下一代長距離波分多工光纖與無線接取網路整合技術之研究

Abstract

長距離(long reach, LR)光接取網路(~100 km)被視為未來極具潛力的架構，由於少了大量的光電組件和訊號轉換元件，成本也因此可以大幅下降。整合了有線(利用被動光網路(passive optical network, PON))及無線(利用光纖微波技術(radio-over-fiber, ROF))的接取網路可在單一且低成本的平台上同時提供固定和行動通訊。LR-PON 和LR-ROF 的整合可進一步透過將網路架構簡易化而降低成本。這種長距離的整合網路更可共用傳輸中相同的光組件，並延伸ROF 的涵蓋範圍。儘管最近整合標準長度(~20 km)的PON 和ROF 的接取網路架構已經受到越來越多的關注；然而整合LR-PON 和LR-ROF的部分卻還未有太多的研究。因此在這個計畫中，我們把研究方向集中在整合LR-PON和LR-ROF 的部份。計畫中主要的研究挑戰包括：高度光色散、缺乏高速無色(colorless)光網絡單元（optical networking unit, ONU）及遠端天線單元（remote antenna unit, RAU）、微波訊號無線及有線的同步問題、光電元件的非線性現象和缺少有效的靈活頻寬分配等。。本期報告將分成二部分: (1) 我們提出並驗證了一個LR-ROF網路，利用由矽環調變器(Silicon-ring modulator)產生單邊帶的SSB-ROF訊號。矽調變器體積小，功耗低，特點是能只調變訊號在其諧振的波長，這使得它非常適合編碼單邊帶訊號。(2) 我們也提出並驗證具有成本效益的長距離光纖與無線接取整合網路。半導體光放大器（SOA）被用在網路的本地交換（local exchange）中作為多波長升頻器(up-conversion)和功率放大器。

The long reach (LR) (~ 100 km) optical access network is considered as a promising candidate for the future. This approach is predicted to generate significant capital and operational cost savings for network operators, since the number of network elements and interconnection interfaces is reduced. An integrated optical wired (using passive optical network (PON)) and wireless (using radio-over-fiber (ROF)) access network can provide broadband services for both fixed and mobile users in a single and low cost platform. The integration of the LR-PON and the LR-ROF can further reduce the cost by simplifying the network architecture, sharing the same optical components and extending the ROF network to cover larger area. Although the integration the standard-reach (~20 km) PON and ROF access network has received more and more attenuation recently, the research of integrating the LR-PON with the LR-ROF is very little. Hence in this project, we will focus on the research of an integrated LR-PON and LR-ROF network. The main challenges in these integrated network includes: high chromatic dispersion, high-cost of the high-speed colorless optical networking unit (ONU) and remote antenna unit (RAU), issue in synchronization of radio signal in both air and fiber links, nonlinear response of the optical and electrical components and also the requirement of effective bandwidth allocation architectures.In this report, we will focus at two main parts: (1) we propose and demonstrate a LR ROF signal transmission and distribution using SSB-ROF signal generated by a silicon ring-modulator. The silicon modulator is compact and has low power consumption. One unique feature of the silicon ring-modulator is that it only modulates the signal wavelength located at the resonant null. This makes it very suitable for encoding data on one of the sidebands of the optical two tones signal without the need of the separation of the sidebands. (2) We propose and experimentally demonstrate a cost efficient hybrid gigabit wired and wireless long-reach PON. Semiconductor optical amplifier (SOA) is used as the multi-wavelength broadband optical up-converter and optical power amplifier inside the local exchange (LE).