波分多工被動光纖網路和光纖微波系統中的瑞利背向散射噪音模型、分析、及 緩和研究

Abstract

爲跟上帶寬增長的需要，現存的接取網路需要一個很大的升級。這些網 路還應該提供雙向，易安裝並且低成本的服務給每一位顧客。當前的有綫 網路基於光纖到戶(FTTH)技術可以給用戶提供巨大的帶寬服務，但是對於 漫遊連接就不夠靈活。從另一方面來看，雖然無綫網路具有移動性，但是 並不能滿足高清電視(HDTV)和互動多媒體應用的大量帶寬要求。因此，結 合有綫和無綫服務在單一未來高帶寬接取網路可以使成本減低，同時滿足 固定用戶和移動用戶的需求。這種混合接取網路可以由光纖微波(ROF)和波 分復用被動光網路(WDM-PON)來實現無綫和有綫的應用。 瑞利背向散射(Rayleigh backscattering)干擾噪音被認爲是載波分佈 混合光接取網路的重要限制因素之一。由於之前的瑞利背向噪音模型具有 不同的限制，我們將研究一個易實現，可有效操作的新型模型，來研究對 於任意的光調變格式，以及任意的光與電濾波器的光譜形狀和頻率響應的 噪音緩和特性。我們已經進行了初步的瑞利反向散射所產生的干涉噪音作 理論分析。不同的噪音先由光信號的功率譜密度(PSD)導出，我們再對其特 性進行分析。在計劃的第一年我們將提出一個更加具體和完善的理論模型， 並在之後的兩年中通過實驗對本項目進行驗證。 基於瑞利背向散射模型，有效的瑞利背向散射緩和方案將會被分析並研 究。本項目將會提出新型的遏制載波（包括雙邊帶，或是高節能的單邊帶） 光調變格式作瑞利背向散射噪音緩和方案。同時會提出一種新的調變器結 構來產生遏制載波單邊帶-調幅相位鍵控(carrier suppressed single sideband-amplitude modulated phase shift keying) 調變格式。初步的 仿真結果顯示這種新的光調變格式同時具有優秀的瑞利背向散射噪音和色 散容差，以及高節能的傳輸優勢。最後由於最近提出的混合接入性結構(ROF 和FTTH)主要強調下行分佈，一種新型的使用波長分離(wavelength splitting)的載波分佈混合網路結構將會被提出。被分離的波長能夠提供 載波給上行的ROF 和 FTTH 使用。初步的仿真結果顯示它也具有很強的瑞 利反向散射噪音容差。

A strong upgrade of existing access network is required in order to cope with the exponential increase of bandwidth demand. These networks should and also provide bi-directionality, feasibility, ease of installation, and lower cost per customer. Today’s wired networks based on fiber-to-the-home (FTTH) access technologies provide huge bandwidth to users but are not flexible enough to allow roaming connections. On the other hand, wireless networks offer mobility to users, but do not possess abundant bandwidth to meet the ultimate demand for high-definition television (HDTV) distribution and interactive multimedia applications. Therefore, integration of wired and wireless services for future access networks will lead to convergence of ultimate high bandwidth for both fixed and mobile users in a single, low cost platform. This can be accomplished by using radio-over-fiber (ROF) systems and wavelength division multiplexed-passive optical network (WDM-PON) to provide wireless and wired applications. Rayleigh backscattering (RB) interferometric beat noise is considered as one of the most limiting factors for these cost effective carrier-distributed hybrid FTTH and ROF access networks. Due to different limitations of previous Rayleigh noise modeling, a novel modeling approach that can be easily realized and used efficiently to study the performance of noise mitigation with arbitrary modulation formats, arbitrary optical and electrical filter shapes and frequency responses will be developed. A preliminary theoretical analysis has been preformed focusing on the interferometric noise generated by RB. The various noise contributions are derived from the power spectral densities (PSDs) of the optical signals and the performance of the scheme is then modeled analytically. Then, a more detail and complete theoretical modeling will be performed during the first year of the project and then verified by using experiment in the second and third years. Based on the RB modeling, effective RB mitigation schemes and techniques can be analyzed and developed. In this project, novel RB noise mitigation schemes based on carrier suppression (including double sideband, or the more power efficient single sideband) will be proposed and developed. A novel modulator architecture generating carrier suppressed single sideband amplitude modulated phase shift keying (CS-SS-AMPSK) will be proposed. Preliminary simulation results suggest this modulation format provides combined transmission advantages in terms of excellent RB noise and chromatic dispersion tolerances, high power efficiency. Finally, due to recently proposed hybrid ROF and FTTH access architectures mainly emphasize on the downstream distribution, a novel carrier distributed hybrid network architecture using wavelength splitting will be proposed. The split wavelength can provide CW carriers for upstream ROF and FTTH applications. Preliminary simulation results suggest this also have a strong RB noise tolerance.