長距離光學OFDM傳輸系統之子載波混頻干擾消除技術

Subcarrier to Subcarrier Intermixing Interference Cancellation Technique in Long-reach Optical OFDM Transmission System

陳星宇(Hsing-Yu Chen) ； 徐達儒(Dar-Zu Hsu) ； 魏嘉建(Chia-Chien Wei) ； 陳智弘(Jye-Hong Chen)

《電腦與通訊》 155期 (2014/02) Pp. 101-108

摘要

長距離（Long-reach；LR）光學正交分頻多工（OOFDM）被動光纖網路（PON）是下世代寬頻接取網路重要的解決方案之一，為了達成一具成本效益之系統，我們選擇使用強度調變直接偵測（IM-DD）的方式，使用商用成熟的10-GHz電致光吸收調變器（EAM）與10-GHz PIN光接收器於高頻寬使用效率的OFDM系統。在長距離被動光纖網路中使用高頻寬使用效率的OFDM系統，可以僅以低速具成本效益之光元件來達到高速傳輸。然而，LR-PON網路系統傳輸距離需大於100-km，色散造成之傳輸通道衰落成為系統很大的挑戰，此外，色散與啾頻相關之子載波混頻干擾和調變器之非線性失真也大幅降低訊號品質，導致傳輸速率受限。此篇論文中我們使用動態多頻段OFDM子載波配置以有效利用衰落通道之傳輸頻寬，並提出一新式子載波混頻干擾消除技術以補償SSII與EAM之非線性來提升訊號品質，並在實驗上僅以10-GHz之光元件即達成一32-Gbps 150-km OFDM-IMDD之傳輸。

關鍵字

長距離被動光纖網路(Long-reach Passive Optical Network；LR-PON) ； 正交分頻多工(Orthogonal Frequency Division Multiplexing；OFDM) ； 子載波混頻干擾(Subcarrier to Subcarrier Intermixing Interference；SSII) ； 調變器非線性(modulator nonlinearity)

並列摘要

Optical OFDM PON has been considered to be one of the most prominent next-generation broadband wired access solutions. To be cost-effective, spectrally efficient OFDM transmission is based on intensity modulation and direct detection (IM-DD), and commercially matured 10-GHz electro-absorption modulator (EAM) and 10-GHz PIN are used in our works. However, the transmission distance of a long-reach PON is more than 100 km, the dispersion-induced power fading become a challenge. Moreover, the dispersion- and chirp-related subcarrier to subcarrier intermixing interference (SSII) and the EAM nonlinearity degrade the performance of the system. In this paper, we propose a dynamic multi -band OFDM subcarrier allocation scheme to efficiently use the fading channel, and propose a novel SSII cancellation technique to compensate both the SSII and EAM nonlinearity, thus improving the SNR of the signal. Experimental results demonstrate that, a 32-Gbps 150-km OFDM-IMDD system is achieved with low-cost 10-GHz EAM modulator.