Leonardo D. Coelho

Modeling nonlinear phase noise in differentially phase-modulated optical communication systems

Using an alternative approach for evaluating the Bit-Error Rate (BER), we present a numerical and experimental investigation of the performance of phase-modulated optical communication systems in the presence of nonlinear phase noise and dispersion. The numerical method is based on the well known Karhunen-Lo;eve expansion combined with a linearization technique of the Nonlinear Schr odinger Equation (NLSE) to account for the nonlinear interaction between signal and noise. Our numerical results show a good agreement with experiments.

Pulse shaping using the discrete fourier transform for direct detection optical systems

Different pulse shapes are presented as alternative to traditional (N)RZ pulses in communication systems using direct detection. The pulses are efficiently generated in the frequency domain using the discrete Fourier transform. The trade-off between spectral occupancy and eye opening is discussed and performance is evaluated by means of simulations.

Stereo multiplexing for direct detected optical communication systems

We propose a novel technique that allows simultaneous detection of two modulated optical sub-carriers. A proof-of-principle experiment is described and subsequently the performance at high data rates (111Gb/s) is assessed by simulations.

Transmission of 111 Gb/s on a 50 GHz grid Using single polarization, direct detection and Digital Subcarrier Multiplexing

Digital Subcarrier Multiplexing (DSM) allows simple direct detection of spectrally efficient multicarrier signals. We show through simulations that, by using DSM, the quality of DWDM transmission with 3 bits-per-symbol at 111 Gb/s is greatly improved.

Impact of PMD and nonlinear phase noise on the global optimization of DPSK and DQPSK systems

Using a global optimization algorithm, we maximize the reach of DPSK and DQPSK systems including PMD and nonlinear phase noise at data rates ranging from 5 Gbit/s to 230 Gbit/s.

Performance of Stereo Multiplexing in systems using direct detection with optimum dispersion maps

We present Stereo Multiplexing, a novel technique that permits simultaneous direct detection of two modulated optical carriers. This is accomplished by modulating the optical carriers with the difference and the sum of two signals. The linear performance of Stereo-multiplexed DQPSK signals is compared to single-carrier DQPSK and dual-carrier DQPSK. Subsequently, by means of simulations, the robustness of each format is compared after DWDM transmission of 55.5 Gb/s through 1040 km of SMF. This is done by searching the optimum dispersion map and input powers for each format and looking at the stability of the performance around the optimum. We show that the best performance and robustness is obtained by sharing the information between two carriers, and that Stereo is only 1 dB below dual-carrier NRZ-DQPSK. This small penalty can be tolerated if cost and complexity at the receiver side must be kept low.

Performance of Stereo Multiplexing in Single Channel and DWDM Systems Using Direct Detection with Optimum Dispersion Maps

We present Stereo Multiplexing, a novel technique that permits simultaneous direct detection of two modulated optical carriers. This is accomplished by modulating the optical carriers with the difference and the sum of two signals. The linear performance of Stereo-multiplexed DQPSK signals is compared to single-carrier DQPSK and dualcarrier DQPSK. Subsequently, by means of simulations, the robustness of each format is compared for single channel and DWDM transmission of 55.5 Gb/s through 1040 km of SMF. This is done by searching the optimum dispersion map and input powers for each format and looking at the stability of the performance around the optimum. We show that the best performance and robustness is obtained by sharing the information between two carriers, and that Stereo is only 1dB below dual-carrier NRZ-DQPSK. We discuss the penalty associated with designing a DWDM system based only on the optimization of transmission of single channel.