The steady growth in data traffic demand in optical fiber networks has propelled researches in various fields from optical and electrical components to modulation formats and digital signal processing. The motivation is always to find the right combination of these technologies to make an optical transmission system more robust and future proof. Orthogonal frequency division multiplexing (OFDM) is an advanced modulation format which was first proposed for fiber optic communication in 1996. Since then OFDM has been investigated for a wide spectrum of applications from access to metro and long-haul fiber communication. For all the cases, the tolerance of OFDM systems towards transmission impairments both linear and nonlinear and the remedy to these impairments together with other OFDM related issues are of major concern.