Orthogonal frequency-division multiplexing in fiber-optic communication

Optical transmission using orthogonal frequency-division multiplexing (OFDM) is extensively studied in this work. Applications in optical access networks, long-haul coherent optical polarization-division multiplexing (PDM) systems and coherent optical spatial-division multiplexing (SDM) systems are discussed within the scope of the dissertation. In the access network (downlink 40 Gbit/s and uplink 10 Gbit/s), system capacity of supported optical network units (ONU) using direct detection and coherent detection are investigated considering fiber nonlinearity mitigation methods and coded modulation. In the uplink, system concepts for solving the uplink time synchronization and carrier frequency offset among ONUs are presented. A field transmission experiment is carried out in Berlin and demonstrates a 37.5-km urban OFDM access network using laser-free ONUs with dynamic bandwidth allocation and Trellis Coded Modulation. Extensive research is conducted in the coherent PDM-OFDM system, algorithms for compensating different system distortions including sampling frequency offset, carrier frequency offset, laser phase noise, fiber nonlinearity, and the preamble-based channel equalization are analyzed and validated through numerical simulations. The ever-growing capacity demand leads to investigation of transmission through few-mode fiber that enables the spatial dimension to be exploited. 41.6 Tbit/s (net data rate of 16.8 Tbit/s) full C-band SDM OFDM transmission through 12 spatial and polarization modes over 74.17 km few mode fiber is demonstrated to illustrate the feasibility of applying OFDM in the SDM transmission.