| In this dissertation, new approaches for all-optical wavelength conversion, all-optical on-off keying (OOK) to differential phase-shift keying (DPSK) format conversion and all-optical DPSK regeneration are proposed and analyzed theoretically.;In order to improve the wavelength conversion bandwidth of cross polarization modulation (XPoM) in a semiconductor optical amplifier (SOA), a novel conversion scheme named differential cross-polarization conversion (DXPoM) is proposed, and it is realized by simply adding an extra birefringence delay line in the conventional XPoM. In this part, both the large-signal simulation and small-signal model of DXPoM are developed, and they successfully predict results that agree with experimental outcomes. The large-signal simulation of DXPoM evidently shows the performance improvement and match well with experimental results. The small-signal model gives more comprehensible and intuitive physical insight of DXPoM.;For format conversion, using the cross-phase modulation (XPM) effect in a nonlinear photonic crystal fiber (PCF), the conversion of OOK-to-DPSK is achieved at 40 Gb/s for the first time. Because the PCF has high linear birefringence, and its birefringent axes remain for entire length, launching the probe at 45° relative to the birefringence axes of the PCF and having the pump-probe detuning (PPD) greater than ∼ 6 nm can realize polarization-insensitive XPM-based conversion. The polarization- and PPD-dependent nonlinear phase shift is investigated theoretically. It indicates improper nonlinear strength could generate insufficient phase shift (< pi) in XPM-based conversion, and the amplitude noise (AN) of an OOK pump will also be converted into the phase noise (PN) of the converted DPSK signal, the penalties induced by these issues are discussed analytically as well.;Because the DPSK format carries information on the phase domain, it is influenced by both AN and PN. Therefore, except amplitude regeneration, the regeneration of DPSK signals has to preserve phase information or eliminate PN. A novel all-optical phase noise averager (PNA) is proposed to reduce residual PN in the DPSK transmission system with phase-preserving amplitude regenerators. It can increase the correlation between the PNs of neighboring bits and greatly reduce the differential PN in the transmission system. Considering various PN, the multiple PN averaging effect is investigated, and the effective PN is convergent regardless of the transmission distance. Furthermore, theoretical bit error rates of the DPSK format with various regeneration schemes is presented for comparison. |
