Fiber optic cable, or simply fiber, contains one or several glass or plastic fibers at its center, or core. Data is transmitted via pulsing light sent from a laser (in the case of 1- and 10-gigabit technologies) or an LED (light-emitting diode) through the central fibers. Surrounding the fibers is a layer of glass or plastic in the strands. It reflects light back to the core in patterns that vary depending on the transmission mode. This reflection allows the fiber to bend around corners without diminishing the integrity of the light-based signal. Outside the cladding, a plastic buffer protects the cladding and core. Because the buffer is opaque, it also absorbs any light that might escape. To prevent the cable from stretching, and to protect the inner core further, strands of Kevlar surround the plastic buffer. Finally, a plastic sheath covers the strands of Kevlar.
Like twisted pair and coaxial cabling, fiber-optic cabling comes in a number of different varieties, depending on its interned use and the manufacturer. For example, fiber optic cable used to connect the facilities of large telephone and data carries may contain as many as 1000 fibers and be heavily sheathed to prevent damage from extreme environmental conditions. At the other end of the spectrum, fiber optic patch cables for use on LANs may contain only two stands of fiber and be pliable enough to wrap around your hand. Because each strands of glass in a fiber optic cable transmits in one direction only-in simplex fashion-two strands are needed for full-duplex combined side by side in conjoined jackets. You’ll find zipcords where fiber optic cable spans relatively short distances, such as connecting a sever and switch. A zipcord may come with types of connectors on its ends, as described later in this section.
Fiber optic cable provides the following benefits over copper cabling:
- Extremely high throughput
- Very high resistance to noise
- Excellent security
- Ability to carry signals for much longer distances before requiring repeaters than copper cable
- Industry standard for high-speed networking
The most significant drawback to the use of fiber is that covering a certain distance with fiber optic cable is more expensive than using twisted pair cable. Also, fiber-optic cable requires special equipment to splice, which means that quickly repairing a fiber-optic cable in the field (given little time or resources) can be difficult. Fiber’s characteristics are summarized in the following list:
- Throughput – Fiber is reliable in transmitting data at rates that can reach 100 gigabits(or 100,000 megabits) per second per channel. Fiber’s amazing throughput is partly due to the physics of light traveling through glass. Unlike electric pulses traveling over copper, the light experiences virtually no resistance. Therefore, light-based signals can be transmitted at faster rates and with fewer errors than electric pulses. In fact, a pure glass strand can accept up to 1 billion laser light pules per second. Its high throughput capability makes it suitable for network backbones and for serving applications that generate a great deal of traffic, such as video or audio conferencing.
- Cost – Fiber optic cable is the most expensive transmission medium. Because of its cost, most organizations find it impractical to run fiber to every desktop. Not only is the cable itself more expensive than copper cabling, but fiber optic transmitters and connectivity equipment can cost as much as five times more than those designed for UTP networks. In addition, hiring skilled fiber cable installers costs more than hiring twisted pair cable installers. However, as technologies improved, fiber optic cables are cheaper and cheaper. (Click to find the fiber optic cable price in Fiberstore)
- Connectors – With fiber cabling, you can use any of 10 different types of connectors. The figures below show four of the most common connector type: the SC (subscriber connector or standard connector), ST (straight tip), LC (local connector) , and MT-RJ (mechanical transfer redistered jack). Existing fiber networks might use ST or SC connectors. However, LC and MT-RJ connectors are used on the very latest fiber optic technology. LC and MT-RJ connectors are preferable to ST and SC connectors because of their smaller size, which allows for a higher density of connections at each termination point. The MT-RJ connector is unique because it contains two strands of fiber in a single ferrule, which is a short tube within a connector that encircles the fiber and keeps it properly aligned. With two strands in each ferrule, a single MT-RJ connector provides for full-duplex signaling. Linking devices that require different connectors is simple because you can purchase fiber optic cables with different connector types at each end.
- Noise immunity – Because fiber does not conduct electrical current to transmit signals, it is unaffected by EMI. Its impressive noise resistance is one reason why fiber can span such long distances before it requires repeaters to regenerate its signal.
- Size and scalability – Depending on the type of fiber optic cable used, segment lengths vary from 150 to 40,000 meters. This limit is due primarily to optical loss, or the degradation of light signal after it travels a certain distance away from its source (just as the light of a flashlight dims after a certain number of feet). Optical loss accrues over long distances and grows with every connection point in the fiber network. Dust or oil in a connection (for example, from people handling the fiber while splicing it) can further exacerbate optical loss. Some types of fiber-optic cable can carry signals 40 miles while others are suited for distances under a mile. The distance a cable can carry light depends partly on the light’s wavelength. It also depends on whether the cable is single mode or multi-mode.
About Fiberstore:
As one of the world’s largest supplier, Fiberstore provides the most comprehensive fiber optic cables including armored fiber optic cables, LSZH fiber optic cables, figure 8 aerial fiber optic cables, ADSS fiber optic cables, etc.
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