Optical Fiber Telecommunications VIB: Chapter 9. Optical OFDM and Nyquist Multiplexing (Optics and Photonics)

New pulse-shaping techniques allow for optical multiplexing with highest spectral efficiencies. We introduce the general theory of orthogonal pulse-shaping and then discuss with more emphasis the orthogonal frequency division multiplexing (OFDM) and Nyquist frequency division multiplexing schemes. Subsequently, we show that rectangularly shaped pulses as used for OFDM can mathematically be treated by the Fourier transform. This leads us to the theory of the time-discrete Fourier transform (DFT) and to a discussion of practical implementations of the DFT and its inverse in the optical domain. The chapter is concluded with exemplary implementations of OFDM transceivers that relay either on direct pulse-shaping or the DFT approaches.