高速且長距離之正交分頻多工強度調變直接偵測系統中的非線性失真補償

Abstract

此篇論文提出一個>50-Gb/s且>60-km之正交分頻多工(OFDM)長距離被動光纖網路系統以滿足下世代網路標準的需求。正交分頻多工訊號擁有許多好處，如可支援動態調變以適應衰落通道。然而，此系統依然存在著許多待解決之議題，如調變器非線性、光纖非線性、色散導致之失真以及不足的系統損失預算等。為了解決這些議題，這篇論文提出了一個子載波間混合干擾(SSII)的理論模型與其相對應的干擾消除機制(SSII消除)，可有效的補償系統中的非線性失真。由於SSII干擾消除技術仰賴於理論模型的精確度，此論文亦提出基於動態權重之Volterra filtering，並以實驗深入比較此兩種補償技術。此外，我們使用分波多工(WDM)技術來展示我們所提出的架構用於多波長系統時的適用性。基於低成本的10-GHz電致光吸收調變器與PIN接收器，我們在未使用中繼放大器與前置放大器的條件下，成功達成一個 200-Gb/s、60 km之傳輸，並且同時具有大於30 dB的損失預算，換言之，此系統可以支援128個光學網路單元，而每個光學網路單元可支援大於1.6 Gb/s的傳輸量。

This work proposes a >50-Gb/s and >60-km optical OFDM long reach (LR) passive optical network (PON) for the next generation network standard. OFDM signal has a lot of advantages such as supporting dynamic modulation to adapt to fading channel. However, there are still several issues in an OFDM system, such as modulator nonlinearity, fiber nonlinearity, dispersion induced nonlinear distortion and insufficient loss budget. To deal with these issues, we propose a theoretical model, subcarrier-to-subcarrier intermixing interference (SSII), as well as the corresponding compensation method, SSII cancellation, which can effectively compensate the aforementioned nonlinear distortions. Since the SSII cancellation relies on the precision of the mathematical model, we also propose an adaptive-weighted Volterra filtering and experimentally compare these two compensation schemes. Moreover, wavelength division multiplexing (WDM) technology is utilized to demonstrate the feasibility of the proposed scheme in a multi-channel system. Based on low cost 10-GHz EAM and PIN, we achieved a 200-Gb/s transmission over a distance of 60 km with a loss budget of >30 dB, while providing support for 128 ONUs at >1.6 Gb/s/ONU without the need for an inline amplifier or pre-amplifier.