Optical Fiber Characteristics and System Configurations

One attractive aspect of optical fibers is their enormous bandwidth compared to other media, such as radio waves and twisted-pair wires. Still, an optical fiber is not ideal; it possesses some unwanted properties. Dispersion and nonlinearity are the major limiting factors in lightwave communication. Fiber dispersion causes different spectral components of a signal to travel at different speeds. Hence, for a given transmission distance different spectral components arrive at the destination at different times. This results in a pulse broadening effect when a pulse propagates along an optical fiber. However, the situation is different when the nonlinearity and dispersion are considered together. In some circumstances, the nonlinearity could counteract the dispersion. In addition, when multiple channels are considered, the fiber nonlinearity results in interactions among channels. The purpose of this chapter is to discuss the effects of dispersion and nonlinearity in terms of their origins and corresponding impairments. Those impairments lead to various system designs intended to minimize deleterious effects caused by dispersion and nonlinearity. This chapter begins with a discussion of dispersion in single-mode fibers, and types of optical fibers based on the value of dispersion. It is then followed by the effects of nonlinearity and approaches to minimize such effects, in Section 2.2. The discussion of system configurations based on the types of transmission optical fiber is presented in Section 2.3. The benefits and trade-offs on different system configurations are also explained.