二區段分佈反饋式雷射於全光網路之應用

Abstract

本論文主要是探討於高速全光網路中，二區段分佈反饋式雷射除穩定輸出時，其可作為全光網路雷射源外，尚有其他應用角色：當有打入外來光信號，可以應用於波長轉換；當輸出週期性光信號時，其為一光振盪源，當有打入外來光信號，可以應用於全光網路的注入鎖定。 我們針對二區段分佈反饋式雷射發展自振盪轉移函數並搭配控制理論中的振盪準則去評估自振盪頻率，並以實驗驗證得到的自振盪頻率與模型所估的自振盪頻率吻合。我們也探討不同參數對於自振盪的重要性，而能掌握到關鍵的參數，包括：具有位移層的區段相對於整個雷射長度所佔的比例、載子濃度、光柵耦合係數、以及群折射係數。我們於雷射自振盪時由雷射腔外另外打入一光傳輸信號，探討光注入鎖定範圍，並實驗觀察到週期性光輸出信號的時脈抖動大幅降低，達到光注入鎖定的效果。 我們以有限差分法模擬二區段分佈反饋式雷射在自振盪其雷射內部光場變化情形。二區段分佈反饋式雷射端面相位對自振盪的影響亦被探討：二端端面的相位差異對於是否產生自振盪有開啟�關閉的效果。 二區段分佈反饋式雷射作波長轉換時，我們利用模擬而決定以僅大幅增加一個區段的注入電流，另一個區段的注入電流微幅增加的方式作為從2.5Gbps反相波長轉換提升至10Gbps反相波長轉換之解決之道。並以實驗驗證得到近10Db的熄滅比。

In this thesis, we analyze and experimentally demonstrate an integrated laser chip can be used as differential functional devices in all optical networks: single mode laser source with high stability, optical clock source by tuning currents, optical clock recovery, and higher speed wavelength converter. We propose a numerical model to estimate the self-sustained pulsation (SSP) frequency for a two-section distributed feedback (TS-DFB) laser. A modulation transfer function is derived from the rate equations for carriers and photons. The SSP frequency can be obtained from the singularity condition of the transfer function. The device parameters varied in the analysis include carrier density, section length ratio, grating coupling coefficient, and the refractive index change caused by adding a shift-layer. The device structure used for the SSP experiments and analysis is a TS-DFB laser with a shift-layer. The results of numerical analysis match well with the experimental data. We also measure the locking range for injection locking. We apply the finite-difference method to analyze the dynamic internal optical field in a TS-DFB, especially the dynamic field patterns under high frequency SSP. We also integrate the facet phase effect on the SSP process. The relationship among output waveform, dynamic internal optical field patterns, and phase variation is also disscussed. We demonstrate experimentally that the TS-DFB module is applied as a wavelength converter for its operation at a higher speed, 10Gbps. The TS-DFB based wavwlength conversion can convert signals with a high extinction ratio, up to 10dB, matched to the numerical result.