Studies On Key Technologies Of Optical Signal Processing Based On Soa/Rsoa In Next Generation Optical Access Networks

The next generation optical access networks (NG-OAN) will support higher bandwidth, larger coverage, higher bandwidth efficiency and multi-access operations, where the fiber acting as the main transmission medium attaches to the users directly. The wavelength division multiplex (WDM)-PON combining WDM technology and PON technology inherently, is able to support flexible access of diversified services, high bandwidth, good scalability, being transparent to the protocols and bit-rates, which becomes a research focus of the NG-OAN.Nevertheless, there remain a number of key issues to be resolved in the WDM-PON, such as poor wavelength adaptability of the optical network unit (ONU), small bandwidth of the ONU and incompatibility of WDM-PON and radio over fiber (RoF). Nowadays, the semiconductor optical amplifier (SOA) and reflective semiconductor optical amplifier (RSOA) based optical signal processing technologies have been considered as one of the most promising solutions for these issues.Supporting by two National Natural Science Foundation of China (NSFC) projects, this dissertation focuses on the above-mentioned key technologies. With the help of the SOA/RSOA based optical signal processing technologies, several novel schemes have been proposed and experimentally demonstrated, including the novel schemes of colorless ONU, RSOA modulation bandwidth improvement and photonic millimeter wave generation. The research achievements and contributions are as following:Firstly, based on the experimental tests of the RSOA and SOA wideband steady-state numerical model, a numerical model for RSOA is established, considering the ASE noise, the inter-distortion between the backward light and the forward light, gain saturation and the dependence of carrier spontaneous lifetime on carrier density. By optimization and validation via experimental tests, the numerical model is capable of simulating the dynamic characteristics of RSOA and calculating fiber-to-fiber gain, ASE noise and small signal electronic-to-optical conversion (E/O) response accurately.Secondly, a scheme of increasing the3-dB bandwidth of RSOA by optimizing the size of active region and physical parameters is proposed and simulated. The simulation results indicate that the3-dB bandwidth of RSOA increases to-10GHz by optimizing the size of the active region, confinement factor, current density and temperature and so on.Thirdly, a scheme of increasing the bandwidth of the WDM-PON uplink by utilizing the Mach-Zehnder interferometer (MZI) is proposed and simulated. The MZI serving as an optical offset filtering can enlarge the bandwidth of the uplink by compensating for the severe bandwidth limitation imposed by the RSOA. The simulation results show that the bandwidth of the uplink can support the transmission of lOGbps no-return-to-zero (NRZ) signals over25km standard single-mode fiber (SMF).Fourthly, a proposed colorless ONU with a fiber Bragg grating (FBG)-based self-seeded RSOA transmitter is demonstrated by experiments. The FBG acting as a wavelength selector is tuned to select the operating wavelength for the colorless ONU adaptively. The self-seeded RSOA transmitter can provide a high power, directly modulated source and obviates the need for centralized light source. The performance of the colorless ONU is evaluated by optimizing the reflectivity of the FBG, the3-dB bandwidth of FBG reflection spectrum and the injection optical power and the DC bias of the RSOA. A2.5Gbps upstream is achieved over a30km SMF using the optimized colorless ONU.Fifthly, we have proposed and simulated a scheme of photonic millimeter wave (mm-wave) signal generation employing non-degeneration four wave mixing (ND-FWM) in SOA. The proposed scheme can be applied to the NG-OAN which combining WDM-PON technology and RoF technology inherently. The simulation results indicate that the proposed scheme up-convert not only baseband NRZ signal and return-to-zero (RZ) signal but also intermediate frequency orthogonal frequency division multiplexing (OFDM) signal to the30-60GHz mm-wave signal.