Clock recovery challenges in DSP-based coherent single-mode and multi-mode optical systems

We present an analysis of clock recovery algorithms in both polarization division multiplexing systems and mode division multiplexing systems. The impact of inter-polarization time skew and polarization mode dispersion in single-mode fibers, as well as the combined impact of mode mixing and mode group delay spread in multi-mode fibers under different coupling regimes are investigated. Results show that although the clock tone vanishing has a known solution for single-mode systems, in multi-mode systems even for low group delay spread, strong coupling will cause clock tone extinction, making it harder to implement an effective clock recovery scheme

Experimental Characterization of 10 x 8 GBd DP-1024QAM Transmission with 8-bit DACs and Intradyne Detection

We experimentally investigate the transmission of 10 × 8 GBd DP-1024QAM over full Raman amplified low-loss fiber spans. For multicarrier systems using 8-bit DACs, a record achievable information rate of 15.7 bit/symbol is observed after 200 km using standard intradyne detection

Frequency offset estimator for digital optical coherent receivers

Orientadores: Aldário Chrestani Bordonalli, Júlio César Rodrigues Fernandes de OliveiraDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de ComputaçãoResumo: Sistemas de comunicações ópticas coerentes digitais permitem a utilização de formatos de modulação que carregam informação através de fase, amplitude e polarização do sinal óptico. Com o processamento digital dos sinais ópticos, é possível compensar as distorções inerentes à transmissão óptica, bem como realizar o sincronismo entre transmissor e receptor. Assim, junto ao avanço da eletrônica digital, a transmissão e recepção de sinais a centenas de gigabits por segundo se torna possível. Dentro desse cenário, os métodos comuns para a estimação de fase da portadora que chega ao receptor possuem baixa tolerância à dessintonia em frequência entre a portadora transmitida e o laser oscilador local. Nesta dissertação, é proposto e experimentalmente demonstrado um método de estimação de desvios de frequência de alimentação direta, com amplo alcance de estimação, eficiente, no ponto de vista de hardware, e compatível com os requisitos definidos pelo Fórum de Interconexões Ópticas (OIF ¿ Optical Internetworking Forum). Resultados obtidos experimentalmente mostram que o método proposto possui alta tolerância à assimetria espectral causada por filtragens no sinalAbstract: Digital coherent optical systems allow the use of modulation formats that carry information through optical signal phase, amplitude and polarization. With digital processing of optical signals it is possible to compensate for distortions associated with optical transmission, as well as to perform timing and carrier synchronization. Thus, by also taking into account the current high speed electronic progress, transmission and reception of signals at hundreds gigabits per second has became possible. In this scenario, common carrier phase estimation methods have low tolerance to frequency offsets between transmitted carrier and local oscillator laser. This dissertation proposes and experimentally demonstrates a hardware-efficient, feed-forward, wide-range frequency offset estimator, compliant with Optical Internetworking Forum (OIF) requirements. Experimental results show that this method has high tolerance to the spectrum asymmetry caused by signal filteringMestradoTelecomunicações e TelemáticaMestre em Engenharia Elétric