Study On Key Techniques Of High-Speed Optical Time-Division Multiplexing Systems

With the rapid advances of the commutative multi-media services, it becomes evident that the communication capability is being increased at exponential speed, so the higher demands are put forward for the transmission band-width nowaday. It has become a hotspot in the field of telecommunication research throughout the world, which is the all-optical network communication associated the ultra-high-speed optical-time-division-multiplexing (OTDM) technology with the dense-wave-division-multiplexing (DWDM) technology, in particular, the ultra-high-speed OTDM technology is the first choice for the ultra-high-speed and ultra-large-capability communications system (Tbit/s). Compared with DWDM, OTDM has at least four advantages. First of all, in OTDM the interference among different channels can be avoided due to the single wavelength. Consequently, the high level of the stabilization of the wavelength is not necessary. Secondly, DWDM could only provide bandwidth in wavelength level while OTDM could provide more flexible and finer bandwidth. Thirdly, OTDM make it easy to realize statistical multiplexing. Finnally, ODSP (Optical Digital Signal Processing) could be introduced in OTDM since the RZ code is used here.In this work, all optical demultiplexing based on SOA interferometer switches, wavelength conversion based all optical switches in OTDM communication systems as well as all chromatic dispersion monitoring are studied theoretically, which include:(1). The pico-second optical pulse sequence oriented SOA system simulative model is established. A set of simulative schemes, which is developed and optimized gradually, is put forward. The simulative scheme is the theoretical foundation for the OSP (Optical Signal Processing) of SOA accounted with the material dispersion, the gain dispersion and the second nonlinear effect as well as the third nonlinear effect.(2). The average linewidth enhancement factor and the component effective linewidth enhancement factor are introduced for the performance analysis of interferometer all optical switches based on cross phase modulation of SOAs. The average linewidth enhancement is the latent physical attribute of SOA that is the groundwork to investigate the OSP based on cross phase modulation of SOA. The enhancement integrated contrast ratio (EICR) and the conjugate integrated contrast ratio (CICR) are introduced to investigate the general integral attribute and the isolate degree between down and pass signals of all optical switches, respectively. The simulative studies on three pump/probe wavelength configurations of UNI are shown. The gain-transparent all optical switches are investigated in detail where the two-wave coupling model is used that is established by J.M.Tang and K.A.Shore. The broadband and strong signal model built by M.Y.Hong is used in the simulation of same frequency and far wavelength all optical switches. The effect done to the switch window by the clock optical pulse energy, the clock optical pulse width, the time delay and the length of SOA are investigated, respectively. The results show that in the condition of gain-transparent the relationship between the phase-shift and the pulsation of the gain of near wavelength all-optical switch is relatively weak and then the xICR is high. The cause of formation of switch window double-peak effect in the condition of large phase shift and long time delay is given and the all-optical switch data pattern effects due to CDP (the carrier density pulsation) is disclosed.(3). The high speed, strong pulse OTDM signal FWM effect oriented simulative study is performed where the separate disturbing model built by A.Mecozzi and J.Mork is used. Since the pump signal and conjugate signal can be expressed separately, it is realized to calculate the conversion efficiency accurately and to select the appropriate filter bandwidth. The results show that the FWM conversion efficiency is unsensitivity to the pump pulse width no matter in the condition of single pulse or of the pulse train. The on-off ratio is keen to the pump pulse width in the condition of single pulse. In the condition of pulse train the on-off ratio is becoming not as keen as that of single pulse and at the same time the on-off ratio itself is decreasing dramatically. We have modified the definition of data pattern effect of N.K.Das and introduced the energy pulsations of output signal train as well as the conjugate signal pulse. The results show that an appropriate temporal residual is necessary for the application of demultiplexing.(4). High-speed signal has limited chromatic-dispersion window. The traditional low speed dispersion map configuration cannot meet the requirment high-speed signal transmission. We provide and investigate two chromatic dispersion monitoring methods from the perspective of CD temporal attribute and CD spectral attribute. The results shown that the former has the advantages of high monitoring range and monitoring sensitivity at the cost of complicated diff-delay interferometer array. The latter is configuration brief and operation simple, but a high sensitivity of O/E detector is required.The maning of OTDM is comprehensive. Our present work only involves two key techniques and both of them are localized within physical layer. Except for the signal generation, multiplexing, dispersion compensation and all optical 3R regeneration in physical layer, there are many problems required to be overcomed, such as time-slot assignment, all optical address recoganization, the design of multiplexing node and switching node.