers are bundled under the same jacket.
This design of the breakout cable adds strength to the cable, although that makes it larger and more expensive than distribution-style cables.
Because each fiber is individually reinforced, you can divide the cable into individual fiber lines. This enables quick connector termination, and eliminates the need for patch panels.
Breakout cable can also be more economical because it requires much less labor to terminate.
You may want to choose a cable that has more fibers than you actually need in case of breakage during termination or for future expansion. collapse