Studies On Key Technologies Of Optical Signal Processing With Advanced Modulation Formats In Optical Access And Optical Switching

Thanks to the flexible bandwidth allocation, resource conflict resolution, and enhancing the rate and the spectrum utilization rate of optical access and optical switching, optical signal processing with advanced modulation formats is considered as the important supporting technology for deploying the next generation optical networks. For example, in wavelength division multiplex passive optical network (WDM-PON) and orthogonal frequency division multiplexing passive optical network (OFDM-PON), the technology of optical signal processing based on reflective semiconductor optical amplifier (RSOA) or other nonlinear medium can realize the colorless optical network unit (ONU), and improve the resources utilization rate. And the optical signal processing with advanced modulation formats in flexible optical switching can help to achieve the bandwidth adjustment, modulation multiplexing, noise suppression, conflict resolution and other functions, and realize the objective of optical switching with colorless, directionless, contentionless and gridless. Currently, the optical signal processing with advanced modulation formats in optical access and optical switching is a hot research topic.Supported by National863project, National Natural Science Foundation of China (NSFC) project, and doctoral education fund, this dissertation focuses on the above-mentioned key technologies. With the help of the nonlinear effects in semiconductor optical amplifier/High nonlinear fiber (SOA/HNLF) based optical signal processing technologies, several novel schemes are proposed and experimentally demonstrated, including the RSOA modulation bandwidth improvement, the scheme of WDM-RoF PON, format conversion and encryption/decryption. The research achievements and contributions are as following:Firstly, to overcome the bandwidth limitation of RSOA, a novel wavelength re-modulation scheme for WDM-PON system using10Gbit/s NRZ signal in downstream and5Gbit/s4PAM signal in upstream was proposed. Based on the simulation results, the4PAM signal has better performance when the bit rate reaches5Gbit/s due to the multilevel needs narrower modulation bandwidth than NRZ signal, and the BER can reduce two orders of magnitude at same received power.Secondly, in order to strengthen the information security of optical network, we propose a scheme of all-optical encrypting and deciphering of8PSK signal based on FWM effect in SOAs. Simulation results show that the scheme does not introduce physical damage, and the security is enhanced due to the longer key information.Thirdly, the advanced modulation signal is very sensitive to nonlinear phase noise. In order to solve this problem, the theoretical model of that the signal is affected by the nonlinear phase noise in the transmission process is established, and a scheme of noise suppression based on cross phase modulation (XPM) in SOA for QPSK signal is proposed, the simulation results show that a power penalty2.3dB is improved after QPSK regeneration.Fourthly, in order to meet the demand of adaptive bandwidth in optical switching, a scheme of parallel multichannel format conversion from QPSK to BPSK signal based on four wave mixing (FWM) in symmetric highly nonlinear fiber loop (S-HNLF-L) is proposed. Simulation results show that the received sensitivity increase3dB after the QPSK converted to BPSK signal. In addition, we proposed a scheme of all optical format conversion from16QAM to QPSK signal using FWM in SOA. Theoretical analysis and simulation of the format conversion scheme is conducted to validate the feasibility of the proposal.Fifthly, in order to improve the utilization of spectrum resource in elastic optical networks. A scheme of modulation multiplexing from OOK signal to QPSK and16QAM signal based on XPM in SOA is proposed. The spectral efficiency of QPSK and16QAM signal incrased by two times and four times.