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.
850 nm High Performance EMB (MHz/km)
850-nm Ethernet Distance
OM3: 1000 m
OM4: 1000 m
OM3: 300 m
OM4: 550 m
OM3: 100 m
OM4: 150 m
OM3: 100 m
OM4: 150 m
Black Box Explains...IEEE 1284
Introduced in 1994, the IEEE 1284 standard addresses data-transfer speeds and distance for parallel interfaces. Standard parallel interfaces support speeds of up to 150 kbps at distances of up to... more/see it now6 feet (1.8 m); IEEE 1284 parallel interfaces can send your data over 100 times faster at up to five times the distance!
Although the Centronics® interface enabled only unidirectional computer-to-peripheral data flow, the IEEE 1284 interface enables bidirectional flow so peripherals can send data to the computer.
The IEEE 1284 standard covers five separate parallel modes, from the original Centronics (with which it’s compatible) to the high-performance Enhanced Parallel Port (EPP) mode. The computer negotiates with the attached device to determine which mode to use. collapse
Black Box Explains...Fiber optic cable construction.
Fiber optic cable consists of a core, cladding, coating, strengthening fibers, and cable jacket.
This is the physical medium that transports optical data signals from an attached light source to... more/see it nowa receiving device. The core is a single continuous strand of glass or plastic thats measured (in microns) by the size of its outer diameter. The larger the core, the more light the cable can carry.
All fiber optic cable is sized according to its cores outer diameter.
The three multimode sizes most commonly available are 50, 62.5, and 100 microns. Single-mode cores are generally less than 9 microns.
This 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.
This 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 buffer coatings are measured in microns (µ) and can range from 250 to 900 microns.
These components help protect the core against crushing forces and excessive tension during installation.
The materials can range from Kevlar® to wire strands to gel-filled sleeves.
This is the outer layer of any cable. Most fiber optic cables have an orange jacket, although some types can have black or yellow jackets. collapse
Black Box Explains...Loose-tube vs. tight-buffered fiber optic cable.
There are two styles of fiber optic cable construction: loose tube and tight buffered. Both contain some type of strengthening member, such as aramid yarn, stainless steel wire strands, or... more/see it noweven gel-filled sleeves. But each is designed for very different environments.
Loose tube cables, the older of the two cable types, are specifically designed for harsh outdoor environments. They protect the fiber core, cladding, and coating by enclosing everything within semi-rigid protective sleeves or tubes. In loose-tube cables that hold more than one optical fiber, each individually sleeved core is bundled loosely within an all-encompassing outer jacket.
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 expand and contract with temperature changes, too.
But gel-filled loose-tube cables are not the best choice when cable needs to be submerged or where its routed around multiple bends. Excess cable strain can force fibers to emerge from the gel.
Tight-buffered cables, in contrast, are optimized for indoor applications. Because theyre sturdier than loose-tube cables, theyre best suited for moderate-length LAN/WAN connections, long indoor runs, and even direct burial. Tight-buffered cables are also recommended for underwater applications.
Instead of a gel layer or sleeve to protect the fiber core, tight-buffered cables use a two-layer coating. One is plastic; the other is waterproof acrylate. The acrylate coating keeps moisture away from the cable, like the gel-filled sleeves do for loose-tube cables. But this acrylate layer is bound tightly to the plastic fiber layer, so the core is never exposed (as it can be with gel-filled cables) when the cable is bent or compressed underwater.
Tight-buffered cables are also easier to install because theres no messy gel to clean up and they dont require a fan-out kit for splicing or termination. You can crimp connectors directly to each fiber.
Want the best of both worlds? Try a hybrid, breakout-style fiber optic cable, which combines tight-buffered cables within a loose-tube housing. collapse
Black Box Explains...Choosing SCSI cables.
1. Quality. Your systems 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 theyre 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
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...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 dont 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...FDDI
Fiber Distributed Data Interface (FDDI) is a networking standard for operating at speeds of up to 100 Mbps. The standard FDDI network is set up in a ring topology with... more/see it nowtwo rings that transmit signals in opposite directions to a series of nodes. FDDI accommodates up to 500 nodes per dual-ring network with spacing up to 2 kilometers between adjacent nodes. FDDI uses the same token-passing scheme as the IEEE 802.5 Token Ring network to control transmission around the loop. collapse
Black Box Explains...Digital Visual Interface (DVI) connectors.
The DVI (Digital Video Interface) technology is the standard digital transfer medium for computers while the HDMI interface is more commonly found on HDTVs, and other high-end displays.
The Digital... more/see it nowVisual Interface (DVI) standard is based on transition-minimized differential signaling (TMDS). There are two DVI formats: Single-Link and Dual-Link. Single-link cables use one TMDS-165 MHz transmitter and dual-link cables use two. The dual-link cables double the power of the transmission. A single-link cable can transmit a resolution ?of 1920 x 1200 vs. 2560 x 1600 for a dual-link cable.
There are several types of connectors: ?DVI-D, DVI-I, DVI-A, DFP, and EVC.
- DVI-D is a digital-only connector for use between a digital video source and monitors. DVI-D eliminates analog conversion and improves the display. It can be used when one or both connections are DVI-D.
- DVI-I (integrated) supports both digital and analog RGB connections. It can transmit either a digital-to-digital signals or an analog-to-analog signal. It is used by some manufacturers on products instead of separate analog and digital connectors. If both connectors are DVI-I, you can use any DVI cable, but a DVI-I is recommended.
- DVI-A (analog) is used to carry an DVI signal from a computer to an analog VGA device, such as a display. If one or both of your connections are DVI-A, use this cable. ?If one connection is DVI and the other is ?VGA HD15, you need a cable or adapter ?with both connectors.
- DFP (Digital Flat Panel) was an early digital-only connector used on some displays.
- EVC (also known as P&D, for ?Plug & Display), another older connector, handles digital and analog connections.