The Investigation Of High Quality Mm-Wave Signal Generation Without Optical Filter Based On The Integrated MZM

Due to the integration of the advantages of the extremely low loss, immune to electromagnetic interference and large available bandwidth of fiber communication and the mobile feature and flexible access of wireless communication, Radio over fiber (ROF) technology is regarded as a promising and attractive solution on the wireless access networks operating at the millimeter-wave (mm-wave) band. Over the past decade, ROF has been a research hotspot for the scholars both at home and abroad. In ROF system, the cost-effective and high quality generation of mm-wave is a key technology. Compared with the conventional electrical method, optical method is a preferable option for mm-wave generation.So far, three optical techniques have been proposed to implement the generation of mm-wave, namely, optical heterodyne, frequency up-conversion and nonlinear modulation of external optical modulator. Among these techniques, the last one has shown great potential for high purity and low phase noise mm-wave signal generation with low cost and simple configuration. For this technique, mm-wave generation without optical filter is an ideal scheme to further reduce the complexity and cost of system, especially for WDM-ROF system. In addition, fiber dispersion is an important influence factor for the transmission performance in ROF system. On one hand, fiber dispersion will lead to code interference because of walkoff effects. On the other hand, it also can lead to the periodical fading variation of the power of the generated mm-wave signal with transmision distance.Integrated MZM is composed of two or more sub-MZMs. Compared with single MZM, high multiplication factor and high quality mm-wave signal can be generated without optical filter if the parameters of integrated MZM are properly adjusted. In order to utilizing integrated MZM for quality mm-wave signal generation without optical filter, it is crucial to deeply understand the modulation chanracteristics of integrated MZM. The implementation principle of the main modulation techniques for the dual-electrodes MZM is derived in detail, and the structure and modulation characteristic of the two integrated MZMs are introduced in brief, which establishes the good theoretical foundation for mm-wave signal generation without optical filter based on the integrated MZMIn this dissertation, Utilizing the integrated Mach-zehnder modulator (MZM) and combining the theoretical analysis, four novel schemes for mm-wave signal generation without optical filter are proposed based on the nonlinear modulation of MZM, including one frequency quadrupling scheme and two frequency sextupling schemes and one frequency octupling scheme, and the feasibility of the proposed novel schemes are verified by simulation and experiment. At the same time, the influence of key factors such as bias drifting, modulation depth or modulation voltage, nonideal phase difference of RF driven signal applied to two sub-MZMs of the integrated MZM, imperfect extinction ratio of sub-MZM or integrated MZM on the quality of the generated optical mm-wave and mm-wave signal is thoroughly discussed and analyzed, and the transmission performance of the generated optical mm-wave distributed over fiber is also investigated and the performance of different cases of the related schemes is also compared. Furthermore, the pervious: octupling scheme is further investigated. In addition, the characteristics of modulation instability (MI) in a fiber grating are thoroughly discussed and analyzed with analytical method.The main research works and novelties of this dissertation are as follows:1). A novel frequency quadrupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of two sub-MZMs is proposed, and two parameters, namely optical sidebands suppression ratio (OSSR) and radio frequency spurious suppression ratio (RFSSR) are defined to evaluate the quality of the generated optical mm-wave and mm-wave signal. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical and electrical filter when an integrated MZM composed of two sub-MZMs with extinction ratio of 30dB is utilized. Based on the analytical expression from the derivation, the influence of bias drifting, imperfect extinction ratio and modulation depth of sub-MZMs is discussed and analyzed. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR higher than 35dB is achieved. RFSSR with 30.0dB and 24.6dB is achieved for BTB and after transmission over 40km fiber, respectively. No obvious linewidth variation of the generated frequency quadrupling mm-wave signal is demonstrated after transmission over 40km of fiber.2). A frequency sextupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of two sub-MZMs is firstly proposed, to our best knowledge. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical and electrical filter when an integrated MZM composed of two sub-MZMs with extinction ratio of 30dB is utilized. Utilizing VPI software, the influence of nonideal RF modulation voltage and nonideal phase difference of RF driven signal applied to sub-MZM of the integrated MZM is discussed and analyzed, and the performance of the generated optical mm-wave signal after transmission over fiber is investigated. Furthermore, the performance of two cases for the proposed scheme is also compared. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR higher than 29dB is achieved. RFSSR both exceeds 19 dB for BTB and after transmission over 40km fiber. No obvious linewidth variation of the generated frequency sextupling mm-wave signal is demonstrated after transmission over 40km fiber.3). Another frequency sextupling scheme for mm-wave signal generation without optical filter based on an integrated MZM composed of three sub-MZMs is proposed. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical or electrical filter when an integrated MZM composed of three sub-MZMs with extinction ratio of 30dB is utilized. Based on the analytical expression from the derivation, the influence of nonideal phase difference of RF driven signal applied to sub-MZM of the integrated MZM, imperfect extinction ratio of integrated MZM on OSSR is discussed and analyzed, and OSSR of two cases of the proposed scheme is also compared. In experiment, high-quality optical mm-wave signal and mm-wave signal are obtained. The OSSR about 31dB is achieved. RFSSR both exceeds 20dB for BTB and after transmission over 40km fiber. After transmission over 40km fiber, no obvious linewidth variation of the generated frequency sextupling mm-wave signal is demonstrated.4). A novel frequency octupling scheme based on two cascaded integrated MZM composed of two sub-MZMs is proposed. The simulation results show high quality optical mm-wave and mm-wave signal can be generated without any optical or electrical filter when an integrated MZM composed sub-MZMs with imperfect extinction ratio is utilized. Moreover, OSSR and RFSSR of two cases are also compared based on simulation results.5). MI in a fiber grating is investigated firstly by analytical method, to best our knowledge. The dispersion relation that determines the characteristics of MI in a fiber grating is solved exactly, and the characteristics of MI in a fiber grating is thoroughly discussed and analyzed based on the analytical solution.