Considerations before Deploying a Fiber Optic Network

Advantages of Fiber

There are many advantages to using fiber optic cable over other types of installations. Typical cable installations cannot handle the bandwidth or distance that fiber optic can. While wireless is a possible option there are disadvantages that include ongoing support costs, possible network intrusions and reduced bandwidth. Once fiber is installed it is very reliable and needs little maintenance or repairs.

Fiber optic network provides the most affordable and capable network you can get. Fiber has become easier to install and test and has become extremely affordable in comparison to other types of installations. If you want to provide the best and most reliable network for your campus environment you can't beat fiber optic. When comparing fiber to other types of installation materials be certain to consider the total cost of installation, maintenance and life expectancy. Fiber is quickly replacing many traditional cable installations due to its increased capacities such as bandwidth. The future will surely hold more need to have increased speeds and bandwidth that likely won't be able to be sustained through standard cable.

Single Mode vs. Multi-Mode Fiber

There are two types of fiber optic cables. It is important to understand the differences between the two and what each is used for. Multi-mode fiber is best for transmitting for short distances. It is best suited for applications such as LAN systems and video surveillance. Single mode fiber is designed for transmitting over longer distances. It is best used for long distance telephony as well as for multi-channel broadcast systems.

Single mode fiber is able to transmit information at a higher capacity. This is because it retains the dependability of light pulses over longer distances. It also provides for lower fiber attenuation than multi-mode fiber. This means that more information can be transmitted over single mode fiber. There are some disadvantages to using single mode fiber. Single mode fiber has a smaller core diameter, which makes coupling light into the core more difficult. In addition, the splices and connectors must be installed with great care because there is little tolerance for weak connections.

There are several types of single mode fiber. In older installations you will find non-dispersion-shifted fiber (NDSF). This type was widely used. Later, NDSF was found to have a high dispersion rate and to compensate for this problem dispersion-shifted fiber (DSF) was developed. Most recently a new classification of single mode fiber was created. This is called non-zero-dispersion-shifted fibers (NZ-DSF). The fiber is now most often the fiber choice for telecommunications systems.

Determining Fiber Loss and Distances

Data can be transmitted over fiber at distances of over a mile without the use of repeaters. This makes fiber an excellent choice for use in long distance applications. By using single mode fiber the distance can be extended to 50 miles. This allows for the LAN to be used outside of a regular building and extended into a campus environment. For example you can connect your main building with your warehouse and branch office locations seamlessly.

To determine the fiber transmission distances you can use the formula

Linklength (km) = (availablepower - linkloss) lengthdependentlinkloss

To make it easier most fiber cable suppliers provide tables that contain this information. The distance that the fiber will be able to transmit varies based on these variables. Choosing the proper switches, converters, cable and connections for your specific installation is vital to the overall performance of the network.

Fiber Optic Connector Types

Fiber optic connectors have always been a concern when using fiber optic cable. In the past the connectors were difficult to install and hard to handle. Manufacturers have standardized the fiber connectors making them easier to use and maintain. There are several types of connectors that can be used for typical installations. The most common types are FC, FDDI, LC, MT Array and NENP. FC connectors are most commonly used for data or telecommunications. FDDI connectors are used most often in the typical fiber optic network. The latest standard of connectors, NENP, are easily installed and require minimal training. The type of connectors you need is predicated upon the equipment that you will be connecting to.

The most important part of the fiber installation is installing the fiber connectors. The installation must be done by a certified and experienced installer. Fiber is very sensitive and must be handled properly to ensure a good finished product. Each connector is placed onto the fiber it must be polished. Polishing ensures that the best connection and transmission possible. Poor connections result in poor transmission. The connectors must be installed on fiber ends that have been cleaned and properly cared for. Exposure to dust and humidity is very harmful to fiber.

Always install more fiber strands than you need. Some may not work properly when connectors are installed while a certain amount can become broken during installation. In addition you should consider potential growth. A good rule of thumb is to install at least 10% more fiber cable than needed for your installation. It is much harder or impossible to go back later to add fiber to the installation. While installed fiber backbone is very stable the cable itself is fragile while it is being installed.

Outside Plant Installation

Outside plant installation of fiber requires some additional considerations. To protect fiber cables you need to use armored cable which has a protective sleeve specifically designed for outdoor use. Fiber optic pavement cable is designed with a high-density polyethylene jacket for use under pavement.

There are three main types of outdoor installation - trenching, direct boring and road/pavement cable. With trenching you will need to dig underground to install a trench to be used for fiber installation. This can get expensive. It may also be very difficult in areas of rugged terrain or other difficult environmental situations. Direct boring is horizontal drilling. Although a minimal amount of digging is required with direct boring, when compared to trenching, underground obstacles may make direct boring difficult. With either trenching or direct boring it often can be too expensive or prohibitive by controlling government agencies in some areas.

Fiber optic pavement cable is a practical and inexpensive alternative to trenching or direct boring. The special fiber cable is designed to be protected from extreme elements as well as high traffic. The cable is sheathed with a protective copper armor and is resistant to abrasions. These cables are installed under pavement and can be covered in pavement making for a clean and complete installation. Another advantage of pavement/road cable is that during the installation there will be minimal impact on high traffic areas such as parking lots or roads.

Conclusion

With many advantages and few disadvantages it is clear that a fiber optic network is the way of the future. New installations are best done using fiber optic cables in order to accommodate the bandwidth needed today and in the future of communications. The newest optic fiber standards make installation easier than ever before. The result will be a highly reliable, wide bandwidth network at an affordable price.

By Fred Wright

Fred Wright is a Technical Manager with The ConnectIT Group, a nationwide installer of fiber optic networks and CCTV cameras. For more information go to: www.ConnectITGroup.com

ﾩ 2008 The ConnectIT Group, LLC

About The Author Fred Wright is a Technical Manager with The ConnectIT Group, a nationwide installer of fiber optic networks and CCTV cameras. For more information go to: www.ConnectITGroup.com