Fiber Optics & Bandwidth Technology

The "Age of Technology" has seen
incredible evolutionary change . . .

The theory of light as a transmission medium surfaced during the 1930's when the first patent for fiber design was produced. Our ability to transmit information and the media we use to do it is perhaps most responsible for the evolution of technology. Through engineering and with time it became practical to use optical fiber as a transmission medium. Our increasing ability to transmit more information, faster and over long distances has expanded the boundaries of our technological development in all areas.

Bandwidth demands
The need for speed and greater bandwidth continues to grow. Internet based businesses are increasing rapidly with the development of e-commerce or e-business. Statistics show that 8,000 people per day join the home working environment and that more than 30 million people in North America run businesses from their homes. With the introduction of personal computers, Internet, full motion video, 3D graphics and video conferencing, people now more than ever require the ability to perform these activities at incredible speeds. Large sound files, computer programs and animated videos require even more bandwidth for acceptable system performance, while virtual reality (VR) and full-length three-dimensional audio/visual presentations require the most bandwidth of all.

People are turning to fiber optics to meet their bandwidth demands. Generally speaking, bandwidth is directly proportional to the amount of data transmitted or received per unit of time. For example, it takes more bandwidth to download a photograph than it takes to download a page of text. The 2001 Multimedia Telecommunications Market Review and Forecast, a publication produced annually by the Telecommunications Industry Association (TIA), reported that the number of fiber miles deployed by carriers jumped an estimated 68.7 percent in 2000 after growing by 55.7 percent in 1999. Fiber is the transmission medium of choice where high speed is required due to its underlying technology.

The Technology
Basic fiber optic cable uses electrical input signals that are converted into modulated light for transmission over the fiber by means of an optical transmitter. The most common devices used as a light source in the optical transmitter are LED's (light emitting diode) and the LD (laser diode). Each light source varies in its characteristics. The light travels along the fiber cable to the output source known as the optical receiver. The receiver converts the optical signal back into a replica of the original electrical signal.

The structure of the fiber is critical in obtaining the correct carrying capacity suitable for your application. Optical fibers are very fine fibers of glass. Once enclosed in protective cables they are tougher than copper cable. Fiber cable consists of a glass core M1 (see illustration below), surrounded by glass optical cladding. The cladding's purpose is not to carry light, however it is a critical part of the fiber and does to some degree actually transmit light. As much as 20% of the light in a single-mode cable actually travels down the cladding. The effective diameter of the cable is a blend of the single-mode core and the degree to which the cladding carries light. As shown in the illustration below, the cladding acts as a refraction point while the angled beam of light travels through the glass core in a zigzag pattern. (see M2)

The glass core is available in three fundamental styles, multi-mode step, multi-mode graded and single-mode step. Multi-mode fibers have multiple pathways for light to travel through and are approximately 63 microns in size. Multi-mode fibers are primarily used for distances of up to 2 kilometers and slower bandwidths. An example would be data networks in buildings or between neighboring buildings.

Single-mode fiber offers an extremely small single path of between 8 and 9 microns in size. Single-mode fiber (SMF) has a far greater carrying capacity than the multi-mode due to its design and precise manufacturing techniques. Glass is a silicon compound. Optical engineers have found that by adding different chemicals to the basic silicon dioxide they can change the optical properties of the glass. They can create glass that has much less attenuation across various frequencies of light than silicon dioxide by itself. Attenuation means intensity decreases as light moves along the fiber. Only one light wave at a time is transmitted down the core of the fiber and because of the narrow channel the light does not refract but stays together instead of bouncing around the core, hence faster data transmission. SMF allows communication between 40 and 200 km's. The disadvantage to single-mode fiber is that it is generally more expensive. It requires the precision of a laser light or LD (laser diode) and the connections are generally more difficult due to the required precision.

Benefits
The process of the fiber optic transmission provides a wide range of benefits not offered by traditional copper cable. These benefits increase rate of transmission and speed which satisfies the needs of today's consumer. Since the bandwidth of fiber far surpasses that of copper it is suitable for today's high-speed multi media needs. The cable is smaller and easier to install because it is lighter and occupies less space. These features make it very adaptable and as a result it is increasingly found in residential installations. Based on these benefits, fiber cable, including it's connectivity parts are competitively priced compared to copper. One must design based on the future and weigh the cost today versus future growth requirements. Also, fiber optic cable is not affected by interference such as lightning or atmospheric conditions and poses no danger of electric shock or fire hazard.

Today's fiber optic cable offers almost unlimited bandwidth and unique advantages over all previously developed transmission media. Fiber optic cable can support higher data rates at greater distances and delivers the information with greater fidelity than copper, making it an ideal choice for the home office with high bandwidth requirements. Presently, with advances in digital technology and the further development of standards, fiber optic technology has become an integral part of today's networks and the foundation for our future.