Studies On Key Technologies Of Ultrafast All-Optical Signal Processings

The optical communication system has advanced dramatically during these years. So far, extensive research and development have been done to realize ultra-fast transmission in optical fiber long-haul links and the single channel of 40Gbit/s became available commercially. Further development of the optical communication system is limited by the bottleneck between high transporting speed in the fiber link and low processing speed inside the network node. As a result, future optical network has been studied by many scientific communities. Ultrafast all-optical signal processings are significant enabling technologies for future optical networks, including all-optical wavelength conversion, optical logics, optical buffering and so on. Optical signal processings aim to resolve several critical problems in the future optical networks, such as all-optical switching, routing, and conflict settling.This dissertation focused on the key technologies of ultrafast all-optical signal processings based on semiconductor optical amplifier assisted Mach-Zehnder interferometer (SOA-MZI), such as ultrafast optical time division multiplexing, parameter optimization and polarization analysis of the SOA-MZI, separation of the header and pay load and so on.In Chapter 1, nonlinear effects of SO A are illustrated, which includes cross gain modulation (XGM), cross phase modulation (XPM), four wave mixing (FWM), and nonlinear polarization rotation (NPLR). The practical applications of all-optical signal processing such as all-optical logical gate, all-optical wavelength conversion, all-optical 3R, all-optical demultiplexing and all-optical buffer are also introduced. A novel optical time domain multiplexer (OMUX) based on graded index (GRIN) lens is proposed and experimentally demonstrated in Chapter 2. A 10Gbit/s return-to-zero (RZ) signal is upgraded to 160Gbit/s. The time-domain accuracy of the multiplexer is evaluated by analyzing the multiplexed 160Gbit/s signal. Experimental results validate the stability of the optical multiplexing behavior and the polarization insensitivity of the proposed multiplexer. The results also show the advantages of the OTDM multiplexer such as the flexible output signal speeds at output of different stages, the low insertion loss and the temperature and wavelength stability.Because there are many parameters in the all-optical signal processing unit, it is not easy to pinpoint the best operating point. A novel characterization method of parameter optimization is proposed in Chapter 3. "P·CR" is used to pinpoint the best operating point of the 80Gbit/s SOA-MZI self-synchronous clock extraction scheme.The influence of polarization effects is analyzed in Chapter 4. There are two situations of polarization influence. One is different polarization directions of different input signals and the other one is the polarization fluctuation of the input signal itself. The method of solving polarization-related problem is also proposed.In Chapter 5, a novel method of header and payload separation based on SOA-MZI scheme is proposed. Through numerical simulations, the validation and the operating characteristics of the proposal are investigated.