在非線性光纖中的超連續光譜現象和光參數效應之應用與分析

Abstract

在本篇論文中，我們研究兩種光纖非線性效應--超連續光譜現象和光參數效應。我們用自己開發的數值模擬程式去分析超連續光譜現象，另一部分則利用光參數效應去設計光通訊元件。 要產生超連續光譜，常將高功率短脈衝的雷射打入高非線性光纖，光纖中的線性和非線性效應互相影響，進而產生同調的超寬頻光源。超連續光譜在光通訊, 頻率量測和生醫影像都有重要的應用，但它產生的機制太過複雜仍停留在研究的階段。我們用自己開發的程式追蹤模擬超連續光譜產生的過程，我們發現高階光孤子(soliton)分裂的現象可能是主要的效應。我們期望我們發展的模擬工具能幫助超連續光譜實驗的進行並實現最佳化。 光參數效應有多項在光通訊網路的應用，像是光參數放大器與光參數波長轉換器。混合多種光纖的光參數放大器能增進增益平坦，我們研究其增益平坦的穩定性，發覺需要精確的光纖色散參數值才能維持增益平坦。這使得它難以在現實生活上應用。另外，我們利用有兩個零色散波長的色散平坦光纖，去設計應用於高速光通訊網路的可調式光參數波長轉換器。我們研究第二個零色散波長造成的影響，並提出一個簡潔的設計方針。

In this thesis, we investigated two nonlinear phenomena in optical fibers -- supercontinuum generation (SCG) and parametric effects. We developed numerical tools to analyze SCG and to design devices based on parametric effects. When injecting short pulses with high peak power into optical fibers, generally fibers with high nonlinearities, coherent broadband light called supercontinuum is generated through complex interplays between linear and nonlinear effects. SCG has applications in areas of optical communications, frequency metrology, medical images, and so on. The mechanism of SCG is still under investigation because too many effects are involved. We develop numerical tools to monitor SCG evolutions. Our results show that fission of higher-order solitons might be the dominant effects. The tools and analyses will help SCG experiment and optimization in the future. Parametric effects have several applications in optical networks such as optical parametric amplifiers (OPAs) and parametric wavelength converters (PWCs). Hybrid-fiber OPA has been proposed to improve the gain flatness of OPAs. We studied the gain-flatness stability of hybrid-fiber OPAs and find that the precise fiber dispersion profiles are required, which might prevent them from practical use. PWCs, by our definition, are tunable wavelength converters for high-speed wavelength routing. We design PWCs using nonlinear dispersion flattened fibers with two zero-dispersion wavelengths. We investigated the effect of second zero-dispersion wavelength and provided a simple guide line for PWC design.