All-optical devices for wavelength division multiplexing (WDM) and optical time division multiplexing (OTDM)

The performances of birefringence switching and XGM for wavelength conversion are studied. The probe signal has a fast conversion speed and a high modulation index in the birefringence switching wavelength-converted signal. Input probe pulses of 23.5ps at 1551nm are regenerated as 20.5ps pulses at 1556nm because of pulse shaping from the polarization switching characteristics. The high extinction ratio of probe signal suggests that this technique may be suitable for simultaneous data regenerations and wavelength conversion. The theoretical model for the temporal response of the birefringence switching and the XGM converters agrees with the experimental results.; For OTDM systems, we propose and demonstrate the polarization independent all-optical demultiplexing using orthogonal-pumps four-wave mixing (FWM) in a SOA. TDM demultiplexing of a 40Gb/s signal to a 10Gb/s with simultaneous wavelength shift of 8.2nm is successfully demonstrated. In the 10Gb/s to 2.5Gb/s, the power penalty for a BER of 10−9 varies between 3dB and 2dB for a large (23.7nm) and small (4.6nm) wavelength shifts, respectively. We also perform format conversion (NRZ to RZ) and 2R (retiming and reamplification) regeneration using orthogonal-pumps FWM in a SOA, operating at 2.5Gb/s.; We also conduct the feasibility study of using optical nonlinearities of silicon waveguide for optical switching. We report the measurements of nonlinear refraction and two-photon absorption (TPA) in a silicon waveguide at 1540nm. Nonlinear refraction in silicon is studied by measuring the spectral changes from self-phase modulation in the waveguide. The nonlinear refractive index coefficient is found to have a magnitude of 4 × 10−18 m2/W and it is possible to achieve a π phase change using 60W of peak-coupled power. The TPA coefficient of silicon is found to be 0.45cm/GW, which is much smaller than for InP/ InGaAsP waveguides because only phonon-assisted two-photon transitions are possible. The small magnitude of the TPA coefficient in silicon at 1550nm should ensure that TPA does not contribute to crosstalk in DWDM components at the optical powers normally employed in communications systems.