Since the invention of optical fibers in the early 1970s, the use of and demand for optical fiber today are quite numerous. With the explosion of information traffic due to the Internet, electronic commerce, computer networks, multimedia, voice, data, and video, the need for large amount of signal transmission is paramount. Fiber optics has proven to be the best solution. Single-mode fiber is one of optical fibers which is designed for the transmission of a single ray or mode of light as a carrier and is used for long-distance signal transmission.
A typical single-mode fiber has four parts: the core, cladding, buffer and jacket. In the center, it’s called the core where the light is “guided” down in the fiber. The core is surrounded by an optical material called the “cladding” that traps the light in the core using an optical technique called “total internal reflection”. The core and cladding are usually made of ultra-pure glass. The fiber is coated with a protective plastic covering called the “primary buffer coating” that protects it from moisture and other damage. More protection is provided by the cable which has the fibers and strength members inside an outer covering called a “jacket”.
Single-mode fiber has characteristics of low dispersion, high frequency and high bandwidth. First, the high dispersion rate will make the signal worse during its transmission over long distances. When the light travels through the core, the core doesn’t retain all of the light. As a result, the dispersion will be caused when some of the light travels along the fiber cladding. Single-mode fiber could erase the dispersion. Second, the frequency at which the fiber optic signal will be transmitted can influence the signal transmission distance. The higher the frequency, the greater distance the system will be able to support. Single-mode systems have 1300 and 1550 nanometers. Third, bandwidth of fiber is described in MHz per kilometer. Typical fiber bandwidth of single-mode fiber has an inherently higher bandwidth and can reach thousands of MHz per km.
Due to the special favorable characteristics of single-mode fiber, it could transmit data with high speed over long distances. And it’s usually used for connections over large areas, such as college campuses and cable television networks. So that’s why single-mode fiber is attractive especially for long distance signal transmission.