Study On Key Technology In Ultrahigh-Speed OTDM System

With the quick development of internet service such as cloud data storage, and online high definition video, they propose explosive demand for high speed backbone network. It has drawn much attentions of the technique to realize ultra-high-speed, ultra-long transmission. As one of the effective techniques for Tbit/s transmission, optical time division multiplexing (OTDM) technique has been extensively and profoundly studied. Under the supports of the National High Technology Research and Development Program of China (863Program), No.2007AA01Z258, this thesis is devoted to investigate key technique of ultra-high-speed OTDM transmission by theory, simulation and experiment. The research contents consist of the coherence of broaden spectrum, mechanism of spectrum modulation, dispersion map design for100km transmission, clock enhancement, demultiplexing solutions based on EAM and highly nonlinear fiber, all optical wavelength exchange. The main innovative research efforts are summarized as follows:1. The process of supercontinuum generation pumped by unchirped sech pulse, Gaussian (m=1) and super-Gaussian (m=2) in HNLF have been analyzed. It consists of the degree of coherence change when optical wave breaking occur, under different input noise and sech pulse with different chirp. The coherence change laws of the supercontinuum generation under different parameters are summarized by simulation.2. The evolutional waveforms and spectrograms of sech, Gaussian pulse (m=1) and super-Gaussian pulse (m=5) generated in normal dispersion region of high nonlinear fiber were numerically studied. The results indicate that the tail at both front and back edge of the pulse not only affects spectrum broadening, but also the flatness of supercontinuum. The chirp of pump pulse has little impacts on the10dB width of generated supercontinuum. The pulse with high power, steep edge and small tail is preferable to generate wideband and flat supercontinuum.3. Symmetric strong dispersion map is adopted for160Gbit/s OTDM100km transmissions, which could precisely compensate the dispersion and its slope, at the same time the intra-channel nonlinear effects is suppressed. Under the guidance of theory results, dispersion map is designed and simulated for160Gbit/s OTDM100km transmissions. At last, it is experimentally studied and verified which keep for over two hours error free status is.4. It is studied and analyzed the relationship between amplitude and each order of clock proportion in160Gbit/s OTDM signals. Based on cascaded EAM and PPL, the proposed setup could simultaneously realize clock enhancing and demultiplexing, which has been experimentally verified. Experimental results show that the power of clock has been enhanced about3dB with the help of proposed setup.5. A structure that bi-directionally using HNLF is proposed for80Gbit/s OTDM demultiplexing, which has been experimentally verified. The proposed setup not only realize two10Gbit/s demultiplexing from a single wavelength80Gbit/s OTDM signal, but also simultaneously demultiplex and regenerate two10Gbit/s from a degraded160Gbit/s (80Gbit/s×2) OTDM/WDM signal. This reduces the number of demultiplexer to half. It is studied the demultiplexing and regenerating theory of nonlinear optical loop mirror in consider of nonlinear polarization rotation, which is also experimentally verified. Experimental results show that the eight base signal can be demultiplexed respectively from a degraded80Gbit/s OTDM signal and they are all error-free.6. Two structures have been proposed to realize wavelength exchange and2R between two degraded OTDM signals. One is based on self-phase modulation (SPM), the other is based on cross-phase modulation (XPM) in HNLF. Both of them have been experimentally verified. The experimental results show that the two data signals with different wavelength can simultaneously exchange their wavelength and regenerate the degraded signal. The regenerated eye diagram is open, and demultiplexed signal can be error-free respectively. The way based on SPM has the merits such as no need for extra optical sources and the setup is simple and can be easily realize. The way based on XPM has the merits such as no strict condition for wavelength interval and have a flexible choice of wavelength interval. However, it needs two extra optical sources.