臺灣大學: 光電工程學研究所林恭如林俊儒Lin, Chun-JuChun-JuLin2013-03-272018-07-052013-03-272018-07-052011http://ntur.lib.ntu.edu.tw//handle/246246/253546本論文將光電振盪器之架構應用於驅動諧波鎖模弱共振腔雷射光源，並將此一光源應用於產生10 Gbit/s歸零訊號。脈衝寬是判斷鎖模好壞的重要參數，而從描述自反饋雷射二極體之速率方程式，並修正主動鎖模理論中的脈衝寬公式，我們可以得知脈衝寬會隨光自反饋功率比以及微波訊號功率增益上升而下降。在90%的光自反饋功率比與微波放大器所能提供最大增益35 dB下，可以得到20 ps的最窄脈衝寬以及0.9 ps的時基誤差。進一步將此優化過之載波藉Mach-Zehnder調變器載上非歸零開關鍵訊號後，可得歸零訊號串列且具有10.2 dB的訊雜比以及13.8 dB的消光比，而其在誤碼率為10-9時的最小接收功率為-18.7 dBm。為達到通道化的系統，我們將此一訊號通過200-GHz通道間隔的陣列波導光柵並得到-16.5 dBm的接收靈敏度。為了進一步提升系統性能，我們嘗試在光電振盪器迴路內加入不同長度的單模光纖，並發現在加入100公尺光纖的系統中性能可以得到最佳的改善，在100 Hz的位移頻率下，相位雜訊可下降到-70 dBc/Hz，脈衝寬可以降到18.5 ps，時基誤差則能下降到0.67 ps。然而當光纖長度超過200 m，系統則會快速劣化，這是因為啾頻、雷射模態分割雜訊、光電振盪器的旁模雜訊、環境擾動這四項劣化因素都會隨腔長增加而上升，因此抵銷了原本預期延長腔長對Q的提升所能帶來的改善。此外，為了要抑制光電振盪器的旁模雜訊，我們使用了雙路徑的光電振盪器架構來消除旁模的共振條件。但傳統的雙腔路徑長設計原則會導致腔內的等效Q值因為腔內能量分布於短腔而大幅下降，因此我們藉由雙腔光電振盪器的閉路轉移函數對理論作修正，並透過選擇雙腔的腔長差來達到使振盪器旁模雜訊最小的效果。然而在實驗中我們並沒有發現顯著的改善，這是因為光電振盪器的腔長仍不夠長，消除旁模所能帶來的改善不大，而雙腔架構又有拍頻雜訊會轉換為相位雜訊以及強度雜訊，這兩個效果彼此抵消使得雙腔架構性能並沒有明顯的提升。A self-triggered harmonic mode-locked weak-resonant-cavity Fabry-Perot laser diode is employed as the 10 Gbit/s RZ data generator. Derived from the rate equation, the pulsewidth formula in actively mode-locking theory is modified and illuminates the shortening of the pulse as a function of optical feedback ratio and microwave power gain. The pulsewidth is narrower with higher optical injection and microwave gain due to the gain saturation of the laser diode and the increase of the modulation depth. The timing jitter, pulsewidth of the pulse train and phase noise of the microwave signal under different biased current, optical injection and microwave gain are measured. The optimized jitter and pulsewidth are 0.9 ps and 20 ps, respectively. With higher microwave gain, the SNR and ER are improved to 10.2 dB and 13.8 dB due to the enhancement of the peak power and elimination of the residual carrier. At the optimized operation condition, the receiving sensitivity of -18.5 dBm and -16.5 dBm before and after channelization, respectively, are obtained with 10 Gbit/s RZ-OOK data. To further enhance the cavity Q-value, 100-m single mode fiber is added in the OEO loop. The minimal single sided-band phase noise of -70 dBc/Hz at 100Hz offset is measured while significant degradation is observed with cavity length longer than 200 m. The optimized pulse train exhibits timing jitter of 0.67 ps and pulsewidth of 18.5 ps with 100-m single mode fiber. Chirping, mode-partition noise, spurious signal and environmental fluctuation are enlarged with longer loop length and these factors oppose the expected improvement induced by longer cavity and the resultant higher Q-value. The optimized RZ pulsed carrier modulated by MZM with 10 Gbit/s RZ-OOK data shows high SNR of 11 dB and lower receiving sensitivity of -19.2 dBm than the system with original cavity length. With 200-GHZ spacing AWG, the channelization is performed and the power penalty of only 2.5 dB can be attributed to the narrow linewidth of 0.77 nm since most signal on the carrier can transmit through the passband of the AWG. To suppress the spurious signal, the dual OEO loop structure is employed. A theoretical analysis based on the relationship between closed-loop intensity transfer function, power ratio between two loops and the cavity lengths is derived for exploring the optimized principle of dual-loop OEO structure. The dual-loop scheme in the proposed system is realized with different cavity length and the optimized condition is 100-m, 120-m loop length with equal power. The spurious signal in the system with longer cavity is vanished with the use of dual-loop structure. The phase noise is about -100 dBc/Hz at 10-kHz and the RMS timing jitter and pulsewidth are 0.67 ps and 18.3 ps, respectively. These parameters have no obvious change compared with single loop case except the elimination of the spurious signal. The SNR slightly decays to 10.9 dB and the receiving power at BER of 10-9 is -19.2 dBm in the optimized condition with 10 Gbit/s RZ-OOK data from PRBS source triggered by the OEO microwave signal.1442706 bytesapplication/pdfen-US歸零訊號弱共振腔雷射諧波鎖模自反饋光電振盪器return-to-zero dataweak-resonant-cavity Fabry-Perot laser diode (WRC-FPLD)harmonic mode-lockingself-feedbackoptoelectronic oscillatorthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/253546/1/ntu-100-R98941095-1.pdf