Investigation On Crosstalk Characteristics Of Multi-Channel All-Optical Format Conversion

All-optical signal processing can overcome the limit of electronic bottleneck oftraditional optical-electrical-optical signal processing technology and decrease the powerconsumption greatly, and has received more and more attention in recent two decades. As weknow, dense wavelength division multiplexing (DWDM) technology is widely exploited inhigh speed and high capacity optical networks, so multi-channel parallel signal processingtechnology is the key for the applications of all-optical signal processing. But there is a basicproblem for multi-channel all-optical signal processing—crosstalk. Supported by theNational973project—Research on mechanism of ultrafast spectrum transformation andcontrolling, and integrated chip for multi-channel all-optical format conversion, we havedone research on the nonlinear and linear crosstalk of multi-channel format conversion.Research contents and main research results are listed as follows:(1) Based on literatures home and abroad, the significance of the multi-channelall-optical signal processing has been clarified. Many schemes of multi-channel all-opticalsignal processing reported recently have been analyzed. The problem of crosstalk formulti-channel all-optical signal processing is also pointed out.(2) The propagation equation for the optical field and the rate equation for the carrierdensity in SOA are derived for analyzing the operational principle of all-optical formatconversion. The operational principle of delay interferometer is introduced. The threeschemes to realize multi-channel all-optical signal processing which are based on SOA andDI, PM and DI, DI respectively are analyzed theoretically.(3) The scheme of two-channel NRZ-to-RZ format conversion based on SOA and DI issimulated. The impact on crosstalk caused by the parameters such as the wavelength of theclock signal, the wavelength of the NRZ signals, the power of the clock signal, the channelspacing of the NRZ signals, FSR of DI, the injection current of SOA and so on is analyzed.The theoretical results are verified by the experiments of two-channel format conversion andfour-channel format conversion.(4) The scheme of multi-channel RZ-to-NRZ format conversion based on DI isanalyzed theoretically. The suppression effect of the band-pass filter on ripple is analyzed.The relationship between the ripple magnitude and the bandwidth of the band-pass filter is also analyzed. Two-channel and four-channel RZ-to-NRZ format conversions based on DIare simulated and the relationship between the ripple magnitude and the channel spacing isobtained. The conclusion was made that the ripple and the crosstalk will be smaller withmore channel interval. In addition, the linear crosstalk can be neglected when the channelspacing is240GHz or above.