Research On Several Key Techniques Of ROF And Coherent Communication

Several novel key techniques and research results in radio over fiber and coherent communication have been demonstrated in this dissertation. The cost efficient scheme to generate millimeter wave and the corresponding radio over fiber system with wavelength reuse technique has been theoretically and experimentally investigated. The electrical optical orthogonal frequency-division multiplexing (OFDM) network, the all optical wavelength conversion technique in radio over fiber system and optical packet switch networking, the all optical OFDM and Nyquist-wavelenth division multiplexing (Nyquist-WDM) technique with coherent detection and the long haul optical transmission network of100G,400G and1T have been experimentally demonstrated.1. We have proposed a novel scheme to generate millimeter-wave and corresponding radio-over-fiber (ROF) system by using frequency-quadrupled up-conversion modulation technique for the first time, and theoretically and experimentally investigated three different schemes to generate optical millimeter-wave and wavelength reuse for up-link connection in the radio-over-fiber systems. In the first and second scheme, the optical millimeter waves (mm-wave) were generated via a LiNbO3(LN) Mach-Zehnder modulator (MOD) with the double sidebands (DSB) scheme to generate the mm-wave with repetitive frequency of40GHz with20GHz RF signal. In scheme III we have experimentally demonstrated a new scheme to generate optical mm-wave by a multiple double-frequency technique to further reduce the overall cost.2. OFDM, which takes the advantages from its high spectral efficiency and the resistance to variety dispersions including chromatic dispersion (CD) and polarization-mode dispersion (PMD) in optical communication, has recently received much attention in long distance optical network. In this paper, we have introduced the OFDM technique into the60GHz ROF and WDM-PON for the first time. We have experimentally generated optical orthogonal frequency division multiplexing (OOFDM) signals by using a phase modulator (PM) to reduce the peak-to-average power ratio of OFDM signal. The generated OOFDM signal can tolerate higher nonlinear effects in fiber than that generated by an intensity modulator because of its lower PAPR.3. We have theoretically and experimentally investigated all optical wavelength conversion of optical OFDM based on single pump four-wave mixing in a semiconductor optical amplifier (SOA) for the first time. Experimental result shows that the newly converted wavelength signals copy the original OFDM signals and its conversion efficiency of the converted signals are proportional to the amplitudes of the input signal and the pumps under the condition of SOA non-saturation, the polarization angle between the pump and signal lightwave affects the optical power of the converted OFDM signal.4. With the rapid growth of data-centric services,400Gb/s or1Tb/s per carrier or per channel is tend to be the next target of the bit rate for optical long-haul (LH) transmission system after100Gbit/s Ethernet. The all-optical OFDM technique has been introduced into400G transmission system for the first time,432Gbit/s optical OFDM (O-OFDM) QPSK transmitter has been proposed and experimentally demonstrated. Two continuous lightwave has been generated by external optical carrier suppression modulation.54Gbaud or216Gbit/s QPSK signal on each peak has been realized by IQ modulation and polarization multiplex. After transmission over400km standard single-mode fiber (SMF), the measured BER is smaller than2×10-5. In the meantime,400Gbit/s optical packet switching (OPS) technique has been proposed and experimentally demonstrated how to realize for the first time. The key techniques for packet generation, colorless detection, label erasure, and wavelength conversion have been demonstrated. Low-power penalty (<1.5dB) and high-speed rate operation (payload up to448Gbit/s) have been realized in our optical network.5. Two novel schemes to generate coherent superchannel sub-carriers with subcarrier spacing of25GHz are proposed and experimentally demonstrated with coherent detection for the first time. By using these coherent optical subcarriers, we have successfully generated10Tbit/s (112×100Gbit/s) single channel no guard-band optical OFDM polarization multiplexing QPSK signal with the optical signal noise ratio greater than20dB (0.1nm bandwidth for each subchannel).; The generation of21coherent optical subcarriers with fixed frequency of25GHz is proposed and experimentally demonstrated. Using these optical subcarriers, we have successfully generated1.96Tbit/s (21x100Gbit/s) optical orthogonal frequency multiplexed (PM-OFDM) polarization multipled QPSK optical superchannel signal with optical signal noise ratio of each subchannel larger than30dB (0.1nm bandwidth).6. We introduce an ’ultra-dense’concept into next-generation WDM-PON systems which transmits Nyquist-WDM uplink with centralized uplink optical carriers and digital coherent detection for future access network requiring both high capacity and high spectral efficiency fot the first time.80-km standard single mode fiber (SSMF) transmission of Nyquist-WDM signal with13coherent25GHz spaced wavelength shaped optical carriers individually carrying100Gbit/s polarization-multiplexing quadrature phase-shift keying (PM-QPSK) upstream data have been experimentally demonstrated with negligible transmission penalty. Performance of traditional coherent optical OFDM scheme and its restrictions on symbol synchronization and power difference are also experimentally compared and studied.