Study On System Technology Of Re-Modulation WDM-PON

With the huge increase of core transport network transmission capacity, and the emerging of variety of multimedia services, access network require new access networks that support high speed bandwidths in each channel for future. The existing TDM-PON can only be a satisfactory solution for current bandwidth demands as its bandwidth is shared by all users. Fortunately, the WDM-PON system provides point to point optical connectivity using a dedicated pair of wavelength for per user, which is widely believed to be the route towards the next generation PONs.The technology challenge of WDM-PON has been to avoid the need for expensive wavelength selective optical components in each optical network unit (ONU), or we can say the ONU should be colorless. The spectrum sliced WDM-PON and Wavelength sharing WDM-PON are two common schemes of colorless ONU.As a kind of wavelength sharing WDM-PON, the re-modulation WDM-PON can not only reduce the cost of ONU, but also simplify the system structure, as the upstream optical carrier is split from the downstream signal there is no need to set light source in ONU. Therefore, the technology of re-modulation WDM-PON is currently an important field.In this paper, we reviewed the architecture and technology challenge of WDM-PON and describe the methods for the ONU colorless. Then we introduced the principle of re-modulation WDM-PON. Several methods for recovery optical carrier from the downstream signal are introduced. Refer to the orthogonal modulation scheme, the narrow FSK modulation WDM-PON, which is based on the frequency chirp effect appears in direct modulated lasers and a re-modulation WDM-PON scheme based on the gain saturation characteristic of RSOA are designed. We wish it could be of importance to the development and research on WDM-PON. Combining theory study and simulation, the writer has done the following work:1.Studied the internal and abroad development instances of optical access network in detail, and deeply studied the international trends of WDM-PON, including its features and advantages.2.For the colorless of ONU in WDM-PON, re-modulation WDM-PON scheme is presented and several methods for recovery optical carrier from the downstream signal are introduced.3.The principle of frequency chirp and narrow FSK modulation is analyzed and a kind of re-modulation WDM-PON system based on narrow FSK is designed. 4.Proposed a re-modulation WDM-PON architecture based on the gain saturation characteristic of RSOA, and analyzed the system performance with simulation software; the determination of parameter values such as inject power and extinction ratio is presented.This article is divided into the following five chapters:ChapterⅠdeales with some background knowledge about this research, describe the technical principle and recent development of passive optical network (PON);ChapterⅡdescribes the system architecture of WDM-PON and the key technologies such as multi-wavelength light source in OLT,the scheme principle of spectrum sliced WDM-PON and wavelength sharing WDM-PON for ONU colorless. Two spectral grids for WDM application: CWDM frequency grid and DWDM frequency grid are also introduced in this section.ChaptersⅢdescribes the scheme principle and key features of re-modulation WDM-PON. Several methods for recovery optical carrier from the downstream signal are introduced in this section, include orthogonal modulation RSOA gain saturation modulation frequency detuning,forward current injection and spectral filtering. Back reflection noise in re-modulation system is also analyzed.ChapterⅣexplains the how the frequency chirp is introduced when direct modulate lasers and describe the principle of narrow FSK.A re modulation WDM-PON system based on narrow FSK is designed in this section, and the system performance is analyzed.ChapterⅤintroduces the principle and characteristics of the reflective semiconductor optical amplifier (RSOA), focus on the gain saturation characteristic. The re-modulation WDM-PON system with RSOA is designed,and the system performance is analyzed.Finally, the writer summarized the existing work and gives an expectation for the next step.