Stable multiwavelength lasing is demonstrated with a novel laser, in which a semiconductor optical amplifier offers optical gain and cascaded sampled fiber gratings serve as a comb filter. Five lasing lines are obtained with a fixed wavelength spacing of 0.8 nm. Optical power fluctuations among the lasing lines are improved by adjusting reflectivity profile through the cascade of two sampled gratings.

Intraband crosstalk contributions in three types of WDM cross-connect topologies based on the Benes architectures are identified. The crosstalk behaviours of the WDM networks are compared and discussed. It is demonstrated that the first-order crosstalk contributions are dominated by the crosstalk from the switching elements. The network scalability is analysed in terms of fibres, wavelengths and nodes. The results show that routing different wavelengths in each switching architecture in WDM cross-connect networks is a reasonable approach to achieve perfect performance in the presence of component crosstalk.

Ten-channel wavelength conversion is achieved by exploiting cascaded second-order nonlinearity in periodically poled LiNbO3 waveguides. No external pump input is required in the converter and conversion efficiency is improved due to the enhancement of pump and signal interaction. Approximate 70-nm conversion bandwidth is realized under pump power less than 25mW at 1550-nm band.

Impacts of residual facet reflection on the performances of wavelength converters based on semiconductor optical amplifiers (SOAs) are theoretically investigated. Residual facet reflection definitely degrades the converter performance. A probe signal feedback scheme is introduced to improve the wavelength conversion characteristics. With the probe signal feedback, the wavelength conversion parameters, including extinction ratio, frequency chirping and modulation response, can be enhanced, and the facet reflection limits are relaxed due to the enhancement of carrier-photon interaction.

Noninverted wavelength conversion has been demonstrated using Fabry-Perot semiconductor optical amplifiers (FP-SOAs), and its mechanism is theoretically analyzed. The noninverted behavior is dominated by the shift of gain spectrum in the FP-SOA. Increasing the input optical power suppresses the spontaneous emission and drives the gain spectrum toward the longer wavelength side due to the enhancement of carrier-photon interaction. The performance of wavelength converters is improved owing to the resonant effect at the probe wavelength and this type of converter provides an effective approach for wavelength conversion in the future broadband networks.