於本論文，我們著重全光調變格式轉換系統之研究，透過三階非線性效應，不但設計出新穎的全光調變格式轉換系統，更進行深入且完整的探討。首先，在低速轉高速格式的轉換系統中，我們與新加坡國立大學合作，建立100 Gbps RZ-QPSK之訊號傳輸平台，並透過四波混頻機制，完成RZ-QPSK 與 ASK 轉 RZ-8QAM的調變格式轉換系統，並進而探討交互相位調變對於轉換效果之影響。緊接著，我們透過交互相位調變，提出一種相對容易實現的方式，能在雙向傳輸架構中以低成本、低系統複雜度與抗背向散射的優勢，完成四路低速的NRZ-OOK 轉一路高速的PDM RZ-QPSK 訊號。而在高速轉低速格式的方向上，我們藉由四波混頻效應，提出相位透明的轉換機制，在雙向傳輸的架構中，完成NRZ-QPSK 轉 2 × BPSK的轉換系統，不僅不需昂貴設備與複雜架構，更可完整保存原訊號的相位資訊。最後，我們設計新型系統，能在一段光纖中，同時完成高速到低速格式，以及低速到高速格式的轉換。其中，在高速轉低速的部分，我們進化成在一路的方向上，完成NRZ-QPSK to 2×BPSK的轉換。而在低速到高速的部分，我們透過自我幫浦的方式，完成兩路PSK to QPSK的調變格式轉換。由於兩道轉換機制可在同一段光纖當中完成，因此可達到降低結構成本與降低架構複雜度的優點。此外，由於兩道機制是在垂直的偏振態、且相反方向所完成的，故可減少反射雜訊的干擾，例如：受激布里淵散射(Stimulated Brillouin Scattering)、雙重雷利背向散射(Double Rayleigh Backscattering)。

All-optical modulation format conversion plays an important role in the future optical communication networks due to the different modulation formats are selectively applied to various optical networks. In this dissertation, we focus on the topic of modulation format conversion. To decrease the capital costs and network complexity for the further all-optical communication networks, we committed to develop a simple, cost-effective and lower-complexity modulation format converter.
We start from modulation format conversion from several low-speed signals to a high-speed one, including all-optical 20Gbps QPSK and 10Gbps ASK to a 30Gbps QPSK signal by using FWM mechanism; XPM-based all-optical 4 12.5Gbps NRZ-OOK signals to a 50Gbps PDM RZ-QPSK signal with a simple and cost-effectively methods.
On the other hands, we keep to investigate the modulation format conversion from a high-speed signal to several low-speed signals. We propose and experimental demonstrated a all-optical phase-transparent format conversion from a 25Gbps QPSK signal to 2 × 12.5Gbps BPSK signals by using FWM nonlinearity in a double-pass scheme.
Furthermore, we propose a multifunctional all-optical format converter based on four-wave mixing in a bi-directional architecture. Multi-functions, including: high-speed to low-speed and low-speed to high-speed format conversions are simultaneously demonstrated both in simulation and experiment. Based on the simple structure, the proposed format converter has great potential to decrease the implement costs and network complexity. Besides, the annoying back-propagating effect, including Rayleigh back-scattering (RBS) and stimulated Brillouin scattering (SBS) can be avoided to affect the other function. In the scenarios of phase de-multiplexing, the converted signals can preserve the phase information of the original signal by adapting two optical pumps. On the other hands, the function of phase multiplexing is also achieved without any additional pumps, which can offers great spectrum efficiency.

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