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Black Box Explains…OM3 and OM4.

There are different categories of graded-index multimode fiber optic cable. The ISO/IEC 11801 Ed 2.1:2009 standard specifies categories OM1, OM2, and OM3. The TIA/EIA recognizes OM1, OM2, OM3, and OM4.... more/see it nowThe TIA/EIA ratified OM4 in August 2009 (TIA/EIA 492-AAAD). The IEEE ratified OM4 (802.ba) in June 2010.

OM1 specifies 62.5-micron cable and OM2 specifies 50-micron cable. These are commonly used in premises applications supporting Ethernet rates of 10 Mbps to 1 Gbps. They are also typically used with LED transmitters. OM1 and OM2 cable are not suitable though for today's higher-speed networks.

OM3 and OM4 are both laser-optimized multimode fiber (LOMMF) and were developed to accommodate faster networks such as 10, 40, and 100 Gbps. Both are designed for use with 850-nm VCSELS (vertical-cavity surface-emitting lasers) and have aqua sheaths.

OM3 specifies an 850-nm laser-optimized 50-micron cable with a effective modal bandwidth (EMB) of 2000 MHz/km. It can support 10-Gbps link distances up to 300 meters. OM4 specifies a high-bandwidth 850-nm laser-optimized 50-micron cable an effective modal bandwidth of 4700 MHz/km. It can support 10-Gbps link distances of 550 meters. 100-Gbps distances are 100 meters and 150 meters, respectively. Both rival single-mode fiber in performance while being significantly less expensive to implement.

OM1 and 2 are made with a different process than OM3 and 4. Non-laser-optimized fiber cable is made with a small defect in the core, called an index depression. LED light sources are commonly used with these cables.

OM3 and 4 are manufactured without the center defect. As networks migrated to higher speeds, VCSELS became more commonly used rather than LEDs, which have a maximum modulation rate of 622 Mbps. Because of that, LEDs can’t be turned on and off fast enough to support higher-speed applications. VCSELS provided the speed, but unfortunately when used with older OM1 and 2 cables, required mode-conditioning launch cables. Thus manufacturers changed the production process to eliminate the center defect and enable OM3 and OM4 cables to be used directly with the VCSELS. OM3/OM4 Comparison
850 nm High Performance EMB (MHz/km)

OM3: 2000

OM4: 4700


850-nm Ethernet Distance
1-GbE
OM3: 1000 m

OM4: 1000 m


10-GbE
OM3: 300 m

OM4: 550 m


40-GbE
OM3: 100 m

OM4: 150 m


100-GbE
OM3: 100 m

OM4: 150 m

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Black Box Explains...Multimode vs. single-mode Fiber.

Multimode, 50- and 62.5-micron cable.
Multimode cable has a large-diameter core and multiple pathways of light. It comes in two core sizes: 50-micron and 62.5-micron.

Multimode fiber optic cable can be... more/see it nowused for most general data and voice fiber applications, such as bringing fiber to the desktop, adding segments to an existing network, and in smaller applications such as alarm systems. Both 50- and 62.5-micron cable feature the same cladding diameter of 125 microns, but 50-micron fiber cable features a smaller core (the light-carrying portion of the fiber).

Although both can be used in the same way, 50-micron cable is recommended for premise applications (backbone, horizontal, and intrabuilding connections) and should be considered for any new construction and installations. Both also use either LED or laser light sources. The big difference between the two is that 50-micron cable provides longer link lengths and/or higher speeds, particularly in the 850-nm wavelength.

Single-mode, 8–10-micron cable.
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. Consequently, single-mode cable is typically used 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 for up to twice the throughput of multimode fiber.

Specification comparison:

50-/125-Micron Multimode Fiber

850-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 550 m;

1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 550 m

62.5-/125-Miron Multimode Fiber

850-nm Wavelength:
Bandwidth: 160 MHz/km;
Attenuation: 3.5 dB/km;
Distance: 220 m;

1300-nm Wavelength:
Bandwidth: 500 MHz/km;
Attenuation: 1.5 dB/km;
Distance: 500 m

8–10-Micron Single-Mode Fiber

Premise Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 1.0 dB/km;

Outside Plant Application:
Wavelength: 1310 nm and 1550 nm;
Attenuation: 0.1 dB/km collapse


Black Box Explains...Insertion loss.

Insertion loss is a power loss that results from inserting a component into a previously continuous path or creating a splice in it. It is measured by the amount of... more/see it nowpower received before and after the insertion.

In copper cable, insertion loss measures electrical power lost from the beginning of the run to the end.

In fiber cable, insertion loss (also called optical loss) measures the amount of light lost from beginning to end. Light can be lost many ways: absorption, diffusion, scattering, dispersion, and more. It can also be from poor connections and splices in which the fibers don’t align properly.

Light loss is measured in decibels (dBs), which indicate relative power. A loss of 10 dB means a tenfold reduction in power.

Light strength can be measured with optical power meters, optical loss test sets, and other test sets that send a known light source through the fiber and measure its strength on the other end. collapse


Black Box Explains... Baseband, broadband, and carrierband transmissions.

Depending on the environment and how the electrical signal is sent over the cable, coax can be used for three types of transmissions.

Baseband transmissions use the entire communication channel capacity... more/see it nowto transmit a single data signal. Many LANs employ Thin coax for baseband signaling.

Broadband transmissions use different frequencies to carry several analog signals simultaneously. Each signal can for be a different type of information—data, voice, even video. Broadband transmissions over coax employ either one or two cables. With single-cable coax wiring, frequencies are split into individual channels for each station; some channels are allocated for bidirectional communication. Dual-cable coax wiring uses one cable for sending and one cable for receiving data, each with multiple channels. Broadband transmissions are ideal for long distances. Thick coax is often used for broadband transmissions.

Unlike broadband transmissions, carrierband transmissions can only use one information channel. Carrierband is best suited for the horizontal subsystems (subnetworks) in industrial settings. Many LANs use Thin coax for carrierband signaling. collapse


Black Box Explains... Guidelines for choosing fiber optic cable.


Fiber optic cable is becoming one of the fastest-growing transmission mediums for both new cabling installations and upgrades, including backbone, horizontal, and even desktop applications. It’s favored for applications that... more/see it nowneed high bandwidth, long distances, and complete immunity to electrical interference.

It’s ideal for high-data-rate systems such as Gigabit Ethernet, FDDI, multimedia, ATM, SONET, Fibre Channel, or any other network that requires the transfer of large, bandwidth-consuming data files, particularly over long distances.

Fiber offers the following advantages:

Greater bandwidth—Because fiber provides far greater bandwidth than copper and has proven performance at rates up to 10 Gbps, it gives network designers future-proofing capabilities as network speeds and requirements increase.

Also, fiber optic cable can carry more information with greater fidelity than copper wire. That’s why the telephone networks use fiber and many CATV companies are converting to fiber.

Low attenuation and greater distance—Because the fiber optic signal is made of light, very little signal loss occurs during transmission, and data can move at higher speeds and greater distances. Fiber does not have the 100-meter (328-ft.) distance limitation of unshielded twisted-pair copper (without a booster). Fiber distances can range from 300 meters (984.2 ft.) to 40 kilometers (24.8 mi.), depending on the style of cable, wavelength, and network. (Fiber distances are typically measured in metric units.) Because fiber signals need less boosting than copper ones do, the cable performs better.

Security—Your data is safe with fiber cable. It doesn’t radiate signals and is extremely difficult to tap. If the cable is tapped, it’s very easy to monitor because the cable leaks light, causing the entire system to fail. If an attempt is made to break the physical security of your fiber system, you’ll know it.

Fiber networks also enable you to put all your electronics and hardware in one central location, instead of having wiring closets with equipment throughout the building.

Immunity and reliability—Fiber provides extremely reliable data transmission. It’s completely immune to many environmental factors that affect copper cable. The core is made of glass, which is an insulator, so no electric current can flow through. It’s immune to electromagnetic interference and radio-frequency interference (EMI/RFI), crosstalk, impedance problems, and more. You can run fiber cable next to industrial equipment without worry. Fiber is also less susceptible to temperature fluctuations than copper and can be submerged in water.

Design—Fiber is lightweight, thin, and more durable than copper cable. Plus, fiber optic cable has pulling specifications that are up to 10 times greater than copper cable’s. Its small size makes it easier to handle, and it takes up much less space in cabling ducts. Although fiber is still more difficult to terminate than copper, advancements in connectors are making termination easier. In addition, fiber is actually easier to test than copper cable.

Migration—The proliferation and lower costs of media converters are making copper to fiber migration much easier. The converters provide seamless links and enable the use of existing hardware. Fiber can be incorporated into networks in planned upgrades.

Standards—TIA/EIA standards are bringing fiber closer to the desktop. TIA/EIA-785, ratified in 2001, provides a cost-effective migration path from 10-Mbps Ethernet to 100-Mbps Fast Ethernet over fiber (100BASE-SX). An addendum to the standard eliminates limitations in transceiver designs. In addition, in June 2002, the IEEE approved a 10-Gigabit Ethernet (10-GbE) standard.

Costs—The cost for fiber cable, components, and hardware is steadily decreasing. Installation costs for fiber are higher than copper because of the skill needed for terminations. Overall, fiber is more expensive than copper in the short run, but it may actually be less expensive in the long run. Fiber typically costs less to maintain, has much less downtime, and requires less networking hardware. And fiber eliminates the need to recable for higher network performance.

Types of fiber cable and standards.

Multimode, 50- and 62.5-micron cable—Multimode cable has a large-diameter core and multiple pathways of light. It comes in two core sizes: 50-micron and 62.5-micron.

Multimode fiber optic cable can be used for most general data and voice fiber applications, such as bringing fiber to the desktop, adding segments to an existing network, and in smaller applications such as alarm systems. Both 50- and 62.5-micron cable feature the same cladding diameter of 125 microns, but 50-micron fiber cable features a smaller core (the light-carrying portion of the fiber).

Although both can be used in the same way, 50-micron cable is recommended for premise applications (backbone, horizontal, and intrabuilding connections) and should be considered for any new construction and installations. Both also use either LED or laser light sources. The big difference between the two is that 50-micron cable provides longer link lengths and/or higher speeds, particularly in the 850-nm wavelength.

Single-mode, 8–10-micron cable—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. Consequently, single-mode cable is typically used 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 for up to twice the throughput of multimode fiber. collapse


DisplayPort cable.

DisplayPort is a digital video interface that was designed by the Video Electronics Standards Association (VESA) in 2006 and has been produced since 2008. It’s incredibly versatile, with the capability... more/see it nowto deliver digital video, audio, bidirectional communications, and accessory power over a single connector.

DisplayPort cables are targeted at the computer world rather than at consumer electronics. DisplayPort is used to connect digital audio/video computers, displays, monitors, projectors, HDTVs, splitters, extenders, and other devices that support resolutions up to 4K and beyond. Unlike HDMI, however, DisplayPort is an open standard with no royalties.

With the proper adapters, DisplayPort cable can carry DVI and HDMI signals, although this doesn’t work the other way around—DVI and HDMI cable can’t carry DisplayPort. Because DisplayPort can provide power to attached devices, DisplayPort to HDMI or DVI adapters don’t need a separate power supply.

DisplayPort supports cable lengths of up to 15 meters with maximum resolutions at cable lengths up to 3 meters. Bidirectional signaling enables DisplayPort to both send and receive data from an attached device.

DisplayPort v1.1: 10.8 Gbps over a 2-meter cable.

DisplayPort v1.2: 21.6 Gbps (4K). DisplayPort v1.2 also enables you to daisychain up to four monitors with only a single output cable. It also offers the future promise of DisplayPort Hubs that would operate much like a USB hub.

DisplayPort v1.3: 2.4 Gbps. (5K)

The standard DisplayPort connector is very compact and features latches that don’t add to the connector’s size. Unlike HDMI, a DisplayPort connector is easily lockable with a pinch-down locking hood, so it can't be easily dislodged. However, a quick squeeze of the connector releases the latch.

The Mini DisplayPort (MiniDP or mDP) is a miniatured version of the DisplayPort interface. It carries both digital and analog computer video and audio signals. Apple® introduced the Mini DisplayPort connector in 2008 and it is now on all new Mac® computers. It is also being used in newer PC notebooks. This small form factor connector fully supports the VESA DisplayPort protocol. It is particularly useful on systems where space is at a premium, such as laptops, or to support multiple connectors on reduced height add-in cards.

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Black Box Explains... Digital Optic Cable

Many new, high-quality Mini Disc, pro-audio, DAT (Digital Audio Tape), CD, DVD, and laser disc players, as well as digital amplifiers, DSS satellite receivers, and computer sound cards, are manufactured... more/see it nowwith digital optical output connectors.

These connectors attach to optical cables, which are constructed with a PVC jacket and a plastic core. The cables transfer information accurately over short distances via digital light signals with low loss and no distortion.

Digital optical cable with plastic-core construction is less expensive than fiber optic cable with a glass core, but it still provides the benefits of optical transmission over short distances.

Digital audio makes it possible to use high-quality digital-to-analog converters, which help to maintain the integrity of sound signals from high-end electronic devices.

The two types of connectors associated with digital optical transmission are TOSLINK®, a Toshiba® trademark, and the 3.5-mm Mini Plug connector. collapse


Black Box Explains...10GBASE-T standard.

In June 2006, the IEEE approved the standard for 10 Gigabit/sec Ethernet, or 10GBASE-T (10-GbE). 10-GbE transmission requires a bandwidth of 500 MHz.

The 10-GbE standards.
The cabling industry is developing... more/see it nowtwo different standards that can be used in 10-GbE applications. One is for use with Category 6 (CAT6) cable, and one is for Augmented Category 6 (CAT6a).

Alien Crosstalk.
Before discussing the standards, a definition of Alien Crosstalk is needed.

Alien Crosstalk (ANEXT) is a critical measurement unique to 10-GbE systems. Crosstalk, measured in 10/100/1000BASE-T systems, is the mixing of signals between wire pairs within a cable. Alien Crosstalk is the measurement of the signal coupling between wire pairs in different, adjacent cables.

The amount of ANEXT depends on a number of factors, including the promixity of adjacent cables and connectors, the cable length, cable twist density, and EMI. Patch panels and connecting hardware are also affected by ANEXT.

With ANEXT, the affected cable is called the disturbed or victim cable. The surrounding cables are the disturbers.

10-GbE using CAT6.
The first set of standards defines cabling performance when using Category 6/Class E cabling for 10-GbE applications. The TIA/EIA version will be the Technical Systems Bulletin 155 (TSB 155). ISO/IEC TR 24750 is a technical report to be used for measuring existing Class E systems.

No matter what the cable length is, CAT6 cable must meet 10-GbE electrical and ANEXT specifications up to 500 MHz. However, the CAT6 standard now specifies measurements only to 250 MHz, and it does not have an ANEXT requirement. There is no guarantee CAT6 can support a 10-GbE system. But the TSB provides guidelines for ways to help mitigate ANEXT. One way to lessen or eliminate ANEXT is to use shielded equipment and cables. Another way is to follow installation guidelines, such as using non-adjacent patch panels, separating equipment cords, unbundling horizontal cabling, etc.

10GbE using CAT6a.
The second set of standards will define Augmented Category 6 (CAT6a) and Augmented Class E (Class Ea) cabling. The newer, augmented cabling systems are designed to support 10-GbE over a 100-meter horizontal channel.

The TIA/EIA version is in draft and will be published as ANSI/TIA/EIA-568B.2-AD10. It recognizes both UTP and STP CAT6a systems. It also extends CAT6 electrical parameters such as NEXT, FEXT, return loss, insertion loss, and more to 500 MHz. It specifies near- and far-end Alien Crosstalk (ANEXT, AFEXT) to 500 MHz. It also goes beyond IEEE 802.3an by establishing the electrical requirements for the permanent link and cabling components. The ISO Class Ea standard will be published in a new edition of the 11801 standard.

These standards specify requirements for each component in the channel, such as cable and connecting hardware, as well as for the permanent link and the channel. collapse


Black Box Explains…CAT6A UTP vs. F/UTP.

CAT6A is currently the cable of choice for future-proofing cabling installations and for 10-GbE networks.

There are two types of CAT6A cable, unshielded (UTP) and shielded (F/UTP). F/UTP denotes foiled/unshielded... more/see it nowtwisted pair and consists of four unshielded twisted pairs encased in an overall foil shield. This is not to be confused with an S/FTP (screened/foiled twisted pair) cable, which has four individually shielded twisted pairs encased in an overall braided shield.

CAT6A UTP
CAT6A UTP is constructed in a certain way to help eliminate crosstalk and ANEXT. (ANEXT is the measurement of the signal coupling between wire pairs in different and adjacent cables.) This includes larger conductors (23 AWG minimum), tighter twists, an extra internal airspace, an internal separator between the pairs, and a thicker outer jacket. These features also increase the outer diameter of the cable, typically to .35 inches in diameter, up from .25 inches for CAT6 cable. This increased diameter creates a greater distance between pairs in adjacent links, thus reducing the between-channel signal coupling. But CAT6A UTP cable is still affected by ANEXT.

According to the standards, ANEXT can be improved by laying CAT6A UTP cable loosely in pathways and raceways with space between the cables. This contrasts to the tightly bundled runs of CAT6/5e cable we are used to. The tight bundles present a worst-case scenario of six cables around one, thus the center cable would be adversely affected by ANEXT. Testing for ANEXT is a complex and time-consuming process where all possible wire-pair combinations are checked. It can take up to 50 minutes to test one link in a bundle of 24 CAT6A UTP cables.

CAT6A F/UTP
CAT6A F/UTP denotes foiled/unshielded twisted pairs and consists of four unshielded twisted pairs encased in an overall foil shield. ANEXT, and the time needed to test for it, can be greatly reduced, if not eliminated completely, by using CAT6A F/UTP. The foil shield acts as a barrier preventing external EMI/RFI from coupling onto the twisted pairs. It also prevents data signals from leaking out of the cable, making the cable more difficult to tap and better for secure installations. Studies also have shown that CAT6A F/UTP cable provides significantly more headroom (as much as 20 dB) than CAT6A UTP in 10-GbE over copper systems.

Bigger isn't always better.
CAT6A UTP cable has an overall allowable diameter of 0.354 inches. CAT6A F/UTP cable has an average outside diameter of 0.265–0.30 inches. That’s smaller than the smallest CAT6A UTP cable. An increase in the outside diameter (O.D.) of 0.1 inch, from 0.25 inches to 0.35 inches for example, represents a 21% increase in fill volume. In general, CAT6A F/UTP cable provides a minimum of 35% more fill capacity that CAT6A UTP cable.

Also because of its large diameter, CAT6A UTP requires a larger bend radius, more pathways, less dense patch panel connections, and extensive ANEXT testing.

CAT6A F/UTP cable is actually easier to handle, requires less bend radius, and uses smaller pathways. In addition, innovations in connector technology has made terminating CAT6A F/UTP cable simpler. In terms of grounding, the requirements for both UTP and F/UTP cable fall under TIA/EIA J-STD-607-A Commercial Building Grounding (Earthing) and Bonding Requirements for Telecommunications.

The advantages of CAT6A F/UTP vs. UTP
In summary, there are a number of advantages of using CAT6A F/UTP over CAT6A UTP in 10-GbE networks.

1. Shielding eliminates ANEXT and EMI/RFI problems and testing.
2. Data line security is enhanced because of shielding.
3. Lighter, slimmer cable provides higher port density.
4. Smaller outside diameter cable is easier to handle and reduces installation costs.
5. Shielded cable uses less space in conduits.

For more information, see the CAT6A F/UTP vs. UTP: What You Need to Know white paper in the Resources section at blackbox.com. collapse


Black Box Explains...Choosing SCSI cables.

1. Quality. Your system’s performance depends on the quality of your SCSI cables. Without high-quality cables specifically designed for SCSI applications, you could be jeopardizing your SCSI lifeline. Inferior cables,... more/see it nowadapters, and terminators can cause random errors, data corruption, or even a system crash! Black Box® SCSI Cables and components are the absolute best-quality products. And they’re guaranteed for life.

2. Length. For peak network performance, make sure your cables are the right length. As cable runs get longer, signals weaken and are more susceptible to noise. Always use the shortest cable for the task. And stay within the SCSI-1 and SCSI-2 standards of six meters or three meters for Fast SCSI. Remember, this is the total length of the bus, including all internal and external cables. collapse

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