Optical OFDM Systems     

Abstract

Communication has four critical aspects: reach, bit rate, connectivity, and energy. Reach is the maximum distance a given communication system can achieve. Bit rate is the amount of information one can transmit in one second and is related to the frequency bandwidth. Connectivity is the ability of a system to connect with one or more devices, and energy is related to the amount of power needed for a system to perform. The design of such systems is a multi-objective problem with conflicting constraints. For instance, if one wants to increase the system's reach, one will expend more energy. To improve connectivity, one must sacrifice the bit rate per user. Fiber optics communications are the only system that can maximize all these aspects; they can operate at hundreds of gigabits per second over hundreds of kilometers of fiber and with high connectivity. Optical networks are broadly classified as access, passive, transport, and datacenter depending on the type of services provided, the reach, and the maximum bit rate delivered.  Different modulation formats are used in these networks. The Intensity Modulation-Direct Detection (IMDD) is the most used due to its simplicity. However it is not bandwidth efficient, and it is limited in bit-rate. More recently, Orthogonal Frequency Division Multiplexing (OFDM) has gained the attention of the scientific community and hardware developer companies. OFDM systems have many advantages over baseband signals; it is widely used in wireless systems, is very flexible regarding the use of their spectrum, and can expand the communication link bandwidth and mitigate some system nonlinearities.

In my talk, I will briefly present the research activities developed at the Telecommunication Laboratory at the Federal University of Espirito Santo in Brazil. Afterward, I'll give a short introduction to Orthogonal Frequency Division Multiplexing(OFDM) for fiber optical communication systems—the main advantages and drawbacks of such a technique for high-speed transmission. We start with the building blocks and all the acronyms from the telecommunications world, then show how these systems can operate.