This chapter deals with coded modulation and impairment compensation techniques in optical fiber communication. Probabilistic shaping is a new coded modulation technology, which can reduce transmission power by precoding, reduce bit error rate and improve communication rate. We proposed a probabilistic shaping 16QAM modulation scheme based on trellis coded modulation. Experimental results show that this scheme can achieve better optical SNR gain and BER performance. On the other hand, in order to meet the demand of transmission rate of next generation high speed optical communication systems, multi-dimensional modulation and coherent detection are sufficiently applied. The imperfect characteristics of optoelectronic devices and fiber link bring serious impairments to the high baud-rate and high order modulation format signal, causes of performance impairment are analyzed, pre-compensation and receiver side’s DSP techniques designed for coherent systems are introduced.
Part of the book: Fiber Optics