| Due to the continuous improvement of client network access rate, existing TDM-PON technology has been increasingly difficult to meet the application requirements, WDM-PON with the advantages of high bandwidth, easy expansion, is generally considered as an important development direction to increase the capacity of fiber access networks in the future. The colorless ONU is one of the effective ways to further reduce the cost of installation, operation and maintenance in WDM-PON. A variety of technical methods to realize colorless ONU have been proposed, in which using centralized light source in the optical line terminal (OLT), wherein, in the ONU side the downlink data remodulated is considered to be the most scheme.According to the future demands, a novel remodulation scheme using LiNbO3based MZM suitable for high speed modulation is proposed in this paper. Furthermore, combing with novle modulation formats, it is reasonable to realize high-speed remodulated WDM-PON with taking MZM as the modulator in ONU.Firstly, starting from the introduction of the principle of WDM-PON, the advantages relative to traditional TDM-PON and the key technologies used in WDM-PON are analyzed. The typical ways to realize colorless ONU are summarized. Secondly, the novel optical modulation format and modulation techniques are introduced. The sturcture and modulation principle of LiNbO3based MZM are discussed in detail. The modulation scheme of several phase modulation formats such as differential phase shift keying (DPSK), differential quadrature phase shift keying (DQPSK) are introduced and their properties of transmission are simulated. Next, RSOA-based WDM-PON is researched, where the principle and characteristics of RSOA as key components in this WDM-PON is discussed theoretically. The influence of the optical of RSOA, extinction ratio of downlink signal and tranmission bit rates on the uplink signal is simulated with the uplink bit rate of1.25Gb/s. A novel scheme of high-speed WDM-PON which using MZM as remodulator to realizing colorless ONU is analysis in the last chapter of this paper. The bit-rates and transmission distances supported by WDM-PON based on RSOA and MZM are respectively simulated with Optisystem8.0. By studying of the two-way symmetric rate of1.25,2.5and lOGb/s uplink transmission performance, the simulation results show that RSOA-based WDM-PON is more suitable for the conditions of both low bit-rate and long-distance. Otherwise, MZM-based WDM-PON dominates the applications of higher bit-rate and short-distance. |
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