Fiber Optic

Driving data? Better check the transmission.

Line drivers can operate in any of four transmission modes: 4-wire full-duplex, 2-wire full-duplex, 4-wire half-duplex, and 2-wire half-duplex. In fact, most models support more than one type of operation.

So how do you know which line driver to use in your application?

The deal with duplexing.
First you must decide if you need half- or full-duplex transmission. In half-duplex transmission, voice or data signals are transmitted in only one direction at a time, as in a CB radio conversation. In full-duplex operation, voice or data signals are transmitted in both directions at the same time, as in a telephone conversation.

The entire bandwidth is available for your transmission in half-duplex mode. In full-duplex mode, however, the bandwidth must be split in two because data travels in both directions simultaneously.

Two wires or not two wires? That is the question.
The second consideration you have is the type of twisted-pair cable you need to complete your data transmissions. Generally you need twisted-pair cable with either two or four wires. Often the type of cabling that’s already installed in a building dictates what kind of a line driver you use. For example, if two twisted pairs of UTP cabling are available, you can use a line driver that operates in 4-wire applications, such as the Short-Haul Modem-B Async or the Line Driver-Dual Handshake models. Otherwise, you might choose a line driver that works for 2-wire applications, such as the Short-Haul Modem-B 2W or the Async 2-Wire Short-Haul Modem.

If you have the capabilities to support both 2- and 4-wire operation in half- or full-duplex mode, we even offer line drivers that support all four types of operation.

As always, if you’re still unsure which operational mode will work for your particular applications, consult our Technical Support experts and they’ll help you make your decision.

While there are many applications for basic T1 rate service (1.536 Mbps), some applications require much more bandwidth. One of the most attractive features of T1 is the number of options available to accommodate these kinds of demands. The important thing to remember is that all of these higher-speed services operate with the same consistent framing formats as the standard T1 service.

T1 is a high-speed service with a clock speed of 1.544 Mbps. It’s made up of 24 64-kbps DS0 (Digital-Signal [zero]) subchannels that together can support throughput rates of up to 1.536 Mbps. But there are higher levels of T1 service that are also available. For instance, T1C service doubles the T1 rate. It supports 3.152 Mbps with a total of 48 DS0s for top-speed applications. In a T1C environment, two T1 lines are combined into one using a special T1 mux.

The next-highest level of service is called T2. It offers 6.312 Mbps over 96 DS0s by multi-plexing 4 T1 lines into a single high-speed line.

The next two levels of service are exponentially larger than T2. A high-speed T3 trunk line is 28 times larger than a standard T1 line. T3 brings 44.736 Mbps to a customer site via 672 DS0s. This tremendous capacity is made possible by multiplexing 28 T1 lines or combina?tions of T2 and T1 lines.

Finally, T4 service offers a bandwidth potential of 274.176 Mbps, made up of 4032 64-kbps DS0 subchannels. At 168 times the size of a standard 1.544-Mbps line, T4 service dwarfs T1. The physical connections require multiplexing 6 T3 lines or 168 T1 lines into a single high-speed trunk.

With so many incredibly high-speed T-level service options available, system administrators have great flexibility to configure their operations for maximum efficiency and economy.

It’s important to remember that these various levels of T1 services can be implemented simultaneously within a particularly large enterprise to support complex network configurations.

Of course, this kind of application has the potential to become somewhat overwhelming from a management standpoint. However, as long as you keep track of the individual DS0s, you should always be able to accurately gauge how much available bandwidth you have at your disposal.

When choosing a fiber driver, you should make a power budget, calculate the speed and distance of your cable run, and know the interface requirements of all your devices.

Many of our fiber drivers are for single-mode fiber optic cable. Compared to multimode fiber, single-mode delivers up to 50 times more distance. And single-mode at full-duplex enables up to two times the data throughput of multimode 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 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.

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