Archive for the ‘100BASE-TX’ Category

Power over Ethernet (PoE) – Explained

Saturday, November 14th, 2009

Power over Ethernet (PoE).

Powering remote Ethernet devices can be a problem when you need to find an AC power outlet to plug a bulky transformer into. But with Power over Ethernet (PoE) you don’t need a power outlet because your Ethernet device draws power from the same Ethernet UTP cable that connects it to the network. You simplify installation by getting power where you need it with PoE.

What is PoE?
The seemingly universal network connection, CAT5 cable, has another role to play: to provide electrical power as well as data. Power over Ethernet (PoE) was ratified by the Institute of Electrical and Electronic Engineers (IEEE) in June 2000 as the 802.3af-2003 standard. It defines the specifications for the transmission of electrical power over CAT5 data cable.

This standard promotes the delivery of low levels of power—just 13 watts or less—over data lines to PoE devices such as IP telephones, wireless access points, Web cameras, and audio speakers. PoE is also ideal for applications such as video surveillance, building management, retail video kiosks, smart signs, vending machines, and retail point of information systems.

By eliminating the need to install separate outlets for data and power, users can save up to 50% in installation costs.

How does PoE work?
Very simply, CAT5 Ethernet cable consists of four twisted pairs of cable. Only two pairs are used for 10BASE-T and 100BASE-TX Ethernet data transmission; the remaining pairs are available for power. The PoE standard offers two options for using the twisted pairs for power. The first option sends the electrical power through the spare pair. The second option uses the data pairs for both power and data.

The data and power transmissions don’t interfere with each other either. Electricity has a low frequency of 50 – 60 Hz or less, and data transmissions have frequencies that can range from 10 million to 100 million Hz. Because data and electricity are at opposite ends of the frequency spectrum, they can travel over the same cable.

PoE devices
To install Power over Ethernet, you need to add a PoE injector (also known as Power Sourcing Equipment or PSE), to insert DC voltage onto the CAT5 cable. The injector is usually installed near the Ethernet switch and may be a single-port model that inserts power onto only one cable or may be a PoE hub, which inserts power onto multiple cables.

At the other end of the powered CAT5 Ethernet cable, you need a way to get the power from the Ethernet cable and back into a device. Many network devices are now made as PoE-compatible devices that can take power directly from the CAT5 cable. These devices are sometimes also described as active Ethernet compatible.

Additionally, you can power some network devices that aren’t PoE compatible by using a device called a picker or a tap. It “picks” the DC voltage from the CAT5 cable and routes it to the device.

PoE applications and benefits:

  • Use one set of twisted-pair wires for both data and low-wattage appliances.
  • Save money by eliminating the need to run electrical wiring.
  • Easily move an appliance with minimal disruption.
  • If your LAN is protected from power failure by a UPS, the PoE devices connected to your LAN are also protected from power failure.
  • Supports the addition of end-span, standalone, and mid-span devices.
  • As PoE becomes more common, the 8-pin modular connector will become the industry-standard power jack.

Power over Ethernet

Fibre Optic Standards – Explained

Saturday, November 14th, 2009

Fibre Optic Standards Explained:

Several IEEE standards have been established for Ethernet over fibre optic media. 10BASE-FL, one of the standards defined by the IEEE, allows Ethernet to operate at 10 Mbps over fibre optic cable. 100BASE-FX and 100BASE-SX both allow Ethernet speeds of 100 Mbps. 100BASE-FX operates at higher wavelengths than 100BASE-SX and can also be used with single-mode fibre cable.100BASE-SX operates at a wavelength of 850 nm and can only be used with multimode cable. The newest standards-1000BASE-SX and 1000BASE-LX -define speeds of 1 Gigabit and distances up to 5 kilometres. Actual distances that can be achieved with Media Converters can be much higher.

Standard Multimode Single-Mode
10BASE-FL 850 nm/2 km 1310/1550 nm up to 100 km*
100BASE-FX 1310 nm/fdx 2 km 1310/1550 nm up to 100 km*
100BASE-SX 850 nm/300 m n/a
1000BASE-SX (62.5 µm) 850 nm/220 m n/a
1000BASE-SX (50 µm) 850 nm/550 m n/a
1000BASE-LX 1310 nm/550 m 1310 nm/5 km
1310 nm up to 30 km*
1550 nm up to 70 km*
* Not part of the relevant IEEE standard

Media converters – Explained

Saturday, November 14th, 2009

Media converters

  • Seamlessly integrate 10, 100, and 1000 BASE-T, ThinNet, Thicknet and fibre optic cabling.
  • Inexpensively connect half- or full-duplex 100BASE-TX and 100BASE-FX!
  • Switch between different wiring systems without adding to your overall network repeater count.
  • Convert to fibre and run cables across an extra-long distance-up to 50 kilometres or more!
  • Have an Ethernet switch with RJ-45 ports? No problem! Use a converter to attach legacy AUI and BNC or new fibre segments.

What are Media Converters?
Media converters are simple networking devices that enable you to interconnect networks or network devices with different speeds, operation types, modes and media types. Operation addresses half- and full-duplex dissimilarities. Mode addresses different wavelengths in a fibre optic environment. And media type can be multimode, single-mode or twisted-pair cable.

Benefits of Media Converters:
Media converters play an important role in today’s multiprotocol, mixed-media networks. For example, LAN administrators can deploy media converters to integrate fibre optic cabling and active equipment into existing copper-based, structured cabling systems while achieving significant cost savings. In general, media conversion can deliver the following benefits for your network environment:

Cost Reduction
You can use media converters with cost-effective Ethernet switches to do the same job as expensive hybrid media switches and reduce your overall networking costs in the process. Media converters can also be used with fibre optic cabling to bridge the last mile in your network or to establish a WAN connection up to 100 kilometres. This type of media converter solution can cost significantly less than one that relies on higher-layer devices such as routers or switches.

Investment Protection
Media converters enable you to protect your existing network investment. As simple network devices, media converters can easily be located or relocated to other areas within the installation, further leveraging the original investment. Additionally, they extend the productive life of your fibre and copper wiring plants by being able to interconnect different devices supporting various media types (coaxial cable, twisted pair, single-mode or multimode fibre), different wavelength modes (850 nm, 1310 nm or 1550 nm) or dissimilar speeds (10 Mbps, 100 Mbps or 1000 Mbps).

Flexibility and Simplification
Media converters offer the flexibility of combining copper with 850 nm and 1300 nm multimode fibre and 1310 nm and 1550 nm single-mode fibre. Slide-in media conversion cards for all cable types can reside in one media conversion chassis. With protocol transparency, Ethernet speed can be supplied anywhere in the network-local or remote-whether it’s a LAN or the WAN environment. Every device can also be smoothly integrated into your workgroup or the enterprise-wide network, regardless of the type of bit rate transparency or the bit rate conversion that’s supported.

Ease of Use and High Availability
Media converters are much easier to handle and to manage than higher-layer devices. Configuring and installing redundant solutions is neither complex nor cost intensive. And by adding management functions to your media converters, you can minimise downtime and make troubleshooting easier.

What Kinds of Media Converters Exist?

Basic Media Converter
A basic media converter is a Layer 1 device that transparently passes through all information. It has a very low path-delay value and does not count as a repeater. Basic media converter functions may include FibreAlert, LinkLoss and single-strand fibre conversion. Along with its all-transparent behaviour, a basic media converter’s key advantage is its low cost.

Switched Media Converter
A switched media converter not only converts media types and fibre mode but also speed and duplex mode. As the name implies, a switch is integrated into the converter to provide additional functionality. This switch function is its key advantage and often enables you to securely combine multiple Ethernet interfaces onto one fibre or prioritise traffic over the link.

Managed Media Converter
A managed media converter can be controlled and monitored locally and remotely. It can support command line interface, Telnet connections or SNMP functions for integration into an element manager or a management platform. Its key advantages are easier troubleshooting and reduced downtime.

Possible Media Converter Features:

LinkLoss™ Feature
When either a twisted-pair or a fibre link is broken, the information about this link loss is transferred to the other media link. For example, when a cable breaks on the fibre segment of a conversion, LinkLoss detects the error and passes this information to the twisted-pair segment. This results in a loss of link on the remote twisted-pair device. If LinkLoss is enabled on that device, the device’s green Link LED goes out, informing the local supervisor that there’s something wrong with the link.

FibreAlert™ Feature
What if only one strand of a fibre segment is broken? The FibreAlert feature enables the media converter at the receiver end to detect this type of link loss. The media converter stops transmitting data and a link signal until it begins receiving a signal or link pulse again. If there’s no signal or pulse, Link LEDs on the media converters at both ends of the fibre segment go out, indicating a fault somewhere in the segment. This way, a local site administrator is notified of a cable fault and can quickly locate it.

Wavelength Division Multiplexing (WDM) Feature
Black Box’s new WDM media-conversion products enable you to double your fibre optic plant capacity by using Wavelength Division Multiplexing technology. With a WDM converter, you can send more than one optical signal through the same fibre strand. WDM modulates each of several data streams onto a different part of the light spectrum. In this way, it increases the amount of data that a fibre optic cable can transport.

There are two flavours of WDM media converters: one fibre link and single-strand fibre. The one-fibre link version transports two links onto one duplex fibre link. The single-strand fibre version transports one link over a single strand of fibre.