| The development of advanced multilevel modulation and detection technologies is important for enabling efficient lightwave transmission of high-bit rate services, such as 40G Synchronous Optical Network (SONET/SDH) and 100G Ethernet. In this dissertation, we proposed and experimentally demonstrated several modulation and detection techniques for different optical modulation formats.;Optimal duobinary was achieved by optimizing LPF, transmitter and receiver bandpass filter, which gains 4.4 dB better receiver sensitivity compared with conventional duobinary. The optimum RZ-duobinary was demonstrated and its performances of receiver sensitivity, fiber chromatic dispersion tolerance, and self-phase modulation nonlinearity tolerance were compared with NRZ-duobinary's. Surprisingly, and contrary to the case of on–off keying, we find the NRZ pulse shape to be superior, compared with RZ, for duobinary transmission in all the cases that were studied.;A new DPSK demodulation scheme employing a frequency discriminator filter followed by direct detection (FD-DD) was proposed, which achieved a 1.2 dB better sensitivity compared with NRZ-OOK. DQPSK operating at 20 Gb/s doubles the spectral efficiency. Our proposed FD-DD demodulation scheme offers 2 times better chromatic dispersion tolerance than conventional delay interferometer followed by balanced detection (DI-BD) scheme. FD-DD demodulation scheme for PolMux DQPSK operating at 40 Gb/s not only quadruples the spectral efficiency of NRZ-DPSK, but also maintains roughly the same chromatic dispersion tolerance of a 20 Gb/s DQPSK.;This research work improves system performances for more efficient next generation fiber communication. |
