A type of an interleaver with tunable bandwidth ratio for a dense wavelength division multiplexing (DWDM) system is proposed, which integrates a nested ring resonator with a Mach–Zehnder interferometer. The merits of the interleaver are its structure simplicity and the ultralarge tunability on bandwidth ratio. Based on the coupled-mode theory, the effects of essential parameter changes on the output waveforms have been analyzed. According to the theoretical analysis and simulation results, the bandwidth ratio is more determined by the coupling efficiency while the bandwidth is controlled by the optical length of the ring resonator. It was found that the bandwidth ratio is adjustable and varies between 1.5 and 10.5. Therefore, the interleaver can provide important implications for the DWDM system.
We theoretically investigate the generation, transmission and detection of the label signal in the optical SCM label switching system and clarify that the degradation of the label signal results from the fiber chromatic dispersion and the incomplete filtering out of the payload carrier. Our theoretical results show that the signal degradation is mainly caused by the fading effect and the expansion of the code edges. We also quantitatively analyze these theoretical results. The deep suppression of the optical carriers at receiver can greatly reduce the fading effect, and the electrical filtering and heterodyne detection techniques can improve the performance of the label signal. The time shift of the code edges leads to the closure of the label codes, which greatly limits the transmission distance as well as the radio frequency to generate the label subcarriers especially for the label with a high bit rate. SSB SCM can not only eliminate the closure of the label codes, but also reduce the fading effect. To our knowledge, this is the first time to develop a detail theoretical model to well explain the experimental results for SCM label switching systems.