Tag Archives: Fiber Optic Cables

Five Basics About Fiber Optic Cable

A fiber optic cable is a network cable that contains strands of glass fibers inside an insulated casing. They’re designed for high performance data networking and telecommunications. Fiber optic cable carry communication signals using pulses of light, faster than copper cabling which uses electricity. They are becoming the most significant communication media in data center. Then how much do you know about them? This post serves as a guide for beginners.

Fiber Components

The three basic elements of a fiber optic cable are the core, cladding and coating. Core is the light transmission area of the fiber, either glass or plastic. The larger the core, the more light that will be transmitted into the fiber. The function of the cladding is to provide a lower refractive index at the core interface, causing reflection within the core. Therefore the light waves can be transmitted through the fiber. Coatings are usually multi-layers of plastics applied to preserve fiber strength, absorb shock and provide extra fiber protection.

Fiber Components

Fiber Type

Generally, there are two basic types of fiber optic cables: single mode fiber (SMF) and multimode fiber (MMF). Furthermore, multimode fiber cores may be either step index or graded index.

Single mode and multi-mode fiber-optic cables

Single mode optical fiber is a single strand of glass fiber with a diameter of 8.3 to 10 microns that has one mode of transmission. The index of refraction between the core and the cladding changes less than it does for multimode fibers. Light thus travels parallel to the axis, creating little pulse dispersion. It’s often used for long-distance signal transmission.

Step index multimode fiber has a large core, up to 100 microns in diameter. As a result, some of the light rays that make up the digital pulse may travel a direct route, whereas others zigzag as they bounce off the cladding. These alternative pathways cause the different groupings of light rays to arrive separately at a receiving point. Consequently, this type of fiber is best suited for transmission over short distances.

Graded index fibers are commercially available with core diameters of 50, 62.5 and 100 microns. It contains a core in which the refractive index diminishes gradually from the center axis out toward the cladding. The higher refractive index at the center makes the light rays moving down the axis advance more slowly than those near the cladding.

Fiber Size

Single mode fibers usually has a 9 micron core and a 125 micron cladding (9/125µm). Multimode fibers originally came in several sizes, optimized for various networks and sources, but the data industry standardized on 62.5 core fiber in the mid-80s (62.5/125 fiber has a 62.5 micron core and a 125 micron cladding. It’s now called OM1). Recently, as gigabit and 10 gigabit networks have become widely used, an old fiber design has been upgraded. 50/125 fiber was used from the late 70s with lasers for telecom applications. 50/125 fiber (OM2) offers higher bandwidth with the laser sources used in the gigabit LANs and can allow gigabit links to go longer distances. Laser-optimized 50/125 fiber (OM3 or OM4) today is considered by most to be the best choice for multimode applications.

Basic Cable Design

The two basic cable designs are loose-tube cable, used in the majority of outside plant installations, and tight-buffered cable, primarily used inside buildings.

loose-tube-or-tight-buffered-cable

The modular design of loose-tube cables typically holds up to 12 fibers per buffer tube with a maximum per cable fiber count of more than 200 fibers. Loose-tube cables can be all dielectric or optionally armored. The modular buffer-tube design permits easy drop-off of groups of fibers at intermediate points, without interfering with other protected buffer tubes being routed to other locations.

Tight-buffered cables can be divided into single fiber tight-buffered cables and multi-fiber tight-buffered cables. single fiber tight-buffered cables are used as pigtails, patch cords and jumpers to terminate loose-tube cables directly into opto-electronic transmitters, receivers and other active and passive components. While multi-fiber tight-buffered cables also are available and are used primarily for alternative routing and handling flexibility and ease within buildings.

Connector Type

While there are many different types of fiber connectors, they share similar design characteristics. Simplex vs. duplex: Simplex means 1 connector per end while duplex means 2 connectors per end. The following picture shows various connector styles as well as characteristics.

fiber cable connectors

Summary

Ultimately, what we’ve discussed is only the tip of the iceberg. If you are eager to know more about the fiber optic cable, either basics, applications or purchasing, please visit www.fs.com for more information.

Shielded Cabling System

Shielded cabling, has been the preferred cabling infrastructure in many global markets for many years. Cables described as foil screened unshielded twisted-pair (F/UTP) and fully shielded cables with an overall braid screen plus individual foil shielded twisted pairs (S/FTP) are now gaining popularity in markets where unshielded twisted-pair (UTP) cabling has traditionally been the most common solution.

There are essentially three types of shielding strategies: braided wires, foil wrapping, and a combination of the two.

Braided shield generally offers 60% to 85% shielding and can only offer about 95% coverage at best. The mass of the braid is higher than a foil shield. As a result, it provides better conductivity and offers a good secure connection to the connectors at the cable ends, providing an excellent ground. Many times shielded cables will utilize both foil and braided shields to ensure the highest level of protection from EMI and RFI.

Common Shielding Options For Ethernet Cables

Traditional category 5E or Cat6 Ethernet Cables have four twisted pairs and no shield. With shielded products, a shield layer is added to help reduce interference to network signals. There are several different types of shielding found on network cabling. The choice of a shielded cable or non-shielded cable often comes with experience. An area such as a production/factory floor where heavy equipment is being used is a prime example of a place where you might consider a shielded cable.

When building a shielded cable plant, it’s important to use shielded cable, shielded connectors, and shielded interconnection points such as patch panels for the shielding to be effective against EMI and RFI. Additionally, proper bonded grounding of all components is crucial to attaining effective shielding. A shielded cable is a type of electrical cable that is encased in a conductive layer. The shield can be of several different materials, such as, braided or non braided copper, aluminum, copper tape, or a layer of a polymer that has a conductive property.

Jacket Types

The shield is normally covered by a jacket. This provides insulation and, allows the shield to become a cage that reduces the electrical noise from interfering with signals and reducing the amount of electromagnetic radiation that could interfere with other electronics.

When designing a cabling plant in harsh environments it is necessary to consider the cable jacket. In some cases robotic equipment is directly connected via Category 5e/6 cables that are constantly moving. The cable also must be constructed with a hi-flex, low-friction jacket as well as robust connectors to ensure a high mean time between failure (MTBF).

Other environments call for cabling that can be exposed to petroleum-based products or other chemicals. Traditional PVC jacketed cables would break down when exposed to these harsh liquids. If protection of equipment or people is a design requirement, consider LSZH Fiber Cable. They emit fewer toxic fumes than standard PVC-based cable jackets. Typically, LSZH cabling is used in confined spaces such as mining operations.

Fiber Optics Has As Grown As An Alternative To Traditional Shielded Cabling

The use of fiber-optic cabling in industrial installations has grown as an alternative to traditional shielded cabling since fiber cabling is impervious to EMI and RFI. Additionally, Fiber Cables can extend great distances compared to copper cables without the use of costly and cumbersome repeaters. Fiber optic cabling is used for longer runs between floors of a building and sometimes underground either a conduit or direct burial to connect multiple campus buildings.

Shielded cabling and components have a higher costs basis than non-shielded products. For this reason, it is not economical to install shielded products where they are not needed. If you find that your network is suffering from interference from some nearby equipment, then shielded cable can often help.